case temp settings

[mrfreeze666]

i used to work for large outfit doing supermakets, through all the einstiens,cpc's and a couple other brands i cant remember, we always kept temps monitored through supply discharge. currently i am with a much smaller co theres no computers on these racks just temp controls for solenoids at cases, all of which are in the return, does it really matter where its monitored or not. i personaly find if differcult to properly maintain temp of supply especially when they leave doors open on the summer and dont like to run much heat in winter. thanks for any advice

[innovator]

supply air monitoring will more accurately depict the condition of the evap coil vs the return which is a combination of heat transferred from the product as well as exterior conditions. It is more common that the stats are mounted from the factory in the supply air, though if you look through the front return air grille you likely will see the t-stat cap tube, it should be ending up in the rear wall above the coil.
Controlling temp using return air would likely result in lower temperatures than required, and monitoring return air will likely result in more frequent high temperature alarms

[markettech]

Originally posted by innovator
supply air monitoring will more accurately depict the condition of the evap coil vs the return which is a combination of heat transferred from the product as well as exterior conditions. It is more common that the stats are mounted from the factory in the supply air, though if you look through the front return air grille you likely will see the t-stat cap tube, it should be ending up in the rear wall above the coil.
Controlling temp using return air would likely result in lower temperatures than required, and monitoring return air will likely result in more frequent high temperature alarms

I agree - not always the easiest to mount conventional temp controls this way though. That's probably why you see alot of them in the return air.

[mrfreeze666]

THANK YOU FOR REPLIES I did work with them all in supply with large company and worked with all the computers, but now boss i work with does everything in return even on rack systems, I find it hard to maintain temp this way in return and sometimes feel like an idiot cause it takes me so long to set them but thanks again i do appreciate it

[Freezeking2000]

I hate return air t-stats on meat cases. Move it to the supply!

[jumperwire]

IF I WAS TO PUT THE T'STAT AT THE RETURN OF THE COIL AND READ 40 DEGREES THAT TELLS ME I SHOULD HAVE A 20 DEGREE COIL AND A 30 DEGREE SUPPLY WITH A TD OF 20 R-22 SHOULD HAVE AROUND 43 # SUCTION AT THE EVAP HUMIDITY ROUGHLY 65 % ON A MEAT CASE THAT IS GREAT SO,PUTTING IT IN THE RETURN AIR ON THE EVAP JUST TOLD ME WHAT ROUGHLY IF I READ 40 DEGREES ON RETURN

[thegoodhumorman]

We have a retailer local which does a TON of business out of all their locations. Small stores, limited cases, always overstocked blocking the returns with product.

"the customers will sell this down to the load line quickly, its no problem..." Common comment from guy working in that dept who is too lazy or not allotted enuff hours to keep up on his stock so overfills.
If they have the manpower it is constantly overfilled- had a few installed with return stats.
Readypak produce 34* without freezing rear shelf? HaaaaHAHHahaahah...there ya go...for today that is...

Relocated after three callbacks, finally had customer agree to empty case to install properly.
Good luck with that- it should work fine in theory but you will be relocating some of those stats sooner or later....just think how critical the air curtain on the open cases has just become.

[innovator]

jumperwire- I am not clear on what application you refer to for the meat case theory. I am assuming for your humidity you are referring to a gravity service case. I think a 20 degree delta is unrealistic and most commonly, temp control for gravity coils should be EPR and suct stop? My main question would be what application you would be setting a return air mounted stat and be capable of acheiving a more consistent avg temp than vs. supply air mounted stat. Lots of variables here, but mainly I dont think there is an argument for return air temp control in any application as being a good idea.

[jumperwire]

I'M TALKING FORCED AIR ON COMMERICIAL REFRIGERATION EVAPORATORS IN THEORY. WHAT YOU APPROX. SHOULD HAVE COMPARED TO WHAT YOU ACTUALLY HAVE. THESE ARE JUST STANDARD INDUSTRY FIGURES BALLPARK LIKE ADDING 30 TO AMB. HERE'S A FEW EXAMPLES FROM THE DESIGNERS OF HEAT CRAFT. WALK-IN REFRIGERATOR R-22 MED. TEMP 35 DEGREE RETURN ACROSS COIL EVAP 25 DEGREE COIL 30 DEGREE SUPPLY TD 10 HUMIDITY 85 %. WALK-IN FREEZER 404A LOW TEMP -10 RETURN -20 DEGREE COIL -15 DEGREE SUPPLY TD 10 SUC AT EVAP APPROX # 16 SUC.REACH IN REFRIGERATOR R-22 MEDIUM TEMP 40 RETURN 20 DEGREE COIL 30 DEGREE SUPPLY 20 TD ALL I'M SAYING IS WHY SOME PUT THE T'STAT IN THE RETURN AIR OF THE EVAP. THE TEMP DEGREE WHEN THEY LOOK AT THE TEMP IT TELLS THEM MORE INFO GOING ON IN THEORY. MAYBE I MISS-UNDERSTOOD THE ORIGIN. ?

[icemeister]

Just as a point of forum etiquette here, please turn off your caplocks key because posting in caps is considered shouting.

I'm getting old but the hearing is quite adequate, thank you very much. ;)

[jumperwire]

THE WAY I SEE THE QUESTION WE ARE TALKING T'STAT OPERATING A SOLENOID. OPEN OR CLOSED DEPENDING ON TEMP I SEEN RACKED SYSTEMS WITH FANS AND GRAVITY COFFIN CASES. ARE WE TALKING FORCED AIR. THEN THE SENSING ELEMENT WOULD BE IN THE RETURN FOR ME LETS DO IT THIS WAY LETS DROP OUR BEAD PROBE ON OUR METER IN THE CASE TO READ TEMPS ON THE CASE RETURN AIR HITS 40 SOLENOID SHOULD CLOSE USUALLY COMMERICIAL REFRIGERATION T'STATS HAVE A FAIRLY WIDE DIFF. TO GIVE THE COIL TIME TO DEFROST ITSELF IN OFF CYCLE OR CLOSED SOLENOID. EVERYONE HAS A METHOD THEY PERFER I GO WITH COPELAND AND HEATCRAFT BOOKS AS MY BIBLE

[jumperwire]

oopppsss sorry about the caps busing pecking here

[jumperwire]

thank you ICEMAN lol

[icemeister]

Originally posted by jumperwire
thank you ICEMAN lol

Thanks for the volume reduction. Now if you could work on arranging your thoughts into separate paragraphs.......

BTW, the name's icemeister. The iceman cometh, but the icemeister knoweth how to do it right. :D:D

[jumperwire]

iceman you're killing me LOL i'm going back to listing used refrig manuals on ebay

[jumperwire]

correct naming icemeister thank you you're cool with me i'll get better at my pecking see ya around hey theres a great 1939 refrig manual on ebay that should be fun to read