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TH115 Floor Heating Thermostat Keeps Tripping
The GFCI in thermostats are Class A, which means below 5mA trip levels. This is a very sensitive trip level required by UL. There are several instances that could cause “spurious tripping” or “nuisance tripping” due to electrical noise on the circuit.
Common instances are:
GFCI on breaker and on thermostat: You should aim to only have one GFCI on the circuit. Ideally keep the one on the breaker and replace your GFCI thermostat with a non-GFCI unit.
Dedicated Circuit: If the power supply is shared with other devices, and especially if these use a GFCI, there may be issues on the line causing the GFCI to trip. In those instances, aim to isolate your floor heating system with a dedicated circuit breaker.
240V Nuisance Tripping: On 240V circuits, it is common for the breakers to be merged in a single physical area of the electrical panel. And in the case of GFCI breakers, all the neutral wires will be connected together to the same neutral bus bar. To resolve nuisance tripping issue, you can relocate your 240V breaker on the panel in a more isolated location, or you can tie the neutral wire (for GFCI breakers) to the other neutral bus bar (alone). Remember that outside of bathrooms, GFCIs are not required for floor heating systems.