MCB tripping after new shower installed

[Cravatekid]

Hi,

I have just had a 9.5kw shower installed, my cable is at least 10mm wide and about 6 meters long, the MCB however is 30amp, my previous shower was 7.5 kw and was fine. Should I return the shower or get a higher rated MCB installed?

Thanks in advance
Newbie[/i]

 

[kevindgas]

Hi,

I have just had a 9.5kw shower installed,

Thanks in advance
Newbie[/i]

suggest the fitter is not competent to have done the work!!

 

[1john]

You need another 7.5kW shower

 

[1john]

The 10mm is the csa of each "live" conductor, not the overall width of the cable too, putting in a higher rated MCB could well cause the cable to overheat and perhaps a fire.

 

[Taylortwocities]

The 10mm is the csa of each "live" conductor, not the overall width of the cable too, putting in a higher rated MCB could well cause the cable to overheat and perhaps a fire.

See WIKI for GUIDANCE on cable sizes
//www.diynot.com/wiki/electrics:cable_types:flatpvccables

 

[Cravatekid]

Thanks for all your help, I think that I'm going to get the cost of a new MCB priced up, if that's expensive I'll return the shower.

Cheers

 

[ban-all-sheds]

You CANNOT just put a higher rated MCB in without considering if it is safe and suitable - there are lots of things to consider when matching load/cable/MCB ratings, and you MUST take all of them into account.

• //www.diynot.com/wiki/electrics:mcbtocable
  
  
• http://www.tlc-direct.co.uk/Book/4.3.1.htm
  
  
• http://www.tlc-direct.co.uk/Book/4.3.11.htm
  
  
• http://www.tlc-direct.co.uk/Book/5.3.1.htm
  
  
• http://web.archive.org/web/20080213151445/http://www.kevinboone.com/cableselection_web.pdf
  
  
• http://www.tlc-direct.co.uk/Technical/Charts/VoltageDrop.html
  
  
• http://www.tlc-direct.co.uk/Book/8.1.1.htm
  

BTW - you may have problems returning a shower which is not faulty and which you have already installed and used.

 

[Cravatekid]

Hi,

Thanks for your help, I've found out that Triton only do a minimum of 8.5kw showers now, so there's no point in sending mine back so I'm going to have to get a pro to upgrade the supply to it.

I can't work out the capacity of the cable, (the plastic is at least 18mm wide by about 8mm) This runs from a 'MEM' 30amp MCB to a fused switch, which then goes through the wall to the shower, cable length is about 6 meters in total.

Any idea of what needs changing, also any idea of cost please?
Thanks again

 

[riveralt]

Hi,
Thanks for your help, I've found out that Triton only do a minimum of 8.5kw showers now, so there's no point in sending mine back so I'm going to have to get a pro to upgrade the supply to it.
I can't work out the capacity of the cable, (the plastic is at least 18mm wide by about 8mm) This runs from a 'MEM' 30amp MCB to a fused switch, which then goes through the wall to the shower, cable length is about 6 meters in total.
Any idea of what needs changing, also any idea of cost please?
Thanks again

Leave the sizing of the cable to a proper electrician - you will need at least 6mm T&E and a 40Amp MCB and RCD protection - before any derating is applied. As per manufacturers instructions.
Cost will depend on whether your current cable is up to the requirments - if it is then the next issue is the whether you current Consumer Unit can take a 40Amp MCB and whether is it fitted with an RCD.
30Amp (is it an MCB or semi rewireable fuse?).
One option is to fit an separate RCD protected 40Amp shower consumer unit linked to your main tails and run the shower from that.

 

[JohnW2]

What riveralt said, but ... if the dimensions you quoted are anywhere near correct, it sounds as if you probably have 10mm² cable (the dimensions sound far to big for 6mm², let alone 4mm²) - in which case replacing the cable may well be one part of the cost that you will be spared. As riveralt said, an electrician will be easily able to determine the size of your cable.

Kind Regards, John.

 

[Cravatekid]

Thanks very much John and Riveralt, I think that I'm going to get a pro in to be completely safe! I am keen on getting an idea of cost as upon further research assuming the cable is okay, I know that the MCB isn't, it's an old MEM 30amp circuit breaker, so I'll have to get this unit replaced - at present there are three fuses, each at 30amps, are there more modern units that can mix fuses, say 2x 30amp and 1x 40amp?

Thanks again, please forgive my naivety.

 

[JohnW2]

Thanks very much John and Riveralt, I think that I'm going to get a pro in to be completely safe! I am keen on getting an idea of cost as upon further research assuming the cable is okay, I know that the MCB isn't, it's an old MEM 30amp circuit breaker, so I'll have to get this unit replaced - at present there are three fuses, each at 30amps, are there more modern units that can mix fuses, say 2x 30amp and 1x 40amp?

You're welcome. Modern Consumer Units can take any mix of MCBs, RCDs and RCBOs of different ratings - but having your CU reeplaced obviously would make it into a bigger job than simply sorting out the shower circuit. You may be advised that a new CU would be a good idea, for other reasons - but, as riveralt said, if you don't go down that route, there would be ways of just dealing with the shower circuit separately. An electrician will be able to advise you about the options, and their relative merits and costs.

Kind Regards, John.

 

[Cravatekid]

Thanks again John.

I'd ideally not want to replace the CU If I can get away safely with just replacing the shower 30amp circuit breaker with a 40amp breaker as that would save me some cash....hopefully.

The electrician is coming to quote at 3pm today so fingers crossed!

Cheers

 

[WabbitPoo]

The question you seem to be dodging is, who the F installed it for you? Are you willing to admit it was you? If it was a "pro" you need to get a refund and/or report him to his professional body. Just don't get the same guy back to upgrade !

IMHO.

 

[17thman]

sorry, i posted useless info as you have already bought the shower