Shower Woes... keeps tripping trip switch

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Durham
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Hi.

Around three months ago we got a new shower installed, a Bristan B85.

Everything was fine until yesterday. My wife switched it on by the pull chord and the trip switch went. This morning it went off twice while I was in the shower.

I have no idea what is causing it. But have made the following observations:

i) the shower was not switched on with the on/off switch yesterday. My wife only pulled the chord. So can it still be a fault inside the shower?

ii) I have been told that the shower should have a 35 amp fuse in the CU. It currently (lol) has a 30 amp one.

iii) the cable is 10mm so I guess that is okay.

iv) the pull switch was replaced around the same time and gets some hammer. Could it be something as simple as a loose wire in the pull switch? I have heard they can loosen after 2-3 months of wear and tear. Probably worth buying an MK one or something?

Any help would be greatly appreciated.

Thanks.
 
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You failed to say what KW rating the shower is, you sure its 10mm not 6mm cable?
It will most likely be the wrong size circuit breaker being used, its being overloaded!
Power / Voltage = Current
On an 8.5Kw on 230v = 8500 / 230 = 37Amps so a 40A breaker would be used providing the correct size cable is installed
If its tripping as soon as the switch is pulled then it could also be a loose wire/faulty switch
 
Sorry. The Bristan B85 is 8.5kw.

It is 10mm cable (I remember checking this when the old shower had been taken off the wall) so I guess I just have to get a 40A breaker then?

Odd how it 'seemed' to work fine for 3 months first though :confused:
 
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Sorry if you're offended by this, but it is a very common mistake - are you sure it's 10mm²? Where and how are you measuring it?

I remember it being quite thick and unwieldy. A lot thicker than, for example, a regular mains lead to a socket. It was about as thick as the one to a cooker.

The plumber then commented about it being 10mm and it "should be fine..."

//www.diynot.com/wiki/electrics:part-p

But I wouldn't be adding anything 'new' to an existing spur. Just changing the fuse for a higher rated one and if the cable is 10mm then shouldn't this be okay?

Does it have more than one heat setting?

It does. I 'think' it has 3 settings but we only use it on the highest.
 
I remember it being quite thick and unwieldy. A lot thicker than, for example, a regular mains lead to a socket. It was about as thick as the one to a cooker.
It is very unusual to find 10mm² used for a cooker.


The plumber then commented about it being 10mm and it "should be fine..."
A plumber. :confused:

So shall we just hope he was right?


But I wouldn't be adding anything 'new' to an existing spur. Just changing the fuse for a higher rated one
That is notifiable work. For good reasons.


and if the cable is 10mm then shouldn't this be okay?
If it is it probably will be, but you really shouldn't bet your safety on ifs shoulds and probablys...
 
It is very unusual to find 10mm² used for a cooker.

Oh... how thick are they then... usually?

A plumber. :confused:
So shall we just hope he was right?

I hear what you are saying :D

If it is it probably will be, but you really shouldn't bet your safety on ifs shoulds and probablys...

Okay, what would you suggest then?

And why has it worked fine for 3 months? I'm at a loss on this one...
 
Oh... how thick are they then... usually?
6mm². 4mm² isn't unheard of, but that isn't obviously "A lot thicker than, for example, a regular mains lead to a socket."

Okay, what would you suggest then?
http://www.competentperson.co.uk


And why has it worked fine for 3 months? I'm at a loss on this one...
Me too.

I did wonder if you'd only just switched to using a higher heat setting, but that's not it.

Could be a fault in the shower.

Could be that the cable has been gradually damaged by overload.

But whatever it is, attempting to mask it by fitting a higher rated breaker when you can't be sure that it matches the cable capacity is a very bad idea...
 
An under rated cable or an under rated fuse is a bit like a bomb with a dicky timer, it won't go off when you think it should.

It will go off when certain conditions such as cable melting or fuse tolerenace is reached.

A 30A fuse will take a 40A load, and eventually go pop. The science it's precise, becasue the frequency of use isn't 24/7 x 365 it's 5minutes here, 10 minutes there.

Outer dimensions of a 10mm TE cable are in the region of 9mm x 17mm, but do vary a bit.

Here's a TLC size list

1mm² CSA T&E has overall dimensions of 7.8mm x 4.25mm
1.5mm² CSA T&E has overall dimensions of 8.2mm x 5mm
2.5mm² CSA T&E has overall dimensions of 10.3mm x 6mm
4mm² CSA T&E has overall dimensions of 11.9mm x 6.25mm
6mm² CSA T&E has overall dimensions of 13.5mm x 7mm
10mm² CSAT&E has overall dimensions of 17.1mm x 10mm
16mm² CSA T&E has overall dimensions of 19.4mm x 10mm

I'd suggest you seek a spark for your own piece of mind.
 
6mm². 4mm² isn't unheard of, but that isn't obviously "A lot thicker than, for example, a regular mains lead to a socket."

Right. Got you. I'm just going off the cookers I've seen being installed... around two :)

I'm pretty sure they were 10mm and I am pretty sure the one to our shower is 10mm also. I know that doesn't exactly fill you with confidence either ;)

I did wonder if you'd only just switched to using a higher heat setting, but that's not it.

Could be a fault in the shower.

Could be that the cable has been gradually damaged by overload.

But whatever it is, attempting to mask it by fitting a higher rated breaker when you can't be sure that it matches the cable capacity is a very bad idea...

I'm hoping for a loose wire in the pull switch or a faulty shower now as I don't fancy the idea of a damaged mains cable. Which (fingers crossed) it isn't. Which it won't be... if the cable is 10mm... :confused:
 
An under rated cable or an under rated fuse is a bit like a bomb with a dicky timer, it won't go off when you think it should.

It will go off when certain conditions such as cable melting or fuse tolerenace is reached.

A 30A fuse will take a 40A load, and eventually go pop. The science it's precise, becasue the frequency of use isn't 24/7 x 365 it's 5minutes here, 10 minutes there.

Outer dimensions of a 10mm TE cable are in the region of 9mm x 17mm, but do vary a bit.

Here's a TLC size list

1mm² CSA T&E has overall dimensions of 7.8mm x 4.25mm
1.5mm² CSA T&E has overall dimensions of 8.2mm x 5mm
2.5mm² CSA T&E has overall dimensions of 10.3mm x 6mm
4mm² CSA T&E has overall dimensions of 11.9mm x 6.25mm
6mm² CSA T&E has overall dimensions of 13.5mm x 7mm
10mm² CSAT&E has overall dimensions of 17.1mm x 10mm
16mm² CSA T&E has overall dimensions of 19.4mm x 10mm

I'd suggest you seek a spark for your own piece of mind.

I've just rang one :D

But I have a question. A question I'd probably rather not know the answer to...

If the cable isn't 10mm the shower is going to have to come out isn't it?

It'd be a pain to upgrade the cable :(
 
6mm cable, if that's what it is might be ok for 8.5kw load.

The factors that need considering are distance between shower and fuse board (not measured as a crow flies, but the actual route), how the cable has been run (on it's own, bunched with other cable, touching the wall surface, hidden inside insulation etc), age (tested with a IR tester).

It's a hard call without knowing exact detail. Give me a minute and I'll upload a calc :D

GALLERY]
 
Thanks for that. So, if it were 6mm cable, it 'could' be okay?

My butt cheeks are beginning to implode with the stress of thinking that something really bad might have happened :eek:
 
I'm suprised that no one has yet asked what make and style your fuse box is.

A photo would be superb, if not, make / model / colour / main switch rating / anything else you can see.
 
Hi.

It is a WYLEX and the only number on it I can see is: Cat. No. NSES5404.

BTW I tried it out last night and it worked fine. Could it be something to do with the time of day / drain on the supply? The mains used to go off at least twice a month around the entire estate.

The other week there were problems with water pressure.

I blame those outdoor Christmas lights... for everything! :)
 

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