8.5 shower

[c.boy]

hi all

At a fault today on shower circuit.kept tripping main r.c.d.

the neutral and earth were melted together at the pull cord ,now they have a daughter who spends one hour in the shower which prob is the cause of the overheating!

after fixing the pull cord a put the shower on for about 5 min to show the tennant that all was good.

however when a went to put the pull cord back up the heat on the cables was pretty hot!!

so the ? is should i recommend that they buy a 8 kw shower as a know the 8.5 is just a bit over.re wiring is not an option. the shower is in 6mm and approx 12 metre run

 

[danzor]

extra work, extra £££ ?

 

[c.boy]

extra work, extra £££ ?

lol!! Not my style pal!!!

 

[danzor]

Me personally would upgrade the cable, but as you say you can't then the only option is to down-grade the shower.

Or your just going to get the same problem again in a few months

 

[c.boy]

In an ideal world rewire would be the way!! But the house is nice, good decor and the good old lamminate thru out! No point in ripping folk off in these difficult times

 

[andyb]

c.boy, did you fit a new switch and what is the rating of it?

 

[c.boy]

yes a did 45 amp d/p pull cord

 

[Mac]

10mm all the way mateNice little earner

 

[andyb]

I'd put a clamp meter on to find out what the shower is drawing. Although Mac is right about 10mm, you have 6mm installed and an 8.5kw should be drawing about 37 amps which should not cause a problem with a 45 amp switch. Fitting an 8kw shower would drop the current to about 34/35 amps and I cant see this making any difference. Also you could check for a high voltage as something is causing the switch to over heat and I don't think it's because it's wired in 6mm.

 

[FaradaysHaircut]

Though the rating of the cable seems correct for this current demand, you also need to know what corrections factors come into play eg. surrounded by insualation, ambient temp etc. I agree with 'andyb' about putting a clamp meter on to check exactly what amps it is pulling. There's really nothing else to suggest except a cable upgrade. I know how you feel about the customers but how would you feel if their house burnt down as result of dodgy wiring. I'm curious as to how this came to be installed in the first place. Perhaps they had a smaller shower to start with and didn't upgrade the cable. I'd make them aware of the safty implications then the decision is theirs.

 

[Spudnik]

Squashed cable in the back box?

Or there could be a bad joint somewhere along the circuit.

 

[legge]

Hi All!
I regularily come accross 6mm wiring with an 8.5kw shower. The actual rating of 6mm is arround 46 amps surface clipped but derated to 37 amps in typical dommestic situations (mini trunking, lagging etc).
An 8.5kw shower typically draws 34-35 amps. As the mcb ratings jump from 32 amps to 40 amps, it is obvious that the derated figure of 37 amps would mean a 40 amp mcb won't protect the cable. It is for this reason that 10mm wiring is required for this size of shower. If a 35 amp mcb were available then 6mm cable would just about do!
I have on many occations fitted a 32 amp mcb to protect the cable and in most situations this will hold as people don't usually stay under a shower for very long. Obviously this would have to be classed as a deviation on the test cert. but it is the only answer in the short term untill either the circuit is upgraded or the shower degraded.
Hope that helps!