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radiant floor heat for commercial garage

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Don't know the design conditions, but what you provided sounds reasonble (if not generous) for 5F - 15F in a <I>working</I> environment where <I>active</I> occupants will likely find 60F VERY comfortable when lightly clothed.

Devil will be in the slab details.

Likely a rather thick slab and I would assume that the tube will be near (say 1") from the the bottom. From everything reported here a good high density rigid underslab insulation will stand up to nearly any reasonable commercial weight above.

Make certain that the slab edges are well insulated. If you're uncertain of the detailing (and it's not already specified) search here and the web for good details.

Above all, make certain that there is a thermal break between the slab and the drive entrances!

Comments

  • Don_194
    Don_194 Member Posts: 4
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    radiant floor heat for commercial garage

    I am figuring my first job for radiant floor heat and it happens to be a commercial maintenance garage for dump trucks measuring 60'x80' with 20' ceilings and four large doors, 3.5" insulation in walls and ceilings. Doors mostly open a few times per day and trucks sit overnight for work next day. I figured heat loss at 96000 btu, 1/2" pex at 12' spacing with 20 btu per sq ft. I could use a Munchkin 140M. This job scares me! Have I figured right or is there something else to use for figuring heat loss?
  • Darin Cook_5
    Darin Cook_5 Member Posts: 298
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    Don

    There is a 5000 sq ft motorcycle garage/salesroom (all radiant slab) that we installed a Munchkin T-80 in and that walks away with it. You can try a different heat loss program but chances are, you are probably oversized with the 140. Hard to believe it, I know.







    Darin

    To Learn More About This Professional, Click Here to Visit Their Ad in "Find A Professional"
  • Don_194
    Don_194 Member Posts: 4
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    How tall were the ceilings?
  • Don Regan
    Don Regan Member Posts: 43
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    What are you doing...

    for insulation and tube holding? Are you using Crete-Heat?
  • Don_194
    Don_194 Member Posts: 4
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    using 2" pink board and cable tieing to rebar
  • Couderay
    Couderay Member Posts: 314
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    In floor

    Just to add, hope they give a good solid subgrade and use a higher density foam than standard grade.
  • Don Regan
    Don Regan Member Posts: 43
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    Nothing like...

    crawling around on the ground all day or better yet having an employee get steel poked in the knee. LOL. oops.
  • Don_194
    Don_194 Member Posts: 4
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    hey guys, thanks for the help. will probably end up using a munchkin 80M boiler. recaculated and instead of a heat loss of 96,000, ended up with a 61,000 loss. don
  • Dave_4
    Dave_4 Member Posts: 1,405
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    Don

    In a slab go with 5/8 or 3/4" and take advantage of longer loop lengths, reducing # of loops. More cost effective.
  • hot_rod
    hot_rod Member Posts: 22,158
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    Pin them down on the infiltration

    mainly how often the doors are open, or left open. The only shops I have had complaints about are repair shops that leave the overhead doors open or cracked a bit.

    Usually they neglect to add an exhaust removal system and the open doors move the fumes out?!

    If they do have a air removal system you may need a pre-heated make up air system. Just be sure to ask these questions. Better now than later. Add the data to your assumption report on the load calc and have the customer sign that.

    On large shops I do 5/8 or 3/4 and run 500 or 600 foot loops. makes it easier to get to a one manifold location on a large building. Fifteen inch on center is often do-able also.

    If it is a 6" slab I would highly recommend the re-bar and tube is elevated on chairs. 6" is way to deep for radiant tube, IMO.

    Layout any equipment that will need to bolt down, cranes, lifts, etc. PAP tube is easier to locate after an install. FostaPex is an excellent durable tube that provides the heavy wall pex with the al jacket for ease of installation and locating.

    hot rod
    Bob "hot rod" Rohr
    trainer for Caleffi NA
    Living the hydronic dream
  • Brad White
    Brad White Member Posts: 2,398
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    Infiltration in Garages

    Just some perhaps idle comparisons to share on this subject.

    I recently completed a truck chassis repair facility. Gas-fired low-intensity radiant tube heaters overhead, interlaced for floor coverage. (This was to be a temporary facility and budget-driven so in-floor, my first choice, was shot down.)

    We chose radiant because the heating form transcends cold air better than "blowing warm air around". Naturally this latter method means you are blowing as much cool air around on the return trip.

    Anyway, they do leave the bay doors open a few feed and exhaust the welding fumes and general crud involved, which we knew. We also told them that the radiant control would likely be "on-off" because of this. Even though they are two-stage, "off" feels like "off" in an absolute sense when the wind is blowing.

    Gas bills were huge to say the least but they are comfortable. The only suggestion I made was to set the heaters on low fire (2/3 capacity) and that seemed to work.

    With constant ventilation in any form as Hot Rod says, there is very little "off time" or "low time" with any system but at least radiant will give comfort more-so than any other system.
    "If you do not know the answer, say, "I do not know the answer", and you will be correct!"



    -Ernie White, my Dad
  • GMcD
    GMcD Member Posts: 477
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    Cold Trucks

    While it would be strictly a wild guess, you should also have some safety factor for the heat required to offset a cold truck's thermal mass. If the truck is pulled in from the cold to "soak" overnight, that radiant slab will also be exchanging substantial heat with a cold mass of steel truck all night too. The radiant cooling coming off the cold truck will affect the mean radiant temperatures in the space for sure.
  • Steve Ebels_3
    Steve Ebels_3 Member Posts: 1,291
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    A few tips and info

    From one we did:

    6,000 sq ft. 18' ceiling height, 1 16x20 insulated overhead door on the North and South end of the building. The building itself is steel frame with the vinyl wrapped fiberglass insulation one would commonly see in that application. Supposedly R-22 walls and R-30 ceiling. It is a very air tight structure when everything is buttoned up. The slab is 6" with 2" blueboard underneath and 500' loops of 5/8" tube spaced 12" on center. We used a Munchkin 140 and it handles the load without breaking a sweat. I use -6* as design temp here.

    The owner and mechanics working there love the heat and the fast recovery after opening the big doors. Fuel consumption is very low for 6,000 sq ft. in a commercial application. The last time I talked with the building owner, he told me that annual fuel use amounted to about 1,700 gallons (LP gas).

    Pay attention to local codes which may require a CO sensor interlocked with a ventilation fan and motorized intake to match. Also make sure you have a good floor plan of where hoists and other shop equipment will be placed. Advise the owner to install an infloor vehicle exhaust system or at the very least purchase flexible tubing that can be run outdoors through a wall flap. Opening the overhead doors to ventilate is such a waste and so uncomfortable. Downright dumb in the light of present day fuel costs.
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