does 60Amp main cut out need increasing??

[martinsayer81]

hi guys, new to this, this is my first post.

a 3 bed, 2 bathroom house with a T-N-S 60Amp main cutout fuse, has a 6 way c/u with re-wireable fuses. (no spare ways)
3x 5A lighting circuits
2x 30A ring mains
1x 15A immersion heater
(oven and hob is gas)

the house is being extended and refurbished, and the architect has requested a new lighting circuit and a new kitchen ring main.

after looking at diversity, am i right in thinking that the demand will be too high for the 60Amp main cut out fuse??

will it need replacing with a 100Amp fuse with new 25mm meter tails,

many thanks for any replies/answers.

i am worried about telling the customer they need to replace the supply(costing them money) if its not necessary

 

[telectrix]

very doubtful that the 60A supply will need upgrading. no 10kW shower. should be fine as it is.

 

[martinsayer81]

thanks for the quick response!

i thought it should be fine too, but when i did the diversity equation i got to about 70Amps?

 

[Plonker 3]

As Tel says.

Doesn't look like much loading on that at all.

 

[Plonker 3]

thanks for the quick response!

i thought it should be fine too, but when i did the diversity equation i got to about 70Amps?

Sometimes common sense gives a lot better idea of maximum demand.

Even with the immersion on, boiling the the kettle while ironing you wont be pulling more than about 30 amps. Why people think they need a bigger supply sometimes I don't know.

 

[JUD]

Are you changing the CU??

New circuits will require RCD protection.

 

[telectrix]

i very much doubt it'll ever pull more than 40A. when, if ever is everything on at the same time.

 

[fog]

Hi you will have to either put in replacement new consumer unit or via henly block put in a new consumer unit for new circuits anyway, ie RCD protection, doubt you need new supply fuse unless extension is going to be huge!
supply and demand unless they boiling kettle in each room they not going to use that much power, drop upstairs ring to 20 amp etc suggest new consumer unit, if new check out smokes on architect specs.

 

[Octopus]

Add up all the MCB's and multiply by 0.4

I have a client with a 5 bed house, integral self contained annex, outdoor lights, pool and tennis court on 60A and they survive!

 

[martinsayer81]

thanks dillb,

 

[Plonker 3]

Why all the mention of installing a new DB, the one in place may already be suitable.

 

[martinsayer81]

yeah im changing the cu to a new split load board, adding new light circuit and ring for kitchen, and im going to put smoke alarms on one of the lighting circuits, with smokes interlinked,

just hope the existing installation doesnt have an underlying fault that will trip the rcd!!!

 

[JUD]

Try doing you calcs on the actual loads of the circuits i.e. just because the lights are on 5/6 amp fuses/breakers doesn't mean they will be drawing 5/6 amps. There may only be 4 or 5 lights on each circuit (500W ÷ 230V = 2.17A)

 

[martinsayer81]

the architect has included about 30 spotlights! i will have to talk to them about maybe using the cfl equivalent.

 

[polo1]

yeah im changing the cu to a new split load board, adding new light circuit and ring for kitchen, and im going to put smoke alarms on one of the lighting circuits, with smokes interlinked,

just hope the existing installation doesnt have an underlying fault that will trip the rcd!!!

Of course, you'll EICR the installation first :devilish: