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UHA UNIT HEATER INSTALLATION OPERATION AND SERVICE MANUAL
20
Figure 10: Automatic Burner Control Sequence
Burner Sequence for Ignition Control
Flame Signal
Start Gas Valve
Ignition Spark
Thermostat 24 V
SHUT DOWN
RUN
START
ts = 10 seconds
Signals Output By Control
Required Incoming Signals
Flue Fan
Pressure
Switch
P
C
NO
NC
30 Sec. Purge*
*Purge time begins at pressure switch change over.
Axial Fan
30 Sec. Delay 90 Sec. Delay
30 Sec. Post Purge
If at any stage the flame fails, the control will retry
for ignition. The control has four trials for ignition
before a one hour lockout.
Figure 11: Gas Valve for Models UHA(S) 150 - 400
Description Part Number
Gas Valve 150 - 225 NG 90032505
Gas Valve 150 - 225 LP 90032506
Gas Valve 250 - 400 NG 90032520
Gas Valve 250 - 400 LP 90032521
½PSI IN
C
ON
OFF
Regulator
Outlet
Pressure
Gas Inlet
Inlet Pressure
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