Heat one room and cool another with an in-wall AC

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I work in a bakery. It gets warm in the summer, but not warm enough for bread to rise without extra heat. We have a 'proofer room' where the bread sits while the dough rises. The room is heated by two baseboard heaters, and another space heater. It's approximately 10 feet by 10 feet. Also, we run a humidifier in the room.

  1. I know that resistive heat is not the most economical way to heat a room, especially as warm as we need it. The electric bill agrees with me.
  2. We'd like the proofer room warmer, but the rest of the bakery cooler, if possible.
  3. Running a space heater in the summer feels foolish.

It seems like a perfect solution to place a through-the-wall type air conditioner (not the window type) in the wall between the rest of the bakery and the proofer room, to push the heat (and humidity) from the bakery into the proofer room. If I understand correctly, this would heat the room more efficiently than a space heater, with the added benefit of cooling the rest of the bakery at the same time.

One problem that I've already considered is that the temperature controls on the AC would be on the "cool" side of the AC. To prevent the room from overheating, I could plug the AC into a thermostat outlet outside the proofer, with a temperature probe inside the proofer. The outlet would shut the AC off once the proofer got to the desired temperature. I'd have to get an AC with a mechanical on/off switch that would run when the outlet turned it on, without having to push buttons.

I can't find any examples of someone doing this. Is this a good idea, or am I missing something?

We would hire the work out to someone else to do, so don't worry about my qualifications as an electrician etc.

Best Answer

I'm not an expert to tell you whether this is actually a good idea, but an AC unit used for heating is called a heat pump. There are two differences between "a heat pump" and "an air conditioner":

  1. Heat pumps contain a reversing valve which reverses the operation so that what would usually be the cold side gets hot and the hot side cools instead.
  2. The thermostat will be suitable for heating (turns on when too cold) as well as cooling (turns on when too warm), and also control the reversing valve to switch modes as needed.

In your case, you only care about the second feature. Thus, buying a heat pump to be installed through your wall is one possible solution which gives you a thermostat that works as desired without needing external control.

However, any prebuilt unit will also be designed to put the compressor noise on the "outside", which would be your bakery and might be less comfortable than making the proofer room noisy.

You could likely get a more pleasant result (noise in the proofer room instead) by getting a system designed and installed for the exact application by a HVAC technician; it would probably be slightly more expensive, but it wouldn't be particularly harder to install and maintain than a more usual cooling installation, I expect.

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