Shower trips MCB.. (edited, it isn`t an RCD) - update....

[DSM]

I have a problem with my shower and need some thoughts.

It is an 8.5 kw shower, has a pull chord isolation switch, and a push button on the shower to turn it on.

One morning we pulled the isolator on, but no power. The RCD on the fuse box had tripped. re-set it, shower worked, but tripped after the shower - i turned the isloator on and off a few times to see if it was stuck..

Since then, we have been able ti sue the shower, but it seems to trip the rcd intermittently. I have left the shower on cold to rule out the heater element, and even turned the isolator swicth off, but it still seems to trip.

Where do i need to lok for the fault - the shower unit, or the fuse box and/or wiring ?

Any thoughts and suggestions ?

 

[davy_owen_88]

Where do i need to lok for the fault - the shower unit, or the fuse box and/or wiring?

All of the above.

Check for loose connections although it is usually at the isolator and it's the neutral conductor that has come loose and burned away.

 

[DSM]

Forgot to mention, i changed the isolator switch but it still trips the fuse box...

opened up the shower and nothing looks untoward - i stress a visual inspection only - ie no scorch marks or burnt wires...

the RCD that flips does feel warm if i go straight down to re-set it though ?

 

[davy_owen_88]

So you changed the isolator to see if that would solve the problem and it didn't? Is the earth conductor sleeved at all points?

Have you put any nails/screws in recently that could have damaged the hidden cable?

 

[luminaire]

You'll need to check the operation of the RCD in the CU. Also the wiring needs an IR test. These can only be done with the right equipment, which will probably mean getting an electrician to do them.

 

[DSM]

Earth conductor sleeved at all points ?


If you mean the earth wire, i have just checked in the loft where the wires come through the ceiling, there does appear to be a centimetre or so of bare wires on both the in and out wires, which i assume is the earth one - but that would have always been like that, unless i pulled it when changing the switch, as i did have to pull the wires a bit.

The old switch had an area of scorched insulating plastic that covered the wire taking current to the little indicator bulb...hence i thought that musty have been the problem..

Dave

 

[Adam_151]

EDIT: sorry, skim reading again

 

[bernardgreen]

the RCD that flips does feel warm if i go straight down to re-set it though ?

RCD getting warm ? Do you mean MCB which will get a bit warm in normal use close to its tripping point.

 

[davy_owen_88]

If you mean the earth wire, i have just checked in the loft where the wires come through the ceiling, there does appear to be a centimetre or so of bare wires on both the in and out wires.

In and out wires? There shouldn't be an in and out wire for an electric shower. There should be a single length of t&e and a single length of green and yellow cable for the supplementary bonding. Can you explain what you actually see? A picture would be great

By earth sleeving I mean the green & yellow sleeve that should be covering the bare earth conductor of the twin & earth cable at all exposed points (shower, consumer unit and isolator)

 

[DSM]

In and out - I mean the wires going into the switch from the supply, and out of the switch to the shower. i can see them in the loft just above the switch. They have been like it for 10 years or more.

Just got of phone to daughter`s friends`s dad - an electrician !!

He reckons it is the heater element of the shower, Triton are coming out on Tuesday, if it is the heater element it will be replaced under warranty by Triton, if not, he will come out and test the wires, and replace if needs be. Says if it was the wires he would expect it to show in other ways as well - like the trip occuring even when the isolator was off, shower not working etc etc...

Cheers

Dave

 

[DSM]

the RCD that flips does feel warm if i go straight down to re-set it though ?

RCD getting warm ? Do you mean MCB which will get a bit warm in normal use close to its tripping point.

Yep, sorry, wrong terminology, we don`t have a RCD, just MCBs..

 

[davy_owen_88]

In and out - I mean the wires going into the switch from the supply, and out of the switch to the shower. i can see them in the loft just above the switch. They have been like it for 10 years or more.

Ah... must have been having a 'dipshit' moment, because I totally didn't think of the isolator

 

[JohnD]

Aha!

I spy with my little eye....

the wiring has been in place for ten years?

How old is the shower?

What is the power rating of the shower?

What is the Amps rating of the MCB that trips?

(as it is an MCB tripping, not an RCD, all previous Q&A and diagnoses are off)

 

[DSM]

Shower is less thasn 2 years old, but gets 30 minutes use a day..

8.5kw shower, 40 amp MCB.

6mm cable, Triton say ok for that shower, but no more.


this morning i showered, all was ok. turned shower to cold, let it run a whole to cool it, then turned off at isolator.

20 minutes later i checked the fusebox, the shower mcb had tripped...even with the isolator off..maybe it trips when i switch it off....?

Dave

 

[JohnD]

mmmmm

If the shower is off, the MCB is on, you turn the isolator (ceiling switch?) on and off, does it trip? If so might be a loose wire in the switch moving about when you yank the cord. If so I would expect to see signs of sparking inside it, as well as some noise.

Or possibly insulation in the cable damaged by heat or nail allowing the movement to cause a short.