e-refrigeration.com

Replacing a Compressor

A complete Compressor replacement is really a job for an experienced tech, the following highlights the tasks needed to correctly carry out this job.

Diagnosis

Probably one of the most important thing to first identify is if the compressor is definitely the defective part especially as its usually the most expensive component to replace.

If the compressor is found to be damaged the next prognosis is what happened to make the compressor die in the first place. Compressor are usually reliable and often something else in the system or its design is causing the compressor to malfunction. If the compressor is no longer working a good first test is to carry out a check of the electrical system including relays, capacitors etc. Is everything tests ok than until a new compressor is installed that works and the system is re gassed it is difficult to further diagnose other problems.

Damaged Compressor Removal

* Firstly disconnect the power supply and carefully remove any electrical components, its a good idea to write down where the wiring assembly as it an take a while before everything will be re attached.

* We now need to recover any gas from the refrigerator, using a safe and approved method to not contaminate the environment or the system.

* Unbraze the tubing from the compressor. Heating copper tubing to high temperatures with the presence of oxygen causes copper oxide (a soft, black, flaky material) to form on the surface of the tubing. To prevent this formation, purge the system with an inert gas before unbrazing it. I normally use Nitrogen as its quite cheap and works very well.

As you unbraze the compressor tubing, allow the nitrogen gas to flow at low pressure through the copper tubing. This prevents the formation of copper oxide inside the tubing, thus preventing system contamination. The nitrogen gas should be bled through the system while the tubing joints at the compressor suction and discharge ports are being unbrazed.

Remember it is possible the compressor is burnt out, if this is the case it might contain acids which are harmful to the skin as well as surfaces so its important to wear gloves and clean up any spills quickly.

Once the welds are dismantled and the compressor is removed cover the open ends of the system with tape to reduce the chances of any further contamination.

Compressor Inspections

We now need to examine the compressor and try and confirm what the extent of the failure was. A quick visual and smell test will give us an idea of whether a serious burn out has taken place, or wither a mechanical problem occurred. If there is evidence of a burnout an acid test kit check will give us valuable information of how bad it was and how contaminated the system might be. If there is evidence of a major burn out a full system clean up will need also to undertaken. If no sign of any acids exists its still a good idea to replace the liquid line filter drier to protect the system of any small contaminations.

Installing the new compressor

Ok, so we now have our new compressor which is identical or as close as possible to the removed broken one. The easiest method of replacement is to get an exact replacement where all fittings and mounts are the same. If this is not available an aftermarket compressor with the same specs can be bought, however extra time is often required to install them.

We now line everything up and re mount the compressor and its time to begin brazing. The same methods will be used to melt the braze by purging the system with nitrogen throught the discharge and suction ports of the compressor. With any braze its a good idea it thoroughly check for any imperfections and small cracks or holes.

Checking and recharging the system.

Our new shiny compressor is now in place, the system should be re sealed by our expert brazing. Its now time to check for any leaks, different methods exist but an electronic leak detector used correctly can usually spot any problems to your new brazed joints. Assuming all is well we can now pull a vacuum and then fully recharge the system with new refrigerant. It is essential to get the charge amount correctly. Most techs now use a set of electronic charging scales done with the amount specified by the factory.

Finally, recheck all the electrical components. Also check operating pressures and the superheat and sub cooling. Verify that the system charge is correct. System pressures, superheat, sub cooling, and the temperature differences across the indoor coil can indicate otherwise hidden problems.

So there we go, our system should be working like new and the job is done.