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Radiators and A/C Install

rhw Member Posts: 49
I am looking to add central A/C to my first floor and was wondering if putting the vents and or return under the radiators would be ok?


  • Jamie Hall
    Jamie Hall Member Posts: 23,675
    Can't see why not -- you probably won't be running both at the same time. You may get a little induced circulation through the A/C ducts that way, but I would expect it to be very small, given the resistance of the ducts.
    Br. Jamie, osb
    Building superintendent/caretaker, 7200 sq. ft. historic house museum with dependencies in New England
  • Bob Bona_4
    Bob Bona_4 Member Posts: 2,083
    I would not do this.
  • ChrisJ
    ChrisJ Member Posts: 15,929
    Bob Bona said:

    I would not do this.

    I'm new to this, but here's my understanding.

    Returns for an A\C only system belong high up on the walls or on the ceiling.

    Supplies need to be able to cause air in the room to circulate. The radiator will impede this and likely cause the air to disperse down low allowing little mixing.

    Returns on a floor make good vacuum cleaners. Not the best idea in general.

    Single pipe quasi-vapor system. Typical operating pressure 0.14 - 0.43 oz. EcoSteam ES-20 Advanced Control for Residential Steam boilers. Rectorseal Steamaster water treatment
    EBEBRATT-Ed Member Posts: 15,849
    @ChrisJ is correct ac returns should be up high but your probably not wanting to rip the house apart to do this. I don't see a problem under the radiators except for access to clean the vents.

    But I wouldn't put them there if you have other choices
    JUGHNE Member Posts: 11,111
    edited June 2017
    Sometimes part of the returns can sometime use the floor of a closet to bring duct up from the basement. Then have wall grill on the high wall area of adjacent room(s). If the closet is between rooms then a grill for each room. The ceiling of the closet can be lowered to cover duct.
    For example custom built rectangular duct of about 5" x 30" might not cut into some old closet space.

    I have a dedicated AC duct system, all returns are high wall. The perimeter of the house uses the standard floor diffusers. There are 3 high wall supplies also which is not a bad place for AC SA. However I am used to radiant heat and having cool air touch the back of the head is sometimes uncomfortable. I dodged a bullet by not putting a high wall SA in our mas bedroom. ;)

    Cutting in floor SA under CI rad would not only disturb the distribution/flow of air but require the rads to be temporarily moved for the cutting of the floor. Sometimes something to avoid.