THP-400A, THP-500A
and
THP-550
Installation and Service Manual
Control Adjustments
Ignition
1. Clean and dry electrodes.
2. Check porcelain insulators for cracks or
moisture. Replace if necessary.
3. Adjust as shown.
4. Secure ignition leads.
5. Replace spark electrode if defective.
Air-Flow Control
Setting control
1. Turn ON/OFF switch to ON.
2. With unit operating at high-fire, turn adjust-
ing screw clockwise until burner goes OFF.
3. Turn adjusting screw counter-clockwise
1/2 turn at a time until burner re-ignites.
To check setting
1. Set remote thermostat on highest setting.
2. Observe that when operating on high-fire,
the switch does not break contact.
Ignition Assembly
Airflow Control
