1. Welcome Hearth.com Guests and Visitors - Please enjoy our forums!
    Hearth.com GOLD Sponsors who help bring the site content to you:
    Hearthstone Soapstone and Cast-Iron stoves( Wood, Gas or Pellet Stoves and Inserts)
    Caluwe - Passion for Fire and Water ( Pellet and Wood Hydronic and Space Heating)

Does an add on furnace make sense for me?

Post in 'The Boiler Room - Wood Boilers and Furnaces' started by cstamm81, Dec 7, 2011.

  1. cstamm81

    cstamm81 Member

    Joined:
    Nov 5, 2011
    Messages:
    25
    Loc:
    Leesport, PA
    I am currently running a large EPA stand alone wood stove in my unfinished basement. My ranch house is about 1900 sq ft in the basement and another 1900 sq ft of living space. It seems to get the heat I really want upstairs I would need to fully and properly insulate my basement. Looks to be a daunting and expensive task.
    I am wondering if putting an add on furnace in it's place would make sense for me. In theory I would not be heating the basement, instead ducting most of the heat to the upper floor. I am specifically looking at the Englander 28-3500, non-EPA with an 800 cfm blower, I cannot afford a more efficient furnace right now.
    Below is a drawing of my current setup. The add on furnace would be placed where the wood stove is now. The furnace would sit under the far end of my main trunk line from my forced air oil burner. I know the add on furnace cannot be piped into the return of my oil furnace. I also do not see how I could use the oil furnace to help move the hot air, since the furnaces would be across the house from each other.
    So, could I in theory just duct from the add on furnace right into the main trunk and hope the built in blower can push air to all of my supply ducting? Or, would I be better off installing a stand alone smaller trunk line and just ducting to certain rooms?

    [​IMG]

    red are supplies and blue returns.

    Helpful Sponsor Ads!





  2. stee6043

    stee6043 Minister of Fire

    Joined:
    Aug 22, 2008
    Messages:
    2,342
    Loc:
    West Michigan
    Hope is not a startegy! ha, sorry, I had to.

    First and foremost, if you think simply adding insulation to your basment would enable your current wood burner to heat the whole house I think you should pursue this option. Insulation can be one of the easiet, most cost effective and best performing "heat system upgrades" available.

    I'm not sure exactly how you invisiton your duct work coming together. But that supply air from your wood furnace would take the least resistent path from wherever it enters the system. If the cold air return is the easiest path to take, this is the way it will go. Properly installed hot air systems, I believe, will have a damper/flap designed to prevent the supply air from going the wrong direction in the system.

    I'd be shocked if you could buy an Englander, build a chimney and install everything for less than the cost of R20+ on every wall in your basement. My guess would be insulation should be less than half the cost??? And last, I would also bet 800cfm will not be enough push to get your whole house heated.
  3. cstamm81

    cstamm81 Member

    Joined:
    Nov 5, 2011
    Messages:
    25
    Loc:
    Leesport, PA
    I agree and it would be nice to insulate the basement. It's not straightforward though as one, my basement is pretty darn big, two, I would have to move a lot of utilities as they are on the rim joists in a lot of places, and three, I have water issues with heavy rains which woulf be ungodly expensive to remedy and would make insulating a nightmare. I could in theory insulate and partition parts of the basement and put the stove in it's own room.

    As for the furnace idea... I would be installing it in place of the existing wood stove as seen in my crappy drawing. So, no need for a new chimney, everything is already in place. It says in Englander's manual you cannot duct into the cold air return of your main furnace, as the excessive heat may cause issues. So, I would be stuck with either ducting into my main trunk or installing new ductwork to key rooms.
  4. KTLM

    KTLM Member

    Joined:
    Dec 17, 2010
    Messages:
    73
    Loc:
    W Pa.
    The 28-3500 does put out heat. Plenty of it. Only potential problem that I see is ducting the heat almost 40 ft. to get it to your furnace plenem. Not that you can't do it but you will lose some heat along the way. Insulation is always a good start in my opinion.
    Make sure the 28-3500 is not too oversized for your house.
  5. jeff_t

    jeff_t Minister of Fire

    Joined:
    Sep 14, 2008
    Messages:
    3,589
    Loc:
    SE MI
    My gas furnace is somewhat centrally located in my basement, and my wood furnace has two 8" round hot air ducts. I couldn't make it work running them both into the plenum, so I ran one on each side of the plenum into the bottom of the main trunk. The Hotblast has two blowers rated, I believe, at 550 cfm each. About 95% of the time they are more than adequate. Really cold and windy, I can run the fan on my gas furnace and push a lot of heat. I was worried about backfeeding into the wood furnace, but actually get a venturi effect with air blowing across the round ducts. This is in a 1600ish ft² ranch about as long as yours.

    I'm not too sure how it would work trying to move heat all the way to the other end with an 800 cfm blower. Running all the way to your oil furnace plenum would also get really expensive. It's also a good idea to pull from your cold air return.

    Have you looked into other furnaces? Maybe something else in your price range has a blower with more balls.
  6. 88bomber

    88bomber New Member

    Joined:
    Oct 28, 2012
    Messages:
    2
    I'd like to resurrect this thread as I'm planning something similar. Take a look at this pic. All duct, air handler and wood furnace are in the unfinished basement. All registers are upstairs. The wood furnace and air handler are probably 20ft apart. I know this isn't optimal, but would it work? I don't want to run the wood furnace supply over to the air handler plenum because I'd have to drop below the floor trusses to do it.

    Attached Files:

  7. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    48,038
    Loc:
    South Puget Sound, WA
    Like the OP's system, you will get much better performance by insulating the basement. The heat loss to the walls and via the ductwork (if also uninsulated) will be major.

    What size is the trunk duct where you want to connect? Usually it is downsized quite a bit from the core plenum. This helps balance air flow to the end of the line registers, but it may work against this setup by trying to feed from the end instead of from the center.

    In theory the set up will work, somewhat. What I suspect will be the down side is that the opposite trunk will be underfed resulting in that end of the house being cooler. It could be improved by not returning air from the basement, but instead ducting the furnace return up to a floor register on the main floor of the house.
  8. 88bomber

    88bomber New Member

    Joined:
    Oct 28, 2012
    Messages:
    2
    Sorry, I should have clarified. My basement is well insulated...as is the whole house...new construction. I just want to supplement my electric heat pump during the coldest months.

    The trunk is 14" where I connect (the englander output is 8"). I'm sure the other side of the house will be underfed, but I have a 10" duct booster fan I could use as well.

    My main concern was when (if) both the wood furnace and heat pump are running, would the 2 sources to the same trunk cause any issues? ... other than less than max efficiency.

    The return is a good idea too.
  9. begreen

    begreen Mooderator Staff Member

    Joined:
    Nov 18, 2005
    Messages:
    48,038
    Loc:
    South Puget Sound, WA
    I definitely would set it up so that they can't run at the same time. It would be bad if either system's pressure kept the other's backdraft damper closed while in operation.

Share This Page