Refrigeration Oil?
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Refrigeration Oil!

The refrigeration oil sight glass was full. Where was all the oil coming from?

What had began as a typical refrigeration repair, was quickly becoming bizarre.

When I arrived on the job the condensing unit was off. The oil pressure safety control had tripped.

After resetting the control, the system seemed to be working great.

Attaching my low side refrigeration gauge to the compressor, I also attached my high side gauge to the oil pump.

Subtracting the pump pressure from the low pressure I obtained an oil pressure of around 35 psi.

So far, so good.

The level in the sight glass was very low but slowly returned to a normal 1/3 to 1/2.

I was pleasantly surprised! The compressor had a crankcase heater.

What caused the tripped control?

I didn't know! Just one of those things.

A few days later, I was back on the roof, same unit, same problem. The oil control was tripped.

Reaching out to touch the compressor I noticed the crankcase was cold. That surprised me.

It should have been warm.

Grabbing my volt meter, I checked the voltage of the heater.

The voltage was OK.

Next I clipped the amp meter onto the heater wire. Just as I suspected, no amperage.

The crankcase heater was dead.

Checking the voltage was not sufficient. I also had to check the amperage.

The refrigeration compressor crankcase heater is perhaps the most overlooked and under appreciated component on refrigeration equipment!

Without one, refrigeration oil and refrigerant readily mix. When the compressor starts, the refrigerant flashes out of the oil.

The violent flashing or foaming causes the oil to leave the crankcase.

Time to install a new crankcase heater.

I hate recalls. When I finish a job I don't like returning to find the same problem! So I decided to closely monitor this unit for a few days.

The next day I noticed the condensing unit running as I approached. A quick touch determined that the new heater was working great!

But now I had another problem. The oil sight glass was flooded!

I had to remove the excess.

You can imagine my surprise When the refrigeration oil flooded the crankcase again!

Once more I removed the excess and once again it flooded!

This continued over and over. The amount of oil I removed from the system was amazing, gallons and gallons.

Where was it coming from?

Apparently over time oil had been repeatedly added.

With no functioning crankcase heater, the excess was washed out of the compressor.

The newly installed heater stopped this cycle. All the excess oil flowing through out the equipment, now returned to the compressor.

Excess refrigeration oil damages the compressor.

It also affects the capacity of the condenser and evaporator. It floods the coils.

Eventually the level stabilized.

Why did the oil pressure control trip?

The oil did not return to the crankcase before the control tripped.

Also, compressor oil pumps do not pump refrigerant very well. Eventually they begin to lose pressure.

Have you checked your refrigerant oil sight glasses lately? Been adding oil, only to add more later?

Better check that crankcase heater!!!








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