Shower circuit MCB intermittent tripping

Joined
29 May 2012
Messages
13
Reaction score
0
Location
Lincolnshire
Country
United Kingdom
Upstairs electric shower (pretty old looking, small and not sure of the power) stopped working 'a few years ago' so I replaced it with a Triton T80 Easyfit+ 10.5kW from Screwfix. I just used the existing wiring coming out of the wall and all has been well until now.
It's mostly the daughter uses it (grownups use 2nd shower downstairs which I also replaced some time ago) but now after her using it for maybe in excess of 20 minutes, the 32A MCB has started tripping. After reset it trips again after a minute or two. The next day it'll be fine for another 20 minutes or so (I know, tell her not to spend so long in there). It's Winter now and I was thinking it's having to draw more power but it's not that cold and the shower's been used just as much when a lot colder.

In the loft, there's nothing on the insulation to say what the rating is on the supply, only 'Delta Enfield Basec'.

upload_2021-12-17_13-20-10.png


It resembles wire for electric cookers in overall thickness but it's multi strand and when coming back up from the pull switch the wiring going down to shower have been joined by a chunky connector block.

upload_2021-12-17_13-24-8.png


I've had this apart and the wires aren't green or anything but the neutral didn't have all the strands gripped though and the block isn't big enough to get strands alongside each other. It still trips out anyway.

What else could be the problem that has made it play up after this length of time? (I know the wiring is all wrong for an electric shower for a start).
 
Sponsored Links
Everything about this is bad.
Get an electrician to rewire it.

10500/240 = 44 amps.
Your MCB is getting overloaded.

Your wire may be 6mm2 which is too thin for being buried in insulation.
 
Others have already correctly stated the MCB is to incorrect for the power of the shower.

I've just tried holding 6mm² and 4mm² cable to recreate your picture with my thumb and I wonder if it's 4mm² in which case it too will be well undersized, as will 6mm² if it's buried in insulation.

Get someone in to check it out properly, in the mean time only use it on lower power.
 
Sponsored Links
For what it's worth, One of my rental properties had a 7.5KW shower unit with 4mm² cable & 30A fuse. My latest EICR highlighted it to be 10.5KW, the replacement had gone completely unnoticed by me in the dozen or more visits since I fitted the replacement 7.5KW. There was no sign of any heat damage or reports of tripping but straightaway I made the changes, in fact the EICR paperwork wasn't even completed as I also made the decision to change the consumer unit.
 
Looking at the trip curves for 60898 MCBs, a B32 takes 1000 seconds to trip at 50A. (16 or so minutes)

There's your answer.

The cable is too small. It is at risk of overheating as its in insulation. It has dangerous joints. It needs rewiring. I really wouldnt use it.
 

DIYnot Local

Staff member

If you need to find a tradesperson to get your job done, please try our local search below, or if you are doing it yourself you can find suppliers local to you.

Select the supplier or trade you require, enter your location to begin your search.


Are you a trade or supplier? You can create your listing free at DIYnot Local

 
Back
Top