Sequence Of Operation - Williamson-Thermoflo GWS-090E Manual

9 Sequence of operation

Follow all procedures given in this manual and "Op-
erating Instructions", Section 10, page 19 and on the
inside of the boiler jacket panel, when operating the
boiler. Failure to do so could result in severe personal
injury, death or substantial property damage.
1. Raise room thermostat to call for heat.
2. Inducer and circulator energize. After pressure switch proves
proper airflow, control module initiates 10-second prepurge.
3. Control module sparks the pilot and opens pilot valve in main
gas valve.
a. If pilot does not light within 15 seconds, pilot valve is closed and
spark generator is turned off. Control module initiates a 15-second
postpurge, then starts a new cycle.
b. If pilot does light and control module senses flame current, spark
generator is turned off and main valve opens.
4. The GWS-090E timer relay delays high fire for the first 60
seconds of main flame.
Figure 12 GWS-090E control module sequence of operation (based on indicator light status)
Part Number 550-110-737/1108
GWS-090E Gas-Fired Water Boiler – Boiler Manual
5. During main burner operation:
a. Control module monitors pilot flame current. If signal is lost, main
valve closes, spark generator activates and sequence returns to
step 4.
b. If power is interrupted, control system shuts off pilot and main
gas valves and restarts at step 1 when power is restored.
6. In the event the limit control shuts down the boiler — The
control module closes the gas valve, but keeps the inducer
operating for 15-second postpurge.
— The circulator continues to operate.
7. Lower room thermostat setting to stop call for heat. Thermostat
is satisfied — Pilot and main gas valves are closed — Inducer
operates for 15-second postpurge — Circulator is shut off.
8. Boiler is now in the off cycle.
9. Repeat steps 1 through 6 several times to verify operation.
10. Return the thermostat to normal setting.
11. Set thermostat heat anticipator setting per wiring diagram,
page 18.
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