L8124A,C,E,L and M
Aquastat® Relays
INSTALLATION INSTRUCTIONS
APPLICATION
SPECIFICATIONS
These immersion type controllers are used with forced
hydronic heating systems that include domestic hot water
service. All models provide high limit, low limit and
circulator control. Table 1 lists the various models and
their applications.
Low Limit:
Setting: 110°F to 220°F (43°C to 104°C), adjustable.
Differential: 10°F to 25°F (6°C to 14°C), adjustable.
High Limit:
Setting: 130°F to 240°F (54°C to 116°C), adjustable.
Differential: 10°F (6°C), fixed.
These Aquastat® relays have a diaphragm powerhead
and MicroSwitch™ assembly that respond to
temperature changes in the boiler water. L8124 can
provide multizone control by using a separate circulator
and R845 Relay for each zone. L8124E and L have large
transformers and extra terminals for supplying power to
low voltage valves. L8124L includes a large transformer
and extra terminals for low voltage zone valves. L8124M
is for use in a wood-coal/gas-oil multifuel heating system.
Circulator is independently controlled by the thermostat.
WARNING
Can cause serious injury, death or property
damage.
Use this product only in systems with a pressure
relief valve.
Explosion Hazard.
Do not use these Aquastat® Relays where the pressure
can exceed 100 psi (690 kPa) on the bulb if inserted
directly or 200 psi (1380 kPa) when using an immersion
well, or where the ambient temperature can exceed
150°F (66°C) at the case or 265°F (129°C) at the sensing
element.
Table 1. Model Descriptions.
No. of V8043 Zone
Electrical Ratings
Can Be Used For
Multizone With
Burner
Control
Number Circuit
L8124A 120V
L8124C
Valves Powered
Without Additional
Transformer
Model
a
Circulators
Burner Circuit
Circulator Circuit
Yes
—
Same as L8124A,C,L
circulator rating.
120 Vac: 7.4A (full load),
44.4A (locked rotor).
240 Vac: 3.7A (full load),
22.2A (locked rotor).
L8124L
3
2
L8124E 24V
1.25A at 24 Vac; 30 VA
(total load) B -B , T -Z.
1
2
v
L8124M 120V
—
Same as L8124A.
None.
a
Multizone control can be provided by using a separate circulator and R845 Relay for each zone.
® U.S. Registered Trademark
Copyright © 2001 Honeywell • All Rights Reserved
95- 6571- 11
L8124A,C,E,L AND M AQUASTAT® RELAYS
BACK OF
CONTROLLER
CASE
IMMERSION
WELL CLAMP
CONTROLLER
CASE
BOILER
IMMERSION
WELL CLAMP
1
IMMERSION
WELL SPUD
ADAPTER
IMMERSION
WELL CLAMP
SCREW
ADAPTER
OLD IMMERSION
WELL ASSEMBLY
SENSING
BULB
(A)
(D)
)
(B)
2
HEAT-CONDUCTIVE COMPOUND
1
2
BEND THE CAPILLARY TUBE TO HOLD THE SENSING BULB IN GOOD
THERMAL CONTACT WITH THE IMMERSION WELL AT POINTS (A) AND (B).
CAPILLARY
TUBE
ASSURE THAT CAPILLARY TUBE FITS FREELY IN THE ADAPTER SO THE
TENSION OF THE CAPILLARY TUBE AT POINT (C) HOLDS THE SENSING
BULB IN GOOD THERMAL CONTACT WITH THE IMMERSION WELL AT POINT (D
SETSCREW
SHORT TUBE
FITS IN CENTRAL
RECESS OF ADAPTER
IMMERSION
WELL CLAMP SCREW
Fig. 2. Position of bulb in immersion well and use of well adapter when required.
LOW VOLTAGE
THERMOSTAT
LOW VOLTAGE
THERMOSTAT
L8124A,C
G
L8124E
2
2
G
T
Z
TV
L1
(HOT)
L1
(HOT)
T
T
1
2
1
2
1K
L2
1
L2
1
1K
1K2
W
R
W
R
B
B
1K1
1K1
LOW LIMIT/
CIRCULATOR
LOW LIMIT/
CIRCULATOR
ZR
ZC
LINE VOLTAGE
CIRCULATOR
R
B
HIGH
LIMIT
C1
C2
LINE VOLTAGE
OIL BURNER
RELAY OR
B
HIGH
LIMIT
1K2
GAS VALVE
3
3
R
B1
TR
TH
B1
B2
B2
C1
LOW VOLTAGE
GAS VALVE
(eg, VR8300)
C2
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
2
3
LINE VOLTAGE
CIRCULATOR
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
M8803
B1 IS 1/4 IN. TAB TERMINAL.
2
3
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
Fig. 4. L8124E single zone connections
and internal schematic.
M8802
B1 IS 1/4 IN. TAB TERMINAL.
Fig. 3. L8124A,C single zone connections
and internal schematic.
3
95-6571—11
L8124A,C,E,L AND M AQUASTAT® RELAYS
T87F
T87F
T87F
L8124A
R845 RELAY
R845 RELAY
ZC
ZR
B1
T
T
T
1
T
2
T
1
T
2
3
2
G
C1
3
6
3
6
C2 B2
4
5
4
5
L1
L2
L2
L1
(HOT)
1
PUMP
PUMP
PUMP
R8184
T
F
C554
T
F
ORANGE
BURNER
AND
IGNITION
BLACK
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.
B1 IS 1/4 IN. TAB TERMINAL.
2
M8822
3
Fig. 5. L8124A in an oil-fired, forced hot water, tankless, zoned, pump system.
TO ADDITIONAL
R845A RELAYS
FOR OTHER ZONES
L2
L1
(HOT)
LOW VOLTAGE
THERMOSTAT
1
2
L8124A,C
G
R845A RELAY ZONE 2
ZONE 2
CIRCULATOR
T
T
1
2
6
5
3
1K
W
R
B
1K1
LOW LIMIT/
CIRCULATOR
4
1
ZR
ZC
LINE VOLTAGE
OIL BURNER
RELAY OR
B
2
HIGH
LIMIT
1K2
GAS VALVE
3
ZONE 2
LOW VOLTAGE
THERMOSTAT
R
B1
B2
C1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
2
3
CONTROL CASE MUST BE CONNECTED TO EARTH
GROUND. USE GROUNDING SCREW PROVIDED.
C2
LINE VOLTAGE
CIRCULATOR
B1 IS 1/4 IN. TAB TERMINAL.
M8827
Fig. 6. L8124A,C multizone system with circulator connections and internal schematic.
95-6571—11
4
L8124A,C,E,L AND M AQUASTAT® RELAYS
1
ZONE 1
THERMOSTAT
ZONE 2
THERMOSTAT
L1
(HOT)
T87F
V8043F
V8043F
L2
2
TH
TR
TH
TR
G
L8124E
L2 L1
C1 C2
T
T
3
TH
TR
TH
TR
2
B2 B1
L8124G,L
3
G
1
T
Z
TV
TH
TR
L1
(HOT)
1K
CIRCULATOR
LOW VOLTAGE
GAS VALVE
(eg, VR8300)
2
1
L2
1K1
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
W
R
B
ZR
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
LOW LIMIT/
CIRCULATOR
ZC
B1 IS 1/4 IN. TAB TERMINAL.
M1796A
LINE VOLTAGE
OIL BURNER
RELAY OR
B
R
1K2
HIGH
LIMIT
Fig. 8. L8124E in a 24Vac, gas-fired,
forced hot water, tankless system.
GAS VALVE
4
B1
B2
C2
C1
LINE VOLTAGE
CIRCULATOR
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
2
UP TO TWO V8043F ZONE VALVES CAN BE POWERED WITH
L8124G,L. ADD ADDITIONAL TRANSFORMER FOR EVERY
TWO OR LESS VALVES.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND.
USE GROUNDING SCREW PROVIDED.
3
4
M1795B
B1 IS 1/4 IN. TAB TERMINAL.
Fig. 7. L8124 multizone system with zone valve
connections and internal schematic.
5
95-6571—11
L8124A,C,E,L AND M AQUASTAT® RELAYS
T87F
T87F
T87F
R845 RELAY
R845 RELAY
R845 RELAY
T
1
T
2
T
1
T
2
T
1
T
2
3
6
3
6
3
6
4
5
4
5
4
5
1
L1
(HOT)
PUMP
PUMP
PUMP
L2
2
G
L2 L1
C1 C2
T
T
LOW VOLTAGE
GAS VALVE
(eg, VR8300)
TH
TR
B2 B1
3
L8124E
AQUASTAT RELAY
®
1
2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND OVERLOAD PROTECTION AS REQUIRED.
CONTROL CASE MUST BE CONNECTED TO EARTH GROUND. USE GROUNDING SCREW PROVIDED.
B1 IS 1/4 IN. TAB TERMINAL.
M1794A
Fig. 9. L8124E in a 24 Vac, gas-fired, forced hot water, tankless, zoned pump system.
1
TO ADDITIONAL
R845A RELAYS
FOR OTHER ZONES
L1
(HOT)
L2
R845A RELAY ZONE 1
6
5
3
L8124E
2
G
T
Z
TV
4
1
1
2
1K
2
1K2
ZONE 1
LOW VOLTAGE
THERMOSTAT
W
R
B
1K1
LOW LIMIT/
CIRCULATOR
R
B
ZONE 1
CIRCULATOR
HIGH
LIMIT
C1
C2
3
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
2
3
TR
B1
B2
THTR
TH
CONTROL CASE MUST BE CONNECTED TO EARTH
GROUND. USE GROUNDING SCREW PROVIDED.
LOW VOLTAGE
GAS VALVE (eg, VR8300)
B1 IS 1/4 IN. TAB TERMINAL.
M8828
Fig. 10. L8124E multizone system with circulator connections and internal schematic.
95-6571—11
6
L8124A,C,E,L AND M AQUASTAT® RELAYS
LOW VOLTAGE
THERMOSTAT
ZONE 1
1
TO ADDITIONAL
R845A RELAYS
FOR OTHER ZONES
L2
L1
(HOT)
L8124L
2
G
T
Z
TV
R845A RELAY ZONE 2
ZONE 2
CIRCULATOR
1
2
1K
6
5
3
1K1
W
R
B
ZR
ZC
LOW LIMIT/
CIRCULATOR
4
1
B
R
1K2
HIGH
LIMIT
3
2
B1
LINE VOLTAGE
OIL BURNER
RELAY OR
ZONE 2
LOW VOLTAGE
THERMOSTAT
B2
C2
GAS VALVE
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
1
2
3
C1
LINE VOLTAGE
CIRCULATOR
ZONE 1
CONTROL CASE MUST BE CONNECTED TO EARTH
GROUND. USE GROUNDING SCREW PROVIDED.
B1 IS 1/4 IN. TAB TERMINAL.
M8829
Fig. 11. L8124L multizone system with circulator connections and internal schematic.
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).
OPERATION
High Limit Controller
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.
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
HIGH LIMIT
SETTING
WARNING
Can cause serious injury, death or equipment
damage.
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
Explosion Hazard.
Use this product only in systems with a pressure
relief valve.
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
1
LOW LIMIT
AND
CIRCULATOR
SETTING
Low Limit and Circulator Controllers
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
On a temperature rise, with the adjustable differential at
the minimum setting of 10°F (6°C), the burner circuit
(R-B) 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. See Fig. 12.
SWITCH MAKES R-B AND
BREAKS R-W ON
TEMPERATURE FALL.
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
At any differential setting greater than 10°F (6°C), the
R-B make temperature and the R-W break temperature
remain the same (control setting minus 10°F [6°C]). The
R-B break and R-W make temperature are the setpoint
temperature plus the difference between the differential
setting and 10°F (6°C).
1
WHEN WATER REACHES PROPER TEMPERATURE, THE BURNER
SHUTS OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING
FOR HEAT).
M1523
Fig. 12. Relationship of setpoints and differential.
7
95-6571—11
L8124A,C,E,L AND M AQUASTAT® RELAYS
On the L8124M, the burner and circulator circuits are
separately controlled; the low limit controls the burner
circuit (R-B) as described above, while the low voltage
thermostat directly controls the circulator circuit.
See Fig. 13.
SETTING
Follow the boiler manufacturer recommendations when
making the L8124 settings. The high limit setting must be
at least 20°F (11°C) higher than the low limit setting. Set
the indicators over the selected temperature marks. The
low limit differential is set by turning the differential
adjustment knob to the desired amount of differential.
The thermostat heat anticipator should be set at 2.0A.
LOW VOLTAGE
THERMOSTAT
2
L8124M
G
CHECKOUT
L1
(HOT)
T
T
L1
L2
Put the system into operation and observe each function
through at least one complete cycle. Be sure the control
operates as intended.
L2
1
1K
ZC
1K1
LINE VOLTAGE
CIRCULATOR
W
R
B
C1
C2
LOW LIMIT
LINE VOLTAGE
OIL BURNER
RELAY OR
B
R
HIGH
LIMIT
3
GAS VALVE
B1
B2
POWER SUPPLY. PROVIDE DISCONNECT MEANS
AND OVERLOAD PROTECTION AS REQUIRED.
1
2
CONTROL CASE MUST BE CONNECTED TO EARTH
GROUND. USE GROUNDING SCREW PROVIDED.
M8804
3
B1 IS 1/4 IN. TAB TERMINAL.
Fig. 13. L8124M single zone connections
and internal schematic.
Automation and Control SolutionsAutomation and Control Solutions
Honeywell
Honeywell Limited-Honeywell Limitée
1985 Douglas Drive North
Golden Valley, MN 55422
35 Dynamic Drive
Scarborough, Ontario
M1V 4Z9
95-6571—11 G.R. Rev. 12-01
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