Curious!

[jdunc2301]

Hey everyone!

I was just wondering how supermarket refrigeration packs work, chances are i will never work on or near one so im just curious. Mostly de-hum, and remote refrigeration for me :) air-con when struggling for work.

Im presuming a pack of compressors will look after different temp applications, frozen and chilled on one pack. Or is it one pack for frozen and one for chilled?

Could someone brielfy explain what's occuring, compressor control etc as demand increases/decreases?

Common suction to shop floor?
Common discharge to shop floor?
Non return valves used?
Pressure regulating valves (to have a common suction)?
common condenser?
Solenoid valves?
EVP pump down?


I know it might sound a strange question, i've never come across any and im not likely to, i've got a general idea floating in my head but not sure.

Cheers All

[Tesla]

Hi jdunc 2301
It's been a while since I worked on them. Packs you say I think you mean Rack Systems. Basicly you have a common reciever with many compressors switching off and on depending on load, serving many different evaperators. To control different evap flows and pressures we use evap press regulators. Some use seperate medium temp racks and lotemp racks, some use a meduim temp rack with a few booster compressors which forms compuond refrigeration - suction from freezer goes into booster comp which discharges into common suction on med temp rack after being desuperheated. As you could imagine differculties are oil return and keeping it all gas tight. Benafits are redundancy and ease of expanding capacity. It was only abou 25 years ago when they were remote open drive units in a noisy hot plantroom. Now some are pumping glycol around supermarkets at -40degC.

[lowcool]

mate thats one hell of a question,i would say the page would time out before a detailed description could be posted,anybody got any links for this fella,next time you have a day off organise with another company to go for a drive and have a look

[Slatts]

Gedday jdunc, I wish I'd known at 21 what I would and wouldn't be doing in the trade in the future. I wouldn't discount commercial refrigeration too soon. It's an interesting and intriguing trade in itself.
Do your self a favour and find a big commercial refrig company that'll take you on and spend a year with them before you decide if it's for you or not.
With AC you can put 5 people in a room and have 5 different opinions of what the temperature should be.
In a commercial system a carton of milk doesn't care so long as it's below 4 and above 0.

[lowcool]

milk whats that ?

[Slatts]

milk whats that ?
It's a drink I give to the kids to keep them away from my beer fridge.

[lowcool]

ha ha forgot about them curious buggers arent they

[Slatts]

yer not wrong.

[Eeram]

Supermarket systems normally consists of racking systyms, or multiplex systems as in my country. There is normally a medium temperature and a lo temperature system. Medium temperature does all dairy, deli, fruit & veg, confectionary, coldrooms, colddrinks/juices, meat. Lo temperature does freezer rooms, island freezers, upright freezers, glass door freezers.

For each multiplex, there is a common suction and liquid line that splits somewhere on the floor area to individual cabinets/rooms. Defrost is normally electric, but hot gas can be used.

Nowadays we are using electronic expansion valves with electronic controllers for cabinets/rooms and compressor pack controllers. The electronic expansion valves are also used as solenoid valves. Compressor pack controllers control compressor capacity on demand to ensure a constant suction pressure or pressure as close to design.

This ensures that we use the optimum performance of each pack and reducing the energy requirements of the complete system.

Medium temp. systems normally operate @ -12 C suction and lo temp @ -30 C suction, without any evaporator pressure regulators or non return valves.

Oil management is a must, as these systems normally runs odd size compressors in parallel.

Common condensers are used per system or multiplex and fans are cut in and out to keep a constant condensing temperature.

Hope this satisfy your curiosity.

[jdunc2301]

Best answer I have seen in a while, cheers mate.
Its exactly what I thought thanks for taking the time to respond.

[Eeram]

Thanks for the reply. It feels that I did something right in the last 30 years, running around in trying to satisfy supermarkets, fruit consortiums, fishing boats, iritated air conditioner users, fishing consortiums, ice suppliers, trying to explain to my wife why I am sleeping in plantrooms, the list can go on!