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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 read
ings exceed the maximum shown in table 13, make re
pairs before operating the furnace.
2 - In addition, measure the AC voltage from Line Hot to
Line Neutral (spade terminals) on the integrated con
trol. See figure 22. This voltage should be in the range
of 97 to 132 Vac
TABLE 13
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 NEU
TRAL AND LOW VOLTAGE “C” TERMINAL
FIGURE 21
CHECK VOLTAGE BETWEEN LINE HOT
AND LINE NEUTRAL
FIGURE 22
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