Lennox SLP99UH070XV36B - J- Proper Ground and Voltage

Page 68
J- Proper Ground and Voltage
A poorly grounded furnace can contribute to premature igni
tor 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 53. A wide varia
tion 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 1, 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 53. This voltage should be in the range
of 97 to 132 Vac
TABLE 33
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
FIGURE 53
+
W915
W951
W914
EAC
HUM
7-SEGMENT
DIAGNOSTIC LED
+
W915
W951
W914
EAC
HUM
7-SEGMENT
DIAGNOSTIC LED