HVAC Question

[Peter H]

I'm hoping someone in this group will take the time to answer this for me.

I'm in the middle of a course on HVAC in high-rises. The instructor has stated that the oil in the HVAC system should be checked regularly for quality and impurities. She says that if refrigerant is detected in the oil then there is a problem. I was always thought that there is oil in the system with the refrigerant and that this oil lubricated the compressor etc.and one would expect to find refrigerant mixed in with it. I thought that this was why you are always told to let a newly delivered fridge stand for an hour or two before turning it on, to let the oil drain back down into the compressor.

What gives?

tia

Peter H

[TURTLE]

This is Turtle.

I'm not a high rise people. The only thing I can think of is if your flooding back liquid freon to the compressor. If you take a oil sample. it will be foaming up and you will have to wait for the freon to flash out of it. Maybe she is thinking as it having a flood back of freon when the oil is foaming when taking a sample.

i will just say this as to the answer awwww she must know something that i don't know.

TURTLE

[Dr. Hardcrab]

Sounds like your teacher needs to be a little more clearer on her explaination OR you need to get another teacher.....

[Stormin Mormon]

Those big skyscrapers sometimes use semihermetic compresssors (like boat motors, or car engines). Which have a crankcase for the oil.

Refrigerators do mix the oil and refrigerant, and so for refrig, that's normal.

As to mixing th eoil and refrigerant, that's a new one to me, I do mostly small stuff, not skyscrapers.

As for the new fridge, I think the major problem is oil in the piston. Cause oil isn't compressable. I've seen a couple cases where folks tipped a fridge to move it. When they plugged it right back in, it killed the compressor.

[Duffaukid]

Have her show you the documentation of her source. It's quite possibe that some reference manuals for large systems provide such instructions.

dk

[SQLit]

I believe you will find in the real world, "if it aint broke don't fix it".

I have never heard of anyone taking and testing oil samples on refrigerant. Unless there was a problem with the unit. Every high rise I ever worked on had compressors and air handlers in a mechanical room. Cooling and heating was transferred either directly (air) or by another medium (water). Being the cost per square foot is so high the idea of huge duct work from the roof or basement has not been used for years. At least not here. Then there is the fire concern with large vertical ducts.

[Matt]

I think she is saying she wants to mix fluids with you.

[Geoman]

Yes, you can take oil samples and send them in to labs. These tests can, depending on what you want tested, show if the compressor is running hot or if there is some flooding, moisture, acid and other issues.

She says that if refrigerant is detected in the oil

I thhink she's talking about liquid here. You will always have some refrigerant in the oil but saturated with refrigerant is a big problem. This can result from migration or flood back.

I was always thought that there is oil in the

I was told to let it settle down because of debris in the crankcase being disturbed coud plug the cap tube. It doesn't matter for me because I always heat the compressor up before plugging ours in.

I'm surprised she didn't mention a MegOhm reading being taken and logged as well.

The reason she is talking about these topics is with typical large highrises the compressors are very expensive. Parts can be limited if its an older or specialty brand. It is normal to test centrifugals and screw compressors. I remember before oil testing we would change the York centrifugals oil out every year and hoped that it didn't need it more. Testing the oil took the guess work out.

I also think its wise to check the quantity of oil in the system.

[Barr]

I know I should comment on this post but, I won't. Just disreguard. There is no useful information in this fallow up.

Barry