R4795A
Flame Safeguard
Primary Controls
The R4795A Protectorelay™ Primary Control
provides solid state electronic flame safeguard
protection for commercial and industrial gas or oil
burners. It provides a prepurge period before each
start, and intermittent pilot.
■ Solid state circuitry eliminates vacuum tube replace-
ment and increases resistance to vibration. Applica-
tion of power not required during Off cycle; no tube
warmup before starting.
■ Easy-to-replace plug-in components result in faster
service and reduced inventory.
■ Flame current jack, located on the amplifier, provides
means of plugging in a microammeter to measure the
flame signal with system operating.
■ Easy mounting and removal through use of captive
mounting screws, which also serve as electrical
connections.
■ 120V models meet the requirements of Underwrit-
ers Laboratories Inc. Standard 795 for mechanical
draft and atmospheric burner inputs from 400,000 to
2,500,000 Btu.
■ Meets Underwriters Laboratories Inc. requirements
for oil burner group 8 when 30, 60, or 90 second pre-
purge timer is used.
■ Selection of solid state, plug-in prepurge timers pro-
vides 7, 10, 30, 60, or 90 second prepurge time.
■ Includes terminals for connection of air flow switch
to prove airflow before prepurge period starts, dur-
ing purge, and during the entire Run period.
■ Choice of interchangeable, color-coded, solid state,
plug-in flame signal amplifiers allows use with rec-
tification or ultraviolet type flame detectors.
■ Safe-start feature prevents start when flame or flame
simulating condition is present.
■ Durable thermoplastic mounting base.
■ Models available with -40°F (-40°C) temperature
rating.
■ Recycles through prepurge if the flame goes out
while burner is running. If pilot flame is not re-
established, safety switch trips and locks out system.
■ A tripped safety switch must be manually reset to
restore operation.
■ Push-to-resetsafetyswitchisdust-resistantenclosed.
■ Optional spdt alarm contacts operate external alarm
on safety switch lockout.
■ Ignition interference circuit (rectification amplifier
only) protects electronic network from high voltage
ignition crossover and provides visual indication
when interference occurs.
CONTENTS
Specifications ................................................. 2
Ordering Information ..................................... 2
Installation ..................................................... 4
Checkout......................................................... 8
Operation ..................................................... 11
Troubleshooting ........................................... 11
Service .......................................................... 13
S.Y. • Rev. 12-94 • ©Honeywell Inc. 1994
60-2285-7
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R4795A
SPECIFICATIONS
TERMINAL RATINGS:
Terminal
Load
Rating
3
Pilot Valve
125 VA pilot duty.
a
Intermittent Ignition 360 VA.
Interrupted Ignition 360 VA.
4
5
Main Fuel Valve(s) 125 VA pilot duty, or 25 VA pilot duty plus one or more motorized
valves with total rating up to 400 VA opening, 200 VA holding.
6-7
8
Airflow Switch
0.6A at 30 Vdc.
Fan or Burner Motor 9.8A full load, 58.8A locked rotor (inrush) at 120 Vac. 4.9A full
load, 29.4A locked rotor (inrush at 220 and 240 Vac.
Isolated Spdt Alarm
Terminals (Optional)
Alarm
3A at 24 volts, or 1A at 120 volts, in a suitable wiring enclosure.
a When ignition is connected to terminal 3, terminal 4 cannot be used.
NOTE: Allowable inrush can be up to ten times the pilot
duty rating.
118702E Remote Reset Cover, 120 Vac, 60 Hz
202471C Reset Cover for R4795A
ADDITIONAL CONTROLS:
Example:
Pilot duty rating = 125 VA.
Order all additional controls separately:
Q270A1024 Mounting Subbase.
At 120V, running current is 125/120 = 1.05A.
Maximum allowable inrush is 10 times 1.05 = 10.5A.
Plug-In Flame Signal Amplifiers, Rectification Type
(Green Backplate): For use with C7004B C7005A,
and B, C7008A, or Q179A,C Rectifying Flame Rods
(for gas); C7003A, C7010A, C7013A or C7014A
Photocells (for oil); or C7012A,C Purple Peeper Ul-
traviolet Flame Detectors (for gas or oil).
R7289A1004 Amplifier: 3 sec nominal flame failure
response.
R7289A1012 Amplifier: 0.8 sec nominal flame failure
response.
R7289A1020 Amplifier: 3 sec nominal flame failure
response, -40°F (-40°C) ambient temperature.
UltravioletType(PurpleBackplate):ForusewithC7027A,
C7035A or C7044A Minipeeper Ultraviolet Flame
Detectors (for gas or oil).
DIMENSIONS (Includes Cover and Subbase): Approxi-
mately 5 x 5 x 5 in. (127 x 127 x 127 mm).
MOUNTING: Q270A1024 Subbase. Ordered separately.
APPROVALS:
Underwriters Laboratories Inc Listed: 120V models us-
ing 30, 60, or 90 second prepurge timers including –
40°F (–40°C) rated models; file no. MP268, guide
no. MCCZ.
Underwriters Laboratories Inc. Component Recognized:
120 volt models using 7 or 10 second prepurge timers
including-40°F(-40°C)ratedmodels;fileno. MP268,
guide no. MCCZ2.
Canadian Standards Association Certified: 120V mod-
els only, including -40°F (-40°C) rated models; file
no. LR95329.
Factory Mutual Approved: R4795A 120V models; re-
port no. 18774. -40°F (-40°C) rated models; report
no. 19608.1.
R7290A1001 Amplifier: 3 sec nominal flame failure
response.
R7290A1019 Amplifier: 0.8 sec nominal flame failure
response.
R7290A1027 Amplifier: 3 sec nominal flame failure
response, -40°F (-40°C) ambient temperature.
ST71A Plug-In Prepurge Timer (ordered separately):
Minimum Timings: 7, 10, 30, 60, and 90 seconds (as
ordered).
American Gas Association Design Certified: File no. 21-6
(F and F1).
ACCESSORIES:
W136A Test Meter (includes 117053 Meter Connector
Plug).
Flame Simulator:
Maximum Timings: 8.4, 12, 36, 72, and 108 seconds
at room ambient temperature.
RecommendedLimits:L404A;L604A,L;L4006A,C,E;
L4008A,E,F; L6006A,B: These controllers were
Underwriters Laboratories Inc. tested for breaking
loads only, at 120 Vac, for the total rating of 9.8A
full load, plus 360VA ignition, plus 250 VA pilot
duty.
203659 Ultraviolet
121708 Rectification
123514B Ultraviolet
117053 Meter Connector Plug
FSP1535 Tester for operational check
Q624 Solid State Spark Generator
Flame Detector: As specified in Plug-In Flame Signal
Amplifiers listed above.
3
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R4795A
INSTALLATION
Installation
Vibration
CAUTION
Do not install the R4795A where it could be subject to
excessive vibration. Vibration shortens the life of the elec-
tronic and mechanical components.
1. Installer must be a trained, experienced, flame
safeguard control service technician.
2. Disconnect power supply before beginning in-
stallation to prevent electrical shock and equip-
ment damage.
Weather
The R4795A is not designed to be weathertight. If it is
installed outdoors, use a suitable weathertight enclosure.
3. All wiring must comply with applicable local
electrical codes, ordinances, and regulations.
4. Voltage and frequency of the power supply
connected to this control must agree with those
marked on the device.
5. Loads connected to the control terminals must
not exceed those listed in the Specifications
section.
6. All external timers must be Listed or Compo-
nent Recognized by authorities having jurisdic-
tion for the specific purpose for which they are
used.
7. Some authorities having jurisdiction prohibit
the wiring of any limit or operating contacts in
series with the main fuel valve(s).
Mounting The Subbase
Locate the subbase where ambient temperature is within
the specified rating.
Mount the subbase so the top and bottom are horizontal
and the back is vertical. The subbase can lean backward as
much as 45 degrees when necessary. See Fig. 1.
Fig. 1—Subbase mounting dimensions in in.
(mm).
VERTICAL
HORIZONTAL
45 DEGREES
MAXIMUM LEAN
8. Perform all required checkout tests after instal-
lation is complete.
Follow the burner manufacturer’s instructions, if sup-
plied. Otherwise proceed as follows.
2-7/8
(73.0)
CAUTION
Ultraviolet sensing tubes have a life expectancy of
40,000 hours of continuous use within the ambient
temperature and voltage ratings. Worn out ultra-
violet sensing tubes can result in failure of the
sensingtubetoproperlydiscriminatebetweenflame
conditions.
4-1/8 (104.8)
KNOCKOUTS (9) FOR
1/2 IN. (13) CONDUIT
M8681
WIRING TO SUBBASE
1. All wiring must comply with applicable codes, ordi-
nances, and regulations. All wiring to the Q270A Universal
Mounting subbase must be NEC Class 1.
2. When wiring the Q270A for use with the R4795A, use
the terminal designations 8, 7, and 6 (printed in yellow).
3. For normal installations, use moisture-resistant No. 14
wire suitable for at least 167°F (75°C).
For systems using R4795A with R7290 Amplifiers, use
C7027, C7035 and C7044 Flame Detectors only on burners
that cycle On and Off at least once every 24 hours. Appli-
ances with burners that remain on for 24 hours continuously
or longer should use the C7012E Flame Detector with the
R7247C Amplifier or the C7076A Flame Detector with the
R7476A Amplifier as the ultraviolet flame detection system.
4. For high temperature installations, use moisture-re-
sistant No. 14 wire selected for a temperature rating above
the maximum operating temperature for all but the ignition
and flame detector F leadwires.
LOCATION
Temperature
Install the R4795A where the surrounding temperatures
remain within the Ambient Operating Temperature Ratings
listed in the Specifications section.
a. For the ignition, use Honeywell Specification no.
R1061012 Ignition Cable or equivalent. This wire is
rated at 350°F (175°C) for continuous duty, and up to
500°F (260°C) for intermittent use.
Humidity
b. For the flame detector F leadwire, use Honeywell
Specification no. R1298020 or equivalent. This wire
is rated up to 400°F (205°C) for continuous duty. It is
tested for operation up to 600V and breakdown up
to 7500V.
Install the R4795A where the relative humidity never
reaches the saturation point. Condensation of moisture on
the R4795A may cause enough leakage to short the flame
signal to ground and prevent the burner from starting.
60-2285—7
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R4795A
INSTALLATION
IMPORTANT: Do not run high voltage ignition trans-
former wires in the same conduit with the flame
detector wiring.
Fig. 3—Wiring hookup of oil system with
interrupted ignition.
5. For ignition installations in a contaminating environ-
ment, use Honeywell Specification no. R1239001 High Ten-
sion Ignition Cable or equivalent. This wire is very resistant
to severe conditions of oil, heat, and corona, and is tested to
withstand high voltages up to 25,000V rms in a salt bath for
one minute without breakdown. It is rated at 200°F (93°C)
for continuous duty and up to 350°F (75°C) for intermittent
use.
4
2
3
2ND STAGE
OIL VALVE(S)
5
4
BURNER
MOTOR
8
2K3
2K2
AIR FLOW
SWITCH
IGNITION
7
1ST STAGE
OIL VALVE(S)
6
3
1K4
3K2
Wiring Hookups
The typical wiring hookups in Fig. 2 and 3 show the
internallinevoltageschematic. Contact3K2closeswhenthe
controller calls for heat. 1K4 closes when prepurge is com-
plete. 2K2 breaks and 2K3 makes when flame is proven.
Also see the Operation section.
F
TO FLAME
DETECTOR
(PHOTOCELL
OR UV)
FLAME
AMPLIFIER
G
1
CONTROLLER
LIMIT(S)
2
5
Fig. 2—Wiring hookup of gas system with
interrupted ignition and intermittent pilot.
R4795A
1
L1
(HOT)
MAIN FUEL
VALVE(S)
L2
5
BURNER
MOTOR
8
2K3
2K2
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
AIR FLOW
SWITCH
4
IGNITION
2
3
4
FOR INTERMITTENT IGNITION,CONNECT IGNITION TO TERMINAL 3.
IMMEDIATE OPENING OIL VALVE V4046B.
7
PILOT
VALVE
OPTIONAL DELAYED OPENING OIL VALVE V4046A OR V4046B WITH
ST70A ELECTRONIC TIME DELAY.
6
3
1K4
3K2
5
REFER TO SPECIFICATIONS SECTION FOR RECOMMENDED LIMITS.
M8683
F
TO FLAME
DETECTOR
(FLAME ROD
OR UV
FLAME
AMPLIFIER
G
1
Retrofitting R4795
DETECTOR)
CONTROLLER
LIMIT(S)
2
CAUTION
3
Make wiring connections as specified in Fig. 2, 3,
or 4. Do not simply plug the R4795 into the old
subbase without first changing the wiring at the
subbase.
R4795A
1
L1
(HOT)
L2
Observe the following when retrofitting the R4795:
1. Requiresalinevoltagecontrollercapableofswitching
the entire connected electrical load.
2. Delayed opening oil valve may be retained but its
delay is not necessary. Integral ST71A Purge Timer meets
the intent of a delayed opening valve.
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
2
3
FOR INTERMITTENT IGNITION, CONNECT IGNITION TO TERMINAL 3.
REFER TO SPECIFICATIONS SECTION FOR RECOMMENDED LIMITS.
M8682
3. Refer to Fig. 2, 3 or 4 for proper wiring connections.
5
60-2285—7
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R4795A
INSTALLATION
Replacing RA890E,F,G with R4795A
R4795C Replacement
1. Disconnect all wires from terminal 1, and splice with
solderless connector. (If RA890 has no terminal 1 wiring,
disregard this step.)
In most cases, the R4795A can directly replace the
R4795C. For standing pilot applications where the pilot
flame was detected during the off cycle, install a relay as
shown in Fig. 5.
2. Remove line voltage controller wire from terminal 6
and connect to terminal 1.
3. Move burner motor connection from terminal 3 to ter-
minal 6 on subbase.
Flame Detector Wiring
See Fig. 6.
4. Remove jumper from T and T and install air switch. If
low voltage control was wired to RA890 T-T, remove low
voltage control and install line voltage control as shown in
Fig. 4.
5. If R482D Relay was used with RA890E, remove it.
The R482D is redundant when R4795D is used.
Alarm Contacts
Models with alarm contacts have three male quick-con-
nect terminals. Three female quick-connect terminals are
provided for field installation. To connect leadwires to the
female quick-connects, strip 1/4 inch (6.4 mm) insulation
from end of leadwire; insert into the quick-connect, and
crimp securely with a crimping tool. Fig. 7 shows proper
alarm terminal connections.
6. Checkforproperoperationthroughatleasttwocycles.
If a line voltage alarm is used with the R4795, mount the
entire control in a suitable enclosure.
Fig. 4—Replacing RA890E,F,G with R4795A on
gas or oil burner.
REPLACING RA890 WITH R4795 ON GAS OR OIL BURNER
Fig. 5—When R4795A replaces R4795C in a
standing pilot application, install relay 1R to
prevent detection of pilot flame during burner
off cycle.
BEFORE
CONTROLLER
HIGH LIMIT
MAIN GAS
VALVE OR
2ND STAGE
OIL VALVE
6
T
T
F
5
4
3
IGNITION
TRANSFORMER
MIAN FUEL
VALVES
5
4
BURNER
MOTOR
8
2K3
2K2
BURNER
MOTOR
PILOT OR
OIL VALVE
7
FLAME
DETECTOR
L1
(HOT)
3
1
2
1R
AIR FLOW
SWITCH
1K4
3K2
120V
6
F
G
L2
1R1
RA890 WITH Q270
TO FLAME
DETECTOR
FLAME
AMPLIFIER
AFTER
G
CONTROLLER
HIGH LIMIT
(FLAME ROD
OR UV
DETECTOR)
MAIN GAS
VALVE OR
2ND STAGE
OIL VALVE
1
CONTROLLER
LIMIT(S)
3
2
6
T
T
F
8
7
6
5
4
2
IGNITION
TRANSFORMER
AIR FLOW
SWITCH
R4795A
BURNER
MOTOR
3
1
L1
L2
PILOT OR
OIL VALVE
SODERLESS
CONNECTION
(HOT)
FLAME
DETECTOR
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD
PROTECTION AS REQUIRED.
L1
(HOT)
1
2
G
120V
2
3
REFER TO SPECIFICATIONS SECTION FOR RECOMMENDED LIMITS.
LOW VOLTAGE CIRCUIT OMITTED.
M8685
L2
RA4795 WITH Q270
M8684
60-2285—7
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R4795A
INSTALLATION
Fig. 6—Flame detector wiring.
Fig. 7—Alarm terminal connections.
PHOTOCELL
FLAME ROD
F
X
X
F
X
X
G
G
ALARM TERMINALS (OPTIONAL)
R4795
C7012 ULTRAVIOLET DETECTOR
N.O.
COM
N.C.
L1
(HOT)
ALARM
2
POWER
SUPPLY
LINE OR
LOW VOLTAGE
L2
ALARM
1
IF A LINE VOLTAGE ALARM IS USED, THE R4795 MUST BE
MOUNTED IN A SUITABLE ENCLOSURE.
1
2
BLUE
F
X
YELLOW
G
X
POWER SUPPLY MUST MATCH THE ELECTRICAL RATINGS OF THE
ALARM. PROVIDE DISCONNECT MEANS AND OVERLOAD
BLACK
BLACK
PROTECTION AS REQUIRED.
M8687
POWER
SUPPLY
1
C7027, C7035, OR C7044
CAUTION
ULTRAVIOLET FLAME DETECTOR
BLUE
F
X
X
Do not overtighten the mounting screws because
damage to the circuit board can result. Maximum
recommended torque is 10 lb-in. (1.13 N•m).
WHITE
G
C7027, C7035, AND C7044 FLAME DETECTOR LEADS ARE COLOR
1
CODED BLUE AND WHITE. THE BLUE LEAD MUST BE CONNECTED
TO THE F TERMINAL AND THE WHITE LEAD MUST BE CONNECTED
TO THE G TERMINAL. THIS CIRCUIT IS DC AND THE UV SENSING
TUBE IS POLARITY SENSITIVE. REVERSING THE LEADS EVEN
MOMENTARILY CAN DAMAGE OR DESTROY THE UV TUBE.
Replace cover and securely tighten thumbscrew.
M8686
Fig. 8—R4795 and Q270 Subbase.
CAPTIVE MOUNTING
SCREWS (10)
Q270
SUBBASE
Mounting R4795 On Subbase
SAFETY SWITCH
RESET BUTTON
IN COVER
Make sure that the power supply is disconnected.
Loosen the thumbscrew and remove the cover (see Fig. 8).
Position the R4795 over the Q270 Subbase. Start all ten
mounting screws and tighten uniformly. These screws com-
plete electrical circuits (terminal 1 excepted) and hold the
R4795 to the subbase.
TERMINAL
BLOCKS
COVER
AMPLIFIER
THUMBSCREW
M8688
PURGE TIMER
7
60-2285—7
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R4795A
CHECKOUT
Checkout
Fig. 10—Internal view showing amplifier and
CAUTION
test jack for flame current test.
Use extreme care while testing the R4795; line
voltage can be present on most terminals when the
power is On.
ARC-GAP IGNITION INTERFERENCE
PROTECTION (R7289 RECTIFICATION
AMPLIFIER ONLY)
ST71A
TEST JACK
PLUG-IN
PURGE
TIMER
CHECKOUT SUMMARY
The following list summarizes the checkout tests re-
quired for each type of installation. Instructions for each test
are included in this section.
PLUG-IN
AMPLIFIER
Preliminary Inspection: All installations.
Flame Current Check: All installations.
Pilot Turndown Test: If a pilot must be proved before the
main fuel valves can open.
Hot Refractory Hold-in Test: Photocell oil installations
only.
AMPLIFIER
CONNECTORS
PURGE TIMER
CONNECTORS
OPTIONAL
ALARM TERMINALS
Ignition Spark Response Test: All ultraviolet detector
applications.
M8680
Safe Shutdown Tests: All installations.
Refer to Fig. 2 to 3 for terminal location, and to Fig. 9 and
10 for location of component parts. Loosen thumbscrew to
remove cover.
PRELIMINARY INSPECTION
Make certain that:
1. Wiringconnectionsarecorrectandallterminalscrews
are tight. Use a meter to check the continuity of all circuits.
2. Flame detector is installed and positioned properly.
Consult the appropriate installation instructions.
3. Ambient temperature at flame detector does not ex-
ceed maximum rated temperature.
4. Correctcombinationofamplifierandflamedetectoris
used. Refer to Plug-In Flame Signal Amplifiers in Specifica-
tions section.
5. Burner is completely installed and ready to fire; fuel
lines are purged of air.
6. Combustion chamber and flues are clear of fuel.
7. Power is connected to system disconnect switch (mas-
ter switch).
Fig. 9—Internal components of R4795A.
2K
3K
CAPTIVE
MOUNTING
SCREWS
(10)
1K
UNDER
COVER
PLUG-IN
PURGE
TIMER
SAFETY
SWITCH
RESET
(ST71A)
BUTTON
8. Safety switch is reset; push in and then release the
green safety switch.
9. All limits and interlocks are reset.
SPRING
CLIP FOR
AMPLIFER
IMPORTANT: Anytime you reset the safety switch, wait at
leastoneminuteafterittripstoallowtheheatertocool
before pushing in the reset button.
TRANSFORMER
PLUG IN AMPLIFIER
(R7289–GREEN–RECTIFICATION)
(R7290–PURPLE–ULTRAVIOLET)
M8679
CAUTION
Make initial pilot lightoff with manual main fuel
shutoff cock closed.
60-2285—7
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R4795A
CHECKOUT
FLAME CURRENT CHECK
2. The flame current is at least two microamperes for
The flame current check is the best indicator of proper
flame detector application. Perform the check at the time of
installation, and at any time service is done on the system,
and at least once a month, or more often, while the system is
in operation. This prevents shutdowns due to poor flame
signal.
R7289A Rectification Amplifier (color-coded green), or at
least1.5microamperesforanR7290AUltravioletAmplifier
(color-coded violet).
IF A STEADY READING OF AT LEAST MINIMUM
STRENGTH CANNOT BE OBTAINED, ONE OR MORE
OF THE FOLLOWING CONDITIONS CAN EXIST:
• Improper supply voltage.
Test by connecting a W136 (or equivalent) to the ampli-
fier and reading the flame current while the burner is operat-
ing. (Fig. 11).
• Defective flame detector wiring including:
— Open circuits.
— Short circuits.
Fig. 11—Connecting meter to read flame
current.
— High resistance shorts caused by moisture, accu-
mulated dirt, or an improper choice of detector lead-
wire for the particular installation.
117053 METER
CONNECTOR PLUG
(SUPPLIED WITH W136)
PLUG-IN
AMPLIFIER
• Impropersighting,improperviewingwindow,ordirty
viewing window for optical detectors.
• Improper application of a flame rod including:
— Insufficient ground area.
W136
— Poor location of flame rod in flame.
— Excessive heat on flame rod insulator, greater than
600°F (316°C).
FLAME
CURRENT
TEST JACK
— Ignition interference.
• Improper application of a vacuum photocell including:
— Temperature over 165°F (74°C) at photocell.
— Dirty photocell envelope.
RED
• Defective sensor.
IF 117053 METER CONNECTOR PLUG IS NOT AVALIABLE
(R7289A RECTIFICATION AMPLIFER ONLY)
PILOT TURNDOWN TEST
IMPORTANT: If the R4795 is used to prove a pilot flame,
perform the following Turndown Test to assure that
the main burner can be lit by the smallest pilot flame
that will hold in the 2K (flame) relay.
W136
-
+
BLACK
RED
F LEAD
G LEAD
F
FLAME
DETECTOR
1. Shut off the fuel supply to the main burner only by
closing the manual main burner shutoff cock. Do not shut off
fuel supply to the pilot valve.
G
R4795
2. Start the system by raising the setpoint of the control-
ler (or pressing the START button). After prepurge is com-
pleted, the pilot will light and pull in the flame relay.
3. Reduce the size of the pilot flame to the turndown
conditionbyslowlyclosingthemanualvalveonthepilotgas
line. At the turndown condition, the pilot will be small
enough so it just barely holds in the flame relay (2K).
a. Slowly turn down the pilot until the flame relay drops
out.
M8689
Insert a 117053 Meter Connector Plug, wired color-to-
color to the W136 leadwires, into the test jack on the ampli-
fier (Fig. 10). This automatically puts the microammeter in
series with the flame detector.
If an R7289A Rectification Type Amplifier is used and a
meter connector plug is not available, disconnect the flame
detector lead from the F terminal; then connect this lead to
the Black lead of the microammeter, and connect the Red
lead of the microammeter to the F terminal.
b. Allow the control to complete prepurge.
c. As the control attempts to restart the pilot, turn the
pilot back up slowly just until relay 2K pulls back in.
You will have 15 seconds to complete this step before
lockout occurs.
d. Again turn the pilot down slightly but not enough so
theflamerelaydropsout. Iftherelaydropsout, simply
allow the control to complete the purge period and
then turn the pilot back up to pull in the flame relay as
in step c. above. The closer the pilot is to the dropout
condition, the more conclusive the test will be.
NOTE:IfanR7290AUltravioletTypeAmplifierisused, the
flame current cannot be read by connecting a micro-
ammeter in series with the F lead.
When reading the flame current, assure that the following
criteria are met:
1. The flame current is steady; meter does not vary more
than a needle width.
9
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R4795A
CHECKOUT
4. If relay 2K does pull in, resight the detector farther out
from the spark, or away from possible reflection. It may be
necessary to construct a barrier to block the ignition spark
from the detector view. Continue adjustments until flame
detector does not respond to the ignition spark.
CAUTION
Do not manually push in the relays.
4. Check that the pilot is lit and relay 2K is pulled in.
5. Open the manual main burner shutoff cock. Main
flame should light within one second. If the burner does not
light within one second, close the shutoff cock and shut off
power to the relay. Proceed to step 7.
6. If the burner lights, repeat step 5 two or three times to
verify lightoff.
IMPORTANT: Repeat ALL required checkout tests after all
adjustments are complete. ALL tests must be satisfac-
tory when the flame detector is in its FINAL position.
SAFE SHUTDOWN CHECKS
Limit Action
With the burner operating, lower the high limit setting to
simulate an overheated boiler or furnace. Normal shutdown
should occur. Restore the normal limit setting; the burner
should go through a normal prepurge and start.
Using manual reset limits is desirable to prevent the
system from cycling off the high limit and to assure that the
condition that caused the limit action is detected as soon as
possible.
7. If the lightoff is unsatisfactory, readjust the flame
detector to require a larger pilot flame to hold in the flame
relay. This usually requires:
a. Resighting a photocell or UV type detector farther
out on the axis of a pilot flame, or
b. Adjusting a flame rod detector so that a larger mini-
mum pilot is required.
8. Repeat the entire turndown test until the flame is
established promptly in step 5.
Flame Failure
9. Turn up the pilot to full flame at the test completion.
Let burner operate five minutes; then manually shut off
fuel supply to simulate flame failure. Relay should drop out
and fuel valve(s) close. The system will purge and then lock
out on safety. Let the safety switch cool for one minute;
reopen manual fuel valve, and reset safety switch. Burner
should start.
HOT REFRACTORY HOLD-IN TEST
(PHOTOCELL OIL INSTALLATIONS ONLY)
If hot refractory holds in the flame relay at the end of the
burner-on cycle, the system cannot restart until the relay
drops out. Check for hot refractory hold-in by observing the
flame relay for immediate dropout at the end of a long
burner-on period. If the relay does not drop out, resight the
photocell so it does not sight the refractory, or decrease
photocell sensitivity using aperture disks or filters.
Power Failure
Let the burner run five minutes. Then simulate power
failure by opening the line switch. All relays should drop out
and the fuel valves should close. After a minimum of five
seconds, close the line switch. The R4795 should go through
a normal cycle.
IGNITION SPARK RESPONSE TEST
(UV DETECTORS)
The flame relay should not respond (pull in) to ignition
spark. To determine flame detector sensitivity to ignition
spark, perform the following test:
1. Shut the pilot and main fuel manual valves.
2. Start the system by raising the controller setpoint or
pressing the START button. This should energize the igni-
tion transformer so spark is produced between the electrode
and ground.
IMPORTANT: At the completion of all Checkout tests,
make sure that the R4795 is not on safety lockout, that
the pilot is turned up to its normal level, and that all
limit settings are correct. Operate the system through
one normal cycle. Replace cover and securely tighten
thumbscrew.
3. Checktheflamerelay2K. Therelayshouldnotpullin.
The flame signal current should not be more than one-fourth
microampere.
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R4795A
OPERATION • TROUBLESHOOTING
Operation
NORMAL OPERATION (REFER TO FIG. 2 AND 3.)
Call for Heat (Limit Switch
Closed)
Terminal 1 energized. Relay 3K pulls in to close contact 3K2 and energize
terminal 8 fan or burner motor.
Airflow Proved
Low voltage airflow switch between terminals 6 and 7 closes to energize the
purge timer.
Prepurge Complete (7, 10, 30, 60, Relay 1K pulls in to close contact 1K4 and energize terminal 3 (pilot valve, first
or 90 Seconds)
stage oil valve(s), or expanding pilot valve) directly and terminal 4 (ignition)
through the closed flame relay contact 2K2. Contact 1K1 closes to energize the
safety switch heater.
Flame Proven (Pilot or First Stage R4795A: Relay 2K pulls in. Contact 2K2 opens to cut off ignition, contact 2K3
Oil)
closes to energize the main fuel valve(s) or second stage oil valve(s). Contact
2K1 opens to de-energize the safety switch heater and reset the purge timer.
Controller Satisfied
All relays drop out; systems shuts down.
SAFETY OPERATION
Flame Failure
R4795A: Relays 1K and 2K drop out. Contact 1K4 opens to de-energize
terminals 3, 4, and 5. If air is still proven, the prepurge period begins. After
prepurge, one attempt is made to start the burner.
Airflow Failure
If airflow fails at any time during the operating cycle, relay 1K drops out.
Contact 1K4 opens to de-energize terminals 3, 4, and 5. Only terminal 8, fan or
burner motor, remains powered. If air is re-established, the prepurge period
starts and the startup sequence is repeated.
Prepurge Timer Failure
If the plug-in purge timer is not properly seated, or is not functioning properly,
the fan motor will start on a call for heat, but the 1K relay will not pull in. The
result will be a continuous purge (safe failure).
Hot Refractory Hold-in (Photocell If hot refractory holds in the flame relay at the end of the running cycle, startup
Installations) is prevented until the hot refractory no longer holds in the flame relay.
Troubleshooting
The first step in troubleshooting the R4795A is to deter-
mine the location of the system trouble. Reset the safety
switch and operate the system on a normal start. Refer to the
Normal Operation subsection in the Operation section. Ob-
serve the operation carefully to determine at what point the
trouble occurs. Then refer to the Trouble List in the Trouble
List section and follow the troubleshooting procedure.
3. Reset the safety switch (push in and then release the
small round button that extends through the plastic safety
switch cover; see Fig. 9).
TROUBLE LIST
Compare the following list of troubles with the actual
deviationsfromnormaloperatingsequence.Selecttheappli-
cable letter(s) and proceed to the corresponding Trouble-
shooting Procedure(s).
IMPORTANT: At the completion of any troubleshooting
procedure, be sure to perform the Checkout Tests
listed in the Checkout section.
A. Relay 3K does not pull in on a call for heat.
B. Relay 3K pulls in but the burner motor does not start.
C. Burner motor starts but prepurge does not stop at end
of purge timing (relay 1K does not pull in).
D. Relay 1K pulls in but the pilot does not light, ignition
does not occur, or expanding pilot valve does not
open.
PRELIMINARY INSPECTION
1. Disconnect power to the R4795 by opening the sys-
tem disconnect switch.
2. Remove the R4795 cover. Make sure all mounting
screws are tight, and that the plug-in amplifier and purge
timer are properly seated; refer to Fig. 10.
E. Pilot lights but relay 2K does not pull in (control locks
out without lighting the main burner).
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R4795A
TROUBLESHOOTING
F. Pilot lights and relay 2K pulls in but the main burner
3. Check the position of the flame relay. If relay 2K is
pulled in, check for flame simulating condition.
4. If the flame relay is not pulled in, clean the 2K relay
contacts.
does not light.
G. Relay 2K remains in after flame is extinguished.
H. Miscellaneous problems:
1. Repeated lockouts or control failures.
2. Ignition interference (flame rod installations only).
5. Replace the purge timer with one of the same timing.
If problem still continues, replace the R4795.
TROUBLESHOOTING PROCEDURES
D. Relay 1K pulls in but the pilot does not light, ignition
does not occur, or expanding pilot valve does not open
1. Make sure that all manual fuel valves are open.
2. Check voltage between terminals 3 and 2, or 4 and 2,
asapplicable. (Terminal3isusedforpilotorfirststage
oilvalve;terminal4forignition.)Checkmustbemade
before control locks out on safety.
CAUTION
1. Use extreme care while troubleshooting the
R4795; line voltage is present on most contacts
when power is On.
2. Open the master switch before removing the
cover, cleaning contacts, removing R4795 from
subbase, or reinstalling R4795 on subbase. See
Fig. 9 for relay location.
3. If zero voltage, clean the 1K and 2K relay contacts;
then recycle the system and recheck the voltage at ter-
minal3or4. Ifterminalscannotbepowered, replacethe
R4795.
4. If correct voltage at terminals 3 and 4, check the pilot
valve and ignition and the circuits.
IMPORTANT:
1. Clean contacts only when instructed to do so in a
troubleshooting procedure. Follow the instructions in
Contact Cleaning section.
2. If, after completing an applicable Troubleshooting
Procedure, proper operation still cannot be obtained,
replace the R4795 (except amplifier and purge timer,
unless noted).
E. Pilot lights but relay 2K does not pull in (control locks
out without lighting the main burner)
1. Use a 121708 Rectification or a 203659 or 123514B
Ultraviolet Flame Simulator to check the flame relay.
Follow the instructions for the simulator.
2. If no flame simulator is available, do a flame current
check. If the flame current is satisfactory, replace the
R4795. If the flame current is not satisfactory, recheck
all items.
A. Relay 3K does not pull in on a call for heat
1. Check for power at terminals 1 and 2 with the control-
ler calling for heat.
F. Pilot lights and relay 2K pulls in but the main burner
does not light
a. Voltage must be within plus 10 to minus 15 percent
of the rated voltage for dependable operation.
b. If voltage is zero, check the continuity of the limit
and controller contacts and check the power sup-
ply. Look for blown fuses, open switches, and bad
wiring connections.
1. Check that the manual main fuel valves are all open.
2. Check the voltage at terminal 5 when the 2K relay
pulls in.
a. If normal voltage at terminal 5, check the main
valve and the external valve circuit.
b. If zero voltage at terminal 5, clean the 2K relay
contacts. If terminal 4 cannot be powered, replace
the R4795.
2. If voltage at terminals 1 and 2 is satisfactory and relay
3K will not pull in, clean the 1K and 3K relay contacts.
Press safety switch button several times to clean the
contacts. If trouble persists, replace the R4795.
G. Relay 2K remains in after flame is extinguished
1. If the flame detector is a rectifying flame rod, install a
new plug-in amplifier.
B. Relay 3K pulls in but the burner motor does not start
1. Check for power at terminal 8 when the 3K relay
pulls in.
2. If the flame detector is a rectifying photocell or C7012
Ultraviolet Detector, plug the back end of the flame
simulator into the jack of the plug-in amplifier.
a. If that does not cause relay 2K to drop out, install a
new plug-in amplifier.
a. If terminal 8 is not powered, clean the 3K relay
contacts and recheck for power. If terminal 8 can-
not be powered, replace the R4795.
b. If terminal 8 is powered, check the fan or burner
motor.
b. If plugging into the meter jack causes relay 2K to
drop out, the trouble is caused by hot refractory
hold-in, detector failure, or other flame simulating
conditions.
C. Burnermotorstartsbutprepurgedoesnotstopatend
of purge timing (relay 1K does not pull in)
1. Check the seating of the plug-in purge timer.
2. Check that the airflow switch contacts are making.
Approximately 20 Vdc should appear between termi-
nals 7 (plus) and G (minus) when airflow switch con-
tacts are made.
(1) Resight the photocell at a cooler or more re-
mote area of the refractory.
(2) Recheck the flame detector current for the
condition recommended in the Checkout sec-
tion. Replace the detector if necessary.
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R4795A
TROUBLESHOOTING • SERVICE
(3) Remove any flame simulating condition such
as false light.
(4) Note that any change made in the detector or its
sighting requires a pilot turndown test.
How detected. The arc gap circuit in the rectifica-
tion amplifier (Fig. 10) protects the R4795 from igni-
tion interference; however, it also prevents operations
when ignition interference is present above the arcing
level of the device. If a shutdown is caused by ignition
interference, the arc gap protector glows.
Continuous interference below the arcing level can
be detected by reading the flame current with the pilot
and ignition on; then with only the pilot on. Any sub-
stantial difference indicates the presence of ignition
interference.
3. If using an R7290 Ultraviolet Amplifier, replace the
amplifier and recheck the flame relay dropout time. If
the flame relay dropout timing is still excessive, re-
place the detector and check its wiring.
4. If trouble persists, replace the R4795.
H. Miscellaneous problems
1. Repeated lockouts or control failures: The most com-
mon causes of repeated failures of the control or flame
detector, or repeated lockouts are:
Intermittent ignition interference may be due to
very turbulent air in the ignition electrode area. For
arc-over elsewhere, examine the electrodes for spac-
ing and for unusual dirt conditions or dust accumula-
tions between the ignition leads and flame leads.
How eliminated (tabulated in order of importance).
1. Provide adequate flame grounding area.
2. Be sure the ignition electrode and the flame rod
are on opposite sides of the grounding area.
3. Check for the correct spacings on the ignition
electrode. Spacing should be 1/16 in. (1.6 mm)
to 3/32 in. (2.4 mm) for 6,000V systems; 1/8 in.
(3.2 mm) to 3/16 in. (4.8 mm) for 10,000V
systems.
a. High ambient temperatures over 125°F (52°C).
Subtract 10°F (6°C) for alarm contacts and 10°F
(6°C) for 50 Hz operation. -40°F (-40°C) models
have a maximum ambient of +115°F (46°C) at
60 Hz, +105°F (40°C) at 50 Hz.
b. Supply voltage variation greater than plus 10 to
minus 15 percent.
c. Marginal flame signal.
d. Faulty flame detector.
2. Ignition interference (flame rod installations only)
What it is. Ignition interference is a false signal
from a spark ignition source superimposed on the
basic flame signal. It is normally associated with a
marginal flame reading, and usually caused by a mar-
ginal flame ground.
4. Eliminate any marginal spacings at other areas
along the lead routes. Replace any deteriorated
leads.
Service
operating conditions (dirt and heat especially), and the cost of
a nuisance shutdown. Include the following in any program:
Annually replace the vacuum tubes in the C7012 Flame
Detector (if used).
GENERAL
1. Only qualified personnel should attempt to service
heating equipment or controls.
2. Perform all checks required in the Checkout section
when replacing the R4795, or when relighting or restoring
power to the system after shutdown.
3. Captive mounting screws carry current; always dis-
connect power before loosening or tightening the mounting
screws.
Perform a flame failure check and pilot turndown test
whenever the burner is serviced, and at least annually.
Inspect and clean the detector and any viewing windows
as often as required by soot accumulation and heat
conditions at the detector.
4. On each service call, check the controller for the ap-
proximately correct calibration and differential; assure it is
mounted securely (see Controller installation instructions).
5. Never use oil on any part of the R4795.
Doaflamecurrentcheckatleastmonthly, andmoreoften
where a shutdown may be costly.
Clean contacts only when required by failure to operate
properly.
6. When cleaning the burner, clean the flame detector.
7. DO NOT MANUALLY PUSH IN THE R4795
RELAYS. This may damage the relays and it is an unsafe
practice because it overrides the protective features of the
relays. Clean relay contacts only as instructed following.
CONTACT CLEANING
CAUTION
Open the master switch before removing cover or
cleaning contacts. Line voltage is present on most
contacts when power is on.
PERIODIC MAINTENANCE
The specific maintenance schedule setup will depend on
several factors including type of equipment being controlled,
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R4795A
SERVICE
IMPORTANT:
2. Some leave an oily residue that will collect dust and
dirt. The residue will also break down to form various
carbonaceous products. Either result will cause early contact
failure.
Do not use an abrasive (sand paper stock, file, etc.) or a
burnishing tool to clean contacts. Its use can cause early
contact failure for these reasons:
1. Do not clean contacts unless absolutely necessary.
2. UseonlyHoneywellContactCleanerpartno.132569.
Do not use any other type of contact cleaner.
3. Use extreme care to avoid bending the contacts or
changing the specifications or configuration in any
way.
4. Do not use an abrasive or a burnishing tool to clean
contacts.
5. Donotusehardpapersuchasabusinesscardtoclean
contacts.
1. Some relay contacts are plated with gold for increased
reliability. Burnishing can quickly remove the plating.
2. The radii or points of the contacts are designed with
specific shapes to best serve the intended functions of the
contacts. Burnishing can rapidly alter these contact configu-
rations.
3. Use of an abrasive loosens fine particles of the contact
material that adhere to the surface of the contract, thus in-
creasing its resistance.
4. Contact specifications (contact pressures, press-back,
and gaps) are carefully controlled during manufacturing to
assure maximum contact life. Burnishing can easily change
these specifications.
If relay contacts must be cleaned, use only Honeywell
Pressurized Contact Cleaner, part no. 132569. Honeywell’s
chemical analysis laboratory has found this cleaner to be
acceptable for this task. Directions for using this cleaner are
printed on the can.
Do not risk using any other types of contact cleaners.
Honeywell’s chemical analysis laboratory tested other pres-
surized type contact cleaners but did not approve them for
these reasons:
1. Some had solvents that could deteriorate plastic parts
and wire insulation.
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Home and Building Control
Honeywell Inc.
1985 Douglas Drive North
Golden Valley, MN 55422
Home and Building Control
Honeywell Limited—Honeywell Limitée
740 Ellesmere Road
Scarborough, Ontario
M1P 2V9
Printed in United States
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