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View Full Version : I've run into a wierd one







David DeBord
19-03-2015, 02:08 AM
Greetings Ya'll!

This is my 1st time here, & I found this site during a search for a possessed Copeland 3PH Compressor MD. #CRN5-0500-TF5-270 / Ser. # 99E42471B. This comp. is 208/230V. 3PH.
It's installed in a Russel Condenser MD.MLH500H22/ Ser. H998868-011
The refrigerant is R-22.

The Service call is for a 12 door cooler that suddenly "warmed up". My customer called me 9 hours after his customers started complaining about warm beer & pop. :>)

Upon arrival, I found 209 volts 3 Phase at the Disconnect, & the unit's condenser fan running, but not the compressor.
I've got 209 V. 3 Ph. up to T1/ T2/ &T3, again without the compressor running.
I checked all 3 terminals for ground at bare metal of the compressor, & no terminal is grounded.I checked the ohms, & the reading is .028, whereas my Distributor Copeland Rep., at SWH, Cinti., Ohio, told me that it should be .6
This unit hasn't tripped the Hi-pressure switch, nor the Low-pressure switch. No breaker, or fuse blew. This compressor is not humming, nor drawing any amps.
As I said, I called SWH Supply, & Mark told me that he had never heard of such a thing, & he suggested trying to get the comp to run in reverse, so as to free it, even though there was no Amperage being pulled.
I then called Russel Coil Tech, & the Tech also said that he had never heard of this happening, but told me that part of the winding of the Comp, could be burnt or broke. Both of these Techs told me that I was most likely looking at selling my customer a new compressor.
I went back up on the roof, reversed the terminals, hit the power, & this puppy started. I shut it down after about 5 seconds & remounted the wires to the proper terminals, & yes, I marked them before taking them down the 1st time.
I put gauges on the unit, & my Lo-side was 75, & the Hi-side 105 with the ambient being 51 degrees. I went down of the roof, for about 30 minutes, & when I came back up, the pressures were exactly the same, & the Comp. RLA was 9.8, whereas the data plate states that it should be 22 A., I realize that is for normal conditions, & on a much warmer day, But I seriously believe that it's waaaay to low.
The Compressor isn't overheating.
I have Serious Flash gas in the site glass, & the moisture indicator is showing dry.
I went into the cooler & I've got a 9 degree temperature drop across the Evaporators (there are 3). Yet, the evaporators, are not sweating. No, I did not get Super heat/ Subcooling readings because my meter fell off the roof, & broke. :>)
I'm going back in the AM. tomorrow, to take temp readings etc., with a new meter.
I called my customer, & after about 2 1/2 hours of operation he said that the walk-in had pulled the temp down to 50, whereas, when it started, it was 67 degrees, with product that had not had cooling for approximately 24 hours. Also this is a 12 door cooler, that is very well stocked.
have any of you run into this before? I'd appreciate any advice.

monkey spanners
19-03-2015, 09:14 PM
The suction pressure seems high, i wonder if it is not pumping well? If it is not pumping properly it can overheat the motor which then trips on thermal overload.

I would try a pump test and see how much of a vacuum the compressor can pull.

Magoo
20-03-2015, 03:11 AM
Possibly dropped a conrod and stalled , changing direction cleared the jam up. Good time to strip down and inspect internals. But interesting the stalled current control did not trip out. Initially thought the internal klixon had protected motor stall , could have reset when you tested windings etc.,

mikeref
20-03-2015, 10:03 AM
Two faults. Possibly 3... 105 PSI, Flash gas and 9 degrees F across the evaporators.

NB: Any new site can be a mine field as we are starting from scratch...IE: Bugger all previous history.

I would do what Monkey Spanners suggested. If the compressor fails to pull and holds at least a 25 inch Vacuum ...then move on to Magoo's post.

105 PSI Head is way too low for R22. Was this kit short of refrigerant prior to your investigation?