Help - electirc shower tripping RCD after 10 minutes in Scotland.

[Zaby]

Hello.

Can I ask for some expert advice please.

I replaced an old 7.5kw shower in my upstairs bathroom with a new Creda 9.5kw last year. I understood that this was acceptable under Scottish regs. After a few months of good operation the pullcord switch fused, and I replaced it. After this, the RCD started to trip once or twice a week, when the shower was used for more than 10 minutes. The RCD then started to trip more regularly, and then every time the shower was on for more than 10 minutes.

On checking the tripped RCD it was very hot, and at that point I knew something was wrong. In retrospect I now know that I measured the cable wrongly, and I have 6mm cable, not 10mm!

So, I urgently changed the shower for a 8.5kw. So at this point I now have an 8.5kw shower, on 6mm cable, with a 45 amp RCD, which I believe is acceptable.

The RBD does not get nearly as hot, but it's now began tripping again after a long shower.

My feeling is that I have been running a dangerous combo of 9.5kw on 6mm for so long, that the RCD is now degraded, and will continue to trip regularly??? Can anyone advise what I should do? Should I buy a new RCD? Is this an acceptable system? I simply can't afford to get an electrician in to change cables, and the bathroom has just been retitled.

Thanks for your replies.

 

[topquark]

I would advise getting the cable Insulation Resistance tested.

 

[malcolmsanford]

Sorry Zaby you may have to do just that and get an electrician in.

Scenarios

Dampness getting into the shower and causing a trip.

You say the RCD is a 45 amp ..............is it an individual RCD for the shower alone then, if it is then do you have overload protection, as the RCD alone will not give you any, or is the RCD an RCBO

If the RCD is an RCBO and was getting warm with the 9.5Kw shower, then you may have damaged the unit by running it hot and therefore it will need changing. So even though you have put a smaller unit in now it will still trip.

By putting an over sized unit in you have said the pull cord burnt out, the RCD???(whateve) run hot, so how much damage as been done to the cable that can't be seen.

Honestly I think you are going to have to get an electrician in to thoroughly check the circuit, for you and your families safety. To be honest it most likely take a good sparks 2 hour to do this and sort it out and it will not be that expensive for piece of mind.

I'm sure that a lad on here would help out, if you post your general area

 

[Electricalserv]

Sounds as though cable insulation may be damaged and when current is flowing and meeting maximum ampage its maybe arcing and causing the RCD to trip.

 

[Octopus]

I would recommend getting a sparky in with the necessary test kit. Given what you've outlined, you are well placed to brief them before they start and that may well save you time and money diagnosing the culprit.

Maybe if you put on your post where you are you may get somebody from here PMing you to come and take a look.

 

[Electricalserv]

I think a new run of cable will sort this.

 

[pushrod]

I wonder if "rcd" is being mixed up with mcb - overload should not trip an rcd. If it is an rcd that is tripping then there is more than an overload problem.

 

[Zaby]

ok, forgive me, but I might be mixing up RCD and MCB?

In my electric cupboard at the front door (3 bed terrace), we have a silver box, which contains several wired fuses, for wall sockets, lights, cooker etc. I take this to be the CU? It's very old looking.

Then next to that, and seperate from it, is a single small plactic box, which houses a single on/off switch and a black 'breaker'. The breaker has a white button in the middle with 45 written on it, and a small red button underneight.

When the shower trips, it is the single, smaller black item that trips, with the white '45' button popping outwards. This is the part that get's hot, although much less hotter than it used to. Is this an MCB, or an RCD?

 

[Zaby]

I believe I have what is known as a wired fuse board. I am in East Kilbride if anyone wishes to PM me.

 

[i=p/u]

my friends dad trained as an electrician bk in the day and hes worked at auto body repairs last 20 years, he change a shower and fryed his son.... pure blue. a shower is one thing i would have done correctly and test equipment is what you need

 

[telectrix]

sounds like a wylex plug in MCB. the older ones with the round reset buttons. only option is professional help. too many possibilities to try and save a few quid. the alternative to phoning a spark might well be phoning the fire brigade or the coroner.

 

[Des 56]

Pushrod may be correct, that sounds like an old type overcurrent with a test/reset button, not an rcd


began tripping again after a long shower.

How long is the long shower by the way ?

 

[telectrix]

usually about 6ft.6in. unless you are very tall.

 

[pushrod]

Yep as mentioned already almost certainly an old wylex push fit mcb. The bad news is that it sounds like all your electrics sound very dated . The old fuse board might still be safe but it sounds as if you have no rcd protection at all which isn't the best. It really should be checked, in the near future, by an experienced electrician doing what is called a "periodic inspection report". In the short term you really need that shower looking at before you use it again - if a 45A mcb is being tripped by a 8.5kW (about 37A max) shower there is something seriously wrong, potentially very dangerous. Do not accept any work that does not involve testing of the circuit - do not be surprised if you are told the wiring needs replacing/ upgrading and putting on its own little shower CU with an rcd and mcb as i suspect that is the minimum that it needs.