How to Fix / Troubleshooting

Danger: Cooling outputs may switch mains voltage. Isolate power before working on wiring.

Step 1 – Verify system type:
- In installer menu, ensure system type is set to Heat + Cool for reversible heat pump systems.
Step 2 – Check cooling output wiring:
- Confirm that the thermostat’s cooling or reversing valve terminals are wired to the correct input on the heat pump or boiler.
- Tighten all connections.
Step 3 – Test cooling call:
- Set thermostat to cooling mode and lower setpoint.
- Listen for relay click and check if the heat pump responds.
Step 4 – Check polarity (if required):
- Some systems require O/B type control (energize in heat or cool).
- Adjust thermostat setting accordingly.
Step 5 – Replace thermostat if output is dead:
- If the cooling relay does not operate despite correct configuration, the output stage may be faulty.
- Replace the Protherm smart thermostat.

E2 error and thermostat cannot control cooling mode on systems with reversible heat pumps.

Possible Causes