We had an electric shower installed about a year ago, which has always
worked fine.

It is an 8.5KW electric shower. At the time, there was not a free fuse
in our fuse box for the new circuit, so a new box was added containing
an RCD (80A) and an MCB(40A). The shower runs from this, alone.

Suddenly this week, the shower started as normal, then there was a
bang, and the water was cold. The RCD had tripped. The MCB was fine.

I reset the RCD, pulled the cord again for the shower, and the light
flicks straight on and then off again. The dial on the shower at this
point is in the off position.

I took the cover off the shower unit, and it looked ok, although a
little damp inside. I also took the cover off the switch, and that
looked ok, not damp. Looking in the loft, there is some damp around
where the wires enter and leave, presumably steam through the hole.

The shower unit itsself is still under warranty, but does it sound as
though this is what is the problem? From what I understand of an RCD
it detects a current leakage?

Sean wrote:

Suddenly this week, the shower started as normal, then there was a
bang, and the water was cold. The RCD had tripped. The MCB was fine.

The "bang" sounds ominous! Where did it come from? RCDs usually at best
give you a "click" when they trip.

I reset the RCD, pulled the cord again for the shower, and the light
flicks straight on and then off again. The dial on the shower at this
point is in the off position.

So the fault lies after the switch then. Most likely in the shower itself.

I took the cover off the shower unit, and it looked ok, although a
little damp inside. I also took the cover off the switch, and that
looked ok, not damp. Looking in the loft, there is some damp around
where the wires enter and leave, presumably steam through the hole.

The shower should not be damp inside. That alone could trip the RCD.
However in this case I would expect that something has gone wrong with
the shower (judging by the noise)

The shower unit itsself is still under warranty, but does it sound as
though this is what is the problem?

Contact the manufacturers support line. Many of them are quite good at
sorting problems like this.

From what I understand of an RCD
it detects a current leakage?

It detects current imbalance - i.e. the current in the live must match
that in the neutral +/- 30mA typically. If it does not then it trips. So
usually you can infer that if there is an imbalance that you are leaking
power either from the protected circuit, or even possibly into it from
another circuit.


--
Cheers,

John.

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Suddenly this week, the shower started as normal, then there was a
bang, and the water was cold. The RCD had tripped. The MCB was fine.

The "bang" sounds ominous! Where did it come from? RCDs usually at best
give you a "click" when they trip.

Unfortunately the person in the shower can not explain where the noise
came from, although a faint bang was heard elsewhere in the house,
which could have just been the click on the RCD.

I reset the RCD, pulled the cord again for the shower, and the light
flicks straight on and then off again. The dial on the shower at this
point is in the off position.

So the fault lies after the switch then. Most likely in the shower itself.

So the shower is still drawing a current when the dial is off? This
was the only reason I didnt go straight to the manufacturer, because I
thought if the dial is off, it wouldn't be this at fault.

From what I understand of an RCD
it detects a current leakage?

It detects current imbalance - i.e. the current in the live must match
that in the neutral +/- 30mA typically. If it does not then it trips. So
usually you can infer that if there is an imbalance that you are leaking
power either from the protected circuit, or even possibly into it from
another circuit.

The RCD has 0.01A written on it. I presume this is 10mA
Thanks for your answer and the explanation at the end. I will contact
Kohler Mira and see what they have to say.

Thanks again.

Sean.

Sean wrote:

So the shower is still drawing a current when the dial is off? This
was the only reason I didnt go straight to the manufacturer, because I
thought if the dial is off, it wouldn't be this at fault.

Since you have a 10mA RCD it will take very little to trip it. The
dampness alone inside the shower may do it. You could try drying it off
with a hairdrier for a bit and then see if it runs.



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/