Operating instructions

1. Thermostat calls for heat completing circuit between terminals T and T on L8124C aquastat controller energizing the 1K relay coil.
2. With 1K relay coil energized, contacts 1K1 and 1K2 are closed. Terminal B1 is energized providing power to R4184 oil burner primary
control. This in turn powers ignition coil and burner motor.
3. With R4184 primary control energized, burner operation starts and burner remains running as long as cad cell senses flame. In the event
of a flame failure or if flame is not fully proven within 45 sec of initial start-up, the R4184 primary control locks out and opens burner
circuit. This requires a manual start-up of burner.
4. As long as flame is proven through cad cell relay, burner remains on until circuit is interrupted by boiler water temperature reaching high
limit setting (opening high limit contacts BR), or thermostat is satisfied breaking T-T circuit.
5. Circulator pump is powered through terminal C1 and runs when boiler water temperature is above low limit setting.
6. If boiler water temperature reaches high limit setting, high limit contacts BR open de-energizing terminal B1 and shutting off burner.
Circulator pump remains running as long as thermostat calls for heat.
7. If boiler water temperature falls 10° below high limit setting, contacts BR close energizing burner.
8. Thermostat is satisfied terminating call for heat. Relay coil 1K is de-energized opening 1K1 and 1K2 contacts. Both burner and circulator
pump cease operation.
NOTE: The high limit setting must be set a minimum of 20° higher than low limit setting.
B. Boiler Without Tankless Coil
AQUASTAT HIGH LIMIT CONTROLLER
The aquastat control’s high limit contacts open and turn off the burner when the boiler water temperature reaches the control’s high limit set point.
The high limit contracts automatically reset after the boiler water temperature drops past the set point by 10° F, which is a fixed differential.
When the thermostat controls call for domestic space heating, the sequence of operation for the burner and circulator is as follows:
1. Thermostat calls for heat, completing the circuit between terminals T and T on the aquastat controller, energizing the 1K relay coil.
2. With the 1K relay coil energized, contacts 1K1 and 1K2 are closed. Terminals C1 and C2 are enegerized providing power to the circulator.
Terminal B1 is energized, providing power to the oil burner primary control. This in turn powers the ignition coil and burner motor.
3. With the primary control energized, the burner operation starts and remains running as long as the cad cell senses flame. In the event of
flame failure or the flame is not fully proven within the trial for ignition period, the primary control will lockout and open the burner circuit.
This will require a manual startup of the burner.
4. As long as flame is proven through the cad cell relay, the burner will remain on unit the circuit is interrupted by the boiler water temperature
reaching the aquastat’s high limit setting (opening high limits contracts BR), or the thermostat is satisfied breaking the T—T circuit.
5. If the boiler water temperature reaches the aquastat’s high limit setting, the high limit contact BR is de-energized turning the burner off.
However, the circulator pump will continue to run, as long as, the thermostat calls for heat.
6. After the high limit contact BR is de-energized, the boiler water temperature must fall 10° F below the aquastat’s high limit setting for the
high limit contacts BR to close and energize the burner.
7. When the thermostat is satisfied, the call for domestic space heating is ended. Relay coil 1K is de-energized, opening 1K1 and 1K2 contacts.
Both the burner and circulator pump operation stop.
PROCEDURE 8—SERVICE HINTS
Avoid inconvenience and service calls by checking these points before calling for service.
HAVE YOUR SERVICE TECHNICIAN CHECK ANY PROBLEM YOU ARE UNABLE TO CORRECT.
Fig. 19—Relationship of Set Points and Differential
A95611
10 F (5.6 C)
DIFF
110 F (43 C)
240 F (116 C)
25 F (13.9 C)
DIFF
10 F (5.6 C)
DIFF
SWITCH BREAKS ON
RISE, TURNS BURNER
OFF. CIRCULATOR
OPERATES ON CALL
FOR HEAT.
SWITCH MAKES ON
FALL. BURNER
OPERATES ON
CALL FOR HEAT.
SWITCH MAKES R-B
ON FALL, BREAKS
R-W. BURNER ON,
CIRCULATOR OFF.
SWITCH MAKES R-W,
BREAKS R-B ON RISE
(25 F [13.9 C]
DIFFERENTIAL).
SWITCH MAKES R-W,
BREAKS R-B ON RISE
(10 F [5.6 C]
DIFFERENTIAL).
HI LIMIT
SETTING
LOW LIMIT
AND
CIRCULATOR
SETTING
—19—