Lennox EL297UH045XV36B Unit Information page 82

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 54. 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
TABLE 30. If the readings exceed the maximum
shown in table 1, make repairs before operating the
furnace.
NOTE - FIGURE 54 is a typical ignition illustration.
Use as reference.
CHECK VOLTAGE BETWEEN LINE NEUTRAL
AND LOW VOLTAGE "C" TERMINAL
W1 W2 G Y2 Y1 C C R DH L O DS
2 - In addition, measure the AC voltage from Line Hot
to Line Neutral (spade terminals) on the integrated
control. See FIGURE 54. This voltage should be in
the range of 97 to 132 Vac.
Furnace Status
Power On Furnace Idle
CAI / Ignitor Energized
Indoor Blower Energized
CHECK VOLTAGE BETWEEN LINE HOT
AND LINE NEUTRAL
FIGURE 54
Page 82
TABLE 30
Measurement VAC
Expected
0.3
0.75
Less than 2
W1 W2 G Y2 Y1 C C R DH L O DS
Maximum
2
5
10