Heater for 26 x 34

[Mr. Roboto]

I've been playing around with the calculators online trying to determine the proper size heater for my garage, but they are all giving me widely different numbers, so I thought I would ask the experts here.

Looking to add a natural gas/propane heater to my garage. The link in my sig goes to my build thread with some pictures of the space, but it's 26 x 34 (just shy of 900 square feet) with 10.5 foot ceilings. R-13 in the walls and I will be doing blown in in the attic space to at least R-30. Walls and ceiling have also been sheetrocked. I live in the Northeast, in New Hampshire to be exact, and would like to be able to heat the garage to 60 degrees. (not constantly, but when I am out there working for sure). It has 1 man door, 2 insulated garage doors, and 2 double pane windows.

I don't mind getting a slightly larger heater than needed just to have some extra wiggle room to make up for heat loss, extreme cold etc. With that being said, I don't have much HVAC experience, so is there any down side to getting too large of a unit?

I am looking at the 80,000 BTU Mr. Heater, which is on sale at Norther Tool right now. let me know what you think:

http://www.northerntool.com/shop/tools/product_200577751_200577751

Thanks in advance!

 

[SteveeP]

Well I have a very comparable building to yours (36x26, 10.5 ceiling, 1 man door, 3 insulated garage doors, 4 thermal windows, r13 walls, r30 ceiling, fully sheetrocked) in Pepperell MA (Hollis/Brookline NH border). I went with a Modine HotDawg 60,000 btu propane unit and could not be happier with it. It heats the space incredibly fast.

 

[Mr. Roboto]

Wow, that's about as similar a setup as I could hope to find for a comparison. I'm in Derry, you're probably 20 miles away from me! Thanks for the reply, sounds like the 80K unit I am considering will be more than enough. Did you install yourself, or have someone local do it?

 

[SteveeP]

Essentially installed it myself. A friend is a mechanical contractor with a gas fitters license, so he pulled the permit and got me the unit and whatever else was needed at his cost.

 

[Randy in Maine]

You will soon discover the advantage of a vented heater vs. a non-vented heater. You have chosen wisely.

 

[Mr. Roboto]

You will soon discover the advantage of a vented heater vs. a non-vented heater.

Care to enlighten me? From the reading I have done, I understand it doesn't come in to play unless you have a very dusty garage, do a lot of painting, or woodworking etc....

 

[Randy in Maine]

This heater you have selected is vented and will exhaust the water vapor portion of the exhaust out of the building.

That is exactly what you want to do or everything inside the building will rust and will rust a lot sooner than you think.

 

[JohnX14]

I've been playing around with the calculators online trying to determine the proper size heater for my garage, but they are all giving me widely different numbers, so I thought I would ask the experts here.

Looking to add a natural gas/propane heater to my garage. The link in my sig goes to my build thread with some pictures of the space, but it's 26 x 34 (just shy of 900 square feet) with 10.5 foot ceilings. R-13 in the walls and I will be doing blown in in the attic space to at least R-30. Walls and ceiling have also been sheetrocked. I live in the Northeast, in New Hampshire to be exact, and would like to be able to heat the garage to 60 degrees. (not constantly, but when I am out there working for sure). It has 1 man door, 2 insulated garage doors, and 2 double pane windows.

I don't mind getting a slightly larger heater than needed just to have some extra wiggle room to make up for heat loss, extreme cold etc. With that being said, I don't have much HVAC experience, so is there any down side to getting too large of a unit?

I am looking at the 80,000 BTU Mr. Heater, which is on sale at Norther Tool right now. let me know what you think:

http://www.northerntool.com/shop/tools/product_200577751_200577751

Thanks in advance!

Well I have a very comparable building to yours (36x26, 10.5 ceiling, 1 man door, 3 insulated garage doors, 4 thermal windows, r13 walls, r30 ceiling, fully sheetrocked) in Pepperell MA (Hollis/Brookline NH border). I went with a Modine HotDawg 60,000 btu propane unit and could not be happier with it. It heats the space incredibly fast.

I have a 28 x 24 with 15' ceilings, 18x10 door and 9x8 door. I also have the Modine HotDawg and it is amazing. R19 walls and R30 ceiling. Heats super fast. Install was a breeze as well. I think mine is only a 45,000 BTU. (I'll check) The 60K will do the trick nicely. I wouldn't use anything else except the hot dawg unless one needed more BTU's

 

[Mr. Roboto]

This heater you have selected is vented and will exhaust the water vapor portion of the exhaust out of the building.

That is exactly what you want to do or everything inside the building will rust and will rust a lot sooner than you think.

Gotcha! I misunderstood. I was getting confused between a vented heater, and one with a sealed combustion unit with an air intake that pulls from the outside of the building. Thanks for clarifying.

 

[Notgrownup]

That heater is some nice stuff... Down here I can use about 10 of those church candles and it will keep it at about 72 degrees...LO>L

 

[Mr. Roboto]

Thanks for all the input. Sounds like the quality of the Modine units are a little better than the Mr. Heater based on what I've read here and elsewhere. I sourced one from a local distributor that I will likely be ordering. For the 75K btu model it's $696 shipped, and it will come set up for propane (whereas I'd have to pay $40 to convert the Mr. Heater from LNG to LP) The documentation and instructions also seem to be much more detailed for the modine, which will take some of the guess work out when it comes time for me to install it.

 

[kwoody51]

60k should be more than enough. I have 36x24 garage with r-21 walls and a living space above it, one double garage door, one single and one man door, all insulated, 2 Windows.

I use a reznor UDAP Heater and it works great to keep the space warm enough all winter long.

 

[Mr. Roboto]

60k should be more than enough. I have 36x24 garage with r-21 walls and a living space above it, one double garage door, one single and one man door, all insulated, 2 Windows.

I use a reznor UDAP Heater and it works great to keep the space warm enough all winter long.

I agree, based on the calculations I did, the 60K should be enough, but the 75K unit is only 21 dollars more, so I kind of figured why not go with the larger one? Unless there is a downside to potentially getting too large of a heater.

 

[kwoody51]

Don't fall into the bigger is better. Too large of heater and you will short cycle it and reduce comfort and efficiency. You don't want it turning on every few minutes blasting a bunch of heat. Ideally it runs for a longer period of time slowly warming up the space.

Ultimately you want a heater that runs for longer durations with enough excess to allow it to recover when to open the door, etc.

As other have told you 60k is likely all the more you need the "only" benefit you'll get from 75k is if you want to quickly go from 50F to 75F. Otherwise 60k should serve you just fine.

 

[jvitez]

+1 on kwoody51's post!

For maximum overall efficiency of a fuel burning heater you need it to run for a certain length of time to get to "steady state" efficiency. Short cycling means it's never running at the max efficiency it's capable of. Ideally, a perfectly sized heater would run 100% of the time on the coldest day of the year.

A too-large heater will also be uncomfortable. The thermostat calls for heat, you get a big, quick blast of air and the thermostat is satisfied, so off goes the unit. Hot air rises, so gradually all the hot air you just paid for ends up at the ceiling and you're down where cold air sits. A smaller heater will run longer, which keeps the fan running longer, which circulates the air longer, therefore lessening this effect (heat stratification.)

If your calculation is 60K, buy a 60K unit.

 

[CNGsaves]

^ ^ ^ ^ This. Listen to the expert. 60K is the sweet spot for that garage (or slightly smaller).

80K is way TOO BIG. Heck you might get by with 50K unit which is the common size by many manufacturers. If you're not opening and closing the big doors a lot, a well insulated shop will retain the heat. Add ceiling fan(s) in garage to push the heat down to get more benefit of your heated air.

 

[Mr. Roboto]

I wish I got the last 3 replies 24hr earlier. I already ordered the 75K. Will I regret this? Up until those posts, I never got any answers why I shouldn't jump to the 75

 

[Mr. Roboto]

I've contacted the company where I purchased the heater. Luckily, they are only about an hour away from me. They said I can bring it in person once it's delivered and swap it for the HD60 and they will refund me the (small) $21 dollar difference.

Thanks again for the feedback everyone.

 

[kwoody51]

You'll be happier with the 60k! Sorry we were all a little slow to respond. It's much better to do it right and be done. The extra time exchanging it will be well worth the enhanced comfort over the life of your heater!!

 

[Mr. Roboto]

You'll be happier with the 60k! Sorry we were all a little slow to respond. It's much better to do it right and be done. The extra time exchanging it will be well worth the enhanced comfort over the life of your heater!!

Nothing to be sorry about. I just made the 2 hours round trip and swapped my unit out for the 60K heater. Will be worth it in the long run, like you said!

 

[jvitez]

Good choice! Let us know how it's working once you've got it up and running.

 

[Narddog]

Hey Mr. Roboto. I am just posting for an update. I will be in a similar situation and I was planning on going with the 80K Big Maxx. Now after reading these posts, I am afraid that might be a mistake. How is your heater working?

 

[Mr. Roboto]

It's working awesome, I think it's just right for my garage. It heats the space up quickly and I have no issues with short cycling the thermostat. Anything larger would just be wasting propane I think. I'm really happy with it.

How large is your space?

 

[Narddog]

I have this going on. It's really weird because of the deep bay in the T-shaped garage. My gas is stubbed out on the top wall in the deep part.

 

[Mr. Roboto]

Looks like you have about 948 sq feet, but an odd layout. Mine is 884 sq feet. How tall are your ceilings? And I'm assuming you have an insulated ceiling with living space overhead? One good thing is you'll easily be able to place the thermostat around the corner form the heater to prevent the heat from blasting it and causing it to short cycle.

Honestly, I think you'll be OK with the 80K unit. Considering it's going to be at the back of a 47 foot deep bay, you may want some extra power to be able to heat all the way up to the garage doors, which is where you'll have your biggest heat loss.