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SEQUENCE OF OPERATION
BOILER LESS TANKLESS COIL:
Aquastat high limit controller:
The aquastat control's high limit contacts open and turn offthe burner when the boiler water temperature reaches
the control's high limit set point. The high limit contacts automatically reset after the boiler water temperature
drops past the set point by 10°F, which is a fixed differential.
INTERNAL WIRING FOR HONEYWELL AOUASTAT L8148A
-- UNE "¢OI.T_E
-- CLa_ I,
IKI
JUMPE_
IK2
)
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 circuit between terminals T & 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 energized
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 until the circuit is interrupted
by the boiler water temperature reaching the aquastat's high limit setting (opening high limit contacts 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 1KI and 1K2 contacts. Both the burner and circulator pump operation stop.
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