Cable calc advice needed...

[Gottssam]

Hi there,

Have just picked up a job to price and i'm struggling to work out the best solution to the problem. Any help would be greatly appreciated.

Scenario.... Large 5 bed house being split into 5 rooms for separate rental. Landlord has decided to install 5 power showers to each of the individual en-suites. I have advised him to go for 8.5kw showers to keep the load down.

There is also a mini-kitchen going into each room with a washing machine, oven (fan assisted) kettle, microwave etc.

I planned to install a 10 way RCD split load consumer unit with 5 40amp MCB's for the showers and 5 32amp MCB's for the kitchens. After applying diversity, i still have a maximum demand of over 100amps. Does it matter that there's only an 80amp 1361 main fuse? There is also already another cu with a few rings, lighting circuits etc from it.

Only just came out my time recently so still earning as i go. Any info/guidance would be great.

Cheers

 

[chiplard]

The showers alone will be over 180A - no diversity allowed. This installation will require a 3 phase supply, something the landlord will have to pay for before you even contemplate carrying out any work.

 

[Sintra]

When you say power shower i take it you mean an electric shower with heater element as a power shower to me is a hot and cold fed shower with an electric pump that uses practicaly no juice.

 

[cg-elec]

Sorry, i meant cold water fed, element heated showers (8.5kw).

I figured that this type of shower fell under "instantaneous water heater" in App1 of IEE OSG? Which states 100% of full load of first two, then 25% of remaining. Even still though that is over the 80amp main fuse. So am i correct in assuming my maximum demand after applying diversity needs to be within the 80amp main fuse rating?

Thanks for your help

 

[chiplard]

You are correct in what you say with allowance for diversity. But these are 5 separate dwellings so personally i would not allow diversity as the showers could be used at the same time.

No you are not correct, the main fuse should be of sufficient rating without diversity applied.