Repedatley compressor burning problem

[pkelectengr]

hi all!

we are facing a huge problem. We have mc quary make water based chiller system for cooling our control room and other halls. the problem is that we have refubrished the whole system. Only condersnors ( forced air - cooled) and frame left original. All other we install by our own. We have installed six copeland 7.5hp sealed screw compressors (original design was also of six compressors). and we installed all other accessories necessary and we got our system installed with some people having great expreince in chiller systems and they professionally do this business. But after 15 days of extremely successfull operation (when it goes on the temperature inside falls from 30 deg C to 7 deg C), suddenly compressors started burning. and we started to replace burned compressors with some refubrished (piston type compressors due to limitation of budget). We also hired some other professionals and they also tried but the problem is persistent.

Both are unable to give us any solid reason or able to fix the problem. Compressors are continously still getting their winding short (even refubrished piston).

We are using honeywell r-22 original usa made refigerant gas and silo compressor oil made for low temperatures.

Kindly help us.

Thanks in advance.

 

[MintJulep]

Moisture in an R-22 system is bad. It reacts with the oil and refrigerant and forms acid.

The acid attacks the motor winding insulation, forming even more acid and causing the windings to short.

If all you do is install another compressor into a system with all that acid, then that compressor will not live long.

 

[berkshire]

Are you installing suction line filters to the new compressors to keep that junk out of them?

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[pkelectengr]

dear mintjulep and berkshire

we are not just adding compressors to the system. When a compressor's winding got burnt we just changed the take it out and purge the other remaining system with high pressure of nitrogen. So hard that all the refrigerant and compressor oil in the system gets out and after that as well, when we connect the whole system then still we leak some r-22 to get rid of any moisture remained. Then we start charging the system.

Also the compressor suction line has refrigerant dryer of denfoss (conating silica gel) to absorb any moisture or any other impurity.

Also we have low suction pressure and high discharge pressure safeties on compressors.

Please now continue and help.

Thanks

 

[berkshire]

I find that using the blow through system ( Which is now illegal in the United States. You cannot intentionally vent HCFCs), does not remove all of the moisture.
You need to pull a hard vacuum and keep it on for at least an hour preferably more, before you start your recharge. Dry nitrogen helps for leak detection. But it cannot get all of the moisture out of a system.

B.E.

The good engineer does not need to memorize every formula; he just needs to know where he can find them when he needs them. Old professor

 

[DRWeig]

I agree it's moisture.

If the moisture level is severe (if you've had a broken evaporator tube, for example) you may freeze pockets of water at low points during the first evacuation. Might need to apply some heat to the low points while vacuum pump is running to get all the water out, or evacuate and pressurize several times.

If you were just changing for an upgrade, and you've already blown it with nitrogen (don't do that again, please) it shouldn't be such a problem.

Pull a good vacuum (at least 400 microns) and leave it for a couple hours, as berkshire suggested. Install new dryers again.

Let us know how it turns out!

Good on ya,

Goober Dave

Haven't see the forum policies? Do so now: Forum Policies

 

[Waramanga]

this problem is definitely not for the HVAC engineer, a high quality technician is required to perform a full review of the system ie acid test of the system, perhaps a complete flush, pulling down the busted compressors to see what killed them (if the windings are all thats shot then you either your compresspr is not getting enough cooling or acid is eating them), triple evacuation, maybe new refigerant, test running each compressor individually, testing the controls for proper sequencing/staging of the compressors. If you have hired professionals to help then there is no moisture in the system (triple evacuation is standard and so is a moisture test) so I really doubt its moisture. If your staging isnt working then you can get very low suction pressures at low load and not enough compressor cooling and hence overheating.
I would say that you need to review your commissioning proceedure thoroughly.

 

[MintJulep]

And use some clean up filter cores.

 

[willard3]

Has anybody thought to check the voltage?

Sounds like low voltage.