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I- Proper Ground and Voltage
A poorly grounded furnace can contribute to premature
ignitor failure. 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 51. 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 34, 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 51. This voltage should be in
the range of 97 to 132 Vac.
TABLE 34
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 NEUTRAL
AND LOW VOLTAGE “C” TERMINAL
CHECK VOLTAGE BETWEEN LINE HOT
AND LINE NEUTRAL
+
W915
W951
W914
EAC
HUM
7-SEGMENT
DIAGNOSTIC LED
+
W915
W951
W914
EAC
HUM
7-SEGMENT
DIAGNOSTIC LED
FIGURE 51
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