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AC Unit Compressor

Post questions and info about pneumatic (compressed gas) powered cannons here. This includes discussion about valves, pipe types, compressors, alternate gas setups, and anything else relevant.
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AC Unit Compressor

Unread postAuthor: saefroch » Sat Jun 18, 2011 1:03 pm

Recently came into possession of an old AC unit. The previous owner accidentally drilled into the heat exchanger, then hid the unit in his attic for a few months. I took it apart, and reduced it to the below. Is what I did correct? I think all I have to do is insert a switch between the purple wire on the compressor and the other side of plug, is that correct?
Image

The label on the compressor, if that's at all important...
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Unread postAuthor: Technician1002 » Sat Jun 18, 2011 2:16 pm

That should work. The worst you can do is fry the switch and pop the circuit breaker.

The LRA number refers to the maximum start current which is 29 amps. This compressor will be good for relatively high volume, but it should not be used for high pressure. If it comes close to stalling, it will draw more than 20 amps and blow your circuit breaker. This thing is much higher volume than a fridge compressor.

It should be good for cannons using between 150 and 250 PSI with a good fill rate.

It was originally built for R22 which runs higher pressures than R134a, so it should perform well.
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Unread postAuthor: saefroch » Sat Jun 18, 2011 2:26 pm

So... this is a low-pressure high-volume compressor, but how does its pressure output compare to the dehumidifier compressor I posted (that I have yet to dismantle fully, waiting on coolant removal), I'm planning on putting them in series for a higher final pressure output... would that work?

Can you identify the "in" and "out" ports on the compressor? I think in on the bottom and out on the top, but I can't be sure...
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Unread postAuthor: Technician1002 » Sat Jun 18, 2011 3:03 pm

The smaller tube is the output. The input is often located near the sealed off process tube.

An AC compressor is defined as a "High Temp" compressor. This designation is based on the expected input pressure based on the temperature of the evaporator.

In an AC compressor the evaporator is held near freezing which is relatively warm. A dehumidifier is also a high temp compressor.

Low temp compressors have a higher displacement and expect lower input pressures associated with much colder evaporators such as ice makers and freezers where the temp is well below freezing. Most fridge compressors are low temp units as that is the temperature of the icebox.

As a high temp unit they are better suited as the final compressor in a multi stage pump for high volume and relatively high pressure. They are quite happy taking in 60 PSI and outputting 250 PSI.
At freezing R22 has a vapor pressure of about 25 PSI. At 45 degrees on the evaporator the pressure would be about 76 PSI. On a hot day the condenser may run 140 degrees and condense at about 340 PSI.

The compressor would work hard but handle an input of about 50 PSI with an output near 300 PSI just fine.

Use a freon chart to see the expected pressures your compressor is designed to work with.

http://www.longviewweb.com/pressure.php
R12 is obsolete. R134a is close to it.

As far as fittings, just google the part number. It's the big number starting with a 2 in the upper left corner of the compressor label.

Do I have to do everything?
http://www.panasonic.com/industrial/includes/pdf/2R7U126A-6A.pdf
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Unread postAuthor: saefroch » Sat Jun 18, 2011 9:16 pm

Based on your description of the input and output, I take it that the output is the top and the input is the bottom? Picture to clarify:
Image

Completed assembly of the electronics. Switch is rated to 20A, I'll start it up sometime tomorrow. I don't expect much coolant to blow out, but I'll be doing it in a VERY well-ventilated area.
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Now I've just gotta get off my ass and get the coolant out of the other one. :roll:
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Unread postAuthor: Technician1002 » Sat Jun 18, 2011 11:24 pm

The coolant is long gone as it boiled off when the temperature went above -40 degrees. From the photos you provided with the green grass, I presume you are well above minus forty degrees at your location.

The only liquid remaining in the unit should be the crankcase oil. If you don't tip it over, it should stay inside it.

If you checked the PDF I linked to, yes the tank on the side is connected to the inlet and the tube on the top is the outlet. That tank is the accumulator. The sealed off short tube on the inlet is the Process Tube where the system was factory charged and sealed.
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Unread postAuthor: saefroch » Sun Jun 19, 2011 1:26 pm

I suspect a fair amount of the oil is missing, because some dripped out of the heat exchangers when I was moving them around :?

Do you have a suggestion on how to replace/refill it?
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Unread postAuthor: Technician1002 » Sun Jun 19, 2011 1:33 pm

A few drops is no concern. More than a few tablespoons would be needed to make changes.
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Unread postAuthor: saefroch » Sun Jun 19, 2011 1:44 pm

Thanks. I just went outside and turned it on. Nasty smell was produced when I first started it up, probably a combination of the fact that the coolant only leaked through a needle-sized hole, and the fact that it sat in an attic with the hole for over a year.

But it worked! :D
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Unread postAuthor: Technician1002 » Sun Jun 19, 2011 1:50 pm

The oil will stink. It's normal. The refrigerant is orderless.
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Unread postAuthor: POLAND_SPUD » Sun Jun 19, 2011 2:31 pm

nice... I wish AC was more common where I live (obviously it isn't because of the climate)... I'd love to get my hands of one of these

have you noticed point 4. in one of the pics ??
compresor housing might reach 150 deg C

lol that's hot
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Unread postAuthor: saefroch » Sun Jun 19, 2011 3:08 pm

Technician1002 wrote:The refrigerant is orderless.
Oh, dang. Thanks for that, never knew.

What about climate prohibits use of AC?
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Unread postAuthor: POLAND_SPUD » Sun Jun 19, 2011 3:53 pm

What about climate prohibits use of AC?

Image
Summers are sometimes really hot (like 40C) but normally the temperature is around 25 deg C so I guess it doesn't make much sense
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Unread postAuthor: Zeus » Sun Jun 19, 2011 5:57 pm

Well this has reminded me to get off my behind and retrieve a few compressors. I've got access to larger air con units (thanks to our weather) and a few fridges.

Perhaps a destruction test on an air con compressor would be in order.

Additionally, one compressor seems to have steel pipes, I presume introducing the pipes to a flaring tool then applying epoxy copiously is the correct approach?
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Unread postAuthor: saefroch » Sun Jun 19, 2011 7:31 pm

I've got a similar pipe problem... The pipes seem to be pretty close to 5/16" OD, but that doesn't correspond to any compression fitting I can find... how should I connect them?
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