In my almost 30 years of performing HVAC and refrigeration service, I’ve encountered many premature compressor failures. These failures weren’t the all same. They were a scattered mess of destruction.
Shorted windings, shorts to ground, leaking electrical terminals, failed internal parts, seized from lack of oil etc, can all happen…But they all can be avoided.
Let’s look at a few common failures.
Compressor Shorted To Ground
This type of premature compressor failure happens when a portion of the compressor windings shift loose from their tight bundle and come into contact with the body of the compressor. In most cases this is known as a dead short and will instantly pop a fuse or open a breaker.
This can be checked with a multimeter set to ohms. Place one meter lead on a compressor terminal pin and the other lead on a good ground reference. Ensure to repeat the process for all compressor pins. There should be no measurable resistance from each pin to ground. If there is, you have a winding short to ground.
Compressor Windings Are Shorted Or Open Windings
Compressor windings in general, have published resistance readings by the manufacturer. For example, the Copeland Mobile app has their resistance readings published for each compressor model. This can be easily looked up by either scanning the compressor bar code or by manually entering the model number.
Shorted windings and shorted to ground are not the same thing. A shorted compressor winding only, can’t be referenced to ground. If a winding has a published reading of 5 ohms for example but reads 1 ohm, with a multimeter, the winding is considered shorted.
If the winding reads 100 ohms when it’s supposed to read 5 ohms, we can consider that winding to be open or partially open. If the winding were to read OL (open line), the winding is fully open.
To check this, set your meter to ohms and check across each set of pins and then check it against the published winding resistance readings.
Seized Compressor
A compressor is seized when it’s internal parts aren’t lubricated enough with oil and metal on metal friction (galling) begins to happen. A lack of oil return or copper plating can cause this. Copper plating is the build up of copper alloys on compressor parts, this puts the tolerances out by adding another layer of metal to moving parts that it wasn’t designed for. Copper plating is caused by acid in a system (which is often a side-effect of moisture).
Best Practices During Installation To Avoid Premature Compressor Failure
Pipe Prep
After a piece of pipe is cut, there is a lip created on the inside of the pipe. This lip can restrict oil flow on it’s way back to the compressor. The lip can also create refrigerant turbulence at the joints and can cause leaks down the road.
The lip should be reamed, ensuring the pipe is pointed downward so any copper filings fall out during the process.
Cleaning the pipe with a Scotch-Brite pad or similar will ensure the pipe is clean and that silfos will penetrate well.
If pressing pipe, the process is very similar. Here’s a video on how to press properly using Rapid Locking System.
Nitrogen Braze
Brazing is done at a high temperature, approximately 1300⁰F. During this process the build up of copper oxide is present. Copper oxide on the inside of a pipe will be swept away by POE oil, acting like a detergent and scrubbing the pipe walls.
Copper oxide can restrict metering devices, this can lead to less suction gas moving back to toward the compressor, less suction gas, more heat and less lubricant. Sounds destructive to me, how about you?
If you wanted to avoid brazing, there are alternatives which can be used in the right situations.
Pulling A Proper Vacuum With Decay Test
Removal of as much moisture as possible is of high importance. Ensuring your evacuation is below 500 microns or even lower is a good start, but we want to ensure our evacuation holds in a decay test.
This is when we shut off our vacuum pump, isolate the pump from the system and watch for a rise in pressure on our micron gauge.
If there is no rise, consider your decay test successful. If it rises and keeps rising, you may have a leak. If it rises and flattens above 500 microns then there might be some more evacuation to accomplish.
Correct Refrigerant Charge
Some systems come pre charged some don’t. On pre-charged split systems it’s a possibility that additional charge might be needed. Follow the manufacturer’s process to add additional refrigerant.
On systems that come without any charge, again, we’ll need to follow the manufacturer’s guide lines.
Other considerations…
Correct wiring and good connection of that wiring, a solid pressure test, unit placement, correct equipment sizing, a proper flare and torque for flared connections and air flow. Air flow air flow air flow. If our air flow is not correct. Don’t expect the system to perform correctly. You can also expect the compressor to potentiality fail prematurely as well.
Maintenance
A quick word on proper maintenance. We can’t expect a compressor to last if we’re not doing a proper maintenance on the equipment the compressor lives inside. If you want to save time (and refrigerant) in your future maintenance tasks, consider adopting a non-invasive system testing technique.
All of the items below will contribute to premature compressor failure. And all can be detected during maintenance.
Wrapping It Up
This article could have been much longer but I know you’re busy out there. I know collectively, we can push away from the beer can cold mentality and avoid premature compressor failure.
Listen to this podcast with myself (Gary McCreadie) and Jeff Kukert from Copeland discussing compressor failure.