Bradford White EF60T125 Service Manual page 14

Serial Numbers including and AFTER GB13006174 and ALL EFR models
Thermostat calls for heat.
1
Combustion blower starts.
2
Blower pre-purge period of 30 seconds.
3
Trial for Ignition. (5 seconds, 3 trials).
4
Flame establishing period (3 seconds), gas valve opens, sparks from spark rod to burner surface to ignite
the gas.
Burner on, flame proving period (2 seconds). Requires a minimum of 0.8 microamp through flame sense
rod to prove flame.
If either blocked vent safety switch contacts (normally closed) or blocked vent pressure switch contacts
(normally closed) are open, then the ignition sequence will not start and an error code 29 (Pressure switch
failed to close or open) will be shown on the display.
5 Steady State Operation: Burner continues to operate until:
Thermostat circuit opens, gas valve closes, blower continues to operate for 30 second post-purge period.
If the normally closed blocked vent pressure switch opens, the gas valve closes, the blower continues to
operate indefinitely and error code 29 will be displayed after a couple minutes with "Service Needed",
"Pressure Switch".
If the normally closed 1
purges, then shuts off with error code 26 displayed in a lockout condition.
6
Thermostat satisfied
7
Gas valve closes, burner extinguished.
8
Blower post purge for 30 seconds.
14
(Excluding EF100T399 model series)
st
Pass Collector vent safety switch opens, the gas valve closes, the blower post-
For models with Honeywell Integrated Control
System w/ Direct Spark Ignition
14