multiple evaps in a supermarket line-up

[kengineering]

When multiple display cases are lined up in a supermarket each section has its own evap but there does not seem to be a phyical divider between the sections. How does each evaporator cycle? Do they operate independantly? Is a Presure control or a t-stat controlling the cycle? Do they defrost together? I am trying to get a better under standing of the multiple evap sey-up. Thanks, Ken

[chillin out]

Hi Ken,

Just think of them as individual fridges, each with their own control.

Defrosting is set up so they defrost in sequence, but this has nothing to do with the layout. It`s to do with the running of the pack.

We try to make sure dividers are kept between cases but it is not essintial. Freezer cases are differant they MUST have dividers (clear perspex ) between the sections so they can defrost effectively and to stop the adjacent cases collecting the defrosted ice.


Chillin

[kengineering]

My goal here is to build self contained air screen display cases that will operate in this manner. I work for a small custom case mfr. and until now have only produced individual self contained case with some remote. I feel ready to forge ahead with this project.....Thanks Ken

[iceman007]

Hi Ken,

As Chillin Out says it's to do with the running of the pack , what you might know in the US as a parallel rack (compressors). It's a case of having individual fridges connected together to the compressors/condenser if thats the best way to phrase it. If you have to do any work with the refrigeration plant as well as the cases, one thing you must get absolutely right is the oil management system for it (correct separator etc). US Iceman would probably be a good source of information. If not I'm still in touch with a few good market techs in the states (don't know where you are though)

[floyd57]

The set up we use on our super market's consist of a rack (multiple compressors) with a controller (Cpc, Microthermo), and over 120 display cases throughout the store. These cases are set into individual systems using 2 to 4 cases per system.
Each system has an individual liquid and suction line piped to it from a dedicated (Suction and Liquid) header back @ the rack. Suction setpoint is set for aprox. 10 deg. Less than the lowest desired system setpoint. Multiple compressors on the rack will run to maintain this set point, while epr's are used to maintain individual tempuratures to each individual system. The newer racks we use utilize an electronic epr. A tempurature sensor sends a temp reading from each individual circuit back to the controller. Then the controller parlays this information to the epr which is then throttled open or closed to maintain closest temp, to setpoint as possible.

Hot gas defrost is used and actuated by pre determined times from the controller. As a system is actuated into defrost. The epr closes as well as the liquid line solenoid preventing flow into these respective headers. Hot gas from the discharge line before the condensor is sent from a header @ the rack out to the individual system in defrost. The hot gas goes through the evap coil around the tx via check valve to a return header piped in around the liquid header. The gas returned to the rack is a liquid/ gas mixture which is then sent the condensor.

This is a cut down version of a running rack. There are many other valves and controls which come into play, as you need pressure differential to keep things flowin' as well as the proper oil recovery system.

Cheers!