Philip wrote:

My consumer unit has two sections lighting to the left, power to the
right. There are 3 or 4 lighting circuits and as you guessed 6 - 10
power circuits. To the right of the power circuits is a switch which
disables all the power circuits in one go.

That's a 'split load' CU. The circuits don't actually *have* to be
split with only 'lighting' on non-RCD protected section on the left.
I'd really expect the immersion heater (if you have one) and cooker
circuit (if you have one) to be on this section too.


It is that switch which trips and not the individual circuit breaker.
Consequently I loose power all over the house.

It's the RCD tripping when it sees too much leakage to earth, it
suggests that the element in your iron is a bit marginal as regards
insulation or that there is a loose wire in it somewhere that is
occasionally touching something.

It could also be that the sum of leakage from other appliances around
the house (computers and cookers are front runners on this front) is
enough so that when the additional leakage of the iron is added the
RCD trips.


The lighting is not affected though.

Well that's one good thing, you're not plunged into darkness when it
happens.


The problem with this problem is that it is not repeatable at will.
Having reset the power we can resume ironing and the problem does not
recur maybe for days or weeks. But there is definately a problem
somewhere, and it always occurs when the iron is in use.

There are a number of possible causes/cures:-

1 The iron really is faulty, i.e. the element's insulation is poor
or there's a loose wire. It could be within specification and still
cause the problem. Replacing the iron would probably fix it. (But
see 2 below)

2 The sum of leakages from many appliances is adding up to trip the
RCD, the iron is just the final increment. Removing some of the
appliances which are likely to be leaky from the RCD side of the CU
might help. For example moving immersion heater and cooker to the
non-RCD side of the CU is quite allowable regulations wise and may
fix the problem. However it's quite a significant thing to change
for only a chance of fixing the problem. It depends on the CU how
easy it would be to do.

3 If 2 is the case then another approach is to add separate RCD
protected circuits for each (or some) of the circuits currently
protected by the one RCD. You can get RCBOs (combined RCD & MCB) to
go in some CUs, moving some circuits to the LHS of your CU and
protecting with RCBOs would probably fix your problem. This is a
relatively expensive cure though, but it does make your installation
much more user friendly.

4 The RCD may have got hyper sensitive and or may be at the
sensitive end of the allowable range. The only way to check is to
replace it really (though an electrician should have proper test
equipment to check it), fairly expensive again.


As a side issue the utility room contains a Washing Machine and Tumble
Drier, and in the past the conbination of these two in operation at
the same time has caused the power to be lost - but NOT house wide.
When they trip out it is only the circuit that goes ie one of the 6-10
little switches on the consumer unit.

That's simply too much load tripping the MCB. It suggests that maybe
some rewiring and/or redistibution of load would be a good idea.

--
Chris Green