Scratching me head

[oharaf]

Right, need to run a sub main.

Main board Wylex Split Load CU spares ways on both sides.

Run is about 15m

Customer would like a shower 10.5Kw plus ring final and lighting circuit x 2 (internal and external lights 2 lights on each) also to be 2 extractor fans, saniflow unit.

I have done my calculations and this is a shade short of 60A, so 10mm SWA supply required, the problem I have is I cannot find a supplier who stocks Wylex 60A MCB's.

Is it me and have i forgotten something??

 

[ban-all-sheds]

Henley... tails.... switchfuse....

 

[LoveRocket]

60A? Is that after diversity? The shower alone is 45A. Does s/he really need a ring final?

The shower, plus a 20A raidal and the two lighting circuits woud probably be OK on 60A, but don't you think you'd be better with a switchfuse henley'd from the tails?

I dunno about the calcs, but would volts drop not be an issue with that big shower load on a 10mm submain (especially as it feeds lighting circuits).

 

[oharaf]

yes I know BAS, thing is the room(s) where the work is is below the main house, the main board is in the garage with concrete floors seperating them.

So ideally need to bring a sub main down to the 'cellar' but with that shower the demand is to large!!

Oh hang on BAS get you, Henley, Switch fuse, SWA (instead of tails) new board(sub main ish)
da dah!!!!!!

 

[oharaf]

LoveRocket, yep, no diversity on the shower then a ring and some lights about 57A!!!!

But like you said, Henleys, Switch fuse, then 10mm SWA to new board in cellar problem solved, could go for a radial i suppose, thou there will be washer and dryer!!!

 

[ban-all-sheds]

Oh hang on BAS get you, Henley, Switch fuse, SWA (instead of tails) new board(sub main ish)
da dah!!!!!!

Yup - I meant tails as in 2 new pairs - Henley to existing CU & switchfuse

 

[Chri5]

4mm radial ? Shower used 5 minutes 3 x a day

 

[oharaf]

chri5!!!!!!!

Yep think you've answered it BAS, looking at the regs tables will mean 16mm SWA £Ouch!!!!!

 

[Lectrician]

16mm is not going to be hugely more expensive than 10mm TBH - especially as most wholesalers will carry huge stocks of 16mm as it is a well used size. There will be pennies in it per meter.

 

[Spark123]

I don't think the normal domestic boards are suited to any MCB over 50A, there may be MCBs available in a similar range but be very careful that they may be intended for the industrial range of boards.
You'll have to check the specifics for that particular board.

The next size MCB available for an industrial type board is 63A, however I think the henley and switchfuse is probably going to be the best idea.

 

[Adam_151]

As spark 123 alludes to, you won't find an NSB above 50A, you can get a PSB 63A which will fit, but not intended to fit in a domestic DB.... if you try you'll find it'll fit, but the fuseboard will no longer comply with BS60439 as it was never type tested in that situation... which could leave you in an awkward situation... particualy if you need to rely on the provisional 16KA fault level tolerance that annex ZA permites you

Oh, and how well do you think the MCB on the ring final will discriminate with the submain MCB?...

 

[ban-all-sheds]

Better than the shower one will....

 

[Adam_151]

Better than the shower one will....

Really?

I would put a fiver on neither of them discriminating at all in a real life situation

 

[securespark]

I agree.

For that reason, I would run all the circuits back to the CU and not bother with a sub at all.

 

[oharaf]

Running all circuits back to CU is just not a sensible option in this case.

Anyway I have listened to you chaps, Will fit Henleys, Fused Switch 16mm SWA to new board.

Just going to have to explain to the customer that for them to achieve what they want it is the best option looking to be around £1500 in total, not including the Saniflow and the shower