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Thread: Uneven produce temps
08-02-2010, 01:31 PM #1
Uneven produce temps
So we had a tech go out on a call for produce sections freezing product. This is a multi deck produce loop on a rack. The cases are fitted with non adjustable expansion valves. The tech recommended that we install stem kits on the valves and adjust superheats. But the service manager recommended installing an EPR because the cases are controlled by pump down right now and he was told by manufactures that non adjustable valves should not be used on pump down systems. Due to poor superheated control.
Can anyone verify that statement.
08-02-2010, 04:38 PM #2
08-02-2010, 05:23 PM #3
In my experience, pumpdown control is probably the least desirable for temperature control of an open single or multideck case where you're controlling from DA temperature...which I assume is what you have here.
I don't think the non-adjustable TEVs has anything to do with it.
Since this run is on a loop, I'd opt for the EPR with a suction stop as a low limit.
08-02-2010, 05:40 PM #4
08-02-2010, 06:04 PM #5
Yeah, I went to the store and found an orit-6 in the case. Set it up for 25SST and get 33 DA across all cases. I agree pump down is poor control. It's just sometimes the service manager is a smart fella.... Then he says things like this. Lol.
08-02-2010, 06:29 PM #6
I'm with icemeister, I don't think poor temperature control has anything to do with the non-adjustables. but if the tstat is cycling frequently, I can see it affecting superheat control, adjustable or not.
evaporator/equalizer pressure is a closing force on the tev.
08-04-2010, 06:55 AM #7
Back when I was doing wallyworld star-ups all the hussmann cases had nonadjustable expansion valves. Before walmart would sign off on the store all case temps. had to be within specs wich ment ------ Novar looks at case B setpoint.case A has to be within 2* of B and case C has tobe within 2* of B. On the hussmann cases the only way to achieve this was to move the txv bulb. Temp. control is stickly done by energizing and denergizing the SORIT. Walmart wants 100% run time on all the SORITS (no cyclng) the superheat at the valves will not be effected on neither the nonadjustable or the adjustable!
08-04-2010, 07:27 AM #8
Pump down on any line up sucks. I use to be told, "it's cheaper that way". No. It means you produce more service calls and that creates income.
There is no fricken reason for it but just poor practices.
I have seen new jobs go in with pump down on fresh meat and just shake my head."The only real security that a man can have in this world is a reserve of knowledge, experience and ability." Henry Ford
08-04-2010, 07:30 AM #9"The only real security that a man can have in this world is a reserve of knowledge, experience and ability." Henry Ford
08-04-2010, 08:00 PM #10
08-04-2010, 08:06 PM #11
08-05-2010, 05:47 AM #12
Example: 36' Dairy -- (Hussmann) Temp. sepoint 36* case A 33* case B 36* case C 39* To bring case A up to within 2* of B you would have to move the bulb out from the evap. coil! To bring case C down to within 2* of B you would move the bulb closer to the evap. Prior to doing this you would see on the graph where the SORIT has been cycling after, the graph will show a staight line (100%) run time! ---- NO PUMP DOWN. After beeing tweaked I have checked the superheat on each case and have them very as much as 4 degrees but wamart is more concerned with the 2* strategy rather than the superheat!