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26
Model VSU Make-Up Air
®
Heater Does Not Operate (Pilot Ignition)
Does not attempt to light (No visible spark)
Troubleshooting
24 VAC between
terminals W1 and X?
Heat switch (S4) off.
Turn heat switch (S4) on.
Heat switch not wired.
Wire heat switch (S4).
115 VAC between
terminals 102 and 101?
Primary fuses blown.
Replace fuses.
Main transformer (TR4) defective.
Replace transformer.
115 VAC between
terminals 106 and 101?
(Optional) high/low gas pressure switch(es)
(PS3 and PS4) tripped.
Correct gas pressure and reset.
Reference: Start-Up - Direct Gas, Check the Pilot Gas Pressure, pg. 15
115 VAC between
terminals 104 and 101?
High limit (HLC1) tripped.
Reset or replace high limit (HLC1).
Check on cause of control loss.
Continuity between
terminals 107 and 108?
115 VAC between
terminals 103 and 101?
(Optional) inlet air sensor (TS4) holding.
Adjust TS4 setting.
Reference: Start-Up - Blower, Set-Up Optional Components, pg. 15
Heat relay (RH) defective.
Replace heat relay (RH).
No
No
No
No
No
No
Yes
Yes
Yes
Yes
Yes
Airflow switch (PS2) holding for proper airflow.
Correct airflow across burner.
Reference: Start-Up - Direct Gas,
Check the Optional High and Low Gas Pressure Switches, pg. 15
Yes
The power light on the flame safeguard should
blink approximately every 5 seconds as it
performs a self-diagnostics check.
At this time the heater should attempt to light.
The pilot light on the flame safeguard should illuminate.