25mm SWA!!

[SparkyDips]

hello guys i overheard a conversation last week about a supply to an outbuilding which will comprise of: 45A Shower, 32A Ring Final and 6A lighting. Total demand = 83A.

outbuilding is 28Mtrs from main house and will have no extraneous conductive parts as the water feed will be plastic.

now the spark was saying that a 25mm SWA buried in the ground will need to be run and can use the house main earth.

whats your thoughts on this guys??

regards

 

[telectrix]

10mm is well adequate. the guy is talking through his arse. has he not heard of diversity?

 

[Jay Sparks]

25mm swa seems abit over the top to me. Doing a rough calc, 83A x 0.4 = 33.2A. Do some calcs and you will know what size cable you need.
Although I useally take out the biggest mcb, then add the rest, divide by 4 then add the biggest back for your total. This gives a slightly higher demand but still no need for the 25mm swa.lol

 

[telectrix]

sorry, jay. you need to allow 45A for the shower, the 0.4 of the rest. that equates to around 60A.

 

[Jay Sparks]

sorry, jay. you need to allow 45A for the shower, the 0.4 of the rest. that equates to around 60A.

Cheers tel, I realised what I had done and edited my post before your reply.lol

 

[SparkyDips]

so 10mm having 60A CCC and 16mm having 78A CCC more than adequate.

25mm having 99A CCC lol

 

[telectrix]

then again that shower may not pull over 40A . manufacturers are overly optimistic with their figures.

 

[SparkyDips]

yes true. i think i may suggest that 35mm "just to be safe" will be better and cheaper in the long run!! lol

 

[Jay Sparks]

I wonder which is the right way of working out demand?? I do the same by taking away the biggest mcb and adding it back to the total but I was tought to divide by 4. I know alot of lads multiply by 0.4. I suppose doing it the multiply by 0.4 way will give you a slightly higher demand and air on the side of caution!!

 

[Knobhead]

Funny how the question is always asked in the 2[SUP]nd[/SUP] inst. It’s never I think it should be what ever, but my friend thinks it should be……….

Funny old world. Or am I a cynic?

 

[i=p/u]

No diversity on shower, any specifics what else will be plugged in? Il say 60A on 63A breaker = 25mm

 

[telectrix]

a lot of confusion arises over the fact that while a MCB may be 32A for a socket circuit, say, the actual load of the circuit may never get above 20A, sometimes even a lot less if it's not a kitchen RFC.

 

[SparkyDips]

too late for calculations Tony!! Saturday night is beer time! lol

with this sort of attitude its no wonder people are put off making a post!!

 

[SparkyDips]

its not a kitchen, will be a small gym comprising treadmill and rower. with shower.

i have been doing the comms cabling and just overheard this conversation.

 

[telectrix]

No diversity on shower, any specifics what else will be plugged in? Il say 60A on 63A breaker = 25mm

you got shares in a copper mine?