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Converting a Horse box to a bar

Postby Hkw » Fri Aug 30, 2019 8:03 am

Hello
I'm converting a horse box to bar, which will contain two chest freezers, Three double sockets and two lights. I'm using a garage cu with a 6a and 32a breaker. I'm finding it hard to work out the incoming cable I need for the unit. I believe I need a H07RN-F (BS EN 50525-2-21) cable which will have to run 25m from the generator. I'm thinking my design current is 2kw for each freezer, plus 200w for the lights and 39w for the sockets, so 18.5A. On 2.5mm flex its volt drop is 19, so (19x18.5x25)/1000= 8.7v. Is my design current correct? And if so then I should be fine with a 32a 240 plug and 2.5mm H07RN-F black cable?
Thanks for any help.
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Postby ericmark » Fri Aug 30, 2019 3:34 pm

I have a chest freezer plugged into an energy monitor at the moment shows 67 watt. The problem with any refrigeration unit not using inverter control is the start current, they have a special overload in case some one switches it off/on without giving it long enough to let the pressure drop, so the start current can be around the 10 amp mark for a few seconds, but it quickly reduces.

So if the volt drop is too much, the over load can trip, and it can re-try many times, and then the over load fails.

However in the main a B10 MCB is ample, they will permit a 100 amp spike before they trip, the main problem is the generator, some generators are designed so on over load the field fails so the generator fails safe, others can over load the generator.

So since both freezers will not it is hoped start together 2 kW is enough for both, a B16 should be ample. 2.5 mm is not really man enough for over 16A anyway.

Standard supply lead for a caravan is 25 meters +/- 2 meters at 2.5 mm sq on a 16 amp MCB and I would say you can use the same. At 25 meters it is just within the volt drop, as to why regulations say no shorter than 25 meters not a clue.
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