I have infloor electric heating installed in our bathroom. The power is supplied by a dedicated 240V/1Ph. circuit that also feeds a couple of baseboard heaters in our bedroom. The infloor heating is controlled by an electronic wall mount thermostat that incorporates GFCI protection. The problem is that the thermostat (GFCI) trips off line whenever the bathroom exhaust fan is switched on or off. The fan is completely isolated from the heating power supply and runs on a separate 120V circuit. What gives? Any ideas?

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    Is it possible the two circuits share a neutral wire? That can cause the GFCI to trip. – littleturtle Jan 25 '15 at 23:39
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    @littleturtle, a 240V heating circuit such as this does not require or use a neutral. – Speedy Petey Jan 26 '15 at 1:43
  • This sounds like an RF interference issue with the GFCI electronics at first blush. How old is the thermostat (and the exhaust fan, for that matter)? – ThreePhaseEel Jan 26 '15 at 23:36

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