Commercial kitchen from home

[pc1966]

Would this single cable come from the spare 32A breaker on my existing board as this wouldn't be enough? I like to understand what's happening and having done a little bit of looking I've seen that henley blocks are used to install sub-consumer units?

Ideally you don't want the kitchen CU off your existing RCDs as the leakage on those ovens is likely to trip it taking out the kitchen and some of your home supply.

If your CU allows internally a 63A (or maybe 50A) MCB off the direct supply (i.e. from main switch to RCD input, not RCD outputs) then it would be better, but still not offering much selectivity. In other words if you have a big fault on one kitchen circuit it will also trip the supply MCB taking out all of the kitchen electrics. So don't put your lights on it with this configuration as that would be very dangerous. Probably you should look at some sealed "non corrosive" LED strip-lights with built in emergency backup anyway, just in case you are running lots of hot appliances and the mains fails plunging you in to darkness.

That is why the usual suggestion is to split the tails feeding your main CU (where the Henley blocks come in) and then have a fused-switch to feed the sub-main cable to the 2nd CU. The selectivity between a 63A fuse and something like a 20A MCB or RCBO for the cookers is quite good so a fault would be localised to the final circuit.

Generally you should have all of the final circuits on RCBO if you can, though if the ovens are hard-wired (e.g. FCU) and the cables not buried < 50mm they could have RCD protection omitted. Socket outlets should always have RCD protection.

 

[stevethesparks]

You really need to list every single item with their rated values. You also need to advise what sort of loads the normal household has. ie electric showers - how many, car charging points, current domestic kitchen set-up etc. What hours would the business side run, could you honestly run the business side and near enough shut off the living arrangements at the same time? If not it looks like there may be a possibility of a total power outage at some stage.

 

[pc1966]

The total mentioned above is 58A without allowing any diversity (I would be cautious about how much is allowable for commercial kitchen?).

So long as no showering and no big EV charging during working hours they may be OK on a normal supply, but wise to check if it is 60/80/100A.

 

[stevethesparks]

The total load was 58 amps before the electric oven was mentioned/added, no mention of a possible microwave?
It really needs someone to visit site and make a proper evaluation.

 

[pc1966]

The total load was 58 amps before the electric oven was mentioned/added, no mention of a possible microwave?
It really needs someone to visit site and make a proper evaluation.

Yes, I should have read it more carefully as the oven (probably 10-15A) and dishwasher (same again?) all pushes up the peak demand.

If they have 100A (or can get upgraded to it) then it is looking OK, but dodgy for a 60A supply.

 

[pc1966]

Out of curiosity I looked up to OSG table A2 for diversity on non-domestic cooking and it suggests:

• 100% of max demand appliance +
• 80% of next biggest +
• 60% of the rest.

Here they are all roughly the same so it is leading to around a 70% overall factor taking 58A to 40A-ish. but the concern would be at start of they day putting on all fryers to get them to temperature and maybe a coupler of other things as well.

 

[stevethesparks]

Plus kettle/water boiler, toaster, I don't think the whole thing has been thought through enough.
I hope I'm wrong and they can make a good go of it.

 

[pc1966]

It is sort of pointing to a 100A supply and 63A fused sub-main as being OK, but as just said it really needs a proper study of what is going in there.