RCD keeps tripping

[andycuz]

HI guys I'm new on this forum so hi.

OK my problem has been going on now for over 12 months.

We moved into a new house in May 07 and at this time we had the consumer unit checked and set up correctly onto a split load with the shower and sockets on the right side of the RCD.

I don't even pretend to know exactly what I'm doing as i work in IT not electrics so, basically whats happening is when the electric shower (Mira 9.5Kw) has been running for 10 mins approx the RCD trips. If the boiler which some bright spark wired into the shower isolation switch has been running then the RCD trips after 5 or so mins.

Ok so I have replaced the shower with a new one of the same wattage in case this was faulty. The RCD still tripped, so I then replaced the isolation switch and moved the boiler supply and fed this from a 13amp socket with its own in line fused isolation switch.

Now when we use the shower the RCD trips, once after around 15 minutes of using the shower and today after not even 3 mins using it.

The problem then is the RCD will not reset for over an hour after I have to keep flicking the switch and trying this for over an hour before it eventually stays on. Once the RCD is back on I can use any socket and there is no problem.

Am I on the right lines if I said there was an earth fault somewhere here? I would have thought if this were a live fault then the MCB for either the shower or the sockets would trip? What I was wondering is if the shower is putting such a heavy load on the ring that there is some kind of neutral to earth fault being set up on the sockets or the neutral bar inside the consumer unit.

Another thing is when the RCD has tripped if I switch the MCB for the sockets off but leave the shower MCB on, the RCD can be reset no problem, but as soon as I flick the MCB back on for the sockets the RCD will then trip and not reset for at least an hour.

Makes me wonder whether when the electrician rewired the CU he has messed on of the neutral or earth connections up in there. I'm not one for going in the CU as I'm not confident, however I will call the numpty electrician and get him back to sort it out.

I hope someone can help me cos this has been bugging me now for over a year.

 

[333rocky333]

Sometimes RCD's will not reset under load, rather than wait one hour unplug any appliances that have gone off, reset RCD , then plug them back in.
Sometimes just turning off the socket MCB's first will suffice, but not in your case.

This will not cure the problem but will save you waiting an hour each time till it is sorted.

 

[2face]

what size cable is it ?

a test on the circuit should fix it very easily but you do need the right tools for the test.

 

[andycuz]

I have gone round the sockets and unplugged everything and tried the RCD but it still trips with nothing plugged in.

The cable to the shower looks like 10mm but with this only being a very short run maybe 12 feet I dind't see this as a problem for a 9.5kw shower.

 

[2face]

10mm is fine for the shower.

sorry i am lost is the rcd tripping on the shower on the main switch on the split load.

 

[hairyben]

Have you tried isolating the shower which I assume is wired correctly with a DP isolator before resetting the RCD?

Obvious one but worth asking... If there's damp getting into the shower it may still "hold" the RCD until others circuits are energised which push N current back through the shower N-E fault which can be misleading...

 

[JohnD]

Earth leakage is most common on watery appliances (showers, kettles, tea urns, washing machines)

However:

Assuming your shower has a DP isolator, then opening that will mean the shower is not causing an earth leak that could trip the RCD, so it should reset.

If it trips and won't reset even after opening the isolator, then I would be thinking slightly differently, and suspect that water from the shower is leaking into the wall or under the floor and causing earth leakage e.g. in a junction box or wall socket. Especially as you say it continues for some time after using the shower (e.g. until the socket dries).

You have already fitted a new shower unit which did not seem to help.

Look for a water leak.

 

[andycuz]

I'm assuming the DP isolator is the main double red switch on the consumer unit?

Basically I have the cooker and lights on the right hand side next to the main isolator and on the left side of the RCD is the shower and sockets.

As I say the shower trips the RCD not the showers own MCB, then when this has tripped I cannot get the RCD to reset for about an hour after. I cannot see how there is any water leaks unless there is a bad junction box somewhere in the wall that goes to the sockets. I've been under the bath and cannot see any wires there, but that doesn't go to say there will be some under the floor.

I have attached the image below so you can see.

View media item 7139

 

[XtraRaptor]

Hi,

There should be a switch near to the shower, generally a pull cord with a red light on it, if you switch this off it will totally disconnect the shower (L & N) and you should be able to reset the RCD.


Is the shower upstairs?

If it is, lift some floorboards and check the waste from the bath/shower to the outside, check it whilst there is water running, to see if there is a leak onto a junction box.



Nick.

 

[2face]

i would get a trade in to have a look, it need testing. with electrics a squashed/trapped cable can give a fault upon load but be ok on normaal usage.
who ever comes can check the rcd to for a fault.

if you turn off the ring mcb before you shower does it still trip

 

[ban-all-sheds]

I'm assuming the DP isolator is the main double red switch on the consumer unit?

No - it's the isolation switch local to the shower which you use to turn the power to the shower on and off.

As in "I then replaced the isolation switch"...

 

[Jaymack]

I'd suspect a neutral to earth fault, it needs a competent electrician to suss out.

Jaymack

 

[andycuz]

Guys you are geniuses yesterday I decided to get a jug and repeatedly threw water at the wall and the corner of the bath after about 10 jug fulls the power went off. When I ripped out the side of the bath there was water running down the wall to the extent it was running down the wall in the kitchen below. I noticed a slight crack in the grout in the tiles so took them and ripped out the old silicone sealant, noticed that all the plaster was crumbling behind, so now dried it out and squeezed as much sealant as would fit between the wall and bath before I put the tiles back on the wall. Looks like whoever did the bath or tiling didn't do it very well.

Amazing I would never have suspected a water leak. Hopefully when this is done no more tripping. Just a shame it cost a new shower, but would an electrician really have been expected to find that?

 

[Lectrician]

An electrician with an insulation tester, and the nouse to use it correctly, would have most likely found the fault on the socket circuit caused by the water, as I am sure you would get a low reading even when 'dried' out.

Well done for finding the fault