MCB broken - Shower setup

[jimmy M]

Hi all,

Looking for some advice here from people who know as I dont have a clue.

I was in the shower the other day and it decided to stop working.

I got out and the MCB was ON but the power (and light) was OFF

I went down stairs and the RCD which only runs to the MCB had been tripped. I turned the MCB OFF and the RCD went back on.

First of all the MCB just wouldnt do anything. The it came back on fully. GREAT I thought and turned it off.

I went to use it tonight and now the RCD trips all the time. The power light on the MCB comes on for a second and then it trips the RCD.

Has the shower blown up? I do hope not as its only new (less than 1 month) can MCB's become faulty?

Please help.

Jimmy M

 

[davy_owen_88]

The power light on the MCB comes on for a second and then it trips the RCD.

Power lights on the MCB? Are you sure you have used the right terminology?

If the RCD is tripping you have earth leakage and you need to call in an electrician to find out where and why. Have you put in any screws/nails recently that might have damaged the cable? Have you done anything by the shower that could have damaged the seals allowing water to penetrate the shower?

Davy

 

[jimmy M]

Davy,

Cheers for the reply mate

I THINK I mean the MCB. It is a large red switch that is the main power ON/OFF switch for the shower that is located in the hallway, it provides power only for the shower.

No I havnt done any DIY that might have damaged the cables. I checked inside the shower and it all looks dry.

Very strange.

I imagine this is going to be a job for an electrician but I would like some idea of what has happened and what needs to be done rather than being in the dark.

Jimmy

 

[davy_owen_88]

Something like this?

An MCB is on of these and is housed inside the consumer unit.

An RCD is one of these and is also housed inside the CU:

If you let me know what is tripping and when you switch what I will be able to give you more useful advice. The first thing I would suggest is to turn off the electric at the MCB in the consumer unit and then check that all the connections in the terminals are nice and tight. Keep an eye out for melted/perished insulation.

Davy

 

[jimmy M]

That's exactly them.

I have the first type (red switch with red light) outside the bathroom

and the bottom type by all main fuse box in the house, it has a test button.
Everytime I try to turn on the MCB the RCD trips.

I did try to look for dodgy looking wiring inside the shower unit.

Would it be possible for an MCB to break? or is that highly unlikely

Many thanks indeed for your help Davy

 

[RF Lighting]

There is a reasonable chance that the isolator (The jobbie with the big red switch) may have failed, melting the wiring behind it causing a short circuit..

The MCB (middle photo) has not failed. It is still doing its job, exactly as it was intended. I recon I see 1 failed MCB every 2 years or so.

 

[JohnD]

The thing you have been calling an MCB is a switch.










("Isolator" is a posh word for this kind of switch)

 

[securespark]

(The jobbie with the big red switch)

Ey up lad, like t' terminology tha's usin'!!

Reet grand, tha nos cocker!

 

[davy_owen_88]

What you have been calling an MCB is actually an isolator (top photo). The RCD (bottom photo) detects earth leakage and an MCB (middle photo) protects the cabling against damage from short circuits and overloads.

If upon switching the isolator the RCD trips, you have earth leakage. As RF said this could be due to melted insulation and a phase to earth short. Turn off the electricity at the MCB and check the terminals in the isolator (switch with red neon). Have a look for melted insulation or scorch marks on the plastic (caused by lose connections overheating). Let us know how it goes but remember to turn off the MCB at the fuse box first.

Davy

 

[securespark]

And check for dead at the shower iso, too!!

 

[JohnD]

And check for dead bodies at the shower, too!!

 

[jimmy M]

Dear all,

Thanks for all your help so far .......... the mystery continues.

I checked the shower today (tried the big red power switch) and it came on and stayed ON - hurray I thought until I tried to put one of the heating elements on ......... the RCD tripped.

First I thought okay my shower is knackered but then I tried something else.

I put the shower to OFF and reset the RCD

The power to the shower stayed ON so I left it on

I went into another room and turned on a light and the RCD tripped?

Even through the RCD tripped it has nothing to do with the function of the light. e.g the light still works when the RCD is off

Do I have a dodgy RCD, is it being over sensitive or is my whole house about to blow up

Please help

Jimmy

 

[davy_owen_88]

I checked the shower today (tried the big red power switch) and it came on and stayed ON - hurray I thought until I tried to put one of the heating elements on ......... the RCD tripped.

Did you check the terminals in the isolator (the big red power switch)?

I put the shower to OFF and reset the RCD

The power to the shower stayed ON so I left it on

I went into another room and turned on a light and the RCD tripped?

Even through the RCD tripped it has nothing to do with the function of the light. e.g the light still works when the RCD is off

So you put the isolator to the off position, reset the RCD and then switched the isolator back on? The lights should not effect the RCD. Could it have been a coincidence that the RCD tripped when the turned on the lights or has it done so more than once?

Have you altered any of the wiring inside the consumer unit?

Could you post pictures of the isolator, the RCD that is tripping and also a general picture of your consumer unit?

Do I have a dodgy RCD, is it being over sensitive or is my whole house about to blow up

It is possible for the RCD to have become over sensitised but you will have to call in an electrician to test it before you can rule out other faults. Namely poor connections at the isolator.

Davy

 

[bernardgreen]

A neutral ( lights ) to neutral ( shower ) fault would cause the effects described. But how it could happen is a mystery.

 

[RF Lighting]

You almost certainly have a neutral to earth fault somewhere on the cable connected outgoing side of the isolator.

The light causing the RCD to trip is unusual but not unknown with this sort of fault.

There is nothing wrong with your RCD. It is doing its job exactly as it designed to. It is disconnecting the power as soon as a wiring fault is detected.

This little device stops your house from burning down.

I would like to place a bet of 10p on the outgoing neutral at the isolator being loose, causing it to overheat, causing the insulation to melt, and causing a short to earth.