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  • New Shop Heating?

    Well i need to gain some information on in floor concrete water heating systems. I am doing most of the work myself. My old shop is so jammed i can barely walk in it. (Its 471 suare feet, my new shops 528 square feet all im allowed by the city.) My Wife allocated funds for a new construction, I already excavated the yard forms are up then it poured hailed rained and tthe new topsoil all washed back into the hole. I removed 10 dump truck loads of dirt and now am shovelling out the mess. I wish to pour soon and need to find out the best way (meaning cheapet and best way of doing the inground floor water heating.

  • #2
    I almost went that route, but now that I didn't I am glad I did not. If you are retired and will be out there every day during the winter, it makes sense.

    I found that I am out there randomly enough (and only for an hour or two on days during the week) that I found that I did better with forced air heat. I first started off keeping the place about 47 degrees when unoccupied and then warmin it up when I went out. The furnace I have is a 125k BTU which is probably a bit large for my building. The building is 30x40x14 and has 6 inches of insulation in the walls with an added airspace and 13" of blown in fiberglass in the ceiling. In the end, insulation is your best investment.

    I found that I can just shut the heat completely off when not there and warm it up to temp within 20-30 minutes with the slightly oversize furnace. I like it about 58-60 to work in during the winter as you don't break a sweat that way. Surfaces remain cold for a while, but with a vented furnace, I do not have condensation problems. This way I am not paying anything but the cost of the pilot light (and modern furnaces do not even use one of those) when it sits idle. The inside temp has never gotten below freezing in between times with the doors closed and the shop unused....both because I get a little heating from the windows and because its well insulated.

    Had I gone with radiant heating in the floor, I would pretty much have to leave it on and running all the time....including both the heater (water heater) and a circulating pump.

    Edit-- in your case, that is sized such that one of the Modine HotDawg heaters should work very nicely...and they are pilotless. http://www.littlegreenhouse.com/accessory/heaters.shtml

    Paul
    Last edited by pcarpenter; 08-11-2008, 04:11 PM.
    Paul Carpenter
    Mapleton, IL

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    • #3
      Thanx Paul

      Yes that makes sense, i wasconcerned about explosive gasoline fumes but that furnace is sealed . I think you are correct if you have to leave the water floor system on all the time it wiould not be truly a money saver would it? I aklso wonder if it would freeze up when not running when it gets down to minus 35 or so. Thanx Paul

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      • #4
        They usually mix an anti-freeze with the liquid to prevent accidents, but they are not cost effective or even practical for non-continuous use. It takes a while to heat the water and then longer to heat all that concrete until it radiates well.

        I did not recall that the HotDawgs were truly sealed combustion. I know they had an outside air supply, however. My Dad built his shop (much bigger than mine with a more traditional furnace. I about flipped out when I saw it sitting in a closet at floor level right next to the restroom he built inside. Turns out, it too was truly a sealed combustion unit...perhaps the safest way to go.

        Edit-- be careful-- they offer sealed combustion models and non-sealed combustion models according to www.modine.com :

        "Q: Where does the Hot Dawg get its combustion air?
        A: The Hot Dawg draws air from within the space being heated (power exhausted, HD model) or from fresh, outside air (separated combustion, HDS model). "


        Mine is an older hanging "unit heater" I found cheap and in decent shape. Even at that, its 11 feet in the air or so at the lowest point. Gasoline vapor is heavier than air so if you are going to have a source of combustion, at least have it up high. The problem with regular furnaces is that the flame is down below your nose level so you can have a gasoline leak that finds the furnace before you know you have one. Still other combustables are lighter than air, however.

        Paul
        Last edited by pcarpenter; 08-11-2008, 05:38 PM.
        Paul Carpenter
        Mapleton, IL

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        • #5
          If you go to this web site there is a lot of info on different heating and cooling options for garages.,
          http://www.garagejournal.com/forum/
          Mike
          Brandon MI
          2003 MINI Cooper S JCW#249
          1971 Opel GT
          1985 Ford 3910LP

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          • #6
            I just poured my shop slab, and put hydronic heating tube in the floor.

            If you are going to be in the shop regularly then it can be economical in the long run. However it does cost more up front. My cost for the manifold, tube, pump, thermostat, etc. was about $1400. I still need to include the water heater and plumbing it up. My shop is 25x35 with a 15' ceiling, so your heat needs will be less.

            The PEX tube gets laid on top of the vapor barrier and ziptied to the rebar.

            Once the concrete is heated then the incremental cost to keeping it warm is low.

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            • #7
              Originally posted by kvom
              I just poured my shop slab, and put hydronic heating tube in the floor.

              If you are going to be in the shop regularly then it can be economical in the long run. However it does cost more up front. My cost for the manifold, tube, pump, thermostat, etc. was about $1400. I still need to include the water heater and plumbing it up. My shop is 25x35 with a 15' ceiling, so your heat needs will be less.

              The PEX tube gets laid on top of the vapor barrier and ziptied to the rebar.

              Once the concrete is heated then the incremental cost to keeping it warm is low.
              No insulation in the floor? In the UK the minimum is now 4" of polystyrene in the floor

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              • #8
                i just put in floor tubes in the floor of my sauna and dressing room. i don;t know if i will ever use it but we do get -40 in the winter here. and if i run it with a small water heater, it won't cost that much for the times i want to sauna, maybe. . . . . . of course the sauna itself is heated with a airtight "kuma" stove from northern minnesota and if i do this right, i should be able to heat the building with about 1 log per day and keep the sauna warm at least when its not in use. fun in the winter, snow and all, pluys i have a well right outside the sauna for getting a real COLD shower when your finished. . . .
                this keeps your line tight and your stick on the ice for sure. . . . . .

                ( put the pipes in your new floor, they are cheap. you may or may not want to use them in the future. good selling point for the next occupants of your property.)
                davidh (the old guy)

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                • #9
                  Heat in the shop? I laugh every time this comes up and say the same thing. When I want heat, I just open the doors.

                  One item to consider when installing in-floor heat. If you ever plan to drill holes and bolt-down equipment, you might run into a problem. A wet problem.

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                  • #10
                    Lots of validity to all remarks, it is a heat pig to get up to temp from cold, there is a lot of mass there, as said once it's up it's just to maintain, a good option is for a relay/timer to turn on the flow for 5-10 mins every hour during heat season to just momentarily boost the temp.

                    I made all my own manifolds etc, I used Kitec instead of Pex, if you do use pex get the oxy barrier, kitec is full 1/2" ID where pex is smaller. You tubing should be placed in 1/2 to upper 1/3 of the slab. I put styro down in the shop but just used dry sand under the house. The kitec conforms very well with bends and holding it's shape the pex is a lot more flexible. I used pull tie to secure it to the rebar, lots of em. Go with a Grundfos pump, you'll never regret it.

                    We use a 50/50 glycol here, propylene I believe the other type than automotive. If you are worrried about knowing where to later drill, take pics, we can throw snow down when heating and see where it melts first and my buddy has access to a thermal imaging camera.

                    A boiler designed for this is way more efficient than a DWH.

                    Opportunity knocks once, temptation leans on the doorbell.....

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                    • #11
                      Shop heat

                      Madman

                      Here's my $.02 on shop heat... Infloor heat? half of the 8 or 9 systems I know of have problems. Too slow heating, poorly laid out heat loops, leaks in the tubing, loss of pressure in the system over time, missplaced tubing (too high or too low in the slab. IMHO, 50% ain't great odds.

                      I'm frankly surprised that radiant heat hasn't been mentioned yet. My 26 x 26 shop is comfortable to work in in roughly 45 minutes at -45C. I keep it a +5 with a thermostat and turn it up when I want to work in the shop. The heater is completely sealed, drawing all combustion air from outside and exhausting back outside. It has a modern "hot plate" ignition so no pilot light. In addition, due to the radiant heat dispersion, there is no air movement-aka no dust blowing around to create paint issues.

                      IMHO, infloor heat is only desireable for shops where you might lay on the floor every day or for a continously occupied basement living space.
                      FWIW, locally, by code, infloor heat requires a minimum of 1 1/2" rigid styrofoam insulation under the slab. Tubing is tied to the re-enforcing steel, typically 6" squares of #10 wire or 3/8"rebar on 24" centers. There are various styrofoam sheets with molded in tubing retainers. Most tradesmen don't like 'em because they're new, but they exist, and may save you some labor at nominal extra $.

                      YMMV,
                      Cam
                      Design to 0.0001", measure to 1/32", cut with an axe, grind to fit

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