Furnace Power Consumption


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Old 05-07-14, 09:39 AM
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Furnace Power Consumption

Gas Furnace is wired on a 15A breaker with about 75' of #14.

I was surprised to see that inside the unit I was only measuring about 3.5A with the blower running. How much more (if much at all) can be expected to be drawing on that circuit?

Figuring there is a low voltage tranny that controls the circuit board (assuming gas valve is low voltage too) I would assume its not very much.

I also assume the starting amperage of the blower is much closer to that 15A threshold.
 
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Old 05-07-14, 10:33 AM
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The furnace should be a dedicated circuit. There should be no additional draw.
 
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Old 05-07-14, 11:22 AM
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The furnace should be a dedicated circuit. There should be no additional draw.
well of course. I was referring to the furnace's additional power draw.
 
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Old 05-07-14, 02:45 PM
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During the ignition cycle, using a hot surface ignitor, my furnace draws around 8 to 10 amperes. Once lit, the furnace draws about 3-4 amperes when operating on the first stage. Second stage may be another 1/2 to 2 amperes due mostly to the increased speed of the circulation blower. I DO have an ECM variable speed blower so that may make a small difference.

The above figures are from memory, it has been a few years since I checked the amperage draw. I DO presently have my Kill-A-Watt meter connected in case you are interested in the average power usage of my furnace over the last few weeks.
 
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Old 05-07-14, 10:10 PM
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My furnace is oil fired and draws about 7A with the oil burner unit as well as both circulating pumps on. It runs fine on a 1500W inverter and deep cycle battery. I don't know much about gas furnaces, but I know the oil furnaces ignite the oil with a few KV arc. That transformer only uses a few watts.
 
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Old 05-08-14, 08:03 AM
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I forgot about the HSI... its like a mini toaster. That is the highest draw on the furnace circuit then... not the blower.... unless there is significant inrush current there.
 
 

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