Blocked line?? Blocked coil??

[cHuckiTh]

Hi guys,

I'm hoping someone can help me out with a problem I'm having with a 2 ton AC unit running on 410a.

I have installed the unit, but every time I turn the unit on the compressor starts hissing as the pressure relief valve has opened up. Yesterday, when I turned it on the compressor was making a klincking noise and then it would hiss and open up the pressure relief valve after about 5 minutes.

It sounded to me as if the compressor was not getting any refrigerant and I changed the txv thinking it was slammed shut, but that wasn't the case.

I was hoping someone might have some input on the situation.

Could it be a blockage in one of the lines? Maybe the a-coil?


Thanks :confused:

[sedgy]

ey chuckith, must ask you , was the system evacuated? was the r410a weighed in ? it sounds like there is too much gas in the system , where the condercer fans running?
can you tell us what the suction , + discharge pressures where ?

[cHuckiTh]

Thanks for replying Sedgy,

I will admit it was a sloppy job and I wasn't happy with the job I did.

I did not vacuum the system, I tried purging the air out of the lines by pumping liquid into the liquid line and depressing the air out of the shrader valve on the suction line... not sure how well it worked.

Also, I used 2 90 degree elbows on the suction line that were too big for the pipe and used sil fos to fill in the extra gap.

The pressures when I first charged the system were (suction 130psi) and (liquid 230psi). Then the suction line pressure would rise when I turned the unit on until the pressure relief valve opened up. It would usually open up when the suction pressure hit around 150psi... not sure why??

And yes, the condenser fan was running...

The first night I had it running all night and it cooled the house to 22 degrees C. Then the pipes froze at night.

I also charged liquid into the suction line while the unit was running and may have gotten liquid in the compressor!


Any help would be appreciated.

[sedgy]

hey chuckith, well looks like we have killed a compressor, < the knocking noise< in europ we have a nasty habbit of pressure testing, evacuating the system, + weighing the gas in , over the years it has saved numerous compressors from liquid slugging,
sorry you need a new copressor + a career change.

[cHuckiTh]

Sedgy, why would the compressor set the pressure relief valve off if the compressor was broken. It seems to be building up pressure in the lines and then the relief valve opens as if there were a block in the line set.

Does the klinking noise automatically mean the compressor is dead? Couldn't it be that there is a restriction in the discharge line?

[paul_h]

The pressure relief is usually discharge line related (or a fault of the pressure relief valve in the compressor).

The klinking means compressor valves
The klinking and pressure relief can mean discharge valves faulty in the compressor cause high discharge pressure in the compressor.

Bottom line: you were looking at suction pressure, adding refrigerant, changing things etc, but wasn't looking at the right thing back then.
Don't worry about it too much, even if you didn't do that, with no evacuation and just a small purge through the suction schrader valve, the compressor would have only lasted a year or two anyway.

[cHuckiTh]

Thanks for the input Paul,

so you think the problem lies in the compressor? Is my compressor broken? Or do you think it is the discharge line?

Or could it be either of them... is there a way to find out aside from replacing the lines or the compressor?

[Brian_UK]

Air in system = high discharge pressures = high discharge temperatures.

You've admitted that it was a sloppy job now you are reaping the rewards.

Change out the broken parts and do a proper job on the repairs/recommissioning.

[james10]

like Brian said it was a sloppy job i think it's time to bite the bullet and get a decent install tech in

[monkey spanners]

I think i'd try a fresh charge of R410a after first having changed the drier, leak checked and then had a proper vacuum pulled.
The pressure relief valves work on differential pressure, though some i think work on temperature too, don't run the system in this condition as the valves don't always seal back up after tripping.
The silphos you used, was this with flux or was it the non flux type? Some types of compressor oil (PVE) used in R410A equipment is not compatible with flux.

[tonyhavcr]

I think i'd try a fresh charge of R410a after first having changed the drier, leak checked and then had a proper vacuum pulled.
The pressure relief valves work on differential pressure, though some i think work on temperature too, don't run the system in this condition as the valves don't always seal back up after tripping.
The silphos you used, was this with flux or was it the non flux type? Some types of compressor oil (PVE) used in R410A equipment is not compatible with flux.


True but he should charge by sub-cooling Poe oil should be changed.

[Coolie]

as a lot of other people have already said, replace the compressor and oil, but get it done by someone who knows what they are doing.
The reason this compressor is faulty is "user error"
Never (unless you really know what you are doing) charge liquid onto the suction line, or you stand a very good chance of shattering the valves.
The fact that you're getting abnormal running pressures can be due to the fact that you've used the incorrect pipe sizes.

Oh, and dont forget your Stetson on the way out!