Helpful ReplyFooling an air conditioner thermostat

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tmiles
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2018/01/11 15:02:28 (permalink)

Fooling an air conditioner thermostat

I am going to build a small walk in cooler to store apples for the coming season. We used to store about 1500 bu out of the 3000 that we grew. The cooler was expensive to build (before I was born) and expensive to power and maintain when I was in the business in the 70s. I still have the charging tools.
 
Now I want a cooler for about 25 bu. Again, they are expensive to buy, and service is costly. The solution for a lot of farmers is to use an air conditioner to cool the storage. They are cheap and reliable. If they stop working, you can buy a new one for far less than the cost of a service call. The trouble is that most bottom out at about 60 degrees, so the thermostat needs to be "fooled" to get the temp down to 40.
 
There are kits that are advertised in grower magazines for a few hundred dollars, but I will use a cheaper option. I'll wire a small light bulb to my new thermostat and use it to heat the a/c unit's thermostat and get the a/c to run right down to 40 degrees. It took less than 5 min to do the research on the internet.
post edited by tmiles - 2018/01/11 15:28:50
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RodBangkok
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Re: Fooling an air conditioner thermostat 2018/01/11 19:35:20 (permalink) ☄ Helpfulby tmiles 2018/01/12 10:08:45
Its a little more complicated than that, if you don't monitor the fin temp on the a/c it will freeze up, also you must monitor and control the temp on the thermostat sensor. 
 I build units for our walk in's and one for our curing chamber for meats.  
It uses 3 temp monitors, fin temp, a/c thermostat temp, and room temp, using a low Ohm power resistor as a heater for the A/C thermostat heater,  controlled by an Arduino here's a link:
http://farmhack.org/wiki/coldsnap-air-conditioner-override-controller
 
This design provides tight control over the temp and is much cheaper than the one on the market by a huge margin.
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tmiles
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Re: Fooling an air conditioner thermostat 2018/01/12 10:15:24 (permalink)
Thanks Rod!! Nothing is as easy as it looks!! The light bulb works for me because the cooler will be turned off at night, and the whole season is only about 3 weeks. I may even skip the thermostat. I only need the apples not to get too warm during those warm late Sept days, so that they will last long enough to blend with my later apples to make cider in mid thru late October. 
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