R404 compressor failure.

[deez]

I have just started looking after a client with a freezer room, which he uses as a cold room, using a thermostat to regulate the temp.

The compressor runs for about a year, then packs up.

Could this be that we are using a LBP compressor on the wron application.

Please help with a solution, thanks

[Recoilzn]

How does the compressor pack up? Is it mechanical failure or electrical?

[deez]

All the windings test fine. The compressor runs at a high amperage for about 30 seconds then cuts internally. From what I can gather, it seems like mechanical failure. I am replacing the compressor tomorrow, then will cut open the old one to see if that is the case.

I am just worried about simply replacing the compressor with a new one and not getting to the root of the problem

[nike123]

client with a freezer room, which he uses as a cold room, using a thermostat to regulate the temp.



Could this be that we are using a LBP compressor on the wron application.


Yep, recipe for disaster! LBP compressor doesn't have motor of correct power to run on higher gas densities!
You need compressor for LBP/MBP. Also, you need considerably bigger condenser, since at higher back pressure and same swept volume, you are moving more heat than at lower back pressure!


http://www.clubedarefrigeracao.com.br/en/downloads/lbp-mbp-and-hbp-applications

[deez]

Thanks nike123

[monkey spanners]

What Nike said^

Had a similar scenario where a customer wanted to change the use of the room, we converted it from R404A to R134a and its been running fine since. (compressor was still good)
If you are going to replace the compressor you would be better to change the whole condensing unit to a MBP/HBP one.

[deez]

That makes a whole lot of sense.

Saved my bacon on this one, thanks guys

[Glenn Moore]

Hi deez
One year of the compressor running in an overloaded condition before failing sounds slightly exaggerated. Before doing any modifications I would strip the compressor to see what the failure is (the answer is always inside the compressor)
What make & model of compressor is it?
What type of expansion valve used standard or MOP ?
Are there any suction line control valves used ie EPR's or CPR's ?
Any pictures of the internals of the failed compressor would be good

[vikky1971]

@deez, if you are suspecting a mechanical failure then some metal debris must have entered the entire system! Not only the capillary tube will get clogged but also the new compressor will get damaged. I hope you would have thought of dismantling the piping at critical sections, blowing with nitrogen to flush out any metal debris, installing a filter cum dryer before the compressor and after brazing new compressor, vacuuming the whole system prior releasing *****.

[nike123]

Hi deez
One year of the compressor running in an overloaded condition before failing sounds slightly exaggerated.

Maybe that particular compressor electrical motor is capable of overcoming higher compression work, but mechanical part of compressor was at its edge. Therefore, after 1 year of running in these border conditions, it finally failed.
Anyhow, LBP compressor is not designed to work in those conditions, and should be replaced with one which is it (and match all other components of system to new working conditions)!

I don't see point in striping compressor which has worked in conditions not suitable for its application range! We already know that cause of failure is work outside designed range!

[Glenn Moore]

deez quote
I am just worried about simply replacing the compressor with a new one and not getting to the root of the problem


Nike , you make to many assumptions as to what the problem is. You have no idea what the compressor make or model is , what the system design is like etc, and deez is worried that further failures will occur. Quote
The only failsafe way to rectify the problem is to fully investigate the problem starting with the failed compressor and the actual system design and operation. All to often Ive investigated compressor failures after the system has been modified , further modified etc all at the customers expense to no avail, all because the initial problem was never fully investigated and sorted once and for all. deez has the right idea and has the customers best interests in mind and I wish him well in his quest to put the plant right. Jumping to conclusions will most likely simply waste more money

[deez]

I went through the electrics today, ie testing the timer and pump down sequence. I found that the solenoid valve is stuck in the open position.

This possibly means that for the past year, on defrost, the compressor continues to run while the evapourator fans are off.

This, in my mind possibly could have contributed to the compressor failure. (along with the wrong application).

[deez]

I similarly found it hard to believe, but the install date on the compressor is just over 12 months ago.

The compressor is a tekumseh FHS2480z 2HP.
Standard expansion valve.
No suction line control valves

I will post pics once i have opened the compressor.

Thanks for help, much appreciated.