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31-5000735 Rev. 0
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 NF80US 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 control will go into soft lockout 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 NF80US 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 GE Appliances.
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 5.
Содержание GE NF80US
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