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daveo
12-07-2011, 06:44 PM
Im building a small compressor out of a old frige motor, it has a relay on the side of the motor. but I did not take the capacitor out with it. I need a recommendation on a capacitor to get it going. I am a electrical idiot.

The motor is 110 it has 115v-60Hz 1ph on it. I thought this info may help! My heart will not be broken if it fails, the two motors I have were free.

Tom S
12-07-2011, 09:04 PM
Can you still read the compressor/condensing unit serial plate? If you can track down the manufacturer they may list spare/replacement parts, including the capacitor that the compressor shipped with.

How do you plan on keeping the compressor cool and lubricated? All the units that we use rely on the low temperature vapor to keep the motor from overheating, and on the oil circulating with the refrigerant. A compressor running without any cooling gets very hot very fast, and a lack of oil is never good for a motor.

-Tom

Jaakko Fagerlund
12-08-2011, 03:50 AM
How do you plan on keeping the compressor cool and lubricated? All the units that we use rely on the low temperature vapor to keep the motor from overheating, and on the oil circulating with the refrigerant. A compressor running without any cooling gets very hot very fast, and a lack of oil is never good for a motor.
The oil generally doesn't circulate, or at least not in any huge amounts. A fridge compressor is a splash-lubed unit that cools down with the refridgerant gas mostly.

I have done a compressor out of one, check http://homeshopmachinist.blogspot.com/2010/12/silent-air-compressor.html. It heats up quite warm during half an hour running, but it has a thermal limit switch preinstalled which hasn't tripped yet once. The initial oil I used was ATF oil, about 200 ml and haven't had any need to replenish that.

Circlip
12-08-2011, 06:03 AM
Definately ATF, (Don't half stain light coloured carpets and is a bugger to wash out). An oil and water trap on the outlet stops "Carry over".

Regards Ian.

daveo
12-08-2011, 08:03 AM
The oil generally doesn't circulate, or at least not in any huge amounts. A fridge compressor is a splash-lubed unit that cools down with the refridgerant gas mostly.

I have done a compressor out of one, check http://homeshopmachinist.blogspot.com/2010/12/silent-air-compressor.html. It heats up quite warm during half an hour running, but it has a thermal limit switch preinstalled which hasn't tripped yet once. The initial oil I used was ATF oil, about 200 ml and haven't had any need to replenish that.

That is exactly what im doing with it. Now if I can just get it running!

Jaakko Fagerlund
12-08-2011, 11:06 AM
If my memory serves, you need about 80 uF per kW. A fridge motor is probably around 100 W, depnding on unit, so you would need a 8 uF capacitor for it. It isn't exact to get it going, but getting the uF rating of the cap close to "designed" gets you most of the power out from it.

And yeah, ATF oil doesn't get off of clothes easily :rolleyes:

madokie
12-08-2011, 05:25 PM
old fridges get scraped out daily,put ad in craigslist under wanted that you need a capasitor off old fridge thats being junked out, the scrapers will give them to you if you go get them, or you can go to scrap metal places and go looking for one, i bet if you find one or 2 that looks right and you tell them what your doing ,they'll just give it to you,not any weight in a capasitor.since ATF is 90% mineral oil ,be carefull what your wearing if you still use mineral oil to clean out the wax from your ears.