Garage heater size

I need a heater in my garage. Size of garage is 24X28 with 10′ high ceilings. Walls have new R15 batting in. Ceiling will be blown in insulation. 12″ I’m thinking.
There will also be a new insulated garage door.

I purchased a 50,000 BTU Mr Heater from menards. It’s vented and would be hanging from the ceiling. LP hooked up off my 500 gallon tank for my house.

I had a guy tell today that heater would be too big for the space in my garage? Anyone have any thoughts?

I tried to find something similar to the Mr heater style in 40,000 btu. Don’t see much out there? Thanks.

Yeah, your garage won’t need as large a heater as a house of the same size, less people going in and out and less windows. It will work but may short cycle, not as critical as an AC unit short cycling. If you find a smaller one it would work but that one would work as well.

I have that exact same heater in my 3car well insulated garage. It’s perfect. Doesn’t short cycle, but doesn’t run constant either. Can get up to 75 from 50 in about 15 minutes when it’s below zero outside. Doesn’t cook you out either when running.

Hardly notice it on the gas bill as well.

riverruns wrote:

I need a heater in my garage. Size of garage is 24X28 with 10′ high ceilings. Walls have new R15 batting in. Ceiling will be blown in insulation. 12″ I’m thinking.
There will also be a new insulated garage door.

I purchased a 50,000 BTU Mr Heater from menards. It’s vented and would be hanging from the ceiling. LP hooked up off my 500 gallon tank for my house.

I had a guy tell today that heater would be too big for the space in my garage? Anyone have any thoughts?

I tried to find something similar to the Mr heater style in 40,000 btu. Don’t see much out there? Thanks.

It will work fine, sure it’s not “sized” for the garage but I would definitely not over think it! Sure it might cycle on and off a little more but it won’t hurt anything. Get a good digital thermostat and you’ll be good to go!

Thats not too big. I have a 75k in my 24×24 detached garage. I don’t have mine running 24×7 but I always keep it about freezing in there. Another thing to keep in mind is get a thermostat with adjustable differential. You can set the differential higher so then the heater kicks in and out less times a hour and will get rid of any short cycling issues if that’s a concern.

I just built a 32×32 with 14 foot sidewalls. I was thinking of 120000 but after reading this I think an 80,000 should do it. Any opinions welcome let me know what you people think.

To much is better than to little. Go 50. You wont have to run it as hot as it can go. well unless its 25 below Brrrr.

river rat randy wrote:

To much is better than to little.

Far from. Too much will short cycle, causing excessive wear on components. It may also not heat up hot enough to allow all the moisture that builds up during startup to dry up and eventually lead to heat exchanger failure. Its also just inefficient, as the startup process uses lots of energy with little gain, and short cycling means excess startups.

dk55403 wrote:

I just built a 32×32 with 14 foot sidewalls. I was thinking of 120000 but after reading this I think an 80,000 should do it. Any opinions welcome let me know what you people think.

How well is it sealed and insulated?

Thanks everyone !

I’m going to install this one I purchased and go with the 50,000 BTU. With the menards price to start with and the 11% off it cannot be beat in price. I’ll take my chances. I agree with what you guys are saying here.

The guy that looked at it today, just made me second guess myself.

I have not insulated yet. I have insulated door. Planned on blow in for the ceiling. Fiberglass in the walls.

dk55403 wrote:

I have not insulated yet. I have insulated door. Planned on blow in for the ceiling. Fiberglass in the walls.

The high ceilings may be an issue. An 80k should easily heat that size with 10 foot ceilings, however I am unsure how well it would work with that much extra height. If anything a couple ceiling fans may be needed if the heat stays too high. I honestly wouldn’t be afraid to get the 80k if it were mine.

We have a 30k BTU ventless in our well insulated 24×30 and it will keep the garage at 60 degrees on setting #1 and will only cycle once every 30 minutes or so for 2-3 minutes at a time to maintain temp, even on the coldest nights. If I put it on setting #5 it will get the garage well over 90 degrees in short order. We do have the built in blower for it as well. Typically we never run it over setting #2, and that is only if I will be working out there.

munchy wrote:

<div class=”d4p-bbt-quote-title”>river rat randy wrote:</div>
To much is better than to little.

Far from. Too much will short cycle, causing excessive wear on components. It may also not heat up hot enough to allow all the moisture that builds up during startup to dry up and eventually lead to heat exchanger failure. Its also just inefficient, as the startup process uses lots of energy with little gain, and short cycling means excess startups.

Munchy Thanks for all that INFO. . . rrr

Browndog wrote:

We have a 30k BTU ventless in our well insulated 24×30 and it will keep the garage at 60 degrees on setting #1 and will only cycle once every 30 minutes or so for 2-3 minutes at a time to maintain temp, even on the coldest nights. If I put it on setting #5 it will get the garage well over 90 degrees in short order. We do have the built in blower for it as well. Typically we never run it over setting #2, and that is only if I will be working out there.

There is a slight difference between a vented and ventless. The efficiency. A ventless has near 100% efficiency, meaning all the available heat it creates is put into the room. A vented typically has a much lower efficiency rating. I believe the Mr Heater Bigg Maxx’s have an 80% rating. So 20% of the available heat is released through the exhaust. Meaning you can use a lower BTU ventless heater to warm the same amount as a vented. Unfortunately the ventless are not 100% safe and they also release moisture from the combustion process which can sometimes be problematic.

The reason I’ll be going with a vented heater in my garage is to eliminate the moisture.

The moisture from a non vented heater gives that cold clammy feeling even though the temp might be still ok. Moisture in a closed space I don’t want.

Just put your thermostat in a neutral location. Mine is under and behind the heater. The last place to heat up.

My garage is 24×24 with i think 9 foot ceilings. The company that did mine installed a 60k btu .

https://outdoorboiler.com/blogs/news/heating-a-garage-pole-barn-or-workshop-heres-how-to-calculate-the-proper-size-unit-heater

I googled and this came up…

Mark

From outdoorboiler.com

Heating A Garage, Pole Barn or Workshop? Here’s How To Calculate The Proper Size Unit Heater!
By:Warren Walborn June 13, 2017

If you want to heat a garage, pole barn, or a workshop, or any space like that, the best way to do this is with one or more unit heaters. These are very effective at providing heat to large spaces – they contain a blower fan connected to a heat exchanger that allows for heat to be provided directly at a desired location. If desired, the unit heater may be connected to a thermostat for ideal temp control.

To calculate the size unit heater required for your space, use the following formula:

Calculate the cubic footage of the space to be heated by multiplying building length x width x ceiling height. A 30 x 40 pole barn with 14 foot average ceilings* will have (30x40x14=) 16,800 cubic feet of space to heat.

Then multiply the cubic feet times the “insulation factor” to get BTUs required to properly heat the space. Insulation factors are as follows:

4 – Excellent Insulation

5 – Average Insulation

7 – Poor Insulation

So if in this example, let’s say you have average insulation and 16,800 cubic feet of space to heat. Multiply 16,800 times 5 equals 84,000. You must have one or more unit heaters that produce a total of 84,000 BTUs of heat.

Importantly, if you have a space that requires a large amount of heat, you may elect to install more than one unit heater to spread the heat around in the space better. For example, a workshop that needs 250,000 BTUs could be heated with THREE 90,000 BTU unit heaters. Just make sure that the sum of the unit heater BTU output is greater than the calculated BTU requirements.

If you have any further questions, click HERE to Contact Us!

Well, it looks like I’ll be oversized according to these calculations. I’m at around 30,000. I’ll just keep my 50,000 heater and try it.

Thanks for the calculation though. Interesting.

That calc is not correct, it’s a guess. You can’t do a heat loss calc without a delta T, or temperature difference between outdoors and indoors. Around this area, a -20 outdoor air temp and a 70 indoor temp would be appropriate, or a 90 delta T.

In Mn you would need a larger unit than in Tennessee because of the delta T

call DJ’s Heating and Cooling, they will tell you exactly what you need and they are honest about it. I originally asked for a 75k btu heater and they talked me into downsizing to a 60k btu unit…

just don’t insulate the ceiling. boom problem solved! lol

Getting close to this being finished. It’s turning into our meat processing garage, kinda.

We put in the ceiling lights and ceiling fan in yesterday. Today another service door and blew the insulation into the attic. Heater is hung and ready as well.

Thinking this is going to be an awesome set up.

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You are close enough just make sure to have you gas pressure adjusted and that the unit is set up for LP or you will have to convert it…which is easy. Djs or other contractors will do a set up for a reasonable fee if needed. A quick way to calculate is take your sq ft and multiply by 50 will get you close enough. You need at least 33,600 btu’s and your 80% heater puts out 40k btu’s. Since they only offer so many btu options your choice is fine. Pro 1 makes a nice t-stat that goes below 45 degrees for garages. You can even wire some heaters so it turns off if your garage door is open…if equipped with an end switch.

Another often overlooked feature is the ability to turn the blower fan on without the heating element. My Reznor has the relay to do this on its motherboard, so I can quickly blow out the hot air in the garage during the summer months via a switch on the thermostat.

Well project is complete. The 50K heater is not overkill. Everything seems good with it. Glad I didn’t go smaller.

Thinking this is going to be an awesome set up.
[/quote] Looks like a AWESOME set up to me Congrats.!! . rrr