What Is The Best Switchboard Configuration?

[Artisi]

A question for the sparkie’s regarding switchboard configuration.

I am at the point with our house project of thinking about the electrics / switchboard etc.

I envisage 3 power outlet circuits

3 water heater circuits

3 a/c units with provision on the board for an extra 2

3 light circuits

1 circuit for outside lights and security

1 circuit to a sub-main in the kitchen for power outlets, oven, exhaust fan and power to the pump house.

Possibly a couple more circuits and a spare or 2 as we think thru it.

The question now is what is the best arrangement for the switch board configuration, price is well down the list of priorities; the main point is safety, function and practicality.

I see 3 options

1. 1 RCBO controlling all circuits via MCB’s – This is ok except a nuisance trip puts all power out.

2. RCBO’s on all circuits – maybe overkill and the most expensive.

3. A split board with the power outlets, water heaters and possibly the a/c units with individual RCBO’s in one group and the remaining circuits in the other group with 1 RCBO and MCB’s. This arrangement seems the most logical – probably just a little more complex in assembly.

All thoughts, comments, and suggestions are most welcome

Thanks.

[electau]

Can you supply information on the load of your electrical installation so the max demand can be calculated?

Will you be using the MEN ot TT earthing system?

Do you invisage using single phase or multiphase supply?

Are you going to use DIN rail MCBs/RCDs or the standard frame MCBs?

With this information one can calculate the size of main switchboard and size of sub board.

You will require the size of the consumers mains and sub mains to be calculated also.

Edited May 16, 2011 by electau

[Crossy]

As (mostly) usual, I'll echo Electau's comments, you really need to do a max demand guestimate, really to be sure you're not going to send the baby meter into orbit. Have you verified with MEA/PEA whether they can supply a single-phase 15/45 or will you get stuck with 3-phase 5/15?

I'd go with the split board with single width RCBOs on the unprotected side, you may consider a non-RCD circuit for your freezer.

I'd also have at least two outlet circuits in the kitchen (I see you're suggesting a sub-main, how big are you thinking?), it doesn't take much to take a single 20A circuit past it's 4.5kW limit. An electric hob will need it's own circuit anyway (check the instructions for breaker size and cable accordingly), if you have a pukka electric oven (not a worktop type) then give it it's own spur and breaker too.

[Artisi]

electau and Crossy

Thanks for your replies, at this stage I haven't established with the incoming supply with the authorities - it is on to do list in the next week or so and the electrics haven't been discussed at length as yet with the contractor other than finding out if they have a qualified sparkie on their team- which they assure me they have. (they usually build industrial projects and resorts). Looking around the housing estate it would seem that it is not MEN and it appears that everyone has 15/45 single phase.

The kitchen sub-board will be - 1 circuit for the power outlets, 1 for the oven, 1 for the pump house, and a spare for a future small external building - I agree that a non RCD for the fridge is probably the way to go - as is the split board with RCBO control.

A quick max demand using AS3000 factoring looks like about 85 / 90 amps.

Again comments most welcome.