Transcript Document
September 2014 Tuesday’s Tech Talk or “3T Meeting”
Fall Training Schedule
Obituary of a Compressor
Will focus on compressor failures and proper clean up procedures in the following categories:
Four Part Series --Electrical Issues(June) --Refrigerant Starvation(July) --Refrigerant Flooding(August) --Refrigerant Contaminants(September)
This final compressor obituary series will focus on system contamination. Contamination is not something that is easily detected and will destroy a compressor without visible warnings. The only prevention for contamination is to follow good refrigeration practices when installing & servicing systems. There are only two items that are allowed in a refrigerant system:
*Refrigerant *Refrigerant Oil
Anything in addition to this (outside of Acid Away®) is a potential contaminant and may generate another compressor obituary.
Where do Contaminates come from & why are they harmful?
Moisture:
Moisture is naturally occurring in air and will be present in any system that is open to the atmosphere. It is critical to pull a deep vacuum & replace the liquid line filter drier any time you open a system. This is especially critical with POE oils used with R-410A refrigerant. Moisture is chemically attracted to POE oils and will cause these oils to break down into organic acids—acids that will destroy a compressor. Do not leave a system open to the atmosphere any longer than necessary--no lunch breaks in the middle of a compressor change.
Acids:
Acid is a compressor killer. A recent study by ARI showed that a mild acidic condition could reduce the compressors life from one million hours to one thousand. Acids will attack the compressor windings and etch the copper refrigerant lines. These copper etchings will plate the compressor bearings and cause a compressor to seize.
Trash:
General trash such as solder, dirt, copper shavings, steel wool, and sand from sand paper have all been found residing in compressor shells. These elements will score cylinder walls and reduce pumping efficiency. A compressor that may appear to have weak valves may be suffering from trash in the system.
Copper Oxides:
Copper oxides come from brazing. The black stuff that you see on copper after brazing may be on the inside of the pipe as well. There are three items needed to produce copper oxides: Copper, oxygen & high temperatures (such as brazing). The only way to eliminate copper oxides from inside the system is to purge with nitrogen. Removing the oxygen eliminates the formation of these black flakes.
Trane & Copeland both recommend the use of filter driers for clean up procedures. To quote Copeland:
“This system cleaning procedure has been used in
countless installations over the years, and when this procedure has been properly followed, we do not know of a single instance where after proper cleaning there has been a second failure.”
Acid test kits are the most accurate & safest way to determine the acidic condition of a system. Refrigerant oil should be clear and non-pungent.
Refrigerant oil that is black or has a strong odor (such as rotten eggs or dirty diapers) is likely burnt. You will need to follow a more aggressive clean up procedure with a suction filter drier.
The bottle on the right is clean refrigerant oil— the two other bottles are severely burnt.
Is your Vacuum holding?
You must use a micron gauge to confirm a good vacuum; this can not be done with refrigerant gauges.
Pull a deep vacuum between 350 & 500 microns.
*A quick rise in vacuum indicates a refrigerant leak.
*A slow rise past 1000 microns indicates there is still moisture boiling off in the system. This moisture will generate acids if not removed— continue the vacuum process and ensure an oversized liquid filter drier is installed.
Are your line sets clean?
Evaluate the inside of the discharge & suction lines. A simple swab test with a clean rag or finger will let you know what’s residing inside the refrigerant tubing. A dirty discharge line lets you know that you have some contaminates in the system. A dirty suction line lets you know that these contaminates have worked their way through the entire system.
Remember, those black oxide flakes that you see on the copper tubing may be circulating inside the system as well.
Our parts department carries the Service First filter driers manufactured by Emerson Technologies (Emerson also owns Copeland). These driers contain Alumina to absorb acid and a Molecular Sieve Desiccant to absorb moisture. Some filter driers will have the letters “HH” listed. This drier contains Activated Carbon which removes varnishes and wax--this is the drier of choice for low temp applications and is also recommended in compressor burnout situations.
Liquid line filter driers should be replaced any time a refrigerant system is opened. The use of a properly sized liquid line drier is all that is required in a relatively clean system. Oversized liquid driers should be used if moisture is a concern. Liquid line filter driers should remain in the system unless the temperature drop across the drier exceeds 2 degrees. An excessive temperature drop indicates a plugged drier that needs to be replaced.
Remember; moisture is a system killer; and POE oils will begin to break down with levels as low at 75 parts per million (PPM). But what is a PPM, and how much water are we really concerned about?
Think of a little shot glass that holds 1.5 ounces. This is enough water to contaminate and break down the POE oils in 10 systems--0.15 of an ounce of water is enough to contaminate an average system. A deep vacuum will remove the moisture & non condensables in the refrigerant lines, but it will not remove the moisture from the POE oils—a filter drier must be used to capture this moisture. A 16 cubic inch liquid line filter drier has enough Molecular Sieve to hold ½ an ounce of water in a “dry” system condition. So if your system somehow obtains a shot glass of water, you would need to replace this drier four times to absorb the water--three driers would be completely saturated. A saturated drier will not show a pressure drop, it just loses its ability to remove any more moisture. A temperature drop across a drier indicates some sort of trash in the system
A suction line filter drier should be used after a compressor burnout or if acids & contaminates are a concern.
Suction line filter driers will generate pressure drops as they absorb contaminates—this leads to a loss of capacity, efficiency and a potential compressor failure. Because of this, it is recommended that these driers be removed once the clean up process is complete (within 72 hours of run time). Suction line driers can be used for permanent installations and remain in the system as long as the pressure drop across the drier does not exceed 3 PSI. POE oils will not break down or harm the materials used in today’s suction line driers—this was a concern of the past.
Filter driers are included in the system warranty. Ask the parts department to add a liquid line filter drier with every compressor order—you can also warranty a suction line drier if you have a burnout condition.
What about oil additives? There are many oil additives on the market that make bold performance statements. Trane has tested Rectorseal’s Acid Away and confirmed that it is a beneficial product to help neutralize acids without harmful affects to the system. Acid Away is an accessory we can use in a clean up process—it is not a replacement for a suction drier.
No other additives are allowed in Trane systems and Copeland makes a similar statement:
“Although Copeland can’t comment on any specific product, from our own testing and
past experience; Copeland generally does not recommend use of any additives to reduce compressor bearing losses or for any other purpose. Furthermore, the long term chemical stability of any additive in the presence of refrigerant, low and high temperatures, and materials commonly found in refrigerant systems is complex and difficult to evaluate without rigorous controlled chemical laboratory testing. Use of additives without adequate testing may result in malfunction of premature failure of components in the system, and in specific cases, may result in voiding the warranty on the component”
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It is not uncommon that system contamination is improperly diagnosed, and this contamination can become extreme if the previous technician did not follow a good clean up process.
These contaminates can plug screens in check valves, metering devices and accumulators. Opt for oversized driers in situations with extreme contamination & burnout conditions. In the event of excessive contamination, remove or replace the screens and accumulator. Accumulators have an oil return pick up hole in the bottom of the suction line that is covered by a screen mesh. Contaminates that plug this screen will inhibit oil return to the compressor. The accumulator will become an oil trap and the new compressor will seize soon after installation.
Obituary of a Compressor
This concludes this 4 parts series!!
Four Part Series --Electrical Issues(June) --Refrigerant Starvation(July) --Refrigerant Flooding(August) --Refrigerant Contaminants(September)
TXV Update!!
What We Discovered
- Labor is also available for the injection process