I've noticed these letters several times written on the circuit breaker panel door. Does someone know what F.A.U. stands for in this context?

2 Answers 2


FAU is likely a "forced air unit" (e.g. a heater or air conditioner). If it's two breaker switches tied together, that's a 240V volt circuit (if there's no tie between the two switches, that's an immediate hazard and must be fixed).

  • Thanks. It is written twice, so as to label a double breaker slot. Would that imply the unit is powered for 220 volts?
    – ojait
    Aug 23, 2015 at 2:03
  • If the breaker handles are tied together so they both operate simultaneously, then yes, it would be a 220/240V circuit. Aug 23, 2015 at 3:11
  • Thanks. So if my furnace uses natural gas as a fuel to heat would that mean that the 220 line voltage is for the blower motor?
    – ojait
    Aug 24, 2015 at 0:27

Yes, FAU is "forced air unit", but this term is not used everywhere. Around here you'll many times see AH, or A/H for "air handler", which is what we would call the inside blower unit of a split air conditioning system.

  • Thanks. I would think they would want to be more specific so as to identify what the breaker is protecting. (Air Con. or Attic Furnace, etc.). FAU is to general.
    – ojait
    Aug 24, 2015 at 0:31

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