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H- Proper Ground and Voltage
A poorly grounded furnace can contribute to poor flame
sense signal. Use the following procedure to check for
ground and voltage to the integrated control.
1 -
Measure the AC voltage between Line Neutral
(spade terminals) and “C” terminal (low voltage
terminal block) on the integrated control. See figure
21. A wide variation in the voltage between Line
Neutral and “C” as a function of load indicates a
poor or partial ground. Compare the readings to the
table below. If the readings exceed the maximum
shown in table 14, make repairs before operating
the furnace.
2 - In addition, measure the AC voltage from Line Hot
to Line Neutral (spade terminals) on the integrated
control. See figure 22. This voltage should be in the
range of 97 to 132 Vac.
CHECK VOLTAGE BETWEEN LINE NEUTRAL
AND LOW VOLTAGE “C” TERMINAL
FIGURE 21
TABLE 14
Furnace Status
Measurement VAC
Expected
Maximum
Power on Furnace Idle
0.3
2
CAI/Ignitor Energized
0.75
5
Indoor Blower Energized
Less than 2
10
CHECK VOLTAGE BETWEEN LINE HOT
AND LINE NEUTRAL
FIGURE 22
