Bosch Appliances Water Heater GWH 345 450 ESR L User Manual

GWH 345/450 ESR

Temperature Modulated with Electronic Ignition

Suitable for heating and recirculating potable water

GWH-345/450-ESR-N - Natural Gas

GWH-345/450-ESR-L - Liquefied Petroleum (LP) Gas

Warning: If the information in this manual is not

followed exactly, a fire or explosion may result

causing property damage, personal injury or death.

Do not store or use gasoline or other flammable

vapor and liquids in the vicinity of this or any other

appliance.

What to do if you smell gas

• Close gas valve. Open windows and doors, and

evacuate the building.

• Do not try to operate any appliance.

• Do not touch any electrical switch; do not use any

phone in your building

Improper installation, adjustment, alteration,

service or maintenance can cause injury or

property damage. Refer to this manual. For

assistance or additional information consult a

qualified installer, service agency or the gas

supplier.

In the Commonwealth of Massachusetts this

product must be installed by a licensed plumber or

gas fitter.

• Immediately call your gas supplier from a neighbor’s

phone. Follow the gas supplier’s instructions.

• If you cannot reach your gas supplier, call the fire

department.

• Installation and service must be performed by a

qualified installer, service agency or the gas supplier.

Upon completion of the installation, these

instructions should be handed to the user of the

appliance for future reference.

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Warning

Warning: The recirculating water

heater must be disconnected from the

gas supply piping system during any

pressure testing of that system at test

pressures equal to or more than 0.5

psig (14” W.C.).

FCC:

This device complies with Part 15 of the FCC rules.

Operation is subject to the following two conditions: (1)

This device may not cause harmful interference, and (2)

this device must accept any interference received,

including interference that may cause undesired

operation.

Caution:

Any

changes

modifications not expressly approved

by the party responsible for compliance

could void the user’s authority to

operate the equipment.

Fig. 1

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Temperature Control

2.1 Features

Selection range: 115°F (45°C) - 190°F (90°C)

Parts

Gas Requirement

• Sealed combustion burner.

Gas connection (inches) - ¾”

Safety

Inlet gas pressure under operation (with a high hot

water flow rate)*

• Ionization flame sensor

• Over temperature protection.

• Propane: 11” - 14” water column

• Natural Gas: 5.5” - 8” water column.

High quality materials for long working life

• Copper heat exchanger

* To measure gas pressure, see Measuring Gas

Pressure, chapter 3.8.

• Compact space saver: mounts on a wall with

supplied bracket.

Venting

Features

3" AL 29-4C single wall sealed stainless steel vent

pipe.

See chapter 3.6 for Venting.

• LCD screen to display temperatures, burner

operation and error codes

• On/Off button and separate temperature controls for

domestic water heating and recirculating water

Water

• Hot water connection - ¾” NPT

• Cold water connection - ¾” NPT.

• Reset button

• Failure codes for diagnostics and repair

• Freeze prevention cycle.

Combustion

• NOx ≤ 100 ppm

• CO ≤ 250 ppm

BOSCH is constantly improving its

products, therefore specifications are

subject to change without prior notice.

• CO level (see table 8 for correct restrictor

dimension).

Dimensions

2.2 GWH-345/450-ESR Specifications

(Technical data)

• Depth (in): 11 ¾” (300 mm)

• Width (in): 15 ¾” (400 mm)

• Height (in): 27 ½” (700 mm)

• Weight: 47 pounds (21 kg).

Approved in US/Canada

Capacity

GWH345 Maximum flow rate: 3.5 GPM (13 l/min) at a

45°F (25°C) rise.

GWH450 Maximum flow rate: 4.5 GPM (17 l/min) at a

45°F (25°C) rise.

Gas types

Natural Gas.

Liquid Propane.

The appliance is not field convertible.

Maximum output

GWH345 - 77,900 Btu/h (22.8 kW)

GWH450 - 98,400 Btu/h (28.8 kW)

Voltage

120 V AC (50/60 Hz)

Maximum input

Amperage

GWH345 - 95,000 Btu/h (27.8 kW)

GWH450 - 120,000 Btu/h (35.1 kW)

Idle - 40 mA

Operation - ≤ 1.5 A

Efficiency in %

Noise

GWH345 Combustion efficiency: 82%

GWH450 Combustion efficiency: 81%

≤ 50 db (A)

Safety devices

Min. Output

• Flame failure device (Ionization flame control)

• Overheat prevention (temperature limiter)

GWH345 - 23,900 Btu/h (7 kW)

GWH450 - 35,500 Btu/h (10.4 kW)

• Pressure switch (blocked vent protection).

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Appliance details

Water resistant

To remove front cover

The front cover is secured with two

IP X4 (protection against water drops)

screws to prevent unauthorized access.

Always secure the control panel and front

cover with these screws.

2.3 Unpacking the GWH-345/450-ESR

heater

This heater is packed securely.

B Loosen the two Philips head screws located as

shown in fig. 2.

The box includes:

• Wall-mounted gas fired recirculating water heater

• Bracket and screws for wall hanging the heater

• Exhaust vent adaptor (with 4 screws and gasket

provided)

• Combustion air inlet adaptor (with 4 screws and

gasket provided)

• Installation manual

• Product registration card

Fig. 2 Screws

• Energy Guide label

• Pressure relief valve

B Pull control panel outwards and then pull it

downwards (Fig. 3).

• Inlet air restrictors

– GWH 345 ESR N: Ø38/40/42

– GWH 345 ESR LP: Ø38/40/42

– GWH 450 ESR N: Ø44/47/50/55

– GWH 450 ESR LP: Ø47/50/55/60

Front cover

Do not lose this manual. Please complete and return

the enclosed product registration card.

Before installing the unit, be certain you have the

correct heater for your type of Gas - Propane or

Natural Gas. Identification labels are found on the

shipping box, and on the rating plate which is located on

the right side panel of the cover.

Low voltage

access cover

Control panel

Fig. 3 Service position to access water and electric

connections

B Lift front cover upward and remove.

The GWH-345/450-ESR is not approved or

designed for:

• Manufactured (mobile) homes, RV's or boats

• Outdoor installation

• Combination venting with other appliances

• Closed loop heating applications.

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11.The heater must not be installed in an unheated area

where temperatures will reach 36°F or lower. If the

heater is left in an area susceptible to such

temperatures, drain the unit and disconnect from

electrical supply. See Chapter 4.7 for additional

freeze prevention information.

2.4 General rules to follow for safe

operation

1. You must follow these instructions when you install

your heater. In the United States: The installation

must conform with local codes or, in the absence of

local codes, the National Fuel Gas Code ANSI

Z223.1/NFPA 54.

12.In areas where water supply has a high mineral

content, a water softener is strongly recommended.

A water softener is required if the water hardness

exceeds 6 grains/gal (103 mg/l) calcium carbonate.

Damage to the water heater resulting from hard

water/scale deposits will not be covered under

warranty.

In Canada: The Installation must conform with CGA

B149.(1,2) INSTALLATION CODES and /or local

installation codes.

2. Carefully plan where you install the heater. Correct

combustion air supply and vent pipe installation are

very important. If not installed correctly, fatal

accidents can be caused by lack of air, carbon

monoxide poisoning or fire.

3. When the unit is installed indoors with ROOM

SEALED (twin pipe) combustion air and venting, it is

permitted to be located in bathrooms, bedrooms and

occupied rooms that are normally kept closed. See

chapter 3.6. If the unit will be installed indoors and

use indoor combustion air, the place where you

install the heater must have enough ventilation. The

National Fire Codes do not allow UNSEALED gas

fired water heater installations in bathrooms,

bedrooms or any occupied rooms normally kept

closed. See chapter 3.2 and 3.5.

4. You must vent your heater. See chapter 3.6 Venting.

5. The appliance and its gas connection must be leak

tested before placing the appliance in operation. The

appliance must be isolated from the gas supply

piping system by closing its individual manual gas

shutoff valve (not supplied with heater) during any

pressure testing at pressures in excess of ½ Psig

(3.5 kPa).

6. Keep water heater area clear and free from

combustibles and flammable liquids. Do not locate

the heater over any material which might burn.

7. Correct gas pressure is critical for the optimum

operation of this heater. Gas piping must be sized to

provide the required pressure at the maximum output

of the heater, while all the other gas appliances are in

operation. Check with your local gas supplier, and

see the section on connecting the gas supply.

8. Should overheating occur or the gas supply fails to

shut off, turn off the gas supply at the manual gas

shut off valve, on the gas line. Note: manual gas

shutoff valve is not supplied with the heater.

9. Do not use this appliance if any part has been

underwater. Immediately call a qualified service

technician to inspect the appliance and to replace

any part of the control system and any gas control

which has been underwater.

10.Failure to install heater correctly may lead to unsafe

operation and void the warranty.

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Appliance details

2.5 Dimensions and minimum installation clearances

Fig. 4 Dimensions

Combustion air inlet adapter (right side only)

Exhaust adapter with CO₂measuring point

Front cover

On/Off button

Reset button

Recirculating water temperature selector

LED - (ON) warning light (blinks when in error lock out)

Domestic hot water temperature selector

Mounting plate

Fig. 5 Minimum clearances

Model GWH-345/450-ESR

12”

TOP

FRONT (B)

BACK

4”

0”

SIDES

½”

12”

BOTTOM

Table 1 Minimum clearances

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Appliance details

2.6 Applications

Caution: the water heater which will be

used to supply potable water shall not

be connected to any heating system or

component(s) previously used with a

nonpotable water heating appliance.

Introduction

The application designs provided in this manual are general guides to be used when installing this recirculating water

heater.

Pump Sizing

Required PS pumps are Taco 007 Bronze or Grundfos 15-42B. PZ pumps should be sized by a professional plumb-

ing contractor based on the specific application.

Caution: Do not overpump the heater.

Maximum 5 gpm water flow permitted

through the heater.

Instantaneous water heater (direct tank load design)

Note: maximum amp draw:

1,5A. Do not connect

additional pump to the

appliance but use a relay panel

if powering multiple pumps.

Fig. 6

Front cover

Low voltage

access cover

Control panel

Fig. 7 Service position to access water and electric

connections

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Appliance details

Pressure drop curves

Note: Flow above 6 GPM is not permitted.

50 feet of head

GWH 345 ESR

40 feet of head

30 feet of head

20 feet of head

10 feet of head

0 feet of head

0 GPM

1 GPM

2 GPM

3 GPM

4 GPM

5 GPM

6 GPM

water flow rate

Fig. 8 GWH 345 ESR

50 feet of head

GWH 450 ESR

40 feet of head

30 feet of head

20 feet of head

10 feet of head

0 feet of head

0 GPM

1 GPM

2 GPM

3 GPM

4 GPM

5 GPM

6 GPM

water flow rate

Fig. 9 GWH 450 ESR

2.7 Water quality

Water quality can have an impact on appliance performance and appliance longevity, and may not be covered by the

manufacturer's warranty.

For water analysis data call your local water department. If on a well system, have well water analyzed periodically. If

water quality is exceeding one or more of the values specified below, Bosch recommends installing a water condi-

tioner or softener.

Descri-

ption

TDS

(Total

Total

hardness

Aluminum Chlorides

Copper

Iron

Manganese Zinc

Dissolved

Solids)

Max.

Levels

range

mg/l or

ppm

mg/l or

ppm

mg/l or

ppm

mg/l or

ppm

mg/l or

ppm

mg/l or

ppm

mg/l or ppm mg/l or

ppm

6.5-8.5

500

100 (6

grains)

0.2

250

1.0

0.3

0.05

5.0

Table 2 Venting Specifications

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Installation instructions

3.1 Introduction

3.3 Heater placement and clearances

Please follow these instructions. Failure to follow

instructions may result in:

The GWH-345/450-ESR is design certified for

installation on a combustible wall (see 3.4 Mounting

installation) provided the floor covering below the

heater is noncombustible. For installations in an alcove

or closet, maintain the minimum clearances to

combustible and non-combustible materials listed

below. See also fig. 5.

• Property damage or personal injury

• Improper operation

• Heater damage

• Loss of warranty.

Please contact Bosch Water Heating with any

questions.

A. Top 12 inches (305 mm)

B. Front 4 inches (100 mm)

C. Back 0 inches

D. Sides ½ inches (12 mm)

E. Bottom 12 inches (305 mm)

3.2 Proper location for installing your

heater

Carefully select the location of the water heater. For

your safety and for proper heater operation, you must

provide combustion air to the heater and a proper

exhaust vent system.

Clearances from any exhaust vent pipe are dependent

upon the clearance requirements of the stainless steel

vent pipe manufacturer. Single wall sealed stainless

steel (AL29-4C) vent pipe (rated for Category III

appliances) must be used when exhaust venting this

appliance. See 3.6 Venting.

Follow the guidelines below:

B 1. Locate the heater where venting, gas and

plumbing connections are feasible and convenient.

3.4 Mounting installation

B 2. The hot water lines should be kept short to save

energy. Centrally locating the water heater is best. It

is always best to have hot water lines insulated.

Warning: before starting installation:

B check that there are no loose parts

inside the appliance

Warning:

The

water

this

recirculating water heater is cold and

always remains cold except for the

times the burners are on. In the event of

power outage in conjunction with

B check that the gas type of the heater

matches the gas supply you will be

connecting to the heater.

B ensure that gas pipe, gas valve, fan and

burner have no damage and are proper-

ly fitted.

freezing

temperatures,

recommended that the heater be

drained to prevent heater from freezing.

See chapter 9 for draining instructions.

Front cover should be removed (see

instructions on page 5) in order to inspect

components visually.

Warning:

Flammable

materials,

gasoline, pressurized containers, or any

other items or articles that are potential

fire hazards must NOT be placed on or

adjacent to the heater. The appliance

area must be kept free of all

combustible materials, gasoline and

other flammable vapors and liquids.

B Secure the wall mounting bracket provided with the

heater to a wall surface.

Warning: Do not install this appliance

on a carpeted wall. The heater must be

mounted on a wall using appropriate

anchoring materials.

If wall is a stud wall sheathed with plasterboard, it is rec-

ommended that support board(s), either 1x4’s or

1/2" (minimum) plywood first be attached across a pair

of studs. Then attach the heater’s bracket to the upper

support board. The heater should be kept level on the

wall surface. See Fig. 10.

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Installation instructions

Single pipe

Although it is permissible to draw combustion air from

inside the structure, it is not the manufacturer’s recom-

mended installation method. Always install a 3 inch

elbow on the combustion air inlet to prevent foreign

objects from falling into the unit (see Fig. 11).

Fig. 11

If a single pipe installation is performed. Use the follow-

ing guidelines when providing adequate combustion air

for the recirculating water heater as well as any other

appliances that may consume air in the space. Always

follow local codes if more stringent.

Fig. 10 Mounting the heater

3.5 Combustion air requirements

Warning: In areas where freezing

temperatures are common the twin pipe

system is recommended. In a single

pipe installation, a negative air condition

may result in cold air being drawn

across the heat exchanger coil causing

it to freeze and burst. This failure is

not covered under the

• Appliances located in unconfined spaces:

– a) An unconfined space is one whose volume is

greater than 50 cubic feet (1.42 cubic meter) per

1000 Btu per hour (292.81 watts) of the

combined rating of all appliances installed in the

space. That would be 6200 cubic feet (175.6

cubic meter) of air required for the GWH-345/

450-ESR alone.

manufacturer’s warranty.

– b) In unconfined spaces in buildings of

conventional

construction, infiltration air is normally adequate to

provide air for combustion.

frame,

masonry,

metal

Warning: When installed in an

environment where corrosive chemicals

or dirty air are present the twin pipe

system is required.

– c) Installations in structures that have been tightly

constructed (air infiltration rate of 0.40 ACH or

less) must provide combustion air per the National

Fuel Gas Code. Consult an HVAC specialist if

your air infiltration rate is questionable. For these

types of installations, the twin pipe system must be

used.

Twin pipe

The GWH-345/450-ESR is designed as a sealed

combustion appliance. It is recommended that the

combustion air be provided by a dedicated 3” pipe to

the outside. If terminating combustion air piping

horizontally, pitch vent down 1/4" per foot towards

termination to prevent rain from entering the appliance.

The combustion air pipe may be constructed of

aluminum flex, PVC or any other rigid or semi rigid

sealed pipe. The combustion air inlet must be located in

such a manner as to provide a minimum 3 foot

clearance from the exhaust vent terminator.

The maximum length of the combustion air inlet is 39

feet with one elbow. Subtract 6 feet for each additional

elbow. Maximum number of elbows permitted is 4.

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Installation instructions

• Appliances located in confined spaces:

The confined space must be provided with two per-

manent openings, one commencing within 12 inches

(304.8mm) of the top and one commencing within

12 inches (304.8mm) of the bottom of the enclosure.

Each opening must have a minimum free area of one

square inch per:

– 1000 Btu/hr (292.81 watts) if all air is taken from

inside the building

– 2000 Btu/hr (585.62 watts) if all air is taken from

the outside by horizontal ducts

– 4000 Btu/hr (1171.24 watts)if all air is taken from

the outside by direct openings.

Or the confined space must be provided with one

permanent opening or duct that is within 12 inches

(304.8mm) of the ceiling of the enclosure. This opening

must have a minimum free area of one square inch per:

– 3000 Btu/hr (878.43 watts) if all air is taken from

the outside by a direct opening.

Louvers, grills and screens have a blocking effect, when

used, increase the sizes of your openings by 400% for

wood louvers (as wood type will reduce the free air by

75%) and 135% for metal louvers (as metal will reduce

the free air by 30%). Refer to the National Fuel Gas

Code for complete information.

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Installation instructions

length is 39 feet with one 90 degree elbow. Sub-

tract 3 feet for each additional 90 degree elbow

used (a maximum of four elbows are permitted in

3.6 Venting

Danger: Do not combination vent this

appliance with any other appliance.

the inlet air supply) .

Horizontal section of vent must pitch upward from

heater 1/4" for every foot of horizontal length, to prevent

the pooling of condensate, and be supported at 4 foot

intervals with overhead hangers. See Table 3. The last

horizontal run including the termination must be sloped

to the outside 1/4" per foot to prevent rain from entering

the venting system.

Warning: Do not reduce the vent

(exhaust and combustion) pipe sizes.

Warning: Failure to vent the exhaust

gases to the outside with sealed

stainless steel vent pipe (AL29-4C)

may result in dangerous flue gases

filling the structure in which it is

installed.

Diam.

Max.

Material

equivalent

length

Exhaust

Vent

3 inches 39 feet with

1 elbow

Sealed stainless

steel (AL29-4C)

Warning: Do not mix vent pipe or

joining methods from different

manufacturers.

Intake

Vent

3 inches 39 feet with

1 elbow

Aluminum flex,

PVC or any other

rigid or semi rigid

sealed 3” pipe

Caution: The vent system must be

installed by a qualified individual or

agency in accordance with these

instructions. If improperly installed, a

hazardous condition such as fire or

carbon monoxide poisoning could

result. Bosch Thermotechnology Corp.

will not be responsible for improperly

installed appliances.

Table 3 Venting Specifications

The minimum exhaust vent length is

3 feet.

The use of a 90 degree elbow is

equivalent to 6 ft in vent length.

The use of 45 degree elbow is

equivalent to 3 ft in vent length.

3.6.1 Vent material and specifications

Establish vent clearances that comply with the vent

manufacturer's specifications. In all cases follow local

codes.

Fig. 12 Minimum exhaust vent length

Note: Listed thimbles or collars are necessary to pass

through wall and ceiling partitions. If the vent system

passes through combustible areas where the vent

clearance requirements cannot be maintained, it is

permissible to chase straight sections of sealed 3 inch

single wall vent through 4 inch (or greater) Type-B vent.

The distance to combustibles using this chase

technique is 1 inch.

Warning: Type-B vent should never be

used as the actual exhaust vent system

for the appliance, as it is not gas tight.

Vent lengths

The appliance should be located as close to the point

of termination as possible.

The maximum equivalent exhaust length is 39

feet with one 90 degree elbow. Subtract 6 feet for

each additional 90 degree elbow used (a maxi-

mum of four elbows are permitted in the exhaust

vent) .

1) or subtract 3 feet for each 45° elbow used

2) or subtract 1.5 feet for each 45° elbow used

The maximum equivalent inlet air supply pipe

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Installation instructions

Z flex

Protech

Heat Fab

3” Horizontal

terminator

TEE only

9390 TEE

Vent pipe

3” Vertical

terminator

2SVSRCF03

2SVEVWCF03

2SVEDWCF03

2SVSEVDP03

2SVEDTK

FSRC3

5300CI

93PLSTEE

9321

Reduce maximum

length 6 ft for each

90 elbow after the

first one and 3 ft for

each 45 elbow.

90°

Condensate

drain Tee

FST3 &

FSDF3

Horizontal

Condensate

drain

FSHD03

N/A

Combustion

air intake

Vertical

Condensate

drain

N/A

Fig. 13 Maximum vent and combustion air lengths

Condensate

Drain Tube

N/A

7000TUBE

Vent material

The GWH-345/450-ESR requires 3 inch sealed single

wall stainless steel vent pipe (AL29-4C). Use of any

other vent material will void the manufactures warranty

and may result in a hazardous condition. For specific

questions concerning vent material, specifications,

usage or installation, contact the vent manufacturer

directly.

Table 5 Approved vent termination and condensate

drain part numbers (subject to change)

Contact your Bosch supplier for stocked vent material.

Vent Safety System

The GWH-345/450-ESR will shut down if inadequate

exhaust venting is detected or a lack of combustion air

is provided to the unit; see troubleshooting section on

page 32. Correct the problem and then reset the heater

before operating.

Company

Z-flex

Contact information

www.z-flex.com

800-654-5600

3.6.2 Vent connections and air inlet restrictors

Exhaust vent connection

ProTech

Industries

www.protechinfo.com

800-766-3473

B Attach the flue gas exhaust accessory (8 705 504

142) to the top of the unit (position 1) using the 4

screws and gasket provided

B Insert 3" single wall stainless steel vent pipe into

exhaust vent adapter 1.5" and tighten the clamp

(position 2).

Heat-Fab

www.heatfab.com

800-772-0739

Note: Failure to fully insert and tighten vent pipe may

cause flue gas leakage or condensate damage that is

not covered under the manufacturer's warranty.

Table 4 Vent manufacturer contact information

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Installation instructions

Fig. 14 Exhaust vent connection

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Installation instructions

Selecting inlet air restrictor

Example

Note: Before installing the combustion air inlet

accessory, the appropriate inlet air restrictor must

be determined using Tables 6, 7 and 8.

Exhaust

• 10 - 3' straight sections

• 1 - 1' straight section

Refer to Fig. 15 for mounting sequence.

Total length 31'

B Determine the total length of the straight sections of

• 1 - 90° elbow

3" stainless steel exhaust and enter that length in line

• 1 - GWH 450 ESR termination.

B Count the number of 90° elbows used and enter that

Intake

value in line 2.

• 5 - 4' straight sections

• 2 - 1' straight sections

B Count the number of 45° elbows used and enter that

value in line 3.

Total length 22'

B For model GWH 345 ESR, enter a 1 in line 4 for

model GWH 450 ESR enter a 1 in line 5.

• 2 - 90° elbows

B Repeat steps 1 through 4 for the 3" intake pipe and

• 1 - GWH 450 ESR termination.

enter those values in the intake section.

Example

B Add the totals from the Exhaust table and the Intake

table to determine the equivalent vent length. Use

this value in Table 6 to determine which restrictor

size to use.

Exhaust

Straight section length

90° elbows (qty)

21 x 1 =

1 x 6 =

0 x 3 =

0 x 15 =

1 x 12 =

Total:

Exhaust

Straight section length

90° elbows (qty)

__ x 1 = ____

__ x 6 = ____

__ x 3 = ____

45° elbows (qty)

GWH 345 ESR termination

GWH 450 ESR termination

45° elbows (qty)

GWH 345 ESR termination __ x 15 = ____

GWH 450 ESR termination __ x 12 = ____

Intake

Total:

____

Intake

Straight section length

90° elbows (qty)

22 x .5 =

2 x 3 =

0 x 1.5 =

0 x 6 =

1 x 3 =

Total:

Straight section length

90° elbows (qty)

__ x .5 = ____

__ x 3 = ____

__ x 1.5 ____

__ x 6 = ____

__ x 3 = ____

Total: ____

45° elbows (qty)

GWH 345 ESR termination

GWH 450 ESR termination

GWH 345 ESR termination

GWH 450 ESR termination

Total equivalent vent length =

Total equivalent vent length = ____

Table 7 Determining equivalent length example

Table 6 Determining equivalent vent length (see

example in Table 7)

Using table 8, the following restrictors would be

required:

• GWH 450 ESR NG - restrictor 55

• GWH 450 ESR LP - restrictor 55.

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Installation instructions

Use table below to define which restrictor to be used.

Combustion air inlet connection

The combustion air inlet accessory can only be

connected to the top right of the appliance. The left side

must remain sealed.

Total equivalent length (ft)

Restrictor Ø

Note: Before installing the combustion air inlet

accessory, the appropriate inlet air restrictor must

be determined using Tables 6, 7 and 8.

Refer to Fig. 15 for mounting sequence.

20 - 38

38 - 78

B Place gasket, deflector, gasket and inlet air restrictor

on the air inlet opening lining up screw holes as seen

in Fig. 15.

18 - 28

28 - 40

40 - 65

65 - 78

Total equivalent length (ft)

Restrictor Ø

20 - 38

38 - 78

Fig. 15 Mounting sequence

18 - 28

28 - 50

50 - 78

Gasket

Deflector

Restrictor

Adaptor

B Attach the combustion air inlet accessory (8 705

504 141) to the top of the unit (position 3) using the

4 screws provided.

Table 8 Restrictors table

After installation is complete, check CO levels per

B Install 3" combustion air pipe over the air inlet

accessory. If using flexible piping, secure with a

clamp (position 4, not included).

chapter 3.9.

Fig. 16 Exhaust air inlet accessory

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Installation instructions

3.6.3 Condensate drain requirements

3.6.4 Room sealed installation (Twin pipe)

An external condensate drain must always be installed

except when using one 90° elbow and less than 3 feet

of horizontal pipe.

Although it is permitted to draw combustion air from

inside, the recommended method is to provide

combustion air through a 3" pipe from the outside. See

Chapter 3.5 for more direction on combustion air.

To reduce pressure differentials between the exhaust

and combustion air intake, it is required that both

terminators exit on the same wall or roof. See Fig. 18 for

an example horizontal twin pipe termination and Fig. 19

for the vertical twin pipe termination example. Use only

approved rain caps. For vertical air inlets use 2 90°

elbows with opening facing down and covered with a

screen.

Note: condensate must be disposed of according to

local codes.

1. Install condensate drain as close to heater as

possible.

2. Use 3/8" ID high temperature silicone tube to

connect to condensate drain port. Do not use copper

piping for any portion of the condensate drain.

3. Form a condensate trap by means of a 3" loop

partially filled with water to form a gas trap. Add small

amount of mineral oil if the trap is drying out.

4. To increase the tube length, connect to end of the

high temperature silicone tubing with vinyl tubing,

PVC or CPVC pipe. Do not reduce the internal

diameter at any point.

6 ft

2 ft

Fig. 18 Horizontal twin pipe termination

Fig. 17 Required condensate drain installation

Fig. 19 Vertical twin pipe termination

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Installation instructions

3.6.5 Vertical terminations

Caution: Failure

Over 12/12 to 14/12

Over 14/12 to 16/12

Over 16/12 to 18/12

Over 18/12 to 20/12

Over 20/12 to 21/12

5.0

6.0

7.0

7.5

8.0

1.52

1.83

2.13

2.27

2.44

install

condensate drain may result in damage

not covered by the manufacturer's

warranty. See chapter 3.6.3. An

approved vent terminator must be used.

See Table 5 for known approved

vertical vent terminations.

Table 9 Termination heights at various roof pitches

Horizontal runs

Interior masonry chimneys

Any gas vent section that is greater than 45 degrees

from the vertical is considered horizontal. Horizontal

sections must slope upwards from heater at least ¼

inch for every foot of its horizontal length and be

properly supported. Under no circumstances should

the exhaust vent pipe pitch downward away from

heater. Pitch the termination to the outside 1/4" per foot

to prevent rain water from entering the pipe.

The single wall stainless steel exhaust vent pipe must

be permanently mounted inside the masonry chimney.

The masonry chimney may have to be tile or metal lined

before the insertion of the gas vent pipe; check local

codes for clarification.

You may not vent any other fuel burning appliances into

any free space remaining in the chimney. The vent

terminator must extend at least 3 feet (0.9 m) above

where the chimney meets the roofline and at least 2 feet

(0.6 m) higher than any vertical wall or similar

obstruction within 10 feet (3.1 m). The top of the

chimney must be sealed to prevent rain water or other

elements from entering the chimney.

Vent terminations

The exhaust vent must terminate above the roof surface

with an approved vent cap not less than 2 feet (0.6 m)

above the highest point where it passes through the

roof and at least 2 feet (0.6 m) higher than any vertical

wall or similar obstruction within 10 feet (3.1m). See

Fig. 20 and Table 9.

Exterior Masonry Chimney

Refer to the National Fuel Gas Code and consult a local

venting HVAC contractor. Not recommended in cold

climates.

3.6.6 Horizontal terminations

Warning: Pitch the last horizontal pipe

and the termination to the outside 1/4"

per foot to prevent rain water from

entering the pipe.

An approved vent terminator must be used. See Table 5

for known approved horizontal vent terminations.

Install a condensate drain if the total straight vent length

is greater than 5 feet or if the exhaust vent pipe passes

through an unconditioned space.

Fig. 20 Vertical vent termination clearances

The exhaust termination tee must project out a minimum

of 10" and maximum of 16” on center from the wall

thimble.

GAS VENT TERMINATIONS FOR LISTED VENT

CAPS

Fig. 21 and table 10 show the required clearances for

the vent termination. Follow local codes if more

stringent.

Roof pitch

H (min.)

feet

meters

Flat to 6/12

1.0

1.25

1.5

0.30

0.38

0.46

0.61

0.76

0.99

1.22

6/12 to 7/12

Over 7/12 to 8/12

Over 8/12 to 9/12

Over 9/12 to 10/12

Over 10/12 to 11/12

Over 11/12 to 12/12

2.0

2.5

3.25

4.0

Table 9 Termination heights at various roof pitches

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Installation instructions

3.6.6.1Requirements for installation in

Massachusetts

4. INSPECTION. The state or local gas inspector of the

side wall horizontally vented gas fueled equipment shall

not approve the installation unless, upon inspection, the

inspector observes carbon monoxide detectors and

signage installed in accordance with the provisions of

248 CMR 5.08(2)(a)1 through 4.

(b)EXEMPTIONS: The following equipment is exempt

from 248 CMR 5.08(2)(a)1 through 4:

1. The equipment listed in Chapter 10 entitled

"Equipment Not Required To Be Vented" in the most

current edition of NFPA 54 as adopted by the Board;

and

Attention residents of the Commonwealth of

Massachusetts:

In the Commonwealth of Massachusetts the following

regulation went into effect on 12/30/2005:

(a)For all side wall horizontally vented gas fueled

equipment installed in every dwelling, building or

structure used in whole or in part for residential

purposes, including those owned or operated by the

Commonwealth and where the side wall exhaust vent

termination is less than seven (7) feet above finished

grade in the area of the venting, including but not limited

to decks and porches, the following requirements shall

be satisfied:

2. Product approved side wall horizontally vented gas

fueled equipment installed in a room or structure

separate from the dwelling, building or structure used in

whole or in part for residential purposes.

(c)MANUFACTURERS REQUIREMENTS - GAS

EQUIPMENT VENTING SYSTEM REQUIRED. When

the manufacturer of Product Approved side wall

horizontally mounted gas equipment provides a venting

system design or venting system components with the

equipment, the instructions provided by the

manufacturer for the installation of the equipment and

the venting shall include:

1. Detailed instructions for the installation of the venting

system or the venting system components: and

2. A complete parts list for the venting system design or

venting system.

(d)MANUFACTURER REQUIREMENTS - GAS

EQUIPMENT VENTING SYSTEM NOT PROVIDED.

When the manufacturer of a product approved side wall

horizontally vented gas fueled equipment does not

provide the parts for the venting of flue gases, but

identifies "special venting systems," the following

requirements shall be satisfied by the manufacturer:

1. The referenced "special venting system" instructions

shall be included with the appliance or equipment

installation instructions; and

2. The "special venting systems" shall be product

approved by the Board, and the instructions for that

system shall include a parts list and detailed installation

instructions.

(e) A copy of all installation instructions for all products

approved side wall horizontally vented gas fueled

equipment, all venting instructions, all parts lists for

venting instructions, and/or all venting design

instructions shall remain with the appliance or

equipment at the completion of the installation.

1. INSTALLATION OF CARBON MONOXIDE

DETECTORS. At the time of installation of the side wall

horizontal vented gas fueled equipment, the installing

plumber or gasfitter shall observe that a hard wired

carbon monoxide detector with an alarm and battery

back-up is installed on the floor level where the gas

equipment is to be installed. In addition, the installing

plumber or gasfitter shall observe that a battery

operated or hard wired carbon monoxide detector with

an alarm is installed on each additional level of the

dwelling, building or structure served by the side wall

horizontal vented gas fueled equipment. It shall be the

responsibility of the property owner to secure the

services of qualified licensed professionals for the

installation of hard wired carbon monoxide detectors.

a. In the event that the side wall horizontally vented gas

fueled equipment is installed in a crawl space or an

attic, the hard wired carbon monoxide detector with

alarm and battery back-up may be installed on the next

adjacent floor level.

b. In the event that the requirements of this subdivision

can not be met at the time of completion of installation,

the owner shall have a period of thirty (30) days to

comply with the above requirements; provided,

however, that during said thirty (30) day period, a

battery operated carbon monoxide detector with an

alarm shall be installed.

2. APPROVED CARBON MONOXIDE DETECTORS.

Each carbon monoxide detector as required in

accordance with the above provisions shall comply with

NFPA 720 and be ANSI/UL 2034 listed and IAS

certified.

3. SIGNAGE. A metal or plastic identification plate shall

be permanently mounted to the exterior of the building

at a minimum height of eight (8) feet above grade

directly in line with the exhaust vent terminal for the

horizontally vented gas fueled heating appliance or

equipment. The sign shall read, in print size no less than

one half (1/2) inch in size, "GAS VENT DIRECTLY

BELOW. KEEP CLEAR OF ALL OBSTRUCTIONS".

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Installation instructions

Recommended exhaust vent terminator position

Fig. 21

Ref.

Description

Minimum distance

Directly below an opening; operable windows, doors and any non-

mechanical fresh air openings

36 in (twin pipe installation)

48 in (single pipe installation)

Below a gutter, sanitary pipework or eaves

24 in

12 in

Below a gutter, sanitary pipework or eaves, protected by metal

shielding

From any internal corner

12 in

7 ft

Above ground or snow pack

Above a paved sidewalk

From an opposing wall or structure facing the termination

From the relief valve of a Ip gas regulator

From a terminator facing a terminator

24 in

36 in

48 in

Vertically between two exhaust vent terminators on the same wall

60 in

12 in

Horizontally between two exhaust vent terminators on the same wall

Horizontally and vertically from the combustion air inlet terminator

36 in

I**

From the gravity combustion air inlet any other equipment

From any external corner

48 in

12 in

Horizontally from an opening; operable windows, doors and any non-

mechanical fresh air openings

12 in

10 in

From wall on exhaust applications

Table 10

* Subject to local codes and anticipated snow level

** Other equipment that operates with a mechanical air inlet may require greater distances, reference manufacturer's instructions

NOTICE: Exhaust and air intake must always be located

on the same wall to cancel wind pressure effects.

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Installation instructions

3.6.7 Exhaust vent configuration examples

Fig. 22 Horizontal side wall venting installation

Fig. 24 Vertical venting installation

NOTE: If appliance uses room air, do not place any

other combustion appliance in the same space, to avoid

depressurizing of the building and winter freeze-up. Use

room sealed operation instead.

Fig. 23 Vertical venting installation

Chimney

Masonry

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Installation instructions

Measure the length of gas supply line and use the tables

in Fig. 26 or the gas line manufacturer’s sizing tables to

determine the pipe diameter necessary to

accommodate the BTU demand of the unit. If there are

more gas drawing appliances on the line, size the gas

line according to the total maximum amount of BTU

draw for all appliances.

3.7 Gas piping & connections

Before connecting the gas supply, check the rating

plate on the right side of the heater to be sure that the

heater is rated for the same gas to which it will be

connected.

In the United States: The installation must conform with

local codes or, in the absence of local codes, the

National Fuel Gas Code ANSI Z223.1/NFPA 54.

In Canada: The installation must conform to CGA B149

INSTALLATION CODES and/or local installation

codes.

Note: Under sizing the gas line may result in diminished

output and improper operation. See chapter 3.8 for the

procedure to confirm gas pressure.

Warning: DO NOT connect to an

unregulated or high pressure propane

line or to a high pressure commercial

natural gas line.

Warning: The heater must be isolated

from the gas supply piping system

during any pressure testing of that

system at test pressures equal to or

more than 0.5 psig. If overpressure has

occurred, such as through improper

testing of the gas lines or malfunction of

the supply system, the gas valve must

be checked for safe operation.

Inlet gas particle screen

Gas piping

Fig. 25

GAS CONNECTIONS

B Install a manual gas shut off valve (installer supplied)

on the gas supply line.

B Install a union when connecting gas supply.

B The minimum diameter required for any appliance

connector used is ¾”.

B National Fuel Gas Code requires that a sediment

trap (drip leg) be installed on gas appliances not so

equipped. The drip leg must be accessible and not

subject to freezing conditions. Install in accordance

with the recommendations of the serving gas

supplier.

When connections are made, check for gas leaks at all

joints. Apply some gas leak detection solution to all gas

fittings. Bubbles are a sign of a leak. A combustible gas

detector may also be used to detect for leaks.

Danger: If you have a leak, shut off the

gas. Tighten appropriate fittings to stop

leak. Turn the gas on and check again

with a gas leak detection solution.

Never test for gas leaks using a match

or flame.

GAS LINE SIZING

The gas supply piping should be sized according to the

applicable code for a maximum draw of 120,000 BTUH

(GWH450ESR) or 96,000BTUH (GWH345ESR).

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Installation instructions

FOR NATURAL GAS

Maximum Capacity of pipe in Cubic Feet of Gas per Hour for Gas Pressure of 0.5 Psig or less and a Pressure drop

of 0.3 in Water Column (0.75mbar).(Based on a 0.60 Specific Gravity Gas) Btu numbers given in thousands.

Follow boxed numbers for piping just one GWH-450-ESR (example: ¾” B.I. Natural Gas pipe for 20 ft

(6.1m). will handle 190,000 btu’s (55.7 kWh). For multiple appliances combine the total btu input load and

then refer to applicable chart below. Follow the shaded numbers for just one GWH-345-ESR.

Nominal

Iron

Length of Black Iron Pipe, Feet

Pipe

Size,

Internal

Diameter

(inches) (inches)

100

125

150

175 200

1/4

3/8

1/2

0.364

0.493

0.622

132

3/4

0.824

1.049

278

520

190

350

152

285

130

245

115 105

215 195 180

170

160

150

130

120

110 100

1 1/4

1 1/2

1.380

1.610

2.067

2.469

3.068

4.026

1050

1600

3050

4800

8500

730

590

890

500

760

440 400 370

670 610 560

350

530

320

490

930

305

460

870

275

410

780

250

380

710

225 210

350 320

650 610

1100

2100 1650 1450

3300 2700 2300

5900 4700 4100

1270 1150 1050 990

2 1/2

2000 1850 1700 1600 1500 1400 1250

3600 3250 3000 2800 2600 2500 2200

1130 1050 980

2000 1850 1700

17,500 12,000 9,700 8,300 7,400 6,80 6,200 5,800 5,400 5,100 4,500 4,100 3,800 3500

Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet

Tube

size,

inches

EHD*

1/2

3/4

18 EHD 82

23 EHD 161 116

30 EHD 330 231 188

162

325

144

292

131

267

* EHD = Equivalent Hydraulic Diameter. The greater the

value of EHD, the greater the gas capacity of the tubing.

1 1/4 37 EHD 639 456 374

FOR LP GAS

Maximum Capacity of Pipe in Thousands of BTU per Hour of Undiluted Petroleum Gases (at 11 inches Water Column Inlet

Pressure) (Based on a Pressure Drop of 0.5 Inch Water Column).

* EHD = Equivalent Hydraulic Diameter. The greater the

value of EHD, the greater the gas capacity of the tubing.

Length of Flexible Corrugated Stainless Steel Tubing (CSST), Feet

Nominal

Tube

size

iron

Black Iron Pipe

pipe

Length of Pipe, Feet

inches

EHD*

Inches

20 30 40 50 60 80 100 125 150 200

1/2

3/4

18 EHD 129

1/2

3/4

291 200 160 137 122 110 94

608 418 336 287 255 231 197 175 155 140 120

1145 787 632 541 480 434 372 330 292 265 227

23 EHD 254 183 151

30 EHD 521 365 297

131

256

449

118

227

397

107

207

359

1 1/4 37 EHD 971 661 528

Maximum Capacity of Semi-Rigid (flexible, non

corrugated) Tubing in Thousands of BTU per Hour of

Undiluted Liquefied Petroleum Gases (at 11 inches

Water Column Inlet Pressure).

Copper

Length of Tubing, Feet

Outside

diameter

Inch

10 20

39 26

92 62

30 40

21 19

50 41

60 70 80 90 100

3/8

1/2

(Based on a Pressure Drop of 0.5 Inch Water Column)

35 31 29 27 26

72 67 62 59 55

* Source National Fuel Gas Code NFPA 54, ANSI

Z223.1 - No Additional Allowance is necessary for an

ordinary number of fittings

5/8 199 131 107 90

3/4 329 216 181 145 131 121 112 104 95 90

Fig. 26

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Installation instructions

3.8 Measuring gas pressure

Static Gas Pressure Reading (see Chapter 3.8)

Connecting manometer

enter here: ___________________

B Turn power off.

B Shut off gas supply.

Operating Gas Pressure Reading (see Chapter 3.8)

B Remove front cover and locate the inlet gas

enter here: ___________________

measuring point (see Fig. 27).

Table 11

B Loosen screw inside test point fitting (do not remove)

and connect manometer tube on test point.

3.9 Checking restrictor plate size by

measuring CO level value.

B Remove brass flat head screw on the exhaust collar.

Fig. 27 Gas pressure measuring (lower tapping)

Static pressure test

Fig. 28 Measuring port

B Turn gas supply on.

B Insert CO analyzer probe into the measuring point.

B Operate all other gas appliances on same gas piping

The tip of the probe should be in the center of the flue

pipe. Avoid air gaps between probe and measuring

port to avoid inaccurate readings.

system at maximum output.

B Keep unit off and record static pressure reading in

Table 11.

B Press On/Off button to turn heater On.

For this test the unit has to be put in Service Level.

Operating pressure test

B Open a hot water tap.

B Press On/Off button to turn heater On.

For this test the unit has to be put in Service Level

B After 10 seconds, press and hold the reset button

B Rotate the recirculating water temperature selector

(left knob) to the minimum and then to maximum.

B Rotate the recirculating water temperature selector

B Release the reset button and the display should

(left knob) to the minimum and then to maximum.

show * (blinking).

B Release the reset button and the display should

B Rotate the hot water temperature selector

to the

show * (blinking).

maximum.

The unit has now entered Service Mode.

B The restrictor size is correct if the CO level is within

B Place a demand for heat by turning external tank ther-

mostat control to maximum for unit to fire at maximum

input.

the values as per table 13.

CO2 value (%)

B Record operating pressure reading in Table 11.

B Press On/Off button to turn heater Off and exit

enter here: ___________________

Table 12

Service Mode.

Note: after verification tighten the screw

inside the test point.

Appliance

CO (%)

GWH-345-ESR-N

GWH-345-ESR-L

GWH-450-ESR-N

GWH-450-ESR-L

6.8 - 7.2

7.5 - 8.0

6.5 - 7.0

7.0 - 7.5

Operating gas pressures lower than 5.5" W.C. for nat-

ural gas or 11" W.C. for LP will result in improper oper-

ation and must be corrected. See Chapter 3.7 for gas

line sizing requirements.

Table 13 CO levels at max. input

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Installation instructions

B If the CO content is too high, use the next smallest

piping. Blow out or flush the lines before connecting

to the water heater.

restrictor.

B After replacing the restrictor, measure CO level

B Full port shut off valves should be installed on both

the cold water supply and hot water outlet lines to

facilitate servicing the heater (see Fig. 30).

again. Repeat procedure until correct level is

obtained.

B Once correct reading is obtained, replace screw with

Connecting the pressure relief valve (PRV)

gasket in exhaust collar.

The listed pressure relief valve supplied with the heater

must be installed at the time of installation. No valve is

to be placed between the PRV and the heater. No

reducing coupling or other restriction may be installed

in the discharge line. The discharge line must be a

minimum of 4” above a drain and installed such that it

allows complete drainage of both the PRV and the line.

The location of the PRV must be readily accessible for

servicing or replacement, and be mounted as close to

the water heater as possible. See Fig. 30. To install the

PRV, a suitable fitting connected to an extension on a

“T” fitting can be sweated to the hot water line.

Support all piping.

B Press On/Off button to turn heater Off and exit

Service Mode.

3.10 Water connections

B When facing the heater, the ¾” NPT inlet is on the

bottom right and the ¾” NPT outlet is on the bottom

left (Fig. 29). Install the heater centrally in the build-

ing if possible and make piping runs as short as pos-

sible.

Fig. 30 Plumbing Connections and Pressure Relief

Valve

OUTLET

Fig. 29

INLET

3.11 Electrical connections

Warning:

For

safety

reasons,

B The use of unions when connecting both water pipes

to the inlet and outlet connections is recommended.

This will facilitate any necessary servicing.

disconnect the power supply to the

heater before any service or testing is

performed.

B Although water piping throughout the building may

be other than copper, we recommend that copper or

suitably rated stainless steel flex line piping be used

for the water connections for 3’ on either side of the

recirculating water heater (follow local codes if more

stringent).

Warning: This heater must be

electrically grounded in accordance

with the most recent edition of the

National Electrical Code. NFPA 70. In

Canada, all electrical wiring to the

heater must be in accordance with local

codes and the Canadian Electrical

Code, CSA C22.1 Part 1. Do not rely

on the gas or water piping to ground the

metal parts of the heater.

B Never sweat any rigid piping directly to or beneath

the water connections, damage can occur to the

internal heater components during the sweating

process.

B Plastics or other PEX type plumbing line materials

are not suitable for connecting directly to the water

heater.

The GWH-345/450-ESR requires an electrical power

supply from a 120VAC 60Hz circuit and must be

properly grounded.

B Keep water inlet and outlet pipes to no less than ¾"

(19.05mm) diameter to allow the full flow capacity.

A means for switching off the 120VAC power supply

must be provided.

The heater is wired as shown in the wiring diagram

(chapter 4.8, Fig. 35).

B If the cold and hot connections to the heater are

reversed, the heater will not function correctly. Be

certain there are no loose particles or dirt in the

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Operating instructions

B Use only your hand to press the on/off control switch.

Never use tools. Follow these instructions exactly. If

control switch is jammed, close the gas supply and

call a qualified service technician. Attempted forceful

repair may result in a fire or explosion.

4.1 Initial filling instructions

Before proceeding with the operation of the heater

make sure that the system is filled with water:

B Turn off power supply to heater.

B Open the cold water inlet supply to the heater fully.

B Do not use this appliance if any part has been under

water. Immediately call a qualified service technician

to inspect the appliance and to replace any part of

the control system and any gas control which has

been under water.

B Open a hot water faucet to permit the water to fill the

heater and the piping and to eliminate the air trapped

in the system.

B Close the hot water faucet after the water flows freely

and all the air has escaped from the system. Turn on

power supply to heater. The water heater is now

ready to operate.

4.3 Startup instructions

B 1. STOP! Read the previous safety information.

B 2. The gas valve must be shut off by putting the ON/

OFF switch to position OFF. Wait five (5) minutes to

clear out any gas. If you smell gas, STOP! Follow the

safety information in Chapter 4.2 above. If you do not

smell gas, go to the next step.

B 3. This appliance is equipped with electronic ignition

for lighting the main burners. When turning the

heater on, follow these instructions exactly.

B 4. Press the ON/OFF switch to the ON position. In

this position, the water heater is ready to use.

B 5. Connect tank Aquastat to the TT (thermostat)

connection on the heater's printed circuit board.

(Fig. 6, page 8). Close circuit on Aquastat to activate

heater.

Fig. 31

On/Off button

Reset button

Recirculation water temperature selector

LED - (ON) warning light (blinks during lock-out error)

Domestic hot water temperature selector

Digital display

B 6. The burners will remain on until the heat demand

is met.

NOTE: upon installation or after

4.2 For your safety read before

operating your water heater

gas line work has been done, air

in the gas line may cause a

lockout error. Reset the unit

(Fig. 31, pos. 5). The heater will

reattempt ignition.

Warning: If you do not follow these

instructions exactly, a fire or explosion

may result causing property damage,

personal injury or loss of life.

When the heater is in operation you may hear its

induced draft vent fan and burner operating. After a call

for heat is satisfied, the fan will continue to operate for

up to 5 seconds to exhaust all flue gases.

WHAT TO DO IF YOU SMELL GAS

B Do not try to operate any appliance.

B Do not touch any electric switch; do not use any

TO TURN OFF GAS TO APPLIANCE

phone in your building.

B Turn off the manual gas shut off on the supply line to

the heater and set the ON/OFF switch to the OFF

position. Note: a manual gas shut off valve is not

supplied with the heater.

B Immediately call your gas supplier from a neighbors

phone. Follow the gas supplier’s instructions.

B If you cannot reach your gas supplier, call the fire

department.

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Operating instructions

4.4 Power

4.6 Temperature and hot water flow

Choose one the following:

• If using a tank mounted Aquastat, set temperature on

Aquastat control (left knob should be in maximum

position).

To start the appliance:

B press the ON/OFF

button.

LED (fig. 31) goes orange.

When the burner is working, the LCD display shows

• To activate and use the appliance domestic

temperature dial, a 12 kOhm thermistor is required

(part number 8 714 500 034) (See 2.6, Page 8 for

wiring diagram).

the symbol

B Connect the 12kOhm thermistor blue wire to the

DHW NTC terminal block.

Install the sensor in the tank well.

Hot water temperature can be set from 50°F to 158°F

using hot water temperature selector

(Fig. 34).

Fig. 32

Off

To shut down the appliance:

B press the ON/OFF

switch to OFF position.

4.5 Recirculating water temperature

Water temperature can be regulated in a range of

113°F to 190°F. The heater modulates the burner flame

according to current demand selected on left knob.

To select water temperature:

B Rotate recirculating water temperature selector

in order to change heating recirculating temperature

(ranging from 113°F to 190°F).

Fig. 34 Hot water temperature adjustment

The display will show this symbol

selected temperature.

and blink the

Thermostat

knob position

DHW

temp.

If the burner is on, symbol

goes ON.

Min.

Max.

approx. 50°F (10°C)

approx. 158°F (70°C)

Table 14 Domestic hot water temperature

adjustment

4.7 Freeze protection

B Do not disconnect the electric supply from heater.

B Do not install in unheated areas which can

experience freezing temperatures.

B Do not use non-potable additives like glycol.

Fig. 33 Recirculating water temperature adjustment

Freeze protection

Freeze protection is always assured by the operation of

the appliance.

If the primary NTC (temperature) sensor detects

temperatures 9°F below the selected temperature, the

appliance starts on minimum power until the sensor

reads selected temperature.

In case of minimum setpoint it will start at 41°F.

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Operating instructions

4.8 Electrical diagram

Fig. 35 Electrical scheme

Flame sensor

Ignitor electrode

Gas valve

Junction box (wiring of tank pump)

Fan

Temperature limiter / ECO

Differential pressure switch

TT connection - under low voltage cover plastic

Domestic hot water temperature sensor (12kOhm only -

under low voltage cover plastic)

LED

Fuse

NOTICE: Except for the fuse, there are no serviceable

parts inside the electronics.

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Maintenance and service

Adjusting parameters

Warning: Always turn off the electrical

power supply, turn off the manual gas

valve and turn off the manual water shut

off valves whenever servicing.

B Rotate hot water temperature selector dial

change the value of the parameter (only parameter

03 and 22).

The unit should be checked once a year by a gas

technician. If repairs are needed, the repairs should be

done by a gas technician

To remove front cover

B Loosen the two Philips head screws (as shown in

Fig. 2).

B Pull control panel upwards and then pull it

downwards.

B Lift front cover panel upward and remove.

Yearly maintenance

Refer to diagrams on pages 35 and 36.

• Inspect venting system for leaks, blockage or other

damage

• Unclip 4 access clips and remove cover to inspect

and clean burner assembly

• Manual operation of the pressure relief valve to insure

correct operation

• If flow is reduced or error AA is activated, flush the

heat exchanger with a descaling solution if mineral

build up is evident. Scale build up will shorten the life

of the water heater and is not covered by warranty.

Descale heat exchanger thoroughly and repeat

annually depending on mineral content of ground

water.

5.1 Service mode

The service mode provides diagnostic information to

the technician with a variety of real time parameters.

See Table 15 for the parameters and their respective

meaning.

Accessing the service mode

B Switch on the equipment.

B Press and hold the reset button

B Rotate the hot water temperature sensor dial

the minimum and to the maximum.

Now the appliance is in the Service Mode.

Selecting parameter

B Rotate the recirculating water temperature selector

(left dial) to scan the different parameters.

Rotating clockwise accesses the next parameter

(increasing).

Once the desired parameter number has been

selected, the digital display will change to the value

stored in that parameter.

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Maintenance and service

Mode

Parameter

Values

Not used

----------

Not used

Displays the last 8 error codes. Use the hot water temperature selector

(right dial) to toggle from newest (left) to oldest (right) error codes.

Error code history

Actual primary circuit

temperature

Displays the actual temperature in the primary circuit as detected by

the internal heating circuit sensor.

Selected primary circuit

temperature

Displays the recirculating water temperature (primary) as selected

by the user during normal operation.

Actual DHW temperature (only

if 12kOhm thermistor used)

Displays the actual temperature of the DHW tank as detected by

the 12kOhm external thermistor

Selected DHW temperature

(only if 12kOhm thermistor used)

Displays the hot water temperature as selected by the user during non-

diagnostic mode operation (only if 12kOhm external thermistor used).

Not used

----------

00 - Open pressure switch - fan is off or there is no exhaust gas flow

Pressure switch

01 - Closed pressure switch - fan is on or there is exhaust gas flow

Temperature limiter

01 - temperature is below the limit (180 F)

E9 - temperature is above the limit (180F)

----------

Not used

Gas valve

00 - gas valve closed

01 - gas valve open

00 - gas valve closed

01-70 - gas valve position min/max

00 - thermostat open

01 - thermostat closed

00 - fan off

Modulating gas valve

Thermostat

Fan

01 - fan on

00 - no flame detected

01 - flame detected

----------

Ionization

Not Used

----------

Not Used

----------

Not Used

----------

Digital display test

Temperature unit selection

All LCD components appear

Use the hot water temperature selection knob to select temperature

units °C or °F.

Table 15

Parameter storage

Exiting service mode

B Keep pressing the reset button

for at least 2

B Press ON/OFF button to turn appliance OFF and

seconds in order to record adjustments. The digital

then back ON again.

display blinks with the symbol

If the appliance is not powered off and

then back on again, it returns to normal

working conditions after 5 minutes.

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Troubleshooting

Fault Indication

Possible Cause

Check

Shut down by the temperature limiter

(over temperature).

•

1. Check position of heating NTC

2. Check temperature limiter, cables

3. Check system with air, air vent

4. Bleed air from system.

No Flame detected (no ignition).

•

1. Check gas inlet pressure, gas

type, air inside gas pipe

•

2. Check flame, ignition

3. Check burner pressure, injectors

4. Check ionisation sensor, cable

•

5. Check electronic unit .

"false flame" (error during self check of

electronic).

1. Check for moisture on the

Electronics

•

2. Check cables, sensor contacts

(corrosion)

3. Check flame inside Burner

chamber

4. Check electronic unit .

Shut down because of low voltage.

Internal error in the electronic unit.

•

1. Check power supply

2. Check electronic unit .

•

1. Check electronic unit connections

and wiring.

• 2. Replace electronic unit.

Fan not working

•

1. No power to fan, check for 115

volts at fan

2. Check wire connections.

Shut down by pressure switch.

•

1. Blocked vent

2. Fresh air supply inadequate

3. Silicone tubes from pressure

switch not connected - clear or clear

and black

•

4. Check wire and connection.

Heating - NTC defect (no function)

•

1. Check heating - NTC

2. Check cable (opened, short)

3. Check electronic unit .

Domestic hot water - Tank NTC defect

(no function)

•

1. Check domestic hot water - NTC

2. Check cable (opened, short)

3. Check electronic unit .

Flow reduced

•

1. Check heat exchanger - flush or

descale if necessary.

LED or LCD of the appliance doesn't No voltage supply, fuse blown,

start up, no function. transformer etc. defect

•

1. Check voltage supply

2. Check fuse

3. Check electronic unit .

Noise; boiling noise (over heating), no Low circulation, air inside installation,

•

1. Check air in system, air vent

2. Check heating circulation

3. Check heat exchanger

4. Check gas type, injectors, gas

valve.

correct function.

bad heat transfer.

Table 16

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Troubleshooting

Fault Indication

Possible Cause

Check

Only tank loading (no heating function). No heat demand by the thermostat,

•

1. Check thermostat position

thermostat not well adjusted, other

defect.

2. Check electronic unit .

Only heating (no tank load function).

Low temperature (domestic hot water).

No heat demand by the NTC, defect.

•

1. Check NTC cable

2. Check water (filter, …)

3. Check Domestic hot water - NTC

(Tank)

•

4. Check electronic unit .

To low burner power, burner ON / OFF.

•

1. Check air vent

2. Check Adjustment of gas, gas

valve

•

3. Check Domestic hot water-NTC

4. Check electronic unit .

Insufficient water flow.

•

Low water pressure

•

1. Check inlet pressure

Filter, taps or heat exchanger with

dirt.

2. Check filter, taps, heat exchanger

and clean.

Table 16

Check connections, fuse or if there are visible damages.

Error lock-out is indicated by the orange LCD blinking. An error lock-out is done for safety reasons. After fixing the

problem, press the reset button to return the heater to service.

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GWH-345/450-ESR Functional scheme

APS - Air Pressure Switch

Fig. 36 Functional scheme

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Interior components diagram and parts list

8.1 Interior components

Fig. 37 Components

Combustion air inlet adapter (right side only)

Exhaust adapter with CO₂measuring point

Front cover

On/Off button

Reset button

Recirculation water temperature selector

LED - (ON) warning light (blinks when in lock out)

Domestic hot water temperature selector

Gas valve

Junction box

Centrifugal blower

Main burner

Heat exchanger

Holding bracket

Outlet water pipe

Inlet water pipe

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Interior components diagram and parts list

8.2 Components diagram

Fig. 38 Components Diagram

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Interior components diagram and parts list

8.3 Parts list

Item

Description

Reference

Item

Description

Reference

Screw

8 703 404 089

8 703 401 069

2 910 952 122

8 701 003 010

8 711 304 287

2 910 619 409

8 710 103 060

8 708 107 008

2 910 642 082

8 708 107 009

GROUP 1

Screw

Front cover

8 705 431 223

2 910 612 435

8 701 103 140

8 704 701 077

8 708 006 130

8 710 203 039

8 700 100 376

8 703 403 012

8 708 003 218

8 705 504 149

8 716 140 939

2 910 612 424

8 711 004 022

8 709 918 779

Screw M4 x 12 phillips

Washer

Cover screw no. 10 x 22mm

Trade mark badge

Gasket

Angle bracket

Screw

Support set

Washer 1"

Grommet set

Ignition electrode

Screw m3.5x6 phillips steel

Flame sensor

GROUP 4

Deflector plate

Screw M4,8 x 9,5mm

Angle bracket

Flue gas accessory

Washer

Gas valve

8 707 021 333

8 705 202 126

8 700 103 014

8 703 305 325

8 700 205 144

2 912 601 120

Connector

Screw 8x3/8" philips

Washer

Washer- fibre 24OD X 16ID X 2MM

Connection bush

O-ring

Throttle disc set (GWH345ESR)

Throttle disc set (GWH450ESR NG) 8 709 918 780

Screw

Throttle disc set (GWH450ESR LP)

Combustion air accessory

Clip

8 709 918 782

8 705 504 148

8 701 201 032

8 701 302 099

8 701 302 235

8 701 302 225

8 708 003 143

GROUP 5

Front cover

8 707 207 219

8 702 000 309

8 705 400 069

8 703 403 074

8 705 400 056

8 708 300 193

1 904 522 745

8 707 204 061

8 703 305 302

8 700 703 049

8 707 406 007

Holding bracket (GWH345ESR)

Holding bracket (GWH450ESR)

Cover

Selector knobs

Cover

Screw

Mounting bracket with screws

GROUP 2

Cover

Printed circuit board

Fuse T3, 15A

Centrifugal blower

Differential pressure line

Set of hose

Heat exchanger (GWH345ESR)

Heat exchanger (GWH450ESR)

Temperature limiter/ECO 104°C

Washer 25OD X 21ID X 2MM

8 705 406 323

8 705 406 329

8 707 206 204

8 700 103 125

8 713 300 018

8 710 103 045

8 700 703 163

8 700 205 135

8 700 400 015

8 703 305 326

8 714 606 002

8 701 309 158

8 743 401 019

8 703 309 001

2 910 642 162

8 716 102 607

Pressure differential switch

(GWH345ESR)

Locknut G 1/2"

Fiber washer 18.6x13.5x1.5

Pressure differential switch

(GWH450ESR)

8 707 406 074

Cold water pipe

O-ring

Screw tapping no6 x 9.5

Cable

2 910 612 410

8 704 401 311

8 704 401 312

8 704 401 309

8 704 401 308

8 704 401 310

8 704 401 267

8 704 401 295

8 701 103 142

Temperature sensor

Connection bush

Wireform spring

Mounting bracket

Screw

Cable

Set of cables

Cable

Set of cables

Power supply cord

PCB wire harness

Junction box

Cage nut

Screw M 5.0X20 DIN 7985

Clip

GROUP 3

Table 17

Main burner LP (GWH345ESR)

Main burner NG (GWH345ESR)

Main burner LP (GWH450ESR)

Main burner NG (GWH450ESR)

8 708 120 625

8 708 120 624

8 708 120 623

8 708 120 622

Table 17

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Protecting the environment

Packing

The packing box may be fully recycled as confirmed by

the recycling symbol

Components

Many parts in the heater can be fully recycled in the end

of the product life. Contact your city authorities for

information about the disposal of recyclable products.

Saving water resources:

B Make sure you close all the taps after any use. Avoid

leaving the taps dripping. Repair any leaking tap.

B Whenever possible use taps with built-in water flow

limiters. They will give you the same comfort level

while saving water.

B Set the water temperature to the desired

temperature or slightly higher. Hotter water

temperatures can result in scalding and wasted

energy.

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Ten Year Limited Warranty

10 Ten Year Limited Warranty

General

costs associated with service, removal or re-installation

of the original water heater or a replaced water heater.

BOSCH PRO water heaters are warranted by the

Manufacturer. Bosch Thermotechnology Corp. will

furnish a replacement heat exchanger and will furnish a

replacement of any part which fails in normal use and

service within the applicable periods specified below, in

accordance with the terms of this warranty. The

replacement will be warranted for the unexpired portion

of the original warranty. This warranty will be valid only

for water heaters in possession of the original purchaser

as recorded on the warranty card.

NOTE: the water heater must be free of

damaging scale deposits and not subject

to gas pressures greater than those

shown on the rating plate, which must not

be altered, defaced or removed.

How to Make a Claim

Any claim for warranty parts should be made to your

local dealer or distributor.

The Heat Exchanger

In most cases, the dealer or distributor will be able to

promptly honor your claim and subsequently notify

Bosch Thermotechnology Corp.. However, all

replacements are made subject to validation by Bosch

Thermotechnology Corp. of in-warranty coverage. The

damaged or defective item must be made available in

exchange for the replacement.

If the heat exchanger fails within five (5) years after the

original

installation

and

operation,

Bosch

Thermotechnology Corp. will furnish a replacement

heat exchanger at no charge. If the heat exchanger fails

during years 6-10 after the original installation and

operation, Bosch Thermotechnology Corp. will cover

50% of the cost of a replacement heat exchanger.

However, if the water heater is installed in other than a

single family dwelling, this heat exchanger replacement

warranty is limited to two (2) years from date of original

installation and operation.

Miscellaneous

No one is authorized to make any other warranties on

behalf of Bosch Thermotechnology Corp.. It is expressly

understood that the replacement warranty of Bosch

Thermotechnology Corp. shall be in lieu of any and all

other warranties, express or implied, including

warranties of merchantability or fitness for a particular

use or purpose, and further that Bosch

Thermotechnology Corp. shall not be liable for any loss

or damage directly or indirectly arising from the use of

the hot water heater, or for any consequential damages

arising from such use (including damages from water

leakage). Bosch Thermotechnology Corp. sole liability

with respect to any defect shall be for the replacement

of the defective part(s). Some states do not allow such

limitations and exclusions, so the above may not apply

to you.

Exceptions

This warranty will not apply:

• 1. to defects or malfunctions resulting from failure to

properly install, operate or maintain the unit in

accordance with the printed instructions provided;

• 2. to damage or abuse, accident, neglect or freezing

and other acts of nature;

• 3. to damage resulting from operation with either the

flame sensor rod or overheat sensor removed;

• 4. to failure of the heat exchanger resulting from the

operation of the water heater in a corrosive

atmosphere or at water temperatures exceeding the

maximum rating, or if the water heater is not supplied

with potable water;

This warranty gives specific legal rights. You may also

have other rights which vary from state to state.

• 5. to defects or damage cause by any attachment

or modification, including any energy-saving device.

• 6. to damage resulting from scale deposits and/or

highly mineralized / unsoftened water supply.

All Other Parts

If any other part fails within one (1) year after original

installation and operation, Bosch Thermotechnology

Corp. will furnish a replacement part free of charge.

Service Labor Costs

This warranty does not cover any labor costs

associated with service, removal or re-installation of

part(s). All such costs must be borne by the Purchaser.

Additionally, this warranty does not cover any labor

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Installer Checklist, to be performed by installer upon installation

Serial Number

___ ___ ___ ___ ___ ___ ___ ___

(8 digit serial number is located on rating plate on right side panel)

Gas Pressure reading*

Static__________

__________

Operating__________

CO reading

Air restrictor size

Building Water Pressure

Installing Company

Installer name

Address

__________

__________ Range if on Well system __________

_____________________________________________

Phone

* See Chapter 3.8 and gas pressure table (to be filled out by installer)

Installation manual should be left with the owner after the installation is tested and completed

BOSCH THERMOTECHNOLOGY

CORPORATION

Bosch Termotecnologia SA

Estrada de Cacia

50 Wentworth Avenue

Londonderry, NH 03053

Tel. 866-330-2730

3801 - 856 Aveiro - PORTUGAL

www.boschpro.com

Recycled paper

Londonderry, NH

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