L8151A
TripleAquastat® Relay
The L8151A is a remote bulb controller for use
with hydronic heating systems that include domes-
tic hot water service.
■ Provides high limit, low limit, and circulator control
■ Shielded capillary allows convenient mounting.
for maintaining boiler temperatures.
■ Consistsofadiaphragmpowerheadandmicroswitch
assembly that responds to temperature changes in
the boiler water.
■ Can provide multizone control by using a separate
thermostat and R845 Relay for each zone.
■ An internal transformer powers the thermostat cir-
cuit.
CONTENTS
Specifications ................................................. 2
Ordering Information ..................................... 2
Installation ..................................................... 2
Operation and Settings................................... 5
Checkout......................................................... 6
J. H. • Rev. 1-95 • ©Honeywell Inc. 1995 • Form Number60-2553—
L8151A
INSTALLATION
IMMERSION WELL MOUNTING
CAUTION
NOTE:Immersionwellmustbeorderedseparately.Foralist
of available wells, refer to form 68-0040, Wells and
Fittings for Temperature Controllers.
• Disconnect power supply before beginning in-
stallation to prevent electrical shock or equip-
ment damage.
• Avoid making sharp bends or kinks in the capil-
lary. Bends should be no less than 1 in. (25 mm).
The boiler manufacturer generally provides a tapping
for the immersion well. This tapping should be located at a
point where typical water temperature can be measured.
The immersion well must never be located close to a hot or
cold water inlet or a steam coil, or where the pressure
exceeds 200 psi (1380 kPa).
IMPORTANT: Terminals on these Aquastat® Relays are
approved for copper wire only.
If the system is filled, drain to a point below the selected
installation location.
Fig. 1—Approximate L8151 dimensions in in.
(mm).
1/8
(3)
Fig 2— Internal view of L8151.
2-3/16
(56)
VOLTAGE BARRIER
GROUNDING SCREW
TRANSFORMER
FOR THERMOSTAT
CIRCUIT
1-7/16
(37)
1-1/2
(38)
13/64 X 21/64 (4)
DIFFERENTIAL
SETTING
CAPILLARY
30 IN. (762)
6-1/8
(156)
CIRCULATOR
RELAY
4-1/2
(114)
LOW LIMIT SETTING
4-5/16 (110)
4-23/32 (120)
M8893
HIGH LIMIT SETTING
1-1/4
(32)
KNOCKOUT
FOR 1/2 IN.
CONDUIT (5)
1-1/4
(32)
13/16
(21)
3-5/16
(84)
1. Screw the well into the boiler, tank, or pipe tapping.
2-3/6
(56)
2. Insert the bulb into the well, pushing tubing until bulb
bottoms in well. Avoid making sharp bends or kinks in the
capillary. Bends should be no sharper than 1 in. (25 mm)
radius.
M8892
3. Attach the retainer clamp to end of well spud. Loosen
draw nut and spread jaws of clamp with screwdriver if
necessary, Fig. 3.
MOUNTING THE CASE
Mount the case in a convenient location near the boiler.
Remember that the shielded capillary must reach from the
case to the immersion well. This maximum ambient tem-
perature of the selected location must not exceed 150°F
(66°C) at the case, 265°F (130°C) at the sensing element.
3
60-2553—3
L8151A
INSTALLATION
All wiring must comply with local electrical codes and
ordinances. The limits given in the Specifications section
must not be exceeded when applying this control. Use
manufacturer instructions when wiring controlled equip-
ment or refer to typical hookups in Fig. 4 through 6.
When the B1 terminal on the device being replaced is
1/4 in. tab terminal, use the existing wiring harness termi-
nals to install the replacement device. When the B1 termi-
nal on the device being replaced is a screw terminal, insert
the provided tab terminal to screw terminal adapter on the
1/4 in. tab terminal of the replacment device. After the
adapter is installed, the existing wraparound wire end can
be reused to make an electrical connection to the B1 termi-
nal.
Fig. 3—Remote bulb installation.
JAWS
SPREAD JAWS
TO FIT OVER
RIDGE ON SPUD
OF WELL
SCREWDRIVER
INSERT— MOUNTING CLAMP
DRAW
NUT
MOUNTING
CLAMP
NOTE: Do not use a push type ratchet screwdriver.
SPUD
WELL
BULB
B
1. Strip 7/16 in. of insulation from the wire end.
2. Wrap the wire at least three-fourths of the distance
around the screw as shown.
3. Using a standard, flat-headed screwdriver, tighten the
screw until the wire is snugly in contact with the screw and
contact plate.
TUBING
M8777
A
4. Tighten the screw an additional one-half turn.
4. With part no.121371AA Retainer Clamp attached to
well spud (be sure jaws of clamp hook over ridge at end of
spud, as shown at points A), adjust tubing to fit through
retainer clamp groove, as shown at point B.
5. Tighten draw nut so that retainer clamp is firmly
attached to well spud and tubing is held securely in place. Be
careful not to damage the capillary.
Fig. 4—Typical hookup for L8151A in a single
zone system.
LOW VOLTAGE
THERMOSTAT
T
THERM.
T
6. Carefully coil the excess capillary at the bottom of the
Aquastat® case.
ZC
WIRING
X
X
ZR
OIL BURNER
RELAY
LINE TERMINAL
2
CAUTION
3
1
X
X
B1
• Disconnectpowersupplybeforewiringtoavoid
electrical shock or equipment damage.
OR
BURNER
X
X
B2
• Be sure the terminal connections are inside an
enclosure that meets local codes.
LINE VOLTAGE
GAS VALVE
C1
CIRC.
C2
IMPORTANT: Terminals on the L8151A Aquastat® Relay
are approved for use only with copper wire. The
terminals allow wraparound wiring only.
1. Strip 7/16 in. of insulation
LINE VOLTAGE
CIRCULATOR
L1
(HOT)
1
1
LINE
2
from the wire end.
L2
2. Wrapthewireatleastthree
fourthsofthedistancearound
G
2
the screws as shown.
3. Use a standard flat-headed
M8843
screwdriver to tighten the
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
screw until the wire is snugly
in contact with the screw and contact plate.
4. Tighten the screw an additional one-half turn.
2
3
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
M8886
B1 IS 1/4 IN. TAB TERMINAL.
NOTE: Do not use a push-type ratchet screwdriver.
60-2553—3
4
L8151A
OPERATION AND SETTINGS
Operation and Settings
HIGH LIMIT
The high limit opens and turns off the burner when the
water temperature reaches the setpoint. The high limit
automatically resets after the water temperature drops past
the setpoint and through the 10°F (6°C) differential.
Fig. 6—L8151A internal schematic.
2
1
WARNING
T
CAN CAUSE PROPERTY DAMAGE,
SEVERE INJURY OR DEATH.
Product is for use only in a system with a pressure
relief valve.
1K
T
HIGH LIMIT
1K2
B2
B1
R
B
ZR
ZC
LOW
LIMIT
LOW LIMIT AND CIRCULATOR CONTROL
On a temperature rise, with the adjustable differential at
the minimum setting of 10°F (6°C), the low limit circuit
(RB) breaks and the circulator circuit (R-W) makes at the
control setpoint. On a temperature drop of 10°F (6°C)
below the setpoint, the R-B circuit makes and the R-W
circuit breaks.
CIRCULATOR
CONTROL
1K1
W
C2
C1
M8884
Fig. 7—Relationship of setpoints and differen-
tial.
Fig. 5—Typical hookup for the L8151A in a
multizone system.
TO ADDITIONAL
R845A RELAYS
240°F (116°C)
FOR OTHER ZONES
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
T
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
HIGH LIMIT
SETTING
THERMOSTAT
ZONE 1
R845A RELAY
2
THERM.
T
10°F (6°C)
DIFFERENTIAL
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
THERMO-
STAT
ZONE 2
1
4
ZC
ZR
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
4
3
5
6
B1
LOW LIMIT
AND
CIRCULATOR
SETTING
25°F (14°C)
DIFFERENTIAL
1
BURNER
3
B2
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
10°F (6°C)
DIFFERENTIAL
C1
CIRCULATOR
ZONE 1
CIRC.
C2
SWITCH MAKES R-B AND
BREAKS R-W ON
TEMPERATURE FALL.
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
CIRCULATOR
ZONE 2
L1
1
(HOT)
1
LINE
2
110°F (43°C)
L2
1
WHEN WATER REACHES PROPER TEMPERATURE, THE BURNER
SHUTS OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING
IF CONTROLLING TWO LOADS USE:
—TERMINALS 3 AND 4 FOR LINE
VOLTAGE LOAD.
—TERMINALS 5 AND 6 FOR LINE
OR LOW VOLTAGE LOAD.
G
2
FOR HEAT).
M1523
HYDRONIC HEATING
CONTROL TERMINALS
1
2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
At any differential setting greater than 10°F (6°C), the
R-B make and R-W break temperatures remain the same
(control setting minus 10°F (6°C). The R-B break and R-W
make temperatures are the setpoint temperatures plus the
difference between the differential setting and 10°F (6°C).
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
3
4
LINE VOLTAGE OIL BURNER CONTROL OR GAS VALVE.
B1 IS 1/4 IN. TAB TERMINAL.
M8885
5
60-2553—3
L8151A
OPERATION AND SETTINGS • CHECKOUT
EXAMPLE: Setpoint of 140°F (60°C) differential set at
25°F (14°C). On a temperature rise, R-B breaks and
R-W makes at 155°F (68°C). On a temperature fall,
R-B makes and R-W breaks at 130°F (54°C); see
Fig. 7.
THERMOSTAT ANTICIPATOR
Set the thermostat heat anticipator at 0.2A.
Checkout
Put the system into operation and observe each function through at least one complete cycle. Be sure the control operates
as intended.
Automation and Control Solutions
Honeywell International Inc.
1985 Douglas Drive North
Honeywell Limited-Honeywell Limitée
35 Dynamic Drive
Golden Valley, MN 55422
Scarborough, Ontario M1V 4Z9
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