“Balancing” oil balancing

By Richard Hawkins, MACS Contributor

Author’s note: I am a bit tardy with this article.  We had experienced a massive ice storm and were without electricity for eight days.  As a result, a lot of my time has been dedicated to dealing with generator operation and other storm related issues..  I am sure a lot of you out there may also have experienced this same storm.  Hopefully, life will return to normal for everyone soon.

What should we do if performing an oil balance and only a 1/4 ounce of oil drains from the original compressor (even if the system did have the proper amount in it)?  If you just follow oil balancing instructions; you would drain all the oil from the replacement compressor (assuming it contained oil) and put a quarter of an ounce back in and then install the unit.  But that presents a problem because with a normal amount of oil in an operating compressor being about 2-to-3 ounces or more, a quarter of an ounce is a very small amount.  As a result, the compressor could suffer from oil starvation during the time that it will take for the full charge of refrigerant (which will hopefully be installed in the system) to move the oil which has been trapped in the evaporator to the compressor.

So, the best thing to do is to remove all the oil from the system by flushing, replace the drier and install the full system charge (8 ounces in this case) in the compressor, rotate it about a dozen times by hand and install it. That way you know for sure the system has the proper amount of fresh oil in it.  Of course, that could create a bit of an issue if flushing were not included when the job was priced out. Even though this is an orifice tube system, and it is easy to flush, there is extra labor involved and there is the cost of the flush solvent and asking the customer to pay more might not be a viable option. Also, not charging for this extra service is going to affect the profitability of the job.  So, what are some other options?

I will not recommend these because flushing the system and installing the full charge is the only way to be sure the system has the correct amount in it.  This just mentions what some shops have done with success when presented with this issue.

1.  They have removed 2 to 3 ounces from the evaporator, lines, or condenser by carefully blowing it out with low pressure nitrogen or low-pressure dry air. Then they have added these amounts removed from the components to the 1/4 ounce drained from the compressor and put that total amount of fresh oil in the replacement compressor.  This is not as good as flushing and installing the full system charge, but it does keep the amount of oil in the system the same. Here is a word of caution from an R-134a MSDS about mixtures of R-134a and air: “R-134a is not flammable at ambient temperatures and atmospheric pressure. However, this material will become combustible when mixed with air under pressure and exposed to strong ignition sources. Contact with certain reactive metals may result in formation of explosive or exothermic reactions under specific conditions (e.g., very high temperatures and/or appropriate pressures).”

2.  They have just put 2-1/4 ounces of oil in the replacement compressor.  In this case that would result in about a 25% overcharge of oil in the system, but there is a bit of “wiggle room” when it comes to the amount of oil in a system, so it is likely that amount didn’t have a huge effect on performance.  Caution: We are talking about an 8-ounce system here.  If dealing with a system with a smaller system such as 4 ounces or less, an extra 2 ounces will have a greater effect.