This code indicates that one of the safety interlock switches present in the unit has tripped. There are several interlock switches that could possibly trip and cause this error. The following four switches are installed and are standard equipment in all boilers.
- Flue ECO – Trips if the flue temperature is excessive. This switch has to be manually reset.
- Boiler module thermal fuse – Trips if there is excessive heat on the rear of the heat exchanger.
- Boiler module front temperature switch - Trips if there is excessive heat on the front of the heat exchanger.
- Blocked vent pressure switch (BVPS) – This switch trips if there is excessive pressure in the flue and automatically resets.
The following switches are optional equipment that may be installed on 500 and 850. These devices have indicator lights on them showing of they are tripped.
- High gas pressure switch – This switch trips if there is excessive gas pressure on the outlet side of the gas valve and must be manually reset.
- Low gas pressure switch – This switch trips if there is low gas pressure on the inlet side of the gas valve and must be manually reset.
- UL 353 Low Water Cutoff – This device trips if the water level in the boiler is low and must be manually reset.
- Check to see if the boiler with the F01 code displayed has any of the optional switches installed.
- If so, check to see if the indicator light on any of the devices is showing that they are tripped.
- If an indicator light is illuminated, investigate the source of the error for that particular switch.
- If there are no optional switches or none of the indicator lights is illuminated on the optional switches then use an ohmmeter to test each of the standard switches one at a time. Turn the power off to the boiler and disconnect the switch to be tested from the boiler to determine which one has tripped. When you find the tripped switch investigate the cause of the fault based on the purpose of the switch. NOTE:
The common reasons for the temperature switches to trip are a) low water flow through the boiler, or b) poor heat transfer from the water to the load.
- If no switches are tripped, push RESET on the boiler. If the boiler tries to ignite or ignites and only runs for a short time and the F01 code returns, investigate the flue for blockage.
