Weil-McLain CGA25SPDN manual How it works, Other boiler components

GOLD CGa Gas-Fired Water Boiler — Boiler Manual

How it works . . .

xControl module

The control module (used on SPARKIGNITEDIPILOTLBOILERS) responds to signals from the room thermostat and boiler limit circuit to operate the boiler circulator, pilot burner, gas valve and vent damper. When room thermostat calls for heat, the control module starts the system circulator and activates the vent damper (causing it to drive open).

When the vent damper has opened completely, the control module opens the pilot valve and activates pilot igni- tion spark.

The control module allows up to 15 seconds to establish pilot flame. If flame is not sensed within 15 seconds, the control module will turn off the gas valve, flash the Flame light, and immediately start a new cycle. This will con- tinue indefinitely until pilot flame is established or power is interrupted. Once pilot flame is proven, the control module opens the gas valve to allow main burner flame.

When the room thermostat is satisfied, the control module turns off the gas valve and deactivates the vent damper (causing it to close).

The control module indicator lights show normal sequence when the lights are on steady. When a problem oc- curs, the control module flashes combinations of lights to indicate the most likely reason for the problem. See page 52 for details.

3TANDING PILOTLBOILERS (controls not shown) use the pilot thermocouple to prove flame. If the thermocouple is satisfied, the gas valve and vent damper will open on a call for heat and close afterwards.

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Transformer

The control transformer reduces line voltage to 24 volts for the gas valve and limit circuit.

Draft hood

The draft hood provides a minimum draft for the boiler, assuring adequate air for combustion if installed in ac- cordance with manual and not modified in any way.

Spill switch

The spill switch will shut down the boiler (requiring manual reset of the switch reset button) if the vent system becomes blocked.

Water temperature limit switch

The water temperature limit switch turns off the gas valve if the temperature in the boiler goes above its setting. (The circulator will continue to run as long as there is a call for heat.)

Boiler circulator

The boiler circulator circulates water through the external (system) piping. The circulator is shipped loose, and can be mounted on either the boiler supply or return piping. The factory-installed circulator wiring harness provides ample length for either location. NOTE — The control module provides a pump exercising routine. If the boiler is not operated for 30 days, the control module will power the circulator for 30 seconds, then turn off.

Vent damper

The vent damper closes during off cycles to reduce heat loss from the house up the vent.

Other boiler components:

a	supply to system	f	pressure/temperature gauge	k	pilot burner, typical
b	return from system	g	relief valve	l	stainless steel burners
c	flue outlet	h	air vent connection	m cast iron boiler sections
d	burner manifold	i	flame rollout switch	n	flue collector
e	gas valve	j	burner orifice	o	junction box

2 Part Number 550-101-009/0107