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  1. #1
    Mark's Avatar
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    Question Sizing a garage heater

    Wanting to put a forced air natural gas heater into a garage (like a Hot Dawg or similar). Typical two car (not oversized), fully sheetrocked. Insulation unknown, but figuring on slim to none. I think the ceilings are like 9ft? Maybe 10.

    How many btu's do I need to be looking for to adequately heat the space?

    Any reccomendations on brands/models to check out that are a decent price? Something I could hang myself & then have the local HVAC guys do the gas/electric hookups would be nice.

  2. #2
    I just installed mine and finished it up last weekend. I have a two stall garage and used the 45,000 BTU low profile heater that you can mount 1" from the ceiling. I ran the gas line, electrical and venting myself since thats what I do. The 3 brands I would choose from are either Reznor, Modine and Cayenne. I went with the Cayenne as one of my HVAC wholsalers sold it to me for cost. Roughly $368 with tax. It is nice having a heated garage and being able to work in it at night in a t-shirt.

    http://www.comfortgurus.com/product_...oducts_id/9477

    They recommend a 45K BTU for a 1.5 stall garage that is insulated. The 60 and 75 are for uninsulated or detached garages. My 45k heats just fine and I also put in a low temp Stat and keep it at 40 Deg when I am not in there.
    Last edited by zillacon; November 4th, 2011 at 06:54 PM.

  3. #3
    I have a Hot Dawg, the smallest one, in my 20x20 garage. Don't know the BTU's, but I'd recommend a larger one. Mine will warm it up OK, eventually, but I'd rather warm it up quicker. Sooner it gets warm, the sooner it shuts off too and the less time it runs.

    This is mine, if I were to do it again I'd definitely go bigger. But you may need a modification to your gas source to provide a big enough feed line. That was a deciding factor in my choosing the small one. JMHO.

    1956 CJ5
    Stored indoors for last 30 years :D , under restoration.

  4. #4
    Quote Originally Posted by rondog View Post
    I have a Hot Dawg, the smallest one, in my 20x20 garage. Don't know the BTU's, but I'd recommend a larger one. Mine will warm it up OK, eventually, but I'd rather warm it up quicker. Sooner it gets warm, the sooner it shuts off too and the less time it runs.

    This is mine, if I were to do it again I'd definitely go bigger. But you may need a modification to your gas source to provide a big enough feed line. That was a deciding factor in my choosing the small one. JMHO.

    ^ Bad Advice! Size it properly for the application.

    What are the consequences of over-sizing a unit?
    -It may heat it up quick but will cause short cycling.
    -Shortens the life of the heat exchanger and venting as it doesnt remove the condensation like it should and will rust it out.
    -Associate cost of install (larger gas lines and Venting)
    -Initial first cost of the larger unit.
    -More gas consumption.
    -Uses more combustion air from the occupied space unless it is a sealed combustion unit.
    -depending on style etc can take up more install space.

  5. #5
    oooo I want one. How much does installation cost?
    2001 KTM 200 E/XC * 2001 Marauder * 1995 F150 * 1968 Mustang

  6. #6
    Mark's Avatar
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    zillacon: Would going with a 60k unit in a two car with unknown insulation be a 'safe' bet? I had been thinking of going with the 75k one just because bigger is usually better, but I wonder if choosing a middle-of-the-road unit like the 60k would be the safer bet? The initial costs of the units seems negligible, I'm seeing like a $100 difference between 45k & 75k units.

    Like Sharla mentioned - can you ballpark what an installation cost would be? If you might be interested in coming up to Loveland to do an install, let me know.

    Good info here - thanks!

  7. #7
    If you just have a standard size 2 stall I would stick with a 45K. If its detached then possibly a 60K. Really tough to throw out a guestimate on a garage heater without looking at the job. Too many variables.

  8. #8
    I mean just to hook up the gas to it? That can't be too ridiculous can it? Does anybody here do that who'd be willing to give us a number?

  9. #9
    The Original Opie-Gone-Bad!!! Aaron's Avatar
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    Quote Originally Posted by Mark View Post
    zillacon: Would going with a 60k unit in a two car with unknown insulation be a 'safe' bet? I had been thinking of going with the 75k one just because bigger is usually better, but I wonder if choosing a middle-of-the-road unit like the 60k would be the safer bet? The initial costs of the units seems negligible, I'm seeing like a $100 difference between 45k & 75k units.

    Like Sharla mentioned - can you ballpark what an installation cost would be? If you might be interested in coming up to Loveland to do an install, let me know.

    Good info here - thanks!
    I installed a 80K BTU furnace in my 1300 sq ft garage that has 12' ceilings and 4 bay doors and 2 man doors . Keeps it 60-70* on the coldest of days and actually cycles correctly and doesn't over run. Do a google search for a BTU calculator. Should help with sizing a lot.

  10. #10
    Quote Originally Posted by zillacon View Post
    ^ Bad Advice! Size it properly for the application.

    What are the consequences of over-sizing a unit?
    -It may heat it up quick but will cause short cycling.
    -Shortens the life of the heat exchanger and venting as it doesnt remove the condensation like it should and will rust it out.
    -Associate cost of install (larger gas lines and Venting)
    -Initial first cost of the larger unit.
    -More gas consumption.
    -Uses more combustion air from the occupied space unless it is a sealed combustion unit.
    -depending on style etc can take up more install space.
    Good points! As usual, I'm the typical geezer that don't know what I'm talking about, and I seem to be getting worse.....

  11. #11

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    Quote Originally Posted by FirecrackerKTM View Post
    I mean just to hook up the gas to it? That can't be too ridiculous can it? Does anybody here do that who'd be willing to give us a number?
    Even the gas line has too many variables.

    Examples: Is the line inside the house or would it be better to tap into it from the outside? Is the run going to be 20ft or 60ft? Is access easy or is drywall going to have to be torn out to get to it? Etc....
    Why is it that common sense isn't so common anymore?

  12. #12
    Quote Originally Posted by CSP View Post
    Even the gas line has too many variables.

    Examples: Is the line inside the house or would it be better to tap into it from the outside? Is the run going to be 20ft or 60ft? Is access easy or is drywall going to have to be torn out to get to it? Etc....
    Yuppers, not to mention is it sized properly for the application, does it need bigger supply line from the Reg into the house terminations, do you need a bigger reg? Will pressures at the main need to be adjusted? Will you need Regs at other terminations for other appliances? One of those things you wont even get close to with a Ballpark figure.
    Last edited by zillacon; November 7th, 2011 at 09:13 AM.

  13. #13
    Ive got the 30k btu hot dawg for my oversized 3 car (1000 sq ft.). It will keep it at 70, but it takes a while to get there. I've got a very well insulated garage though. If I used my garage more often I would probably recommend a larger unit.
    Rubicon unlimited, 5"tera lcg pro, 1" body, 37" KM2, Pro Rock 60, winch, sliders, warn bumpers.

  14. #14
    Mark's Avatar
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    The local HVAC company wanted $2,900 to install a garage heater complete with permits. $15 a foot to run gas line.

    They're nucking futs. Anyone know an HVAC guy in NoCo willing to do side work?

  15. #15
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    Quote Originally Posted by Mark View Post
    They're nucking futs. Anyone know an HVAC guy in NoCo willing to do side work?
    and Colorado Springs
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