These are high quality 24V Magnecraft SPST relays rated for 15A at 120VAC or 12A at 240/277VAC.
I've told people about FanHandler already. It is working so well. Our second floor is now only 1 degree different from the first floor compared to 7 or 8 degrees last year. We have also only burned 1/4 tank of oil so far compared to more than half a tank by this time last year. What a great investment!