20k natural gas hanging furnace??


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Old 11-29-22, 08:21 AM
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20k natural gas hanging furnace??

I have a 12 x 20 garage with 9' ceiling. All drywall edges and insulated.
240 sq. feet. The smallest hanging natural gas furnace i find is 50k btu... way too big.

But I don't want to give up wall space for a vent free wall mount heater.

Any recommendations?
 
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Old 11-29-22, 09:38 AM
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I'd go with the 50k heater.

My shop is poorly insulated so I only heat when I'm working. I like a generously oversized heater so when I want to work I can turn on the heat and get the building up to useable temperature quickly. Also, since the shop is cold most of the time everything (building, concrete floor, materials and machinery) are all cold. It takes a lot more than what you'd think to warm it up at first.

At first my heat runs for a long time. Then the longer I have the heat on the furnace runs for shorter periods, further apart. It's not perfect but it works well for a space that is only occasionally heated. If you will be keeping your garage continuously up to temperature then I think "household" furnace sizing makes more sense since you don't have to overcome the hurdle of bringing everything up to temperature. You just have to provide enough to keep it warm.

I have noticed with a cold soaked building and contents having a fan aimed up at the ceiling helps a lot. When the furnace is off the air striates very quickly as the cold sinks and my warm air rises to the ceiling. I have a pedestal fan and in winter I aim it straight up and turn it on low. It doesn't create a draft you can feel but it stirs the air enough to keep the temperature more uniform.
 

Last edited by Pilot Dane; 11-29-22 at 11:07 AM.
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Old 11-29-22, 10:53 AM
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Modine makes a 30k BTU model, but I'm with Pilot Dane on this one...oversize is better unless you plan to heat it 24/7 and even then oversize doesn't hurt much. And it's not like you would save much money.
 
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Old 11-29-22, 02:24 PM
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I hope to keep the shop heated to at least 50 or maybe even 60 all the time.

 
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Old 11-29-22, 05:21 PM
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Well there's always the mini-split option; they have become a really popular way to heat/cool shops and garages. The inside unit takes a bit of wall space, but it can be up high where it's not really in the way.

There are multiple DIY options out there for them now, if you are so inclined.
 
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Old 11-29-22, 06:08 PM
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The mini split units are really nice, perfect AC solution for a ductless home. But, the don't heat when its very cold out. Now, an attic mounted ducted furnace could work... empty attic above the garage...
 
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Old 11-29-22, 07:35 PM
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Mitsubishi and others make mini splits that work efficiently down to -5F, and some even colder.
 
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Old 11-30-22, 06:51 AM
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that work efficiently down to -5F
They work, but I would question the efficiency in cold weather.

No way your going to get 30-50K btu out of one of them and like a GEO (which I have) or heat pump, walking out to a cold garage and flipping the switch is going to take hours of run time for a few degrees of temp rise!

I had a 4 car garage many houses ago, with one of those heaters. Didn't take long to get the temps up to short sleeve in a reasonable amount of time!
 
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Old 11-30-22, 09:51 AM
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A heat pump is not a "flip the switch" solution in any application.
A heat pump only maintains high efficiency by running pretty much full time.
 
 

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