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Harvesting Waste Heat From Appliances to Feed HPWH

SommerBros | Posted in General Questions on

So, here’s an idea has been bouncing around in my head for a while. Is it worth it to consider collecting the wasted heat from appliances such as fridge, freezer & heat pump dryer to feed to a heat pump water heater?


I’ll explain in more detail. The layout for this scheme is the following. 


Low load, 1800ft2 1.5 story home
Slab foundation.
Open web floor trusses

The Rheem ProTerra Hybrid 65gal HPWH will be located on the main floor under the stairs. The area that the HPWH is in, is a decent size but does not quite have enough CU/FT to avoid ducting the unit so I’m toying with idea of grabbing warm air from other appliance sources nearby. An upright freezer will share the space with the HPWH, so that’s easy and the fridge in the kitchen is reasonably close. The heat pump dryer will be located in a closet on the second floor above a portion of the mech room that the HPWH is in. 


My thought was to essentially create a cold air style return behind the fridge that is open to the open web floor joist cavity,  the ceiling in the mech room would be left open. A similar arrangement for the HPD as it will be located above the mech room and a chase could be open through the floor into the same joist cavity.  


Lastly, since the stair case that the mech room is locate under has a mid point landing, I’m thinking of letting some of the exhaust air from the HPWT vent into the landing area where there is minimal traffic and the cool air is les likely to be felt directly by the occupants. 


Is this a logical idea or a complete waste of time? What am I missing?

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  1. walta100 | | #1

    Seems to me you plan is break even in terms of BTU inside the building. I would be surprised if you could collect enough warm air to feed the HPWH air that is 5° above ambient and I do not think 5° is enough to change the COP of the water heater much.


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