mira sport shower trips electric

[kevin_robson]

This morning our shower tripped the electric off. Its a mira sport 10.8kw.

I put the power back on but it trips off all the time now even in standby mode. If I leave it off at the isolator pull-cord everything is fine, but as soon as I pull the cord and allow power to the shower it trips again.

It was fitted 4 years ago and IS definitely connected using the 10mm cable onto its own switch in the RCD box thingy. A full rewire was done at the same time, so it should all be OK.

Strangly the other day we noticed a burning smell whilst I was having a long shower. Like a PCB/low power component burning smell.

Have had the front off the shower and cant see any visual signs of burning, but haven't yet investigated any wiring further down the line.

I'm guessing mira would charge >100 quid to even come out, so am tempted to just buy a new identical shower and plug it in, but only if I can be sure it is the shower rather than wiring that is at fault.

Of course, if anyone knows the exact bit that will be wrong I could have a go at replacing just that.

Any ideas? Is it likely to be the shower itself or the wiring to it?
Thanks

 

[Taylortwocities]

Could be anything, I'm afraid. Lets have a look..

Untitled

• Taylortwocities
• 17 Apr 2008
• 30

The crystal says that you should turn off the power and firstly have a look to see if there is any sign of cable overheating/damage where the cable goes into the shower or in the isolation switch (do you have one - a pullswitch in the ceiling?)

If that all looks OK then (still with the power off) remove the power feed from the shower and insulate the bare ends.
Turn the power back on and see if the RCD thingy trips. If it doesnt trip then the problem is probably with the shower.

 

[kevin_robson]

Thanks. I realise it could be one of many things, just wondered if there were any 'common' faults associated with these showers.

There is an isolator. It doesn't trip if that is in the 'off' position, its only when the power goes through to the shower. I've not even inspeacted the isolator switch yet but will have a look at the wiring on that.

Didn't have time this morning but as suggested will take the wires out of the shower and see if it still trips. If not then as you say I guess that means its the shower. It trips even on standby so doesn't appear to be any kind of 'load' issue.

I'll ring mira when they are open and see if they have any ideas. I'm sure they'll just want to book an engineer though.

Thanks

 

[JohnD]

I wonder if it is the RCD that trips or the MCB

I wonder if you have looked for the source of the burning smell, and if you found it in the switch, the cable, or the shower uniut.

I wonder what rating the MCB is

I wonder when the circuit and shower were installed, who by, and to what standard

I wonder if you know any good electricians.

 

[kevin_robson]

I wonder if it is the RCD that trips or the MCB
The consumer unit is split in two. It trips out the whole bank i.e. half of the house. Thats all I can tell you as I dont understand the terminology. The individual switch was tripped initially too, but I believe it is just tripping the main one now.

I wonder if you have looked for the source of the burning smell, and if you found it in the switch, the cable, or the shower uniut.

I've yet to have a good look. Nothing obvious inside the shower, but not looked elsewhere yet.

I'll answer the last 3 together. I've no reason to doubt the quality of the work. It's been certified and working for 4 years without any hassle.

I wonder what rating the MCB is

I wonder when the circuit and shower were installed, who by, and to what standard

I wonder if you know any good electricians.

 

[YorksSparks]

I've recently replaced one of these for a customer - with an identical one! Only 2 1/2 years old but daily tripping the RCD (not the MCB) on that half of the board. Seems they have a fairly common(ish) fault with heater elements going "leaky" in both senses (water and electricity). One common symptom is that it doesn't seem to get as hot as it used to (when it works that is!). They had the same "burning" smell too and taking the front off shows no apparent burnt component or damage.

Did an autopsy on the old one and could find very little wrong without ripping the tank/heater/element assembly to bits. No probs with the replacement and it's been in nearly a month now.

If you look carefully you can pick them up on Ebay for a lot less than retail. Replacing like-for-like makes the whole thing very straightforward - did it in around 45 minutes.

 

[kevin_robson]

I took the isolator pull switch down last night and it has had a major burn out in there. Eventually it looks like the insulation melted/burned off and the live wire eventually touched the earth.
Hopefully the RCD or whetever has done its job and the shower itself will prove to be OK.
Not sure why this has happened, but hopefully a new isolator switch will do the job. I'll update how I get on.

 

[bernardgreen]

Not sure why this has happened, but hopefully a new isolator switch will do the job. I'll update how I get on.

The the screws in one of the terminals probably vibrated loose or was never fully tightened.

The copper in the burnt wire will have been softened by the heating and is NOT suitable to be reused in the terminal as it will slowly deform under pressure from the screw and the same loose screw heating will occur. If there is enough slack on the cables then cut away the scorched ends before connecting to the new switch.

 

[kevin_robson]

Thanks,
yes there is plenty of slack, and to be honest there isn't enough left to even consider putting it back together as was.

 

[stargazer]

This is a common problem caused by ramming and bending thick high current conductors into a small box as the shower switch is pushed back into position.
If you can, arrange it so that the cables push up into the ceiling as you push the isolator switch into its housing.
Every year or so check the switch terminals for tightness.

 

[kevin_robson]

For info I replaced the pull cord over the weekend and all seems well. The existing undamaged terminals were also pretty slack, so I'm sure that is what has caused the problems.
It has been fully tightened this time.

Thanks to all who replied.