Compressor Efficiency Test

[jedi]

Hi All

I have not been doing this long so apologies if this is very basic to most of you, but anyway my question is:

I was wondering if anyone could tell me the correct method of carrying out a compressor efficiency test on a split system.

At college we did this on a rig but there was service valves available which aren't the same type on the splits.

Also am I correct in saying that both the service valves on a split where the install piping connects are actually both on the low side???

Any advice will be greatly appreciated.

[chemi-cool]

You can only test compressor efficiency as you described, on a rig test.

In real life, you have to check simultaneously, suction, head pressure, discharge temp, ambient temp, amp. drawing and work it out if the results are within normal to the unit.

Also am I correct in saying that both the service valves on a split where the install piping connects are actually both on the low side???

Yes. the small pipe is called by mistake liquid line but it is actually part of the evaporator as it is after cap tube.

[jedi]

Thanks Chemi-cool for your response. Obviously there's still a lot to learn.

I went to a site yesterday and suspected there was liquid in the compressor on start up due to the knocking noise. At college this was referred to slugging. My Intitial thought was that the reed valve must be bent or not seating properley, but due to my short experience did not want to tell the client to change it unnecessarily.

Once again thanks for the reply.

[taz24]

Thanks Chemi-cool for your response. Obviously there's still a lot to learn.

I went to a site yesterday and suspected there was liquid in the compressor on start up due to the knocking noise. At college this was referred to slugging. My Intitial thought was that the reed valve must be bent or not seating properley, but due to my short experience did not want to tell the client to change it unnecessarily.

Once again thanks for the reply.

Don't worry about the learning bit we are all still learning (well except Brian who does know more than most )

On a split you are right with the pipes and you will struggle to test the comp because you can't isolate it from the system. You could fit your gauges and shut the smaller service valve and see if the system pulls a vac But and this is a big BUT, you will only see it pull avac if the comp is ok and does not have an LP fitted in the system. Also if the system has a leak it could draw air into the system. You must give this one some serious thought.

Cheers taz.

[wambat]

If you have a clean filter and measure for proper air CFM:
You can do an efficiency test by measuring the compressor’s amp draw using the common line from the compressor and write down the suction and discharge pressures then compare this to the compressor manufacturer’s data sheet.
If the amperage reading is within plus or minus 10 percent of the manufacturer’s specification this would mean the compressoris running within acceptable limits. If you have an inefficient compressor this would result in abnormally high suction pressure and lower-than-expected discharge pressure.

[boy]

jedi,
1.get a gauge manifold ,connect to high and low side comp isolation valve.
2.front seat valves.
3.start comp and watch high press reading reach 350 psi.
4.shut off comp and observe both press reading
5.if after say 20 mins readings still the same,safe to say comp pass the test
6.run comp and chrck amp draw.
hope it helps
boy

[jedi]

Great help guys,

Taz, I can understand your concerns about pulling into a vac, afterall it was drummed into our heads at college that "AIR IS THE ENEMY"..

I guess it will be necessary to link out LP switch.

Wambat, this is a very interesting point and would prove one way or other without compromising the system with air. My only question is that would I need to consider differences for an inverter system as I understand its proportionally controlled based on heat load, ambient temp etc?? Will this become obvious with experience or would I gain this information from the manufacturer??

Boy: This method was taught to us at college, but as I've discovered the real world is a bit different!! I tend to work on splits a lot and unfortunately these do not tend to emulate the test rigs at college.

But hey you live and learn right!!



Thanks for all your advice. I will have a play when I next have a bit of time...

[taz24]

jedi,
1.get a gauge manifold ,connect to high and low side comp isolation valve.
2.front seat valves.
3.start comp and watch high press reading reach 350 psi.
4.shut off comp and observe both press reading
5.if after say 20 mins readings still the same,safe to say comp pass the test
6.run comp and chrck amp draw.
hope it helps
boy

Boy your advice is good but if you read the original post again you will see he knows how to do the pump test on a compressor, his problem is how do you pump test a split aircon??

taz.