Lennox EL180UHE Series Manual page 23

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
Power On Furnace Idle
CAI / Ignitor Energized
Indoor Blower Energized
CHECK VOLTAGE BETWEEN LINE NEU­
TRAL AND LOW VOLTAGE "C" TERMINAL
FIGURE 21
Measurement VAC
Expected Maximum
0.3 2
0.75 5
Less than 2 10
Page 23
CHECK VOLTAGE BETWEEN LINE HOT
AND LINE NEUTRAL
FIGURE 22