shower circuit

[sevetaz]

Morning all,
i had an electrician/plumber out to my rented house, ie not allowed to sort myself job!! whilst he was here i queried our wiring for the shower.

it is a 230v 8.2 shower with 6mm cable that was running to non RCD side of the CU on a 32 amp MCB.
i queried with him that surely the 32 amp isnt enough and shouldnt it be on the RCD side of the CU, my workings out are that a 8.2kw shower = 36amps

he agreed with RCD part and moved it over but has kept 32amp MCB, he explained to me that its the cable he is protecting not the shower, 6mm cable ref method B = 41amps.

can someone explain to me in laymans terms this theory as i am struggling to get this, i can see that we need the mcb/rcd to trip before the cable burns out so needs to be lower amps than the cable but i cannot understand if you have a shower that can draw 36 amps why the next nearest MCB of 40 amp isnt used, surely with a 32 amp MCB fitted it has the potential to keep tripping should we run the shower at max temp??

appreciate any replies

Nigel

 

[DaveyD]

Hi

Have you confirmed it IS ref method B? The whole length?

 

[sevetaz]

Hi
the first part is of about a metre then the second part in the loft is clipped uncovered of no more than another 3-4 mtrs (ref c)

 

[Octopus]

You've previously stated you have the 17th, don't you have the books still??

 

[telectrix]

if 6mm cable is ref. method C, that's a max. current of 46A, then a 40A MCB would be OK. if you get the insulation monkeys round , though, that would be significantly reduced, so a 32A MCB is being cautious. bear in mind that the MCB will withstand a load of 1.45 X it's rated value for approx. 1 hour, so should not trip in the time it takes to have a shower.

 

[sevetaz]

doesnt help i was looking at wrong table, should be 6E1.... so 38 amp ref b and 46 amp ref c

 

[sevetaz]

Many thanks to all, just a matter of the old grey matter not working today and need to get my eyes tested to look at right table in the first place, fully sunk in now appreciate everyones help

 

[chopper76]

Does it matter?, the next trip below is a 20a which would deffo trip, if its worked so far with no problems I wouldn't look at increasing the possible fault current