l have a bought a 10.5 kw shower for my house and would like a bit of advice if possible. l have not had a shower before but whoever live here before must have as there is a cold water copper pipe run from the airing cupboard to the loft and across to above the bathroom and capped off there. Also on the consumer board there is a mcb for power to shower and the cable runs up to the loft and over to above the bathroom and into a insulating block so all the set up for the shoer is there but what l would like to know is about the electric side . The consumer board has a 40a mcb for the shower and it looks like 6mm cable, will this be alright for a 10.5 kw shower, or if it's not what kw shower would be alright for a 40a mcb with 6mm cable.. and what amp isolating switch would l need ....
10.5 kw shower...
- Thread starter ray316
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Ray could you survey the route between CU and shower, we need the approcx length (do not under estimate it !), and how it appears to run.
ie in plaster, in wall gap, trunking, surface etc.
6mm really wasn't designed for the sort of load you mention, unless the Cu to shower distance is very short and the cable is surface run.
ie in plaster, in wall gap, trunking, surface etc.
6mm really wasn't designed for the sort of load you mention, unless the Cu to shower distance is very short and the cable is surface run.
40A breaker is good for 9.6KW, but that doesn't mean that the cable is..
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Unlikely that 6mm cable will be rated 40A although it could be if 90deg cable is used often white rather than grey.
In theory
32 = 7.36 Kw
40 = 9.2 Kw
45 = 10.35 Kw
In practice we often overload slightly as it takes time to trip and that time is longer than it takes to shower.
But it was common to use 6mm in early days and many showers have been since changed and also insulation added and as a result overloading is also common and those in the trade often post the results.
Since it will come under Part P as a bathroom I would consider to be safe this should be an electricians job to test and fit new shower. Although you may consider it as a replacement it may have been removed because the previous occupants knew it to be faulty.
In theory at change of occupant all wiring should be tested and you should have paperwork telling you all test results. However in practice only rented property seems to get tested.
Any errors have such disastrous results I would say not worth the chance. Likely RCD protection and other things are missing. If my house it would be fully tested before re-use and even then if I could re-new I would. I never trust old wiring which is not in service. It could have all sorts connected to it etc.
In theory
32 = 7.36 Kw
40 = 9.2 Kw
45 = 10.35 Kw
In practice we often overload slightly as it takes time to trip and that time is longer than it takes to shower.
But it was common to use 6mm in early days and many showers have been since changed and also insulation added and as a result overloading is also common and those in the trade often post the results.
Since it will come under Part P as a bathroom I would consider to be safe this should be an electricians job to test and fit new shower. Although you may consider it as a replacement it may have been removed because the previous occupants knew it to be faulty.
In theory at change of occupant all wiring should be tested and you should have paperwork telling you all test results. However in practice only rented property seems to get tested.
Any errors have such disastrous results I would say not worth the chance. Likely RCD protection and other things are missing. If my house it would be fully tested before re-use and even then if I could re-new I would. I never trust old wiring which is not in service. It could have all sorts connected to it etc.
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Ok here goes... the cable goes from the CU in some plastic trucking around the cupboard which is under the stairs then up behind a false board intended to take all the new house wiring up to the next floor. It then goes up inside the airing cupboard into the loft and along to above the bathroom.. the cable do not go into the wall or any trucking apart from about 4ft of plastic trucking in the downstairs cupboard and the length is 24ft... if the cable and mcb is not suitable for a 10.5kw shower what shower kw would be, as l will take it back and get a lower kw shower.. and what isolating s/w amp will l need .. Thanks
If the ambient temp in airing cupboard is less than 30C, an 8m run, surface clipping then it 'just' copes with 45a load (10.5kw).
If the run is that straight forward then I'd suggest you change the cable to 10mm, keep the extra omph in the new shower and upgrade the MCB to a RCBO rated at 45a.
Your need to fit a shower isolator (normally pull switch) between the new run cable and the cable extending to the shower unit.
If the run is that straight forward then I'd suggest you change the cable to 10mm, keep the extra omph in the new shower and upgrade the MCB to a RCBO rated at 45a.
Your need to fit a shower isolator (normally pull switch) between the new run cable and the cable extending to the shower unit.
l said it might be 6mm cable but not sure as l see no markings on the grey cable, is there any way l can confirm if it's 6 or 10mm cable. If it's 6mm l will take the shower back and get a lower kw shower as the cable run means taking floorboards up and more expense for cable, if it's 10mm cable l will change the 40a mcb for a RCBO 45a
6mm t&e will have a single solid CPC (earth) and have an outside diameter of approximately 13mm.
10mm t&e will have a multi stranded CPC (earth) and have an outside diameter of approximately 17mm.
10mm t&e will have a multi stranded CPC (earth) and have an outside diameter of approximately 17mm.
If your CU has a max rating of 60A, then its very likely that the biggest individual circuit that it can take is 30/32A which would just be suitble for a 7.5kw (if you remember to calc the headline rating at 240v...)
It looks like you need someone in either to upgrade thf fuseboard, or to nstall a separate shower one alongside
It looks like you need someone in either to upgrade thf fuseboard, or to nstall a separate shower one alongside
there's also the consideration of RCD protection..
Max rated is 65a, so on the info l have gave you say a shower of 7.5 kw , l was looking at fitting a 8.5kw shower as l thought this would be adaquate enough on a 65a c/u with 6mm cable and 40a mcb.
How will you feel if you install a lower performing shower and find that it's carp?
Upgrade the circuit.
Upgrade the circuit.
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