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Originally Posted by OhioTech

It looks as though the float on the seperator is hanging up and not allowing the oil to go to the oil receiver. Quoted customer new float assembly,henry oil level control for compressors and oil safety that did not trip on low pressure. Confirmed safety is wired correctly but,is bad. Compressor that is still running tripped on low oil overnight. Not getting oil from receiver. BECAUSE THERE IS NONE!. Added oil to receiver to get unit running. Told and documented to customer that work needs done and unit will fail. They have not approved work. Anyone in need of previousley frozen food? Waiting for the Saturday /Sunday call of high temp.

Is it a helical separator or a conventional "impingement" type separator?

If it is a conventional type, you might want to look inside and see if the screen inside is ruptured.

Thanks for the info EngineerDave

Thanks Eng Dave for info

It looks as though the float on the seperator is hanging up and not allowing the oil to go to the oil receiver. Quoted customer new float assembly,henry oil level control for compressors and oil safety that did not trip on low pressure. Confirmed safety is wired correctly but,is bad. Compressor that is still running tripped on low oil overnight. Not getting oil from receiver. BECAUSE THERE IS NONE!. Added oil to receiver to get unit running. Told and documented to customer that work needs done and unit will fail. They have not approved work. Anyone in need of previousley frozen food? Waiting for the Saturday /Sunday call of high temp.

Originally Posted by engineerdave

http://www.sporlanonline.com/110-136_012002.pdf

Nail head, meet hammer, ;-)

Originally Posted by Senior1

newbie here, common suction? How is the oil separator piped and is the oil pressure switch wired correctly? Unloading? Staged? Pump down or selinoid drop? Just thinking out loud.

http://www.sporlanonline.com/110-136_012002.pdf

Originally Posted by OhioTech

New compressor vibrating badly,low oil pressure.Oil is grey and full of metal. Shut unit down.They have common suction/discharge,an oil seperator,henry oil Thanks

newbie here, common suction? How is the oil separator piped and is the oil pressure switch wired correctly? Unloading? Staged? Pump down or selinoid drop? Just thinking out loud.

Once upon a time, I figured out that a respected voice on HVACTalk, Marvin, lives here locally in my part of the world. Thats led to any number coffees, a few breakfasts, a few lunches. Every one of those visits has left me just a little bit more smarter. OhioTech, JPSmith1cm is another of HVACTalk's respected voices. Even if you've got your current problem solved, gas up the rig and go have that coffee.

Just my two cents.

Originally Posted by OhioTech

Central Ohio

Little far.

If you were closer to Northeastern OH, I'd offer a cuppa joe and a chat about your unit.

Central Ohio

Where in Ohio are you located?

Some really good suggestions have been made, would like to add a lil about the comp sh.

20* is a great number across the board, you could see a lil less if your evap is close coupled, nothing to be too concerned with if everthing is running right. (in general)

Anything higher than 20* at the compressor could be a problem - depending on your SST. 40* to 60* comp sh on a low temp system with a -10* SST and 30* to 50* suction gas temp would be fine. Plenty of motor cooling there.

On the other hand 40* comp sh on an a/c system with a 40* SST would give you 80* return gas and the compressor motor would not be happy if that were to continue for any length of time.

Just something to think about.

Not that you have much control over the actual gas temp entering the compressor, its usually not a big problem if the evap sh is inline.

Someone mentioned CCH, those things go out all the time and they are very important for a recip comp. I have seen current sensing switches installed on the CCH line and wired into the CC control circuit.

Very Important

Lots of people rush to adjust superheats.

Wait til the system is at its normal operating temperature for a day at least.

Also make damn sure all the defrost heaters are working as they should.

Also verify crankcase heat function. Almost sounds like bearing washout from diluted oil.


See any foam?

Also, when compressor was changed, is the piping the same? the compressor the exactly same? If not, one compressor may be getting more mass flow then the other.

Balance is absolutely critical.

Don't let the ice scare ya.

When you are dealing with freezers, a LACK of ice should scare you.

I would say the suction line is 100-125ft insulated untill it gets to the accumalator. Accumalator is a ball of ice.The compressor that has failed is thr first one after the accumalator. I will check the superheat in the full load, both compressors running.

Originally Posted by icemeister

I know you meant to say, "...no less than 20ºF SH...".

Yes, you caught me.

Originally Posted by OhioTech

OK then 20-25 deg superheat at compressor. I am confused at the 6 deg at the evaps than was recommended and then 20-25 at the compressor. I guess maybe I should check the total tonnage of the compressors and the evaporators to make sure they are correct size. There is one solenoid valve to shut off liquid line to all three evaps. From what I could see on the short time I was there, the compressors come on when the solenoid energizes and the pressure rises. The compressors go off when tstat satisfies and closes the solenoid for pump down. No unloaders.

I'll take this time, though, to say that a cold compressor is a happy compressor.

Taking "no less than 20" to it's logical end, we could easily run 50-60-80 plus superheat at the compressor. Not difficult to see on a low temp unit, really.

No less than 20, but, IMO, not much more than 30-40 degrees SH at the compressor.

The 3-6 at the evaporator and 20 at the compressor really come into play when you see a longer or an uninsulated suction line.

300+ feet of suction line can add quite a bit of superheat to a system, even if it is insulated.



Set the SH at the evaps, then check it at the compressor and see how it is. Depending on system operation and conditions, you MAY need to tweak the evap SH up a bit to get SH at the compressor, which is your overriding concern.

OK then 20-25 deg superheat at compressor. I am confused at the 6 deg at the evaps than was recommended and then 20-25 at the compressor. I guess maybe I should check the total tonnage of the compressors and the evaporators to make sure they are correct size. There is one solenoid valve to shut off liquid line to all three evaps. From what I could see on the short time I was there, the compressors come on when the solenoid energizes and the pressure rises. The compressors go off when tstat satisfies and closes the solenoid for pump down. No unloaders.

Yep. Freezers want 3-6 deg of S/H.Usually.

I am getting replies from all of you so fast I am falling behind on your replies. I noticed someone said 6 degrees of superheat on the evaps.

20-25 puts you in the Gold Zone.

No less than 20 degrees superheat? So like 10-15 Just want to make sure on the same page