508096-01
Issue 2037
Page 14 of 34
A microamp DC meter is needed to check the flame signal
on the integrated control.
Flame (microamp) signal is an electrical current which
passes from the integrated control to the sensor during
unit operation. Current passes from the sensor through the
flame to ground to complete a safety circuit.
Primary Limit Control (Figure 7)
The primary limit on A80UH1E / 80G1UHE units is located
in the heating vestibule panel under the combustion air
inducer. See Figure 7. When excess heat is sensed in
the heat exchanger, the limit will open. If the limit is open,
the integrated control energizes the supply air blower
and closes the gas valve. The limit automatically resets
when unit temperature returns to normal. The switch must
reset within three minutes or SureLight
®
control will go
into Watchguard for one hour. The switch is factory set
and cannot be adjusted. The switch may have a different
setpoint for each unit model number.
Figure 7. Primary Limit Under Combustion Air Inducer
Primary
Limit
Gas Valve (Figure 6)
The A95UH1E / 95G1UHE uses an internally redundant
valve to assure safety shut-off. If the gas valve must be
replaced, the same type valve must be used.
24VAC terminals and valve switch are located on the
valve. All terminals on the gas valve are connected to wires
from the integrated control. 24V applied to the terminals
energizes the valve.
Inlet and outlet pressure taps are located on the valve. A
regulator adjustment screw is located on the valve.
LPG changeover kits are available from Allied. Kits include
burner orifices and a gas valve regulator spring.
To Measure Flame Signal - Integrated Control:
Use a digital readout meter capable of reading DC
microamps. See Figure 8 for flame signal check.
1.
Set the meter to the DC amps scale.
2.
Turn off supply voltage to control.
3.
Remove sensor wire from integrated control.
4.
Connect (-) lead to flame sensor wire.
5.
Connect (+) lead to Terminal FS on integrated control.
6.
Turn supply voltage on and close thermostat contacts
to cycle system.
7.
When main burners are in operation for two minutes,
take reading.
Flame Signal in Microamps
Normal
Low
Drop Out
≥ 1.5
0.5 - 1.4
≤ 0.4
Table 6.
