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Is it possible to create a heat pump system to exchange cool air from a ground floor bedroom with the heat from a third floor bedroom? I only know of heat pumps being used to exchange cool air & heat between a home and the outside, not between rooms within a home. I've seem peoples post about using fans for this purpose but feel the difference would be lost trying to move air between three floors.

The ground floor bedroom is always several degrees, (4+) cooler than any other room in the house and the third floor bedroom is naturally always the warmest as that is were all the heat in the home rises to.

Running either the heat or AC always blasts the ground floor bedroom even with the vents closed while the third floor bedroom never reaches a comfortable warmth or coolness desired for sleep without making the ground floor bedroom uncomfortable.

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    What type of HVAC system do you currently have? Apr 12 at 3:23
  • The problem with doing exactly what you suggest rather than just moving air, is that the compressor half of any split system is designed to be outdoors, so it will be noisier and uglier than you would want in your downstairs room. If you don't care about that it should work.
    – jay613
    Apr 12 at 11:48
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    If you're going to install a heat pump to solve this problem, a simpler way to do it would be to just install a window AC or mini split upstairs. The central one will keep circulating air but upstairs will get more cooling.
    – jay613
    Apr 12 at 11:50
  • Assuming you have only a central return duct, adding a small return to the upstairs bedroom would help also. Upstairs would get a much larger share of the cool.
    – jay613
    Apr 12 at 12:09
  • I'm not familiar with HVAC stuff.. but here's a funny idea: What if you just took two separate pipes (I was thinking PVC, but aluminum ducting might be better) and connected them between the ground floor bedroom and the third floor bedroom and then put quiet fans (large computer fans?) at different intervals throughout the pipe to blow the air up and down? It wouldn't cover the entire floor, but you did focus only on those two bedrooms. Apr 12 at 14:46

4 Answers 4

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What you've suggested is possible, yes, however residential-grade commercially available systems don't support that mode. There exist mini split heat pump systems supporting multiple indoor units but those I'm familiar with operate the entire system in a heat-only or cool-only mode. They would pump heat from the upper room to outdoors, then from outdoors back in to the lower room.

There do exist systems that do what you want, but they're commercial - meaning priced higher than residential and also too much capacity for most residential use.

It may be possible to improve operation of your system with changes to the duct arrangement: factors such as the cross-sectional size and number and shape of elbows can make a big difference. Location of the equipment matters too. Unfortunately that's all fairly beyond our capacity to address in the Q-and-A format of DIY.

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My best solution so far, for my minisplit system, is to close doors as much as possible to keep heat from going up and down the stairwell... Plus experimenting with a homebrew "return duct" with a fan to circulate aur back down. Currently that's just a flex duct down the stairwell driven by a quiet fan; I'm still pondering how to do it more elegantly.

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Unfortunately that issue lies in the air duct design.

Changing that might be tricky. You could try a zone control.

You could get very creative and install two heat exchangers.

You could simply try to change the fan speed (just some wiring)

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You can use a heat transfer kit. Your hardware stores will stock these kits that come with a inline fan, duct, vents and controller. They are for DIY and very cheap. I have used one to transfer heat from a 2nd floor attic to a downstairs toilet, successfully. The controller has a thermostat and a winter/ summer toggle switch.

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