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  1. #1

    Retro-fit hot water coil in air handler?

    I just moved into a big old foreclosed rowhome in Baltimore. I've had guys working in there to straighten it out for month now - it's an old beast that ate the previous owner's shirt, and I am a first-time homeowner myself. ~3500 sqft on 3 finished floors, over an unfinished basement. Dual-zone AC system installed. Heating system is old natural gas boiler + radiators.

    The house will be empty almost all day M-F, so I've been investigating how I can supplement the heating system so we can keep the boiler temp low but be able to quickly bump the heat up when we get home. I suggested branching a new pipe from the supply side of my boiler and running it to the basement air handler located 15' away on the same wall, and installing a hot water coil inside the air handler. I figure my idea was a cheap and simple way to force hot air to the main floor when we get home, but both my contractor and his HVAC subs thought it was a strange/difficult solution. Is the problem that I need an air handler specially designed for hot water heating, or that I'd have to have a cutom water coil sized? Or are these guys incorrect? My contractor is suggesting gas fireplace installations, and his HVAC guys said to install an electric heater in the air handler.

  2. #2
    Join Date
    Jan 2004
    Location
    Lancaster PA
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    68,334
    I have the set up your talking about installed in some homes with radiant heat. It works well. Apparently your GC and HVAC subs don't have much experience with such setups.

    The radiators can be setup as first stage heat, and the hydro coil as second stage. this will give you quick ecovery, and allowed for tjhe rads to take over once the house is warmed back up.
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  3. #3
    Join Date
    Aug 2004
    Location
    North Richland Hills, Texas
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    14,915
    As an add on to an existing air handler, the hydro coil would be in the duct external to the air handler.
    There are a number of manufacturers that make coils for that. This is just one: http://www.firstco.com/products/hwc.asp

    The problem you may have is with the required space for the coil and any duct transitions needed.
    If more government is the answer, then it's a really stupid question.

  4. #4
    Join Date
    Oct 2009
    Location
    God's country - Shenandoah Valley, VA
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    Quote Originally Posted by mark beiser View Post

    The problem you may have is with the required space for the coil and any duct transitions needed.

    We have coils that most of the time will fit right into the plenum; they're 4 inches wide and all that needs to be done is to put a 4 inch channel in to hold the the coil. First Co. coils are okay but sometimes hard to get in a size that doesn't require duct transitioning.

    As BeenThere stated, you could hook it to the 2nd stage of a multistage thermostat and it would only come on when the rads need back up or when the t'stat is turned up more than 2 *.

    You could connect it as another zone off the boiler or possibly use the return line between the rads and the boiler with either a 3 way zone valve or an injection circ. depending on your piping arrangement and size. If you have a cast iron boiler, it's very important that the return temp doesn't drop below 130* for a sustained period: you may need a thermostatic bypass valve or primary / secondary piping.
    Bob Boan


    ​You can choose to do what you want, but you cannot choose the consequences.

  5. #5
    This is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise, commentary or ask questions of the OP here. Please apply to the AOPC today, thank you.

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    Last edited by beenthere; 10-02-2012 at 04:33 PM. Reason: Non Pro * Member

  6. #6
    Join Date
    Jan 2004
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    Jim Brown39,, this is the Ask Our Pro's forum, and only Pro members that have been vetted by the AOPC may post advise here. Please apply to the AOPC today, thank you.

    You can find the rules for posting and qualifications here.

    Your post has been deleted.
    Further infractions may result in loss of posting privileges.
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