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Old 11-20-2012, 12:16 PM   #1
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Heater fan current draw

I've looked everywhere in the info books that came with our 2000 Winnebago Adventurer G37, to try to determine the current draw of the furnace fan.
I just today found out that I need not run the Gen. to turn on the furnace, Duh! While reading another thread it was said that the heater fan on his unit is 12 volts. I went out and checked mine, guess what, mine runs on 12 volts also.
What I'm trying to find out is, just how much draw the fan will have on the 2 - 6 volt house batteries.
Last year at Quartzsite we fired up the Gen about 30 to 45 min. during the night and ran the furnace because the temp inside got uncomfortable.
Now that I know the Gen doesn't need to run just to run the furnace, I'd like to know how many hours we can use the furnace and not run down the batteries.

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Old 11-20-2012, 07:41 PM   #2
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I do not know what the amp hour draw of your fan motor is, but as a general rule with good batteries, you can run the furnace during the night and charge the batteries up the next day. If you are saying you are not hooked up to electricity, then you would need to run your generator to re-charge your batteries. Hope this helps.


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Old 11-20-2012, 07:55 PM   #3
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It will vary by the make, model & btu rating of the furnace, but if you figure 5-7 amps you will be in the right ball park. A 20,000 btu furnace typically draws around 5 amps, while a 32,000 btu model is typically around 7-8 amps. You can easily see how the furnace can draw down a battery overnight if its cold and it runs a lot.
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Old 11-20-2012, 08:25 PM   #4
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So lets say that your battery bank has 200 amp total capacity. You don't want to run them below 50% discharge, preferably you want to keep them at @ 70% capacity, so u have @ 60 amps for the heater fan. (30% x 200 amps = 60 amps available)

If the heater draws 6 amp, and the fan runs 1/2 the time, you could in theory run the heater for 20 hours.

Now the problem is figuring out how often the fan runs relative to time and outside temperature.

I know that in my RV with 25 degree outdoor temps, my system would run @ 10 mins every 30 mins to keep a 70 deg interior temp.

So my 2x12v battery (Group 27 - 85 amps) give me @ 170 total, x .30% discharge, would give me @ 50 amps to drain.

Since my fan is also 6 amps, running 20 minutes per hour, I could in theory run 24 hours. But you generally only have to heat like that at night, so I could in theory go 2 days before recharging.

I hope this helps, IAN...
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Old 11-20-2012, 08:30 PM   #5
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My 30K btu Suburban is rated at 4.5a. I measured it and it draws 3a. The amperage should be on a plate on the furnace.
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Old 11-20-2012, 10:03 PM   #6
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My outfit is in storage but if I remember correctly it is 40,000 BTW and the fan draws 11 AMP. Like it was said before the numbers should be on the furnace nameplate data, or call the Manuf with the model #.
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Old 11-20-2012, 10:29 PM   #7
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The only time I had an issue with running the furnace all night was when a visitor had flipped the compartment light switch on. I woke up about 2 am and heard the fan running really slowly. I had to start the generator and run for an hour. Now I have an LED indicator light on the dash that shows when the compartment light switch has been left on. You should be able to use the furnace through the night if you started with charged batteries.

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Old 11-21-2012, 04:37 AM   #8
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I got around that problem by installing a catalytic heater in the bedroom area. It uses much less propane than the furnace and zero electricity. It won't warm the whole 5er, but it keeps us toasty warm in bed. You need to keep a window cracked, but we open one at the far end so it doesn't interfere with our heating.

Mine is an an Olympian Wave 3, but there other brands and there are also larger Olympians. If you expect to use it at high altitudes, check out the specs. The low oxygen sensors on some brands will turn them off at around 6,000 ft.


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fan, heater

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