Water Air Exchanger Install Considerations

chabot Posted By chabot, Apr 15, 2017 at 10:05 AM

  1. chabot

    chabot
    New Member 2.
    NULL
    

    Apr 15, 2017
    2
    0
    Loc:
    MA
    Hi,

    You guys seem to be knowledgeable in this area so I want to know if you think I'm on track with my thoughts.

    I will be installing a water/air exchanger into my furnace plenum hopefully next week. There are a number of things I need to consider when doing this.

    The boiler is a bit oversized so one concern is short cycling of the boiler. To make this more complicated I only want to heat a portion of my house meaning I'll be shutting down registers causing potential excess pressure within the duct work.

    There are a number of things I need to consider and want to run this by a few people here.

    My furnace blower is the permanent split capacitor (PSC) type and from what I've read closing registers will cause this blower to work harder, waste energy, stress the motor, while at the same time slowing motor down.

    I believe I can lower speed myself and be ok as long as I take measurements and stay within a static pressure of appr 0.5 inches water column across the return/supply duct.


    Once I find a motor speed that works I can apply heat to my water/air exchanger. I will then measure the temperature rise across the heat exchanger to make sure it's within the furnace manufacturer's specs. I could also verify that I'm pulling enough heat off my measuring the supply and return temperatures on my boiler to ensure I'm close to a Delta T of 20.

    If I'm not pulling enough heat off the exchanger with the lower fan speed I could either manually slow the rate of water flow to the exchanger via ball valve and/or lower my boiler temperature within the Aquastat (not a bad thing).

    If I'm still short cycling the boiler after all this I could pull more heat off the boiler by installing a radiator or two in other areas such as my shop or open a few more registers in the home.


    There will be no oil fire so I won't have to worry about flue gasses.

    Does this make sense? If so is there anything else to consider? Any other thoughts?

    Thanks in advance
     
  2. leon

    leon
    Feeling the Heat 2.
    NULL
    

    Feb 3, 2013
    405
    17
    Loc:
    Southern Finger Lakes Region of New York
    ==========================================================================================

    There is no sense in reinventing the wheel, either install storage for more hot water or fill the firebox half full of firebrick to the flue breech to make a smaller hotter fire so you have a smaller fire and better combustion.

    Purchasing full size firebrick and adding thermal mass with the firebrick will cost you less money than investing in storage.
    and you will have a smaller hotter fire that will burn cleaner with little smoke.
     
  3. chabot

    chabot
    New Member 2.
    NULL
    

    Apr 15, 2017
    2
    0
    Loc:
    MA

    Well that made things much easier. I always tend to overthink things. Thanks
     

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