New Guy-New Thread, Morris Ice Maker
A little background; I have been involved with commercial refrigeration for almost 40 years. First, as a maintenance supervisor on a large produce farm, and the last four years as a partner in in a service company. This company does daily PM on 4 large produce farms in the area and monthly PM for dozens of smaller commercial companies, i e restaurants, drive thru's, etc. Most of my education has come from the school of hard knocks, with a couple of winters spent taking courses through the RSES.
Now to the question:
I am presently working on a Morris Ice Maker, Model #NIM-40-15. This unit uses a Copeland DS6-4000-TSN compressor running R-22 refrigerant. The unit uses hot gas for harvesting of the ice on a timed schedule. (Makes ice for 8 minutes, harvests for 1 minute). It has experienced some trouble with the hot gas valve not closing on occasion and last week we replaced the valve. Upon restart, the compressor is running extremely hot, 300 degrees cylinder head temperature in about 1 minute of operation with a suction pressure of 40 lbs and a discharge pressure of 170 lbs. Normal suction and discharge should be 35 lbs and 215 lbs with about 200 degrees of cylinder head temperature.
Thinking that there must be a problem with the new valve we recovered all the refrigerant and disassembled the new valve, finding no problem. We then made a call to a compressor rebuilder and they told us that the compressor must have been slugged on start-up (which it wasn't) and had broken valves. We then reluctantly pulled the heads and checked all valve plates and valves and they look like new, no discoloration, no broken or bent parts, no blown gaskets. We called them back and were told that it must be the internal relief valve that had stuck open. Ordered a new one, pulled the compressor and replace the valve.
Thursday, we reinstalled the compressor, evacuated the system for 24 hours (100 microns), and recharged with 117 lbs of virgin refrigerant. We refired the unit on Friday afternoon with exactly the same result, 300 degrees of head temperature in about a minute and lots of turmoil in the crankcase (looks like a hurricane in there).
We had our wholesaler talk to Copeland tech and they say we need a head cooling fan. My problem with that is this unit has run for 25 years without one, and the other three ice makers in this group have also run for 25 years without one. They are all the same model number using the same Copeland compressor and all operate within the same temperature range (200 to 208 degrees of head temperature @ 35 lbs suction and 215 lbs discharge pressure.
Sorry for the long post, but thought I needed to explain the whole situation.
I believe that somehow this compressor is returning discharge gas directly to the crankcase, causing the low discharge pressure, high suction pressure, and high head temperatures.
Wanted to edit my post, but can not find the edit button!! The compressor model number is a Copeland 6DS3-4000-TSN. Don't know how that DS6 got in the original post, CRS is setting in I suppose.
Did you install the new valve plates or reuse the old ones? Also did you check cylinder walls and for piston movement? Doubt you had a problem with internal relief as HPS would have tripped. Verify rods are good. Tech support advising head fan sounds real dumb, good luck with that.
Originally Posted by codgy
We reused the old valve plates with new gaskets. We did pull the composition discharge valves apart to check for debris and foreign material. They looked like new. This compressor is a reman and was installed in Sept of 2010. It has run flawlessly until this time.
Yes, pistons and walls were checked. Can still see a cross hatch pattern in walls with no score marks. Didn't check rods, but did run an oil pressure check, 38 lbs.
Whatever is wrong happened while unit was shut down for hot gas valve replacement or on initial startup after the replacement of valve.
Anybody ever seen a compressor crankcase with an internal crack which would allow discharge gas to enter the crankcase??
"Tech support advising head fan sounds real dumb, good luck with that."
My thoughts exactly!
I would pull and replace valve plates, while they are off bump start compressor and make sure all pistons move properly. Valve issues are sometimes hard to see and plates are cheap, gaskets might be reused since they have no run time. (do not stand over pistons when bump starting)
Valve plates for this compressor are $1679.00, and without seeing any damage we chose not to replace. There is absolutely no noise or rattle when this unit runs. The rebuilder had used permanent marker on the tops of the pistons to mark the oversize (.020) and that marking is still there after several thousand hours of run time.
Thanks again. Maybe tomorrow we will pull the heads again to check piston movement.
Use aftermarket valve plates not copeland. Good luck and let us know what you find. Are all heads same temp?
Head temps are within 20 degrees. We can't let it run for more than a minute or so to stabilize across the compressor. Scared it is going to self destruct if run any longer. When one sees the paint starting to bubble, it IS TIME TO SHUT IT OFF!
Are you checking discharge at valve on compressor or farther downstream, seems like possible discharge restriction if all heads are the same. Did any parts come out of original compressor when it was changed. I know it sounds crazy but I've found dicharge valve parts partially blocking line, stuck in turns of service valves etc., even found one five years after when it vibrated a hole in condenser from the inside blowing 200 lb.. Still seems like HPS would trip.
No parts from old compressor, electricial failure and not a burn out. I do not have high discharge pressure (170 lbs), just high temps on heads. I haven't checked discharge temp at discharge service valve. I have been shutting down the unit before I have actually had time to check 4 places. Have not had a high pressure trip, don't build any discharge pressure to speak of.
Originally Posted by codgy
You must have broken rods, just check when you pull the heads. Thats all I can see from here.
pump it down into the receiver, perform an efficiency test.
If the compressor is mech sound, as it seems, Hi suc superheat or a facsimile of that is really the only thing that could cause it.
Ie the HG solenoid is leaking during freeze, oil sep stuck, don't think the M&A have one.
What brand HGS solenoid....alco's have had a 'silent' TSB. shhhh.
Hot gas valve is what we replaced prior to this problem. It was a Jackes-Evans, now is a Sporlan E47 series, 1 5/8". I should mention we did this same change out to one of the other machines and it has performed well.
There is no leakage thru the new valve that we can determine by temperature readings. We did recover and open the new valve to see if by some chance there was any debris in it. None found.
Yes, there is an oil seperator and it has a sight glass before the dump into the suction line. Nothing abnormal there either. There is an angle valve right at the suction, we have closed it and tried running the machine just to eliminate the seperator as a suspect. Same issue, 300+ degree temps within just a few minutes. Still runs about 170 high and 40 suction.
I am going to try closing the suction service valve and see if the compressor pumps down. If it does it at least means the issue is somewhere else in the system.
If compressor valves were the problem, wouldn't the high and low side pressures equalize almost immeadiately upon shutdown? We are checking pressures at the compressor service ports. The system utilizes a TXV and liquid line solenoid.
I will also pump it down into the receiver for an efficiency check.