Modulation - Greenheck IG Installation, Operation And Maintenance Manual

Troubleshooting
4:1 Modulating Furnace Will Not Light
24 VAC across R and X?
Yes
24 VAC across W1 and X?
Yes
24 VAC across 22 and 21?
Yes
N.O. contact on
heat relay (RH) closed?
Yes
DT1 displayed
on furnace controller (SC1)?
No
OT1 displayed
on furnace controller (SC1)?
No
Blank screen
on furnace controller (SC1)?
No
24 VAC across
terminals S and T?
Yes
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Model IG / IGX Make-Up Air
No
Main disconnect (DS1) open or defective
No
Heat switch (S4) open or not wired
No
No
Check for loose connections. Repair or replace heat relay (RH)
Yes
Discharge air sensor (TS2) not wired or defective
Wire or replace discharge air sensor (TS2)
Yes
Outdoor air sensor (TS1) not wired or defective
Wire or replace outdoor temperature sensor (TS1)
Yes
Furnace controller (SC1) defective or not powered
Replace or wire furnace controller (SC1)
No
Discharge temperature was above high limit control (HLC1)
Adjust inlet air sensor setting (refer to 4:1 Modulation Start-Up section)
Furnace controller (SC1) defective
Close, repair or replace
Main transformer (TR1) fault
Replace main transformer
Close or replace heat switch (S4)
Heat transformer (TR2) fault
Replace heating transformer
Heat relay (RH) is not energized
Wait for high limit to cool and reset
Inlet air sensor contact open
Replace furnace controller (SC1)
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