Electric Shower burn out

[Bugwug]

Hi ya wonderful people,

My electric shower has been in situ for around 9 years, certainly preceeds my ownership, and a couple of days ago i noticed that it was not heating water.

The pull cord was still illuminated so i removed the shower casing and i noticed immediately that the neutral connections on the main power areas appear to have been heat damaged.

I could replace these and recify that however, it makes me wonder if anything underlying is wrong with the existing cabling or shower itself that needs work first as the first real problem.

If its bad cabling then i'm surprised its lasted so long, so could the shower be at fault and if so what should i check? Do electric showers commonly do this? Is the cabling wrong and bad practice?

Any help would be very much appreciated!

Ta

Nat

 

[Johnmelad]

Loose neutral connection.

 

[Bugwug]

Hi Johnmelad,

Ta for replying. I have just tugged the neutrals quite keenly and they all seem to be firmly connected (granted they may have fused if they had been arching (if that was the thought?))

Ta

Nat

 

[Bugwug]

Hmmm ok, have read some other similar type threads and it seems that it is a reasonably common problem with burn out on neutrals (not specifically but debatedly more common than Live) and that it may be that with frequent heating and cooling that the wires have worked themselves loose to then do what they have done.

A thread here for example;

//www.diynot.com/forums/viewtopic.php?t=221401

So perhaps can presume i can simply clean up the wires, buy a new terminal block and replace then be as good as new?

Ta

Nat

 

[securespark]

No, 'fraid not.

You'd need to cut back the cable to good bright copper. If you reconnect the tarnished copper, you'll get the same thing all over again.

What's that mark around the cable level with the bottom of the can?

It's on the neutral side of the cable but does not appear on the other side.

But there's a bigger question: what size is the cable, fuse or breaker and what size is the shower? How is the cable installed?

It could be the circuit was originally installed for a smaller shower and a larger one has replaced it, overloading the circuit.

 

[Bugwug]

Hi Securespark,

The mark you mention, is it this?

If so then it looks man made at some point as its far too sheer, but will bow to greater wisdom!

The breaker is a 45A, cable appears to be 25mm. The shower is a 7.8 to 8.5kW Triton Amber 2 and i believe this would have been the first and only shower in this property as its a very old house (i have papers of it exchanging hands in 1862) and the previous owners seemed to be just purchasers for renovation for resale. Evertything seemed new when i first moved in.

Ta

Nat

 

[ban-all-sheds]

That's not good.

cable appears to be 25mm

No.


//www.diynot.com/wiki/electrics:flatpvccables

 

[bernardgreen]

That nick on the cable appears to be on the red.

The cores appear to be twisted across each other under the clamp to get them to match the terminal block. Not good.

If they are twisted and the cable cannot be twisted before the clamp then when replacing the terminal block it may be worth exchanging the Live and Neutral to match the cable. But only do that if the terminal block is not labelled with L and N

 

[Bugwug]

Hi Bernardgreen,

Thats a good idea to switch the wireplacements in the TB.

I have removed the old one which was poor on the neutral side (which was expected) and the worse wire was the mains side neutral, perhaps that was the loosening wire?

I want to ensure i have bought the correct rated TB, i bought a 30A as it looked the same size (I hadnt removed the old one at this point to compare) and was the highest rated one i found in the electrical section at Wickes but have been Googling to ensure that that would be adequate and its hard to fine anyone specifying what it should be. All posts or instructions simply refer the TB as where the wires go, not what rating it should be.

Is 30A correct in any of your experiences?

Many thanks.

Nat

 

[viewer]

No - and it isn't experience but calculation 8500/230 = ?
Clue ? over 30A

 

[ban-all-sheds]

The shower is a 7.8 to 8.5kW...

And indeed 230²/7800 is pretty close to 240²/8500.

So why do you think you should be working out 8500/230?

 

[Bugwug]

Hi

Thanks, i got the math but as i could only find 30A and under at Wickes and Homebase it made me wonder if there were higher ones available as it seems odd that they should be so hard to find. This is why i asked as 30A seemed too low.

I found 60A as the next standard but again, that seems far too high as if this reoccured wouldnt it be even more damage as less likely to burn out?

Ta

Nat

 

[securespark]

You could ring Triton and ask nicely if they could pop one in the post FOC.

You'd be amazed what you get if you ask nicely.

 

[viewer]

45/50A pull switches are easy to find - B&Q or electrical shop, but check the old base fixing. Most the base is fixed to the ceiling and the pull switch part screwed to that, but some other way round. The practical difference is where and into what the screws go and whether it covers the hole in the plaster.
The switch rating is just the amount of current the switch is designed to switch; a larger than necessary one will not cause any problems, but one which is too small is likely to burn out. A 60A would be fine.

 

[ban-all-sheds]

... it may be worth exchanging the Live and Neutral to match the cable. But only do that if the terminal block is not labelled with L and N

Thats a good idea to switch the wireplacements in the TB ... I want to ensure i have bought the correct rated TB, i bought a 30A as it looked the same size (I hadnt removed the old one at this point to compare) and was the highest rated one i found in the electrical section at Wickes

... as i could only find 30A and under at Wickes and Homebase it made me wonder if there were higher ones available ... I found 60A as the next standard but again, that seems far too high as if this reoccured wouldnt it be even more damage as less likely to burn out?

45/50A pull switches are easy to find ... The switch rating is just the amount of current the switch is designed to switch; a larger than necessary one will not cause any problems, but one which is too small is likely to burn out. A 60A would be fine.