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LOW VOLTAGE
THERMOSTAT
ZONE 1
T
Z
TV
1K
R
W
LOW LIMIT/
CIRCULATOR
1K2
HIGH
LIMIT
Fig. 11. L8124L multizone system with circulator connections and internal schematic.
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.
WARNING
Explosion Hazard.
Can cause serious injury, death or equipment
damage.
Use this product only in systems with a pressure
relief valve.
Low Limit and Circulator Controllers
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.
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).
L1
(HOT)
L8124L
2
G
1
2
1K1
B
ZR
ZC
B
3
R
B1
B2
C2
C1
LINE VOLTAGE
CIRCULATOR
ZONE 1
L8124A,C,E,L AND M AQUASTAT® RELAYS
1
TO ADDITIONAL
R845A RELAYS
L2
FOR OTHER ZONES
LINE VOLTAGE
OIL BURNER
RELAY OR
GAS VALVE
1
POWER SUPPLY. PROVIDE DISCONNECT MEANS AND
OVERLOAD PROTECTION AS REQUIRED.
2
CONTROL CASE MUST BE CONNECTED TO EARTH
GROUND. USE GROUNDING SCREW PROVIDED.
3
B1 IS 1/4 IN. TAB TERMINAL.
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).
HIGH LIMIT
SETTING
LOW LIMIT
AND
CIRCULATOR
SETTING
1
WHEN WATER REACHES PROPER TEMPERATURE, THE BURNER
SHUTS OFF OR THE CIRCULATOR PUMP STARTS (WHEN CALLING
FOR HEAT).
Fig. 12. Relationship of setpoints and differential.
7
R845A RELAY ZONE 2
6
5
3
4
1
2
ZONE 2
LOW VOLTAGE
THERMOSTAT
SWITCH BREAKS ON
TEMPERATURE RISE.
BURNER TURNS OFF.
CIRCULATOR OPERATES
ON A CALL FOR HEAT.
SWITCH MAKES ON
TEMPERATURE FALL.
BURNER OPERATES ON A
CALL FOR HEAT.
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
SWITCH MAKES R-W
AND BREAKS R-B ON
TEMPERATURE RISE.
SWITCH MAKES R-B AND
BREAKS R-W ON
TEMPERATURE FALL.
BURNER IS ON TO
MAINTAIN MINIMUM
WATER TEMPERATURE.
CIRCULATOR IS OFF.
ZONE 2
CIRCULATOR
M8829
1
M1523
95-6571—11
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