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BTR TANK TYPE HEATERS
SERVICE HANDBOOK
A.O. Smith Water Products Service Handbook
Irving, Texas ©2000 Training Department
16
BTR SEQUENCE OF OPERATION
1. Thermostat calls for heat
2. Flue dam
p
er o
p
ens
3. Intermittent
I
g
nition Control
5. Main gas valve opens
7. Thermostat satisfies
4. Pilot gas opens,
Pilot sparks and
flame
p
roves
6. Main burner i
g
nites
8. Main and pilot
burners "OFF"
SEQUENCE OF OPERATION
To understand BTR tank type water heaters, an examination of their sequence of
operation is necessary.
When the thermostat calls for heat, the relay in the draft hood assembly activates, de-
energizing the flue damper motor. The damper opens and power flows to the IID
(Intermittent Ignition Device). This activates the IID module to open the pilot valve
and begin sparking at the pilot burner assembly. Once the pilot flame is established
and confirmed back to the IID, the sparking is stopped and the main gas valve is
opened, allowing gas flow to the main burner. When the thermostat satisfie’s, main
and pilot gas is shut off.
9. Flue dam
p
er closes