# What size inverter needed to power a 20" box fan?



## Jan Sears

We have a 640 sq. ft. cabin in the woods & the only power we have is a 700 Watt inverter. The inverter is hooked up to a deep cycle battery which powers 2 lights. We now find that we need to have a fan up in the loft so that we can keep the downstairs warm. We heat with an old wood cookstove, which is our only heat source. It was suggested to us that if we had a fan in the loft to circulate the hot air back down stairs it might help in this cold weather -30C. Can anyone tell me how many Watts I would need to power a 20" box fan? (Our 700 Watt inverter won't cut it). We want to keep to using an inverter & deep cycle batteries. All help greatly appreciated.


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## Jim-mi

Look on the fan for its power requirements. Should be in *watts*

Chances are good that your present inverter just will not handle the surge (inrush) currant needed to start the fan.

Nobody here, can tell you "how much" untill the the fan power requirements are known.
Even then its better to buy an even bigger unit so as to have a good 'fudge factor' . . . you don't want to be running an inverter right up at its limits . . .heat=short life.
Be aware that running that fan constantly will suck your batterys down in a hurry.


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## fordson major

jan,why not just get a 12 volt electric fan from a car or truck?


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## joseph97297

My brother put together a fan/radiator combo from an older truck and just piped hot water that he got from using his heater into it and had the fan cut on and off, did a decent job for his little hunting cabin and requirements were low. 

This year he even upgraded to PVC versus rubber....makes a difference, or so he says.


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## greg273

Jan Sears said:


> We have a 640 sq. ft. cabin in the woods & the only power we have is a 700 Watt inverter. The inverter is hooked up to a deep cycle battery which powers 2 lights. We now find that we need to have a fan up in the loft so that we can keep the downstairs warm. We heat with an old wood cookstove, which is our only heat source. It was suggested to us that if we had a fan in the loft to circulate the hot air back down stairs it might help in this cold weather -30C. Can anyone tell me how many Watts I would need to power a 20" box fan? (Our 700 Watt inverter won't cut it). We want to keep to using an inverter & deep cycle batteries. All help greatly appreciated.



Yeah, it should say somewhere on the motor what the amperage draw is. Just be aware that, as jim-mi just mentioned, all induction motors have a surge draw when they first start, typically twice their normal amperage. Most inverters should be able to handle this momentary surge with no problem. Seems kind of strange that a '700watt' inverter couldnt handle a box fan... those things usually only draw about 65 watts when running on high.


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## mikellmikell

I have several Kill A Watt meters and mine says 68 watts at high speed


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## 12vman

I ran one on my cheepie 400 watt Wagner..


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## gwest

Why not use a 12 volt dc computer case cooling fan or fans you can use this site
http://www.simetric.co.uk/si_watts.htm to figure your amps,watts or whatever for any electrical device or use this site http://www.powerstream.com/Amps-Watts.htm?nowritefs powerstream.com also has a lot of other goodies. I've used 12 volt computer fans in two of my active solar heaters and am very pleased with them. They manufacture some of these fans in large diameters,some of them can really move a lot of air.


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## 12vman

I use 2 of these. They operate directly on 12 volts D.C. They move a good bit of air for what power they use..

http://www.lowes.com/lowes/lkn?action=productDetail&productId=5012-59644-1078&lpage=none


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## 12vman

I use 2 of these. They operate directly on 12 volts D.C. They move a good bit of air for what power they use..

http://www.lowes.com/lowes/lkn?action=productDetail&productId=5012-59644-1078&lpage=none


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## MELOC

how about floor registers in the back end of the loft to allow natural air circulation to the lower level?


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## mightybooboo

Hey 12V,2 fans so you had to post twice,eh?


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## 12vman

LOL.. silly glitches


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## Jan Sears

Thanks everyone for your input. We will try some of these out & see what works best. We were initially hoping that our old Findlay Oval cookstove (not airtight) would heat the place handily. It did over Christmas but since the weather got so cold it just wasn't cutting it. We can't get back there as much as we would like as my MIL lives with us & we can only leave her when her caregiver comes.


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