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UHA STANDARD UNIT HEATER INSTALLATION OPERATION AND SERVICE MANUAL
28 of 51
11.2 Begin Start-Up
11.2.1 Before Operating the Heater
To ensure that all the controls are in safe working
order, operate the heater for the first time with the
isolating gas valve turned off and power supply
turned on.
1. Turn off the isolating gas valve.
2. Turn up the thermostat above room
temperature. The automatic ignition
sequence will now begin as described
on Page 28, Figure 13.
There will be no ignition of the burner and lockout
will occur, which proves the controls are operating
correctly.
Figure 13: 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 Blower
Pressure
Switch
P
C
NO
NC
30 Seconds Purge*
*Purge time begins at pressure switch change over.
Axial Fan
30 Seconds Delay 90 Seconds Delay
30 Seconds 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.