supermarket packs

[Hamza Alg]

am looking to learn more about supermarket packs and systems. common faults, how they work....ect
is there any materials out there i can study or learn from.

[750 Valve]

They can only be learnt at 2am on a saturday morning with $100K of stock melting in freezers and a controller that does't want to play the game anymore…

Start by looking through old threads, they are essentially just a DX system with multiple stages of compression available with a few bells and whistles thrown at them (floating suction, discharge, drives, hot gas/kool gas defrost, heat reclaim, etc). Some rack manufacturers (especially US) have good published info such as Hill Phoenix, Kysor Warren, Hussmann, etc. Try on their websites.

[Hamza Alg]

how about the the different controllers that need to be used in pack systems?

[RONB]

There are lots of different plant controllers. They all roughly do the same job but they all have their own way so be set up. The main ones in the UK you will come across are Danfoss.RDM,CDK,JTL,Stonegate,Radford,ELM. There are others but these are the common ones. The case controllers are also manufactured by these manufacturers. I'm afraid that the only real way to learn about these control systems is to be hands on, but for this you need to get into service/ commissioning. I doubt that there is anyone out there that is fully conversant in every aspect of all of the systems but the manufacturers do offer a technical help desk. I've been in this trade for over thirty years and there's still things to learn about the control systems, they are always bringing something new out so you need to be on the ball to keep up to date. So to answer your question you really need to get a job in Supermarket engineering and start from there.

[Hamza Alg]

thanks for your reply. i have just started a job in supermarket refrigeration as an apprentice and am learning as i go.

i came across a pack controller which went to back up. it was running on the lp over ride switch (looks like normal lp switch)
do you know how those lp over ride switches work and what do they maintian since they can't shut in compressors off as each compressor has its own lp switch.

[NewmanRef]

If your pack is in override, the LP switches your talking about are being used to control staging in and out of compressors from the system suction pressure. The other switches that you mentioned that are on each compressor are the safety hp/LP switches. These will be set exactly the same on each compressor to prevent each compressor from running into a vacuum and also to cut out the compressor in the event of system high pressure. The override LP switches will be set differently for each compressor, staging each one in and out as suction pressure rises and falls. This will allow the pack to maintain cabinet temperatures in the event of pack control fault or failure. The override will be set to kick in if suction pressure rises too high suggesting compressor control failure.

[Hamza Alg]

thanks a lot, i don't think anybody could have explained it to me any better.