Furnace Fan Voltage

Does anyone know whether the furnace fan is 12 volt or 120 volt? Also..if 12 volt, how long will it run on a full battery charge?

The furnace runs on 12 volts. It's hard to tell how long a battery will last. Several factors come into play. Battery size in amp hours, other 12 volt usage like lights, exhaust fans, water pump etc. The furnace draws a lot of amps so I wouldn't expect it to last more than a day depending on how often the furnace runs.

Depending on the size furnace (BTU) the fan can draw as much as 8 amps during operation. The colder the weather, the more the furnace will have to operate, more amps will be needed, more amps requires more battery power. It is impossible to calculate with all the variables.

Forrest

I agree too many variables, but you can get a ball-park number by looking at your battery(s) and taking the total reserve amp hours and dividing by 8 amps. This number assumes the furnace is running all the time (100% duty cycle- worst case scenerio). If you assume it will only run 1/2 the time ( 50% duty cycle), then mutiply the number by 2 etc ..etc.

From practical experience, my batteries (two 6 volt in series) will run the furnace for 3-4 days in below freezing temps ( at night 30 % , Day 15% duty cycle) before needing a charge.

Many thanks. Actually I was thinking of only overnight..as we'll be traveling to Florida next March from Waterloo, Ont..and would likely need to use a Wal Mart or Flying J on the first night..as most campgrounds in MI and OH are closed that early. I have two, Group 27, 12 volt Deep Cycles which would be about 100 AH each so the 8 amps from the furnace fan would burn up some 64 amps in an eight hour period..and considering I should drain the batteries to only about 50%..I should be OK if I don't run too many lights, etc for too long. Anyone see anything wrong with my math?

Nothing wrong with your math. That is if you are assuming that the fan will run, non-stop, for the 8hours. That seems unlikely. I think there would be a much less drain on the batteries.
Fred

Thanks for the clarification. You are right! The fan would only run 50 to 65% of the time, depending on temperature. The good news is, I'm certain we can easily get a night out of the batteries.