Replies

1. GBA Editor
   Martin Holladay | Apr 08, 2015 10:28am | #1

   Brad,
   Minimum dimensions (volume) for rooms where heat-pump water heaters are installed are specified by the heat-pump manufacturer. The minimum dimensions vary somewhat from manufacturer to manufacturer.

   For more information, see Heat-Pump Water Heaters Come of Age.

2. 
   charlie_sullivan | Apr 08, 2015 12:22pm | #2

   I'm not sure the manufacturer's number will apply directly to your situation, but it's a good starting point. What is your climate? Which of the walls will be insulated and will the floor be insulated? How about under the slab? If the slab is uninsulated, and all the walls are, the room temperature would approach the ground temperature under the slab. If the water heater chilled it below the ground temperature, you'd then pull heat from the ground through the slab to heat the water. The question might be whether it then gets colder than you want for the water heater to work well or for the target food storage temperature. If both, you could let in some warm air from the rest of the basement.

   The humidity removal provided by the heat pump water heater could be very useful in preventing condensation on the cold floor.

3. 
   Irishjake | Apr 08, 2015 01:10pm | #3

   Martin,

   Thanks, figured the manufacturer would give specs, just don't have that doc right here to look at.

4. 
   user-2890856 | Apr 08, 2015 01:14pm | #4

   Locate the heater in a space that is larger and run the vent to what you want to be your cool storage room .
   There are now HPWHs that can vent inside during summer and outside during winter usage . A few even promote drawing the intake air from the attic in summer and elsewhere during winter .

5. 
   Irishjake | Apr 08, 2015 01:22pm | #5

   Charlie,

   I'm in Zone 6A. The floor will be insulated with 4.5" of Neopor under slab, with Stego 15mil vapor barrier between the Neopor and slab. Foundation walls are sandwich wall construction - 6" interior concrete wall, 4.5" Neopor in the middle, and 3-4" exterior concrete wall. So it is well insulated.

   I realize that HPWH will cool the space and some question whether it should be used in the Northeast...here are some other thoughts I have:

   I was planning to have make-up air supply for my stove come in from the sill, through a short run in the basement (same room as the HPWH and then release via a vent behind the fridge. This will increase the efficiency of the fridge by cooling the fins and temper the incoming air. My thought was that this cool air from the HPWH could also be shed via a second (passive) vent up behind the fridge where the air would get tempered and further increase the fridge efficiency.

   The basement will be conditioned heated space, so there will be loss from the mini-splits to heat the air that is supplied to the HPWH. The room will be more than big enough for the HPWH. I intend for the HPWH to dehumidify and cool the extra storage/ seasonal junk storage/ food storage, but want to make sure there is adequate warm air for it to operate efficiently too.

6. GBA Editor
   Martin Holladay | Apr 08, 2015 01:57pm | #6

   Brad,
   You wrote, "I figured the manufacturer would give specs. I just don't have that doc right here to look at."

   If you have Internet access -- and I suspect you do, since you are posting comments on GBA -- you can find the information you seek by visiting the water heater manufacturer's web site.

7. 
   Irishjake | Apr 09, 2015 12:16pm | #7

   Martin,

   Got it thanks. Not sure why I didn't why I didn't think to check there...