Refridgeration

[PhilCumbria]

I have a friend that has had two Commercial Fridge counters installed each with a compressor that has a max operating current of 16A. The company that has installed them have plugged them into the ring main via extension leads. Should these not be on their own dedicated supplies?? Apparently the compressors keep blowing because there is not enough power on startup. Can anyone help with this?

 

[Marvo]

I doubt it. If the compressors are hermetic then they have protection against issues caused by low voltage. It would be a bit iffy plugging them into a ring final circuit with a 13A plug though....do they blow the fuse in the plug?

 

[PhilCumbria]

Hi Marvo

I'm not sure, apparently it is the fridge engineers saying that there is not enough power, I will ask the question about the fuses mind. It is a butcher that has put these fridge counters in a "farm shop" Apparently there is a 40v volt drop when these compressors start up....

 

[telectrix]

tou will need to find out if this volt drop is a preoblem with the customer's installation or a DNO supply problem before you can tackle it.

 

[Marvo]

If the compressors are single phase then the voltdrop momentarily on start-up would be expected. As a rule of thumb a single phase compressor will draw roughly 5 times its run current for a fraction of a second during starting, hence the voltdrop is expected within limits.

Plugging a 16A load into a 13A socket would be bad practice and I'm assuming against the UK regs but if the compressor is starting cleanly ie the start relay isn't chattering and it's not cycling on the Klixon thermal safety or the internal winding thermistor then it's probably not a power issue. These symptoms of low voltage are firstly pretty obvious so the fridge guys would be able to state categorically that it was the cause. Secondly there's sufficient protection installed around the compressor to prevent permanent damage occurring as a result of voltage dips so if compressors have failed I'd be investigating other possible causes as well.

When fridges are rated for maximum current draw it's a worst case scenario where the condenser is blocked and the air temp across the evaporator is high and high external ambient temps. Under normal circumstances a well maintained fridge could be running at 60% of it's rated maximum current or even less possibly so depending what other loads are on the circuit it may or may not be overloaded.

 

[pennychew]

I remember the klixon safety device from your post on overload devices in the trainee forum!

 

[PhilCumbria]

From what I can see the sub CU that is supplying the shop is on a 10mm SWA From another 3 phase Board supplied from the main board via a 25mm SWA. Until the compressors kick in voltage is fine.

 

[Pete999]

Would imagine the RFC your refrigeration plant is protected by a 32 a cb typeB I would hazard a guess that these cabinets should be on their own dedicated circuit designed correctly and protected by a C type OCPD to allow for inrush on start up, remember these cold cabinets are cycling on and off due to the loading of the chiller, won't do a plug top fuse much good. That's my take anyway.