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  1. #1
    Join Date
    Jul 2011
    Location
    NEW YORK
    Posts
    58

    AHU Recommended Insulation

    Dear Sir,
    Commercial AHU inside an MER. Where would it be advantageous to have insulation on a air handler unit that has a supply and return fan that is located indoors. We have a new unit that doesn't have any insulation on the return/oa ductwork that is indoors?

    What is the preferred insulation recommendations and why?

    Thanks,
    Bob C.

  2. #2
    Join Date
    Jul 2003
    Location
    Orange County N.Y.
    Posts
    1,176
    Quote Originally Posted by CHAMBERS87 View Post
    Dear Sir,
    Commercial AHU inside an MER. Where would it be advantageous to have insulation on a air handler unit that has a supply and return fan that is located indoors. We have a new unit that doesn't have any insulation on the return/oa ductwork that is indoors?

    What is the preferred insulation recommendations and why?

    Thanks,
    Bob C.
    In my experience there is only what the engineer preferes. Some like the regular 1-1/2" or larger roll type soft fiberglass insulation, some like internally lined insulation, some like having you install duct board over the ducts, and I've even had to insulate with different types of styrofoam insulations. It seems to be more about cost and efficiency than about what is more effective. Engineers have the final say for the most part.

    ...Ron
    Roof Rat

  3. #3
    Join Date
    Jul 2011
    Location
    NEW YORK
    Posts
    58
    What we have is insulation wrap. What is the recommended ductwork to be insulated? The OA Ductwork to return, mixing area?

    Please advise?
    Thanks,
    Bob C.

  4. #4
    Join Date
    Jul 2011
    Location
    Croatia
    Posts
    51
    ductwork that carries air with state equal or very similar to design indoor air conditions is not insulated as there is no purpose to have insulation.

    there is number of occasions where carried air is not of the same state, like return air lines through unconditioned spaces, return that exhausts heat directly from lighting fixtures and similar.

    you would need to look through the whole layout of your return ductwork to be able to decide whether and/or where insulation is needed (or not).

  5. #5
    Join Date
    Jul 2011
    Location
    NEW YORK
    Posts
    58
    1-So the indoor air handler unit (inside MER) that uses econ outside air damper to lower the supply temp and mixes with the return in the mixing chambers does not need insulation on the outside of the duct?

    2-Also the unit that has an extra DX coil aft the preheat to precool the mixed air should have insulation?

    I was under the idea from the OA ductwork to the return mixing area due to heat loss/and/or heat gain, insulation wrap on interior is recommended as per ASHRAE?

    Is that correct?

  6. #6
    Join Date
    Jun 2010
    Location
    Philadelphia PA
    Posts
    2,198
    If it sweats then you NEED insulation. For energy considerations, probably more important to see if doors / panels fit to reduce air leakage
    You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!

  7. #7
    Join Date
    Jul 2011
    Location
    Croatia
    Posts
    51
    Quote Originally Posted by CHAMBERS87 View Post
    1-So the indoor air handler unit (inside MER) that uses econ outside air damper to lower the supply temp and mixes with the return in the mixing chambers does not need insulation on the outside of the duct?

    2-Also the unit that has an extra DX coil aft the preheat to precool the mixed air should have insulation?

    I was under the idea from the OA ductwork to the return mixing area due to heat loss/and/or heat gain, insulation wrap on interior is recommended as per ASHRAE?

    Is that correct?

    1- this looks like free cooling at winter time, anyhow, outside temperature is not the same as indoor temperature, most of time, so you do need insulation as per previous post.

    2- Similar to point one, dx coil will seemingly lower temperature, and again you need insulation.

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