RCD trips when shower is turned on

[Multiplex]

Had an electric shower installed two days ago. Before the shower was plumbed in the electrician came and wired the shower unit. 10mm cable with a Contactum shower RCD and a new 45amp cartridge fuse on my very old Wylex unit.

Anyway, I plumbed in the water to the shower today and went to test the shower. As soon as I switched the shower on the RCD tripped. Now the shower will trip the RCD the moment it is turned on (and btw, this is only turning the cold water on, not even the heat element!).

HELP!!

When the electrician left he turned the shower on (with no water) and the light was on, the RCD did not trip.

This is what has changed since he left:

1) Water plumbed in.
2) 45amp fuse pulled (as was borrowed from neighbour) and new 45amp fuse replaced.
3) I used expandable polyfiller foam in a very large hole the electrician drilled for the 10mm cable. Probably not a good idea.

Nothing else has changed!!

Before I phone the electrician up and moan, does anyone have an idea of what could have happened?

Thanks,

Simon.

 

[breezer]

yes. you have got a short, the rcd is doing as it is supposed to
see here for how an rcd works.

turn it off at the mains and remove all the "pollyfiller" as its the only thing that shouldn't be there

 

[AdamW]

I don't think this would be causing the problems you are finding, but I am not certain that having a 45A fuse in an old Wylex is a good thing...

Have you checked all the plumbing? You don't have any leaks that could be causing this do you?

I am not convinced that the polyfilla would be causing a problem. I mean, it is only surrounding the insulation, isn't it? You haven't got any near any of the terminals have you?

 

[breezer]

I am not convinced that the polyfilla would be causing a problem. I mean, it is only surrounding the insulation, isn't it? You haven't got any near any of the terminals have you?

I am thinking that is exactly what has happened (oh and its polyfiller e x p a n d i n g foam)

 

[securespark]

I'm with Adam here.

The big change since the spark left was the plumbing. Water & rcd's hate each other.

Is the interior of shower unit wet? Is there a leak on any electrical wiring within the shower unit?

And, just to eliminate pure coincidence, it IS the shower tripping the rcd isn't it?

 

[breezer]

I'm with Adam here.

The big change since the spark left was the plumbing. Water & rcd's hate each other.

Is the interior of shower unit wet? Is there a leak on any electrical wiring within the shower unit?

And, just to eliminate pure coincidence, it IS the shower tripping the rcd isn't it?

normally i would agree, but there has been no mention of water leek, and if you re read post it is expanding foam

 

[Multiplex]

Ok it's got worse...

Now the RCD doesn't even trip anymore. It's as if there's no power there at all.

Now this is the complicated/interesting part. The electrician wired two flats for the shower, and now the new shower circuits on both flats appear not to have any power.

Also, where I placed the expanding foam was only where it branched off for the first flat.

The only other thing I did (here we go...!!) is to squeeze a tiny bit of Gripfill/No more nails in a hole where both cables went through together.

The shower in the second flat was plumbed in before the electrician came and was tested and worked.

Somehow, I find it hard to think that a squeeze of gripfill has damaged both cables?!! But what else could it be?

Simon.

 

[brown-nought]

I'd ask the electrician to come back - I'm not 100% sure your foam - however horrible it is could be causing the problem. It may be a cables slipped out of its terminal etc. Pull the fuse and call him back.

If you wired it with copper pipe have him continuity test it as well.

Finally, I'm such a bore I know, but expanding foam and PVC are not always a good mix check its compatible with PVC sheafng on your cable. It may degrade it over time.

BN

 

[Multiplex]

Thanks for the reply. I'll get him back to take a look.

Just out of interest, what could explain this...

When we found the problem this is exactly what happened:

1 - Pull double pole switch, red light on. Turn shower on. RCD trips.
2 - Ditto. Same again
3 - Red light on double pole switch is dead. RCD dead. No power.

Does this indicate something has burnt out?

RCD now dead on other flat too. Light on DP switch also dead.

Would it be possible, that the burn out would melt the cable for the second flat, if it was seated in the same surface mounted conduit?

Do you think that it might just simply be a case of replacing the cable?

Simon.

 

[sparkydom]

Hi,

You mention that their is no power to the pull switch (no red light) and no power to RCD? This would indicate that the 45A fuse has blown. This can be rewired easily (making sure you use the correct fuse wire!).

However, this will not solve the problem of the RCD operating.

You mentioned also that the wiring for the both yours and next doors shower was done by the elctrician?

Now this is the complicated/interesting part. The electrician wired two flats for the shower, and now the new shower circuits on both flats appear not to have any power.

Surely the electrician has not wired two showers into the same 45A fuse. this might explain that the fuse only started to blow once the shower had been plumbed? i.e it draws more current because of heating element e.t.c

Just a thought.................

 

[Multiplex]

The two shower circuits are totally independent.

Except that the consumer units are both next to each other 30m away from each flat (yes it's true).

The two cables join each other for about 16m until they both go into their respective CUs.

I went out this morning and bought a new fuse (last one in B&Q) so it's not that.

And the shower tripped the RCD before the heating element was even turned on. How come the RCD won't even trip anymore and seems totally dead, given I've changed the fuse for a good one?

Help!! This doesn't make sense to me!

Simon.

 

[brown-nought]

Simon,

If you keep doing the test sooner or later the result might SHOCK you. Seriously it sounds like there is a wiring problem and the RCD is doing its job.

When the sparky's been let us know what it was - we are all as curious as you.

BN.

 

[Multiplex]

Ok this is what happened...

The electrician wired up each flat to each others CU. This meant that when I pulled the fuse from one flat, to test the other flat...I was actually cutting the circuit for the flat I wanted to test!!!

Anyway, I changed the cable between the RCCB and the DP switch where I had previously squirted the expanding foam. I found a loose wire in the DP switch so I thought I had found the problem! But unfortunately the RCCB still trips immediately I switch the shower to run water through it.

The RCCB is fine with the shower in standby mode (light on), and the DP switch on (light on)...but just switching the shower on trips the RCCB.

Just a thought...because we have two flats with two meters off the same mains fuse could this cause an imbalance to the RCCB? I assume...the answer should be no!

Simon.

 

[securespark]

Is it a split-load board?

If so, is the neutral attached to the "wrong" busbar?

 

[ban-all-sheds]

Given the latest news, it wouldn't surprise me if he'd wired the neutral to the wrong CU, let alone bus bar....

Was he a real electrician? Did he have a van, or a horse? How did you find him?

You need to get him back in, but one thing nobody has mentioned as a possible cause of all this - faulty shower.