Greenheck MSX (470658) - Manual (Page 31)

31 Modular Supply Make-Up Air Unit
®
Troubleshooting
Electric Heater Does Not Operate (optional)
Supply fan must be on for heater to operate
24 VAC between
terminals W1 and X?
24 VAC between
terminals 22 and 21?
24 VAC between
terminals I and 21?
24 VAC between
terminals T1 and 21?
24 VAC between
terminal A2 on heat relay (RH)
and X?
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Heat Switch (S4) Off
(Turn Heat Switch (S4) On)
Heat Switch not wired
(Wire Heat Switch (S4))
Main Transformer (TR2) defective
(Replace transformer)
Heat Relay (RH) is not energized
(Check for loose connections). (Repair or replace Heat Relay (RH))
(Optional) Inlet Air Sensor (TS4) holding
(Adjust (TS4) setting. Reference Blower Start-Up Step #6)
At this time the heater should be energized.
(The heating elements will not be on if the leaving air
temperature is above its set point on the Remote Adjuster (RA))
Pressure Differential Switch (PDS) open
(Check on cause of control loss)
Automatic and/or Manual Reset Cutouts (A and M) tripped
(Reset/Replace Automatic and/or Manual Reset Cutouts (A and M))
(Check on cause of control loss)