Cooker appliance earth leakage problem
 

Anyone help me with this one ?

Recently bought a "new" AEG double oven/grill cooker off ebay, at a
small fraction of its retail cost, no gtee/returns, usual risks etc

The catch is, when plugged in/installed as per AEG documentation, my
mains RCD keeps outing.

It does this:-

i) When I switch the top oven on
ii) After I've switched the grill onto full, & the element has warmed
up.

The bottom (fan) oven seems ok.


Taking resistance readings with a digital multimeter between one of
the offending element poles
and the cooker case/earth (after disconnecting the relevent element
poles from any other cooker circuitry) I find that

i) for the grill element it reads 1.5Megohms (when cold - probably
leaks more as it heats up, hence errors) and

ii) for the top oven element it's an alarming 0.5 Megohms.

For the fan oven it was about 2 megohms.

I noticed that for my previous Ariston cooker - soon to be ebayed
(??!!??) - the earth leakage resistance was higher than the meter
could register.

What would one expect a new element, correctly fitted (not wired in)
to read in terms of earth leakage ?

I don't want to buy & fit another & have the same problem.


Is my RCD over-sensitive ?

I read somewhere that cookers are notorious for high earth leakage.


The cooker had previously been supplied to a customer (I think) &
returned without any signs of use, utensils pristine & bagged up. The
cooker looks like it's been handled heavily in it's short life, dents
to externals, minor cosmetic issues etc.

Any comments, aside from the obvious "back to ebay" ones would be
welcome!

NGCook

On Sat, 30 Oct 2004 16:20:06 UTC, (Niels Cook)
wrote:

The catch is, when plugged in/installed as per AEG documentation, my
mains RCD keeps outing.

I noticed that for my previous Ariston cooker - soon to be ebayed
(??!!??) - the earth leakage resistance was higher than the meter
could register.

I read somewhere that cookers are notorious for high earth leakage.

They are... the elements get damp if not used, which exacerbates the
problem.

Try temporary connection to a non RCD protected circuit, turn it on for
an hour or two and then try again.


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In article ,
Niels Cook wrote:
Is my RCD over-sensitive ?

I read somewhere that cookers are notorious for high earth leakage.

If they use mineral insulated elements, this can be true.

If you've isolated the faulty one, change it for a new one.

IMHO, the fact you have an RCD in circuit wouldn't be a reason to get a
refund from an auction purchase unless it specifically said it could pass
this test.

I've got a split load CU and the oven isn't RCD protected - there's no
real reason why it should be.

--
*What do little birdies see when they get knocked unconscious? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
I've got a split load CU and the oven isn't RCD protected - there's
no
real reason why it should be.

--
Indeed, it's just asking for trouble, why would you normally have the
oven or hob on an rcd?

In article ,
(Niels Cook) writes:
Anyone help me with this one ?

Recently bought a "new" AEG double oven/grill cooker off ebay, at a
small fraction of its retail cost, no gtee/returns, usual risks etc

The catch is, when plugged in/installed as per AEG documentation, my
mains RCD keeps outing.

It does this:-

i) When I switch the top oven on
ii) After I've switched the grill onto full, & the element has warmed
up.

The bottom (fan) oven seems ok.


Taking resistance readings with a digital multimeter between one of
the offending element poles
and the cooker case/earth (after disconnecting the relevent element
poles from any other cooker circuitry) I find that

i) for the grill element it reads 1.5Megohms (when cold - probably
leaks more as it heats up, hence errors) and

ii) for the top oven element it's an alarming 0.5 Megohms.

For the fan oven it was about 2 megohms.

I noticed that for my previous Ariston cooker - soon to be ebayed
(??!!??) - the earth leakage resistance was higher than the meter
could register.

What would one expect a new element, correctly fitted (not wired in)
to read in terms of earth leakage ?

I can't remember off-hand what the allowed resistance is
in the PAT test guidelines, but the guidelines accept that
such elements may be out of spec when cold, and allow you
to get them to operating temperature and dry out before
making the measurement.

Also, the measurement should be done with a 500VDC source;
a multimeter will give you a different reading in most cases.
(0.5 Megohms is only 0.5mA which isn't enough to trip an RCD.)

I don't want to buy & fit another & have the same problem.

Is my RCD over-sensitive ?

Not from any evidence you have provided.

I read somewhere that cookers are notorious for high earth leakage.

That's why they aren't normally put on RCD circuits, and
because they don't justify it on safety grounds. Check
the circuit earth is up to spec though.

--
Andrew Gabriel

"richard" wrote in message
...


"Dave Plowman (News)" wrote in message
...
In article ,
I've got a split load CU and the oven isn't RCD protected - there's
no
real reason why it should be.

--
Indeed, it's just asking for trouble, why would you normally have the
oven or hob on an rcd?

Why would you have anything on the RCD then ?

Peter

Andrew Gabriel wrote:

I can't remember off-hand what the allowed resistance is
in the PAT test guidelines, but the guidelines accept that
such elements may be out of spec when cold, and allow you
to get them to operating temperature and dry out before
making the measurement.

Class I heating appliances: 300 kohm insulation resistance or a leakage
current of 0.75 mA per kW (5 mA max.) if using the touch current method.

--
Andy

"Peter" wrote in message
...

"richard" wrote in message
...


"Dave Plowman (News)" wrote in message
...
In article ,
I've got a split load CU and the oven isn't RCD protected -
there's
no
real reason why it should be.

--
Indeed, it's just asking for trouble, why would you normally have
the
oven or hob on an rcd?

Why would you have anything on the RCD then ?

Peter


The rcd is to protect a person from death by electrocution. Protection
against electrocution from a faulty fixed appliance such as an oven is
by earthing the case of the oven and equipotential bonding in the
surroundings, leading to the operation of the protective device while
keeping fault potentials to earth at a safe level. An Rcd is more
important when feeding socket outlets for portable stuff - more likely
that a person is gripping the equipment in the first place, more
likely that flexes etc will be damaged and more likely to be outside
any equipotential zone.
But I bow to Andrew Gabriel's wisdom on this matter and stand to be
corrected.
Rich

"richard" wrote in message
...
"Peter" wrote in message
...

"richard" wrote in message
...


"Dave Plowman (News)" wrote in message
...
In article ,
I've got a split load CU and the oven isn't RCD protected -
there's
no
real reason why it should be.

--
Indeed, it's just asking for trouble, why would you normally have
the
oven or hob on an rcd?

Why would you have anything on the RCD then ?

Peter


The rcd is to protect a person from death by electrocution. Protection
against electrocution from a faulty fixed appliance such as an oven is
by earthing the case of the oven and equipotential bonding in the
surroundings, leading to the operation of the protective device while
keeping fault potentials to earth at a safe level. An Rcd is more
important when feeding socket outlets for portable stuff - more likely
that a person is gripping the equipment in the first place, more
likely that flexes etc will be damaged and more likely to be outside
any equipotential zone.
But I bow to Andrew Gabriel's wisdom on this matter and stand to be
corrected.
Rich

but the oven may be connected to a socket outlet on a flex ? Plus isint it
more likely to get electrocuted in an earthed bonded zone ? The oven may
be within reach of water taps and sink etc which are bonded.

Peter

Any comments, aside from the obvious "back to ebay" ones would be
welcome!

Yes, you just need to run off the RCD for a few hours to dry out the
element. If you don't have a suitable socket, (such as a non-RCD fridge
freezer socket), you could always try it at a mates house.

I would never suggest that you plug it in with the earth connection
disconnected for a few hours whilst sitting on an insulated surface (i.e.
cardboard box or lino). Not unless you knew what you were doing, anyway, and
knew some basic safety rules, like not touching the thing, keeping the
family out of the room and disconnecting any gas supply.

Christian.

"Christian McArdle" wrote in message
et

Yes, you just need to run off the RCD for a few hours to dry out the
element. If you don't have a suitable socket, (such as a non-RCD fridge
freezer socket), you could always try it at a mates house.

I would never suggest that you plug it in with the earth connection
disconnected for a few hours whilst sitting on an insulated surface (i.e.
cardboard box or lino). Not unless you knew what you were doing, anyway, and
knew some basic safety rules, like not touching the thing, keeping the
family out of the room and disconnecting any gas supply.

Christian.


That’s what I do, & I’m dangerously underqualified to do these things
but hey if your hungry LOL!

Joking aside, everytime our fan oven is cleaned as soon as it’s switched
on it trips the RCD in our house.
As the oven is built in there’s no way I was going to remove it to try
it on non-RCD wiring (maters House)
All I have done to get round this is to disconnect the earth wire &
switch on the oven for 5 minutes, after which the earth was reconnected
& the oven behaves itself, as it should.

But as Christian said I couldn’t advise you to do the same. :-)





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