8.5kw shower wires in 4mm, burnt terminals

[westward10]

I suspect the root cause of this was a loose connection and not conductor csa although it is obviously undersized.

 

[robo83]

I've told llthe landlord to get other electrican to call me if he has any issues returning to sort, also when I undid the isolator Fascia the cables just fell out the back.

I checked over the board before I disconnected the supply and some of the terminals were LOOSE :/

 

[telectrix]

but was not undersized for the 7kW shower, and was suitably protected with a 32A MCB. a bit like the chandelier i just repaired for a customer. 105VA transformer supplying 10 x 10w G4 lamps. he'd fitted 10 x 20w G4s and wondered why the transformer failed.

 

[robo83]

The landlord said they told the electrican what shower they were getting. And the sparks installed it with the cable, he must have known it was 8.5kw.

 

[telectrix]

The landlord said they told the electrican what shower they were getting. And the sparks installed it with the cable, he must have known it was 8.5kw.

even so, the 4mm would have handled that 8.5kW. it's down to poor terminations.

 

[Octopus]

^^ even if I knew it was going to be a 7kw shower, I would still have fitted 6mm cable

 

[The Ghost]

B+Q

Q+Q more like

 

[Ian1981]

even so, the 4mm would have handled that 8.5kW. it's down to poor terminations.

May depend upon the reference method used for installation as 4mm installed in trunking de rates to around 30 amps

 

[Lee42]

I've told llthe landlord to get other electrican to call me if he has any issues returning to sort, also when I undid the isolator Fascia the cables just fell out the back.

I checked over the board before I disconnected the supply and some of the terminals were LOOSE :/

Sounds like he had plastic wrists

 

[Lee42]

I had a similar situation yesterday.
Reports of shower isolator getting hot. Go to check it out. 6mm installed last year supplying a 9.5kw shower. Burnt out connections.
I would always install a 10mm if wirring for a new shower.

 

[davesparks]

^^ even if I knew it was going to be a 7kw shower, I would still have fitted 6mm cable

Which is fine, and if you wish to do that then there is nothing preventing you from doing so. But if the calculations show that 4mm is suitable then you cannot criticise someone for installing 4mm, whatever your personal preference in the situation.

 

[westward10]

10.0 doesn't prevent loose connections and burnt conductors.

 

[Lee42]

10.0 doesn't prevent loose connections and burnt conductors.

You're quite right.
I always tighten connections. Leave them a minute to settle then u can normally get another quatre turn on them.
The reason we always wire a new shower supply in 10mm, is so the customer has some flexibility when coming to choose a shower.
And like ive seen before, when the customer decides on him/her self to uprate the shower to a 10.5kw. Not realising the existing 6mm will not be adequate. (Normally a trip back to b and q for them)
I would always recommend not installing a electric shower, much better of a combi, but needs must sometimes

 

[Wilko]

I had a similar situation yesterday.
Reports of shower isolator getting hot. Go to check it out. 6mm installed last year supplying a 9.5kw shower. Burnt out connections.
I would always install a 10mm if wirring for a new shower.

View attachment 37616

Hi - not to disagree at all with ccc etc, but this pic does look like the heat is concentrated at the termination rather than evenly along the cable. And as the neutral seems unaffected (?) it perhaps suggests in this case the cause was poor termination of the line conductor?

 

[Lee42]

Hi - not to disagree at all with ccc etc, but this pic does look like the heat is concentrated at the termination rather than evenly along the cable. And as the neutral seems unaffected (?) it perhaps suggests in this case the cause was poor termination of the line conductor?

Hi wilko. Yes that was indeed the problem.
Only been in for 8 months, so someone with plastic wrists must of installed it.
I just think it's good practice to always install a 10mm cable for a new shower install.