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Thread: Furnace in Workshop?

  1. #1
    Join Date
    Jul 2004
    Location
    Vernon, Connecticut
    Posts
    501

    Furnace in Workshop?

    This past summer, I built a 2-story, 24x30' workshop. When the weather gets warmer, I will begin insulating and sheetrocking the walls, and making it look nice in general.

    I'm considering adding a Gas, hot-air furnace with A/C coil. You know, the kind that most homes have. I am thinking about a "real" furnace for the following reasons:

    1. 95% efficient
    2. tax credit
    3. integrates A/C without much difficulty
    4. Can heat and cool both floors
    5. Avoids window A/C units that block my view
    6. Ductwork provides the best air circulation to prevent hot/cold spots
    7. The upstairs may become a nice living area at some point (especially if the wife kicks me out for spending so much time/money for the shop)

    My quote from a local HVAC contractor is $7900 for everything, including 2 ton A/C and furnace. I can buy the exact same furnace and A/C coil/compressor for less than $2000. I'm considering installing it myself and have been doing some research. I think I can do it with help from some friends.

    I haven't seen many people taking this approach. Is it the cost or complication? Please let me know your thoughts.

    Bob

  2. #2
    Join Date
    Feb 2008
    Location
    Topeka, Kansas
    Posts
    311
    sounds nice man. i think its probably something you could do mostly yourself. you might be required to have someone thats certified actually make the connections for the freon or whatever but the ducting and stuff should be easy
    If you don't make mistakes, you don't learn.

    -- Sam Maloof

  3. #3
    Join Date
    Jun 2008
    Location
    Indianapolis, IN
    Posts
    159
    I have a household furnace in my shop. I didn't hook up the cooling coils but the furnace itself is nothing to hook up. Mine is electric so you will have an additional hookup than I had but its still not hard.

    Why not put it in place, run the duct work and electrical and rough in the gas and AC lines then have someone come out and do the final hookup/test. Can't be that much if everything is in place and all they have to do is hook up a couple connections and charge the AC.

    I think you will find you won't need much ductwork in a shop that size with a full on furnace.

  4. #4
    Join Date
    Nov 2007
    Location
    Milwaukee, WI
    Posts
    903
    I'm sure it's cost...seems like a lot even DIY. You will go through filters like crazy, ducts will build up dust. Won't have a dramatic effect on cold spots, you'll still have 'em. I would have gone in floor radiant when you had a chance, that would eliminate cold spots. As far as AC I go without.

  5. #5
    I have a regular fuel oil furnace with dual fuel electric plenum on it and AC coil. I have a high efficiency filter system on the return air. I also have a dust collector and air cleaner. I haven't had any problems with the filter. The high efficiency ones actually work better when they have some minor debris in them. The filter is about $25 and you could probably vac them a time or two before replacement. I also haven't had any problems with filling my ductwork with dust. My shop is hobby-only and a full-time shop may have issues if it were daily dust, so I cannot answer that question. If a furnace filter gets all the dust, then a person is not dealing with the dust issue correctly with the dust collector and air cleaner. Sooner or later your lungs will look like the furnace filter if you don't address the dust in the shop to begin with.

  6. #6
    Join Date
    Jan 2008
    Location
    Bradenton, Fl
    Posts
    496
    Have you looked at a split system. I have one in my in my 1000 sq ft shop and it works well. I don't use the heat side as much living in Florida but the air gets a work out. Also you may need a permit to install your system. It is required here.

  7. #7
    Join Date
    Dec 2006
    Location
    Toronto Ontario
    Posts
    6,543
    Hi Bob. can you install air conditioning without a license where you live?

    Where I live you cannot purchase refrigerant, or install it without a license, and then inspection by the Technical Safety and Standards Association.

    Regards, Rod.

  8. #8
    Have you considered a Direct vent wall furnace? Space saving, no fumes and good output. The narrow, tall models fit between the studs.

    Mac

  9. #9
    Join Date
    Jan 2008
    Location
    Bangor, PA
    Posts
    1,722
    I like the indirect fired gas or propane furnaces for a shop. I had an old hot air furnace. I removed all filters. That let the dust go through the heat exchanger and basically burn away. It worked well for about 30 years. I just disconnected it this year when the oil tank became suspect. I replaced it with a ceiling mounted Modine propane indirect fired furnace. 30K btu makes it very toasty. My air conditioning is a wall mounted unit to which I added a secondary filter. I clean it weekly. I didn't spend $1500 for heat and air combined.
    Even with a dust collector and air cleaner, dust is a real problem and plays havoc in a wood shop. Keep your HVAC simple and have the filters easy to access.
    fmr

  10. #10
    Join Date
    Oct 2007
    Location
    New Hill, NC
    Posts
    1,738
    Quote Originally Posted by Bob Winkler View Post

    I'm considering adding a Gas, hot-air furnace with A/C coil. You know, the kind that most homes have. I am thinking about a "real" furnace for the

    Bob
    Bob, in my previous two workshops I had an old "take out" high efficiency gas furnace, and it worked great. For a vent, a simple rectangular duct was placed on the discharge end with a standard vent grill on one side.

    The installation was a breeze, and I think that I had less than $200.00 in the entire furnace. No AC coils hooked up in mine though.

    It works great, as long as you don't vent your dust collection system outside (messes up the draft). Yes, you will go through a lot of filters but you can't beat the price.

    Scott

  11. #11
    Join Date
    Feb 2003
    Location
    Washington, NC
    Posts
    2,121
    As Scott mentioned, one BIG consideration- will you have a dust collection system and will it discharge outside? If so you run the serious risk of reverse flue gases (including very deadly carbon monoxide) being pulled in to the shop if you have a gas or oil-fired furnace.

  12. #12
    Join Date
    Jul 2004
    Location
    Vernon, Connecticut
    Posts
    501
    Thanks for all the great comments. Here are a few answers to comments.

    I will have a HVAC guy fill and purge the system.

    I plan on adding an overhead air cleaner to my dust collection. Neither will exhaust to the outside because I want to keep conditioned air inside.

    I looked at mini-split systems but determined that they would be too expensive to heat/cool 2 floors.

    I looked at wall furnace, and they are cheaper, but also had the 2 floor problem. It would save about $1000, but I worry that the fan could'nt move enough air over the 30' length of the shop. Plus, I would need window A/c upstairs and down.

    Overall system cost should be in the $3000 range. My biggest concern is putting the trench t run the gas line from the house. After digging the 100' for the electrical, I'm not looking forward to it. I will probably rent a Dingo or Ditch Witch this time.

    Thanks for all the great ideas.

    Bob

  13. #13
    Join Date
    Sep 2007
    Location
    Bucks County, Pennsylvania
    Posts
    934
    Congratulation on the new shop!

    Getting the system properly designed is often the biggest problem regardless of who does the work. You mention insulation - have you looked into having spray foam installed? The performance difference is really unbelievable and results is marked reductions in Heat and A/C needs.

    The use of the two spaces is also an issue. Are you planning on keeping both spaces at the same temp all the time? How fast do you want the spaces to get to the proper temperature if you are planning only occasional use? Any partition walls or other rooms or are both spaces one room?

    The products that are available have improved greatly in the last few years but how you are going to use the spaces and a proper heat/cool load is the starting point.

  14. #14
    Join Date
    Jul 2004
    Location
    Vernon, Connecticut
    Posts
    501
    The spray foam idea is interesting to me, and I have not yet researched it thoroughly. I have 2x6 walls, so I was going to go with the R19 fiberglass.

    My initial worry about spray foam is cost and health issues. I know that health issues are supposedly resolved, but I can't help but remember the spray foam installation disasters from the 70's and 80's where people had to tear out walls to make houses liveable.

    The other issue beside cost and safety about foam is that wiring and plumbing must be difficult to add after the walls are foamed. Since I often move or add things, this mean more work.

    All issues aside, I will do more research since I'm a firm believer of good insulation. I'm really sorry that my shop included 2 overhead doors because they are difficult to seal and insulate properly.

    As far as plans for the rooms, my intent was to have both shop and upstairs single zoned and at the same temp. I would keep it at 50 all winter and bump it to 60-65 when I'm working there.

    To answer the questions, the upstairs and downstairs are not partitioned. Downstairs is 24x30x10' and upstairs is 16x30x8'.

    Thanks for the continued views and comments,

    Bob
    Last edited by Bob Winkler; 12-16-2009 at 10:27 AM.

  15. #15
    Join Date
    Mar 2007
    Location
    Omaha, NE
    Posts
    133
    I first found an HVAC contractor that would do the sweating (410a refrigerant requires a bleed of nitrogen while soldering), check the charge (heat pump came with enough refrigerant to charge up to 15' of lineset) and do any sheet metal work as necessary.

    I then ordered online and my two boys and I installed it. I got a permit from the city (OK to do myself if < than 5 HP A/C ... 1 HP ~ 1 ton) and it's worked out great.

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