help needed

[bluemoon32]

Recently moved into our new home & today a plumber we know put in a new electric shower for us ( 8.5) & it tripped the consumer unit. He told us to go out & buy a new 45 amp circuit breaker to replace the 32 amp one used for the old shower but it still trips as soon as i put the shower on???
Someone else i asked about this said i may only be able to use a 7.5 on the present wiring etc....not sure if i've explained it all properly but i don't really know much about electrics
Any help would be much appreciated

 

[andy]

by 8.5 i assume you mean the KW rating of the shower. 8.5KW is approx 35 amps. obviously youll need a 45A breaker. before you change this make sure the cables are up to the new load. what size are the cables? what is the lenght of the cable?

EDIT: does the RCD trip or the breaker? most faults av been asked about showers trippin RCD turned out that the plumber out the neutral return on the non-RCD neutral block

 

[bluemoon32]

by 8.5 i assume you mean the KW rating of the shower. 8.5KW is approx 35 amps. obviously youll need a 45A breaker. before you change this make sure the cables are up to the new load. what size are the cables? what is the lenght of the cable?

EDIT: does the RCD trip or the breaker? most faults av been asked about showers trippin RCD turned out that the plumber out the neutral return on the non-RCD neutral block

1. the cable is 10mm i think & it's about 30 ft long
2. the rcd trips

 

[bluemoon32]

by 8.5 i assume you mean the KW rating of the shower. 8.5KW is approx 35 amps. obviously youll need a 45A breaker. before you change this make sure the cables are up to the new load. what size are the cables? what is the lenght of the cable?

EDIT: does the RCD trip or the breaker? most faults av been asked about showers trippin RCD turned out that the plumber out the neutral return on the non-RCD neutral block

1. the cable is 10mm i think & it's about 30 ft long
2. the rcd trips

Not really sure how to measure cable to be honest....it's 10mm both sides....does that mean it's 10mm cable??
No sarky posts please lol

 

[andy]

if the RCD trips and not the MCB, sounds like the neutral is in the wrong place (as mentioned above).

if the cable is 10mm then it will be able to take the load.

to make sure it is 10mm (or 6mm) you can measure it. 10mm cable is approx 8x17.2mm and 6mm is approx 6.7x13.4

back to teh RCD, do you have a split load board or all potected by RCD (if split load, isolator will be at one side with MCBS, gap then MCBs and RCD)
if split load ull need to move the wire if it is in the wrong place. not hard but make sure the power is isolated (from external isolator if there is one) before you do anything

 

[Damocles]

A load of 35A would not trip a 32A mcb quickly. These things will sustain a small overload for a certain time. And it would be better to have an overloaded mcb than an overloaded cable.

The rating of the MCB will have no effect on whether the RCD trips. An RCD trip is not because of anything being overloaded, it is because some of the current going out on live does not come back on the neutral through the RCD. It is intended to very quickly detect earth shorts, but is sensitve to incorrect connections.


10mm cable means that the cross sectional area of the cable is 10 square millimetres. It is a stranded cable, so if you had the tools you can measure the diameter of each strand, calculate the cross section area and then add up for all strands. Otherwise go to B&Q and look at some cables to see the difference between 6 and 10. Cables may vary slightly in thickness from brand to brand.

 

[dw3101]

He could also have screwed through the cable when fixing the shower up, it really needs the cable disconnecting from the CU and testing properly before connecting up.

David

 

[bluemoon32]

Thanks for all your help
Plumber had wired it up wrong

 

[andy]

Thanks for all your help
Plumber had wired it up wrong

useless plumbers. they shud leave the wirin to a sparky

 

[dingbat]

useless plumbers. they shud leave the wirin to a sparky

I'd be happier if we just cooperated more. I'd gladly tell a plumber how to go about doing the electrics for showers, for instance, if he'd tell me the secret of replacing old immersion heaters without splitting the tank!

 

[andy]

useless plumbers. they shud leave the wirin to a sparky

I'd be happier if we just cooperated more. I'd gladly tell a plumber how to go about doing the electrics for showers, for instance, if he'd tell me the secret of replacing old immersion heaters without splitting the tank!

they shud have a lesson in how to wire a shower MCB and to make sure they put the neutral on the RCD neutral bar instead of the non RCD. i would of thought they would test to make sure it works tho, and realize they wired it wrong

 

[ban-all-sheds]

Thanks for all your help
Plumber had wired it up wrong

Not really sure how to measure cable to be honest....it's 10mm both sides....does that mean it's 10mm cable??

You really do need to check this out - if the cable is too small it could overheat. As suggested, go into a shed and have a look at some.

Also, if you look here: http://www.tlc-direct.co.uk/Main_Index/Cable_Index/Twin_and_Earth/index.html they list the dimensions for each cable size.