Immersion - RCD or non-RCD?


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D

Dave Fawthrop

| Should my immersion heater be RCD protected?

Probably a bad idea. RCDs are to stop the electricity killing *people* the
chances of anyone touching an immersion heater supply are slim indeed.

The chances of a 30milliAmp leakage in immersion heater itself and causing
nuisance trips are high.

Not that I would take one out if already fitted.
 
T

tony sayer

Dave Fawthrop said:
| Should my immersion heater be RCD protected?

Probably a bad idea. RCDs are to stop the electricity killing *people* the
chances of anyone touching an immersion heater supply are slim indeed.

The chances of a 30milliAmp leakage in immersion heater itself and causing
nuisance trips are high.

Not that I would take one out if already fitted.
Muggins here once put his mitt round the back of a HW tank once to find
out the hard way that the cover had been left off!. Hand bounced back
and forth a few times with the current repelling it and the wall
knocking it back on;!.

Yes, if you want an early warning when the heather elements are
corroding. No if you can't have any trips.

I've just been informed by the one protecting the office/workshop that a
fluorescent light is on its way out with excess live -> earth leakage.

As to your original question we've got the whole house on a 30 ma one
and no problems, except that some accidental live contacts have
happened!.....
 
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John Rumm said:
Nope... no need for it,
True.

and it is more likely to cause nuisance trips.
I would love to know how a non-faulty immersion heater can trip an RCD.

If it does then its probably time to replace the heater or the trip as one
is duff.
 
L

Lurch

Circumstances.





I'm probably being pedantic but dpending on earthing arrangements and
locations it may require an RCD.

If it doesn't _need_ one then I agree, put it on a non-RCD circuit.
 
M

meow2222

I would love to know how a non-faulty immersion heater can trip an RCD.
Earth leakage. Theyre famous for it. They'll continue working happily
for a long long time while being a bit leaky, and the leakage in the
circumstance doesnt cause any safety problem.

Even heavy leakage is ok when youre not on a TT setup. Had one that ran
like that for a long time. Most of the element had long gone, the water
took its place.

If it does then its probably time to replace the heater or the trip as one
is duff.
not at all. If it works fine and its no danger, there's no problem.

Its counterintuitive for folk that were brought up believing water and
electricity dont mix, but of course that was never an accurate belief.
Commercial electrode heaters are still being installed new, and have
proven quite safe, despite common assumptions.


NT
 
L

Lurch

Earth leakage. Theyre famous for it. They'll continue working happily
for a long long time while being a bit leaky, and the leakage in the
circumstance doesnt cause any safety problem.
But nonetheless, still faulty though, technically.
 
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A

Andrew Gabriel

I would love to know how a non-faulty immersion heater can trip an RCD.
The insulation is Magnesium Oxide, which is hygroscopic
absorbs water). After a few moment's operation, the moisture
will have been driven away from the element and it will not
leak, but if you can't turn it on in the first place because
it trips an RCD, then you can't get it working.

When PAT testing such appliances, they are allowed to leak
initially before they get warmed up, and you then take the
real measurement.

Secondly, a leaking immersion heater doesn't represent a
significant safety risk.
If it does then its probably time to replace the heater or the trip as one
is duff.
Many immersion heaters get used once in 10 years when the
boiler packs up. To have an RCD stop it working at that point
for no good reason would not be a good thing.
 
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J

John Rumm

Lobster said:
If you are on a TT install then *all* circuits should be RCD protected.

However in these cases it is usual to have more than one RCD, with a
whole installation one (usually 100mA trip, with a time delay) and then
a downstream one for the things that one would normally RCD protect on
other types of earthing arrangement (socket circuits likely to be used
for portable appliacnes outside etc). Often accomplished by replacing
the incomer switch on a split load CU with the the time delay RCD.
 

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