Filter
Top Products
19
NOTE: The McDonnell Miller low water cut off incorporates a 10 second delay to prevent nuisance burner cut-off due to rapid
water level fluctuations. The LWCO also has a time delay of 15 seconds which allows additional fill time after water touches the
probe. Red LED indicates a low water condition.
BOILER SEQUENCE OF OPERATION WITH FLOAT LWCO
When the thermostat calls for heat, it energizes the cad cell primary control, bringing on the burner. The burner will operate until
the thermostat is satisfied or the limit setting on the high limit is reached. When the high limit control restores the circuit on a
drop in pressure, the burner will start if the thermostat is still calling for heat. The low water cut off will shut down the burner if the
water level in the boiler drops too low. The control resets and restarts the burner with a call for heat a few seconds after the water
is returned to its normal level.
On burner start, if the cad cell does not see flame within approximately 45 seconds, primary control will lock out on safety and
must be reset before burner can be restarted.
When there is no demand for heat, the operating control will maintain the boiler water temperature at the selected setting for
proper operation of the domestic water heater, if equipped with optional tankless heater.
Fig. 20: Wiring Diagram for Steam Boilers with McDonnell & Miller #67 LWCO,
Beckett AFG Burner and Controls, with or without Tankless Heater
Fig. 19: Wiring Diagram for Steam Boilers with Optional McDonnell & Miller PS-804-120 Probe LWCO,
Beckett AFG Burner and Controls, with or without Tankless Heater
TS-39- -C Rev. O