in-wall 220v a/c unit: adding thermostatic control

[terminaldegree]

Hi folks,

I'm renting an apartment with an old, manually controlled in-wall a/c unit. I will spend some time away from home this summer and wish to control the temperature (and, by association, humidity) in the apartment to protect a nice piano I own and want to keep as stable as possible.

Some greenhouse supply shops have thermostatically controlled plugs (for lack of a better word) that turn on at certain temps and then turn off at other temps. You plug your a/c into an adapter that goes into the wall outlet.

Is there some reason I can't find a 220v version of this? The 110v ones are easy to find and are roughly $20.

Thanks for any advice! I don't want to leave the old wall a/c on constantly while I'm gone, and don't know how much to trust the manual temp knob adjustment to keep things stable with changing outdoor temps...

 

[brianl703]

You could wire one up to a 110V contactor (basically a heavy-duty relay), so the contactor controls the AC.

You could also get a 24V transformer, a regular thermostat for a central-air system, and a 24V contactor and do the same thing.

 

[Ursae_Majoris]

Is wiring accessible? I'd put a 240V programmable thermostat on it. It is not that difficult. $50 at HD. My bathroom electric heater has one. Works like a charm.

hmm, just realized that you rented....Never mind, then.

 

[duaneb9729]

what is wrong with using the one that is built into it?

i know they are not marked in degrees but that would be easy enough to figure out, using the room thermostat for the heating as a guide.

 

[brianl703]

Originally Posted By: Ursae_Majoris
Is wiring accessible? I'd put a 240V programmable thermostat on it.


All the 240V ones I've seen are heat-only. I suppose there must be some heat/cool ones around though.

 

[eljefino]

Can you get into the AC unit? If the temp control knob has real thin wires leading away from it to a relay that controls the main power, you could tap into the temp control knob and run it off a $30 LUX digital thermostat from Lowes. If you have hurdy gurdy thick wires leading from the knob... naturally... that's full voltage and requires additional precautions (and I wouldn't mess with directly).

You need the electrical knowhow to spot parts and stay safe, naturally, and to put things back when you move out.

Another wild idea would be to get a logging weather station with indoor/outdoor temp and humidity... you could even set it up so you can check on your place over the web. Watch 24 hr worth of logs to see if the AC is kicking in appropriately... and watch a mild day vs hot for the same.

I have an image in my head of one of those horrid motel units with the pushbuttons and 90 dB oversized fan that kicks on and off every 45 sec...

 

[terminaldegree]

Thanks for the ideas so far. I'd rather not have it running constantly while I'm out of town for 3 weeks. Does anyone know if the temp control knob on this old thing maintains an actual temperature or just has the compressor cycle on every "x" times an hour?

Fwiw, I'll try negotiating with my landlord for an updated unit with a digital thermostat as a condition of renewing my lease...so hopefully I won't have to rig some sort of solution myself before warm weather arrives.

 

[duaneb9729]

the fan will run constantly, the compressor will cycle on and off with the built in thermostat

 

[mechtech2]

He really does not want a thermostat, but a timer.
This is certainly not something you'll find at the corner quick mart.
I'd dive in with Google.

 

[eljefino]

I presume window ACs are banned? (Like the windows don't open etc) You could get a $79 special from walmart and just cool the piano room. Get a chunk of plywood, cut it up, block the door, vent it into your kitchen... who cares, you aren't home.

 

[brianl703]

Originally Posted By: eljefino

I have an image in my head of one of those horrid motel units with the pushbuttons and 90 dB oversized fan that kicks on and off every 45 sec...


The industry term for those is "wallbanger unit".