High Limit Exceeded.
- Check circulation pump operation
- Assure that there is adequate flow through the boiler by accessing the status menu and assuring that there is less than a 50°F rise from the return thermister to the supply thermister.
- Check thermister reading on supply thermister. Replace switch if faulty.
- If this is a new installation, disconnect the two light grey wires from the zone control, and twist the wires together. Depress the S4 reset button. If the fault clears, the problem is outside the boiler
- If this is an existing installation with glycol in it, check the condition of the water pressure switch. It may be necessary to jump out the water pressure switch (temporarily only, as a trouble shooting aid) The 24 VAC signal, may have grounded through the glycol if the water pressure switch is leaking.
