GFIs? Also, my furnace heating registers have toggle switches for fan speed - high, off, low. I have two fan switches in the living room (zone 1), one fan switch in the bathroom (zone 2), and one fan switch in the bedroom (zone 3). I don't know about the basement (zone 4) whether it has a fan switch or not - never looked for one. I would guess the furnace fans are 12v though. The GFIs are all on 110v circuits?