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View Full Version : Self contained ice cream freezer , unexplained pressures ?







fridg
29-09-2007, 03:06 AM
I am working on a small self contained ice cream freezer and it seems to have a high low side pressure and a low high side pressure.

300 kpa low side
500 kpa high side
R134a

unit is not cycling
it has a full bore of liquid to the metering device.

any ideas.

BigJon3475
29-09-2007, 03:14 AM
What's the amperage draw as opposed to RLA? or even better what is it compared to the compressors performance chart?

fridg
29-09-2007, 03:28 AM
Have not checked the amp draw as yet.



but as a guess i would say it would not be too high as the thermal overload does not trip.

BigJon3475
29-09-2007, 03:31 AM
Okay heres what you need to do check superheat, subcooling, Outside temp, amperage draw and the pressures all at the same time. When you get those then we can make an informed decision till then we would all be guessing. Someone answered you on the other site by the way.

fridg
29-09-2007, 04:08 AM
Cheers , thanks for the help.

750 Valve
01-10-2007, 01:56 PM
comp inefficient, valves shot likely.

fridg
12-10-2007, 08:13 AM
I had a few minutes of time to check all the system operating temps and pressures.


The amp draw on running is 1.60 , which does seem to be in the range it should be.


The manufacturer states it should have a RLA of 1.90 at an evaporating temp of 10 degrees celcius which is my 313 kpa.


The charge that is in it should give me an evaporating temp of -25 degrees celcius which equates to a current draw of 1.22 , so the amp draw is slightly high in this aspect.



condenser SC was 0.8 degrees celcius

evap SH was 16.8 degrees celcius

ambient was 24 degrees celcius

chillyblue
12-10-2007, 10:24 AM
Hi

I assume you have 16.8 degrees of superheat or is 16.8degrees the temperature you measured at the evap outlet??

If you have 16.8 degrees of superheat then i would assume the expansion device is either shut down or blocked. If it is blocked then that would explain the low discharge pressure.
Whats the cabinet temperature.
i assume it is a gylcol filled bunker chiller.

I believe you are evaporating at around +9deg C.?



CB

fridg
17-10-2007, 09:24 AM
Finally did the comp change , and all went well , only thing now is the system runs in a vacuum at - 50 kpa and the case is not cooling.


The operation of the system has totally reversed itself , when the comp was changed the whole system was flushed out to prevent blockage and there was an abnormal amount of oil in the tube.

N2 was used while brazing.


System has a fine bore cap tube , so now i suspect waxy oil is logging around the system.