Lennox COWB2

31
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 ame. In the event of ame
failure or the ame 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 ame 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 satised breaking the TT 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.
When the thermostat is satised, 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.
seQUeNCe OF OperaTiONs
BOILER LESS TANKLESS COIL:
Aguastat 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 contacts automatically reset after
the boiler water temperature drops past the set point by 10°F, which is a xed differential.
iNTerNal WiriNg FOr HONeYWell aQUasTaT l8148a