Overheating compressor

[oztech]

Hi guy's, got a problem i can't work out - overheating compressor due to suction line not cold enough (not cold or condensating).


Arrive to the job, little water cooled temperzone package unit, scroll compressor, approx 2hp.

Through the gauges on, 75lb x 290lb - on R22. Felt suction line, veagly cool.

Dropped a bit of gas out down to 60lb x 270lb thinking it might be overcharged by another techo. Felt suction line after 5 minures - same !!

After a few more minutes compressor drops out on overload. Being its a small unit and only holds 600grams of gas, i dropped the charge (recovered if you like), thinking their could be a koktail or incorrect gas in it, vacced out and recharged back to 60 x 270.


Same thing happens. Called techo's at temperzone, came to agreement, compressor probly a bit inneficient - changed compressor, but for a recip hermatique, as they can handle heat far better than scrolls (sais the compressor supplyer).

Charged her up - overheated again, grrrrrrrrrrrrrrrrrrrrrrrrrrrrrrrr.
Disconnected water exit from condenser, opened inlet, and out poored tunns of water into a bucket, so no blockage in condenser. Returned water back the other way - same again, so no blockage at water filter.

Im a bit perplexed guy's, why can't i get nice cold gas returning to the compressor no matter if i over charge a touch, or undercharge a touch, or what seems to be the norm in system pressures on 22 at 60 - 65lb suction x Around 250 - 280 head.

Coil temp for the first four runs is nice, cold and sweating, then just tapers off towards the top runs.

Any ideas fella's.
Cheers, John Mac (Sydney).

[Sandro Baptista]

After all you have done it occurs to me that if the suction pressure is much below the normal and the suction line is hot it could be happens the capillary is smashed causing lack of liquid supply to the evaporator.

[flyinkiwi]

What are your SC, and water in and out temps at those pressures?

Could the heat exchanger be scaled or otherwise fouled?

What is your suction superheat like?
Could the high head pressure be holding up your suction, and masking an undercharge by previous techs?

How is the water flow controlled? If it is not controlled on pressure, and your heat exchanger is not fouled, your EWT would have to be quite high for a head pressure of 290.

The compressor stopping on overload would make me think more of a high side problem.

[chillerman2006]

http://www.refrigeration-engineer.com/forums/showthread.php?37938-Compressor-overheating

[al]

Alright john,

Swap them hands for a decent thermometer, get some subcooling and superheat settings and i reckon you'll find your answer.

al

[mikeref]

Thinking that a 600 gram charge on R22 was not a suitable gas for that chiller. Why it worked previously is anyone's guess. I would remove the R22 and weigh in R134a.

What led me that thought is because you said.."Coil temp for the first four runs is nice, cold and sweating, then just tapers off towards the top runs."
On a capillary,and at 600 grams, suction would be around 42 PSI. R134a should give you something like 22 PSI and a much lower running current. (My 2 cents worth but something to think about.)

[Royal241]

txv equalizing line open, replace txv

[frank]

What is the flow rate on the water side?
Water entering temperature?
Water leaving temperature?

[R. skiffington]

Go back to basics, (don't put R134a in it, that is bad advice)
You have a problem with superheat, problem is either gas charge or expansion device. Check with temperzone on gas charge, weigh in correct charge, if you still have too much superheat, change expansion device. Sometimes you have to charge those temperzone units to superheat rather Han a weighed charge.

[oztech]

Hi everyone, sorry for not getting back, i thought replies came back via emails etc. Anyway's, ripped out the compressor yesterday as the so called 'new chelf compressor' with no box, capacitor or relay, was drawing 12.5a - rated at 9.5, change cap from 30 (recommended) to 25, still no good. Taking back today.


I'd like to thank you all for responding to my little unit issue. After reading them this morning (7/2), i recken, my issue 'could' be coming from either gas charge level, capillary or condenser transfer issue - STILL NOT sure though.

Going back monday to whack this other compressor in.

From their, will check and charge to superheat settings, water in / water out (at present, cold in from tower, and around 3degr C diff on exit, but wondering if im actually getting the transfer). Can't change txv as it's capillary (wonder if it's partiall scaled up ??), will change very small drier (could be partially blocked, but suction pressure not dropping, and coil not starving).

600 grams is the recom spec from Temperzone, but could probly vary slightly (critical charge etc). Also once i get my 'cool' suction and 250 odd hp, any more gas added qwikly rises both hp /lp sides.

In saying this, i disconnected the supply fan, charged to a full evap coil (all frosted up), then ran it on low (less load), and slowly the sewaty suction line back at the compressor tapered back to a cool temp.

Anyway, great and helpfull advice from all, really appreciate it, have taken all on board and will again give it another shot - but thats it, im pretty over it.

As for 'chillerman' - im with ya brother, lol.