Air Conditioning Compressor

To put it maybe too simply, the air conditioning compressor pumps refrigerant through the system.

To be a little more technical, the air conditioning compressor takes in low pressure, low temperature, refrigerant vapor, and discharges it at a higher pressure and temperature.

My personal preference for a description is that it transforms refrigerant from a low pressure, low temperature vapor into a high pressure, high temperature vapor.

The compressor is designed to exactly match the capacities of the evaporator and condenser, so that it can maintain a certain condensing condition, and a certain evaporating condition.

If you're looking for a replacement air conditioning compressor and can't find the exact same compressor; once you find a possible replacement with the correct voltage rating, make sure the btu capacities match.

When you compare btu capacities, make sure the chart shows the same refrigerant and the same evaporating temperatures as the original compressor.

You also want to be sure the compressor is designed to be used with the refrigerant in your system, and make sure the oil in the new compressor matches the oil in your air conditioning system.

If you're looking for parts or service information; Carlyle, Copeland, Bristol, Hitachi, and Tecumseh have information on their web sites, and thanks to the competitive nature of the industry, I would expect most other major manufacturers, or their distributors, would respond to your inquiries.

Copeland's site has an interactive compressor troubleshooting flow chart that you might find helpful.

Are you trying to figure out whether or not your compressor is working at full capacity?

You need to get a copy of the performance chart for your compressor.

It is a graph that will show you how many btu's your compressor is moving; calculated from the amp draw, superheat, evaporating conditions, and condensing conditions.

If you're working on a 5 ton air conditioning compressor, and the chart shows your compressor moving 60,000 btu's, it's working at 100% capacity.

So if there's a concern that a unit isn't cooling efficiently, the chart will show you how much heat the compressor is moving, which is information that can help when you're troubleshooting.

If you work on single phase air conditioning compressors, any time you work on one that doesn't have a hard start kit on it, do your customer a favor, and add one.

It will help the compressor last longer, it's inexpensive, and easy to install.

When trouble shooting a compressor with a high amp draw, or when checking during scheduled maintenance, take an amp draw on either the start or run lead at the run capacitor.

There should be an amp draw through the run capacitor when the compressor is running.

If there is no amp draw through the run capacitor, you need to find out why.

The possible causes would be:
1. The capacitor has failed,
2. One of the leads is open between the capacitor and the motor terminal,
3. The start winding is open.

If you find an air conditioning compressor that is hot, with the internal overload open, cool the compressor dome down with ice.

While it's cooling down, inspect the compressor terminals, capacitors, relays, wiring, coils, and blowers for possible causes of the overheating.

You may find a dirty condenser coil, undersized condenser fan blade, failed condenser fan motor, a refrigerant leak, or air and non-condensables in the system.

If you're checking for grounded windings with a standard multi-tester, the windings should show infinite resistance to ground.

Any resistance that's readable with a standard multi-tester is an indication that the winding is grounded.

You need to test the windings with a megohmeter, and look for more than 1 megohm to ground.

Less that 1 megohm indicates a bad winding.

Change the compressor before it burns out severely and contaminates the entire system.

Test the system for acid, and clean the system up if it needs it.

I hope this page has helped, and please, feel free to contact us with any specific HVAC questions you might have, including questions about air conditioning on Guam, and refrigeration on Guam.

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