Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

Lee wrote:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.
It is not likely to be the problem in itself. More likely to be other
things on the same RCD taking the cumulative leakage nearly up to the
trip threshold and switching spikes on the hood taking the total over
the limit.

In article ,
Lee writes:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

Check for cobwebs.
I had a double insulated desk fan trip the RCD.
Turned out to be a spider in the plug, which had created a nest
bridging the live and (unused) earth pin.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On 28/12/2017 21:35, Lee wrote:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

It could just be an indication that you are close to the trip limit
through cumulative leakage elsewhere on the circuit. The cooker hood
will have an induction motor that may have a reasonably large inrush
current. That transient switching can cause enough leakage elsewhere
(typically through mains filters on other connected appliances) to nudge
the RCD over the limit.

Cable damage elsewhere could be another cause (say a neutral earth short
in its supply somewhere).

--
Cheers,

John.

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

Is it perhaps the switch itself getting carbonised or polluted by gunk from
the cooking.
Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Lee" wrote in message
...
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only when
changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the manual)
and there is no measurable DC resistance from any metal parts of the unit
to mains earth. There's no DC resistance from L OR N of the mains plug to
any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is the
cause of the problem.

There was a case in a kitchen where slightly carbonised deceased Ants got
into a switch causing intermittent problems like this. A wag I knew called
it the Pink Panther problem.
Deadant deadant, I'm sure you remember the tune.

Brian

--
----- -
This newsgroup posting comes to you directly from...
The Sofa of Brian Gaff...

Blind user, so no pictures please!
"Andrew Gabriel" wrote in message
news
In article ,
Lee writes:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

Check for cobwebs.
I had a double insulated desk fan trip the RCD.
Turned out to be a spider in the plug, which had created a nest
bridging the live and (unused) earth pin.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]

On Thu, 28 Dec 2017 21:35:04 +0000, Lee
wrote:

Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.


Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.


Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

--
Cheers,

John.

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

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it.Â* It could be the result of a
Neutral toÂ* Earth fault anywhere in the house.Â* This can cause a
leakage current just insufficient to trip the RCD.Â* When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cablingÂ* to trip the RCD.

A friendÂ* once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped.Â* The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.


Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

---
This email has been checked for viruses by AVG.
http://www.avg.com

Our cooker hood is plugged into a 13A socket with a built in RCD and
that trips every time we try and change the speed. So we always turn it
off move the speed switch and turn on again - clearly not a serious fault!

Peter

On 29/12/2017 12:20, John Rumm wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))


Did this a few months back when we were chasing an intermittent tripping
fault with the oven, which turned out to be a grill element.

Only change made as a result of trying to fault find that issue* was to
replace the MCBs with RCBOs, of course that could well be the issue in
itself but it's been fine for the several months since then.

*I posted about it tripping the RCD as the oven was turned off. The
suspicion from the start was grill element but it never showed up on IR
checks, hot or cold. Put cooker on non RCD circuit and the grill element
eventually failed in a nice shower of sparks and melted metal

On 29/12/2017 12:24, Peter Andrews wrote:

snip

Our cooker hood is plugged into a 13A socket with a built in RCD and
that trips every time we try and change the speed.Â* So we always turn it
off move the speed switch and turn on again - clearly not a serious fault!

Interesting that while it seems a rare issue, it's not unknown.

Lee wrote:

Only change made as a result of trying to fault find that issue* was to
replace the MCBs with RCBOs, of course that could well be the issue in
itself but it's been fine for the several months since then.

That way you've got 30mA of allowed leakage per circuit, rather than
30mA combined for half (or all of) your circuits.

the grill element eventually failed in a nice shower of sparks and
melted metal

There I was thinking finding my faulty oven element was a
boring/unsatisfying fix on the grounds it looked in good nick ...

On 29/12/2017 12:24, Peter Andrews wrote:

Our cooker hood is plugged into a 13A socket with a built in RCD and
that trips every time we try and change the speed. So we always turn it
off move the speed switch and turn on again - clearly not a serious fault!

I had one that gave a flash and a bang on switch on once and the gave
all appearances of being dead. Checked the fuse and it was ok. Then
realised there were now vaporised tracks on the small PCB the switch was
mounted on! Repaired those (this time with a wire that would take the
full motor inrush current in every situation!) and all was well again.


--
Cheers,

John.

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

On 29/12/2017 13:00, Huge wrote:

Can you get RCBOs that are a straight swap for MCBs? We have a Legrand
CU that was installed in the late 1990s.




Yes FSVO, we used NOS MK 6936S which are a straight swap in our older MK
CU.

https://uk.rs-online.com/web/p/resid...rcbos/4253719/

The jury is out on whether the current MK 7936S RCBOs are are straight
swap or not.

https://uk.rs-online.com/web/p/resid...rcbos/7116001/


I believe they are the same same electrically but they are different
mechanically.
Some people have said they can be made to fit, others have said they
will not.

Or these maybe:

http://www.cef.co.uk/catalogue/categ...b-curve-rcbo-s

On 29/12/2017 13:00, Huge wrote:
On 2017-12-29, Lee wrote:
On 29/12/2017 12:20, John Rumm wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))


Did this a few months back when we were chasing an intermittent tripping
fault with the oven, which turned out to be a grill element.

Only change made as a result of trying to fault find that issue* was to
replace the MCBs with RCBOs,

Can you get RCBOs that are a straight swap for MCBs? We have a Legrand
CU that was installed in the late 1990s.



Probably easier and cheaper to swap the CU for an all RCBO installation.

I did see an ad for shortened RCBOs not so long ago that might fit your CU.

--
Adam

On 28/12/2017 21:35, Lee wrote:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about new
installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts of
the unit to mains earth. There's no DC resistance from L OR N of the
mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

First of all check the polarity at the hood connection.

However I suspect that the fan control switch is opening the neutral
before the live or that the suppression capacitor is duff.

--


Adam

On 29/12/17 11:41, Lee wrote:
Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

The [problem is that te real culprit never does show up.

You need to isolate all the circuits completely from the consumer unit,
unplug everything and check for an earth neutral short. On every single
one. And then find it.



--
Of what good are dead warriors? €¦ Warriors are those who desire battle
more than peace. Those who seek battle despite peace. Those who thump
their spears on the ground and talk of honor. Those who leap high the
battle dance and dream of glory €¦ The good of dead warriors, Mother, is
that they are dead.
Sheri S Tepper: The Awakeners.

On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but
not the 4th.

Go to garage and make up a special screwdriver with 3 convoluted bends
and a sharp turn at the end so you can painfully slowly remove the
last screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough clearance
to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it vanishes
as soon as it appears.

Spend several hours investigating and finding nothing consistent
until you realise fault comes back when someone walks along upstairs
landing. Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you leave
that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?

On 29/12/17 12:56, Huge wrote:
On 2017-12-29, John Rumm wrote:
On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:

[17 lines snipped]

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.


Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

No fault found. Put CU back together. Trips again the following day.


Then use 100mA RCD and 30 mA RCBOs on the relevant cuircuits

Rinse and repeat.



--
Gun Control: The law that ensures that only criminals have guns.

On 29/12/2017 12:51, Andy Burns wrote:

That way you've got 30mA of allowed leakage per circuit, rather than
30mA combined for half (or all of) your circuits.

cough 15 mA, if that. RCDs need to trip by their rated current and
should pass half their rated current, but some only just manage that.

So a 30 mA nominal RCD must trip if there's 30 mA leakage. It should
just allow 15 mA leakage. Some RCDs can be close to the 15 mA limit
so it's best to keep a comfortable margin below 15 mA to avoid
nuisance tripping.



--
Graham Nye
news(a)thenyes.org.uk

On 29/12/2017 12:51, Andy Burns wrote:
Lee wrote:

Only change made as a result of trying to fault find that issue* was to
replace the MCBs with RCBOs, of course that could well be the issue in
itself but it's been fine for the several months since then.

That way you've got 30mA of allowed leakage per circuit, rather than
30mA combined for half (or all of) your circuits.

the grill element eventually failed in a nice shower of sparks and
melted metal

There I was thinking finding my faulty oven element was a
boring/unsatisfying fix on the grounds it looked in good nick ...


Several people did suggest using a non RCD protected circuit as a test:-)

And that is not the same as the suggestion of disconnecting the earth!

--
Adam

On 29/12/17 15:28, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but
not the 4th.

Go to garage and make up a special screwdriver with 3 convoluted bends
and a sharp turn at the end so you can painfully slowly remove the
last screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough clearance
to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it vanishes
as soon as it appears.

Spend several hours investigating and finding nothing consistent
until you realise fault comes back when someone walks along upstairs
landing. Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you leave
that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?



Ah, Peter. you live in the 'not installed last week' world



--
Future generations will wonder in bemused amazement that the early
twenty-first centurys developed world went into hysterical panic over a
globally average temperature increase of a few tenths of a degree, and,
on the basis of gross exaggerations of highly uncertain computer
projections combined into implausible chains of inference, proceeded to
contemplate a rollback of the industrial age.

Richard Lindzen

ARW wrote:

Andy Burns wrote:

There I was thinking finding my faulty oven element was a
boring/unsatisfying fix

Several people did suggest using a non RCD protected circuit as a test:-)
And that is not the same as the suggestion of disconnecting the earth!

I could have run an extension reel from the shed back to the kitchen, I
suppose.

In article , Huge
wrote:
On 2017-12-29, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the
CU and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but not
the 4th.

Go to garage and make up a special screwdriver with 3 convoluted bends
and a sharp turn at the end so you can painfully slowly remove the last
screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough clearance
to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it vanishes
as soon as it appears.

Spend several hours investigating and finding nothing consistent until
you realise fault comes back when someone walks along upstairs landing.
Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you leave
that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?

*applause*

Worth leaving quoted.

And I thought it was just me that got into these "ha'porth of tar"
cascades that start with putting the Christmas decorations and end up
with me cutting down a tree in the garden.

It happens to the best. Barnes Wallis went adjust his garden gate - which
had swollen. Gets out plane, finds it's not very sharp, turns on powered
grinding wheel, finds it's running rough - bearing failure. Spends day
rebuilding motor, never gets round to the gate. ( His son was a close
neighbou - back in the '60s).

--
from KT24 in Surrey, England

On 29/12/17 16:28, charles wrote:
In article , Huge
wrote:
On 2017-12-29, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the
CU and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but not
the 4th.

Go to garage and make up a special screwdriver with 3 convoluted bends
and a sharp turn at the end so you can painfully slowly remove the last
screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough clearance
to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it vanishes
as soon as it appears.

Spend several hours investigating and finding nothing consistent until
you realise fault comes back when someone walks along upstairs landing.
Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you leave
that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?

*applause*

Worth leaving quoted.

And I thought it was just me that got into these "ha'porth of tar"
cascades that start with putting the Christmas decorations and end up
with me cutting down a tree in the garden.

It happens to the best. Barnes Wallis went adjust his garden gate - which
had swollen. Gets out plane, finds it's not very sharp, turns on powered
grinding wheel, finds it's running rough - bearing failure. Spends day
rebuilding motor, never gets round to the gate. ( His son was a close
neighbou - back in the '60s).

I was a close neighbour back in the 50s.

Walked past his house on the way to skool..


--
Socialism is the philosophy of failure, the creed of ignorance and the
gospel of envy.

Its inherent virtue is the equal sharing of misery.

Winston Churchill

On 29/12/2017 14:56, ARW wrote:
On 28/12/2017 21:35, Lee wrote:
Double insulated cooker hood with the usual plastic cased motor is
tripping the RCD it's connected to, but only intermittently and only
when changing the fan speed.

Thing I don't understand is how? Arcing maybe?
I did find a couple of discussion threads, but they were more about
new installations. This has worked fine for the last ten years*...

It's definitely not earthed (dire warnings against doing so in the
manual) and there is no measurable DC resistance from any metal parts
of the unit to mains earth. There's no DC resistance from L OR N of
the mains plug to any metal parts either - in case any one asks

* At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

First of all check the polarity at the hood connection.

However I suspect that the fan control switch is opening the neutral
before the live or that the suppression capacitor is duff.

I have sometimes removed suppression caps for the tripping problem to
simply disappear.

In article , The Natural Philosopher
wrote:
On 29/12/17 16:28, charles wrote:
In article , Huge
wrote:
On 2017-12-29, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in
the CU and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but
not the 4th.

Go to garage and make up a special screwdriver with 3 convoluted
bends and a sharp turn at the end so you can painfully slowly remove
the last screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough
clearance to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it
vanishes as soon as it appears.

Spend several hours investigating and finding nothing consistent
until you realise fault comes back when someone walks along upstairs
landing. Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you
leave that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?

*applause*

Worth leaving quoted.

And I thought it was just me that got into these "ha'porth of tar"
cascades that start with putting the Christmas decorations and end up
with me cutting down a tree in the garden.

It happens to the best. Barnes Wallis went adjust his garden gate -
which had swollen. Gets out plane, finds it's not very sharp, turns on
powered grinding wheel, finds it's running rough - bearing failure.
Spends day rebuilding motor, never gets round to the gate. ( His son
was a close neighbou - back in the '60s).

I was a close neighbour back in the 50s.

Walked past his house on the way to skool..

Then you must have lived near where I live now. Barnes lived, AIR, near
Efffingham Junction station.

--
from KT24 in Surrey, England

On 29/12/2017 12:56, Huge wrote:
On 2017-12-29, John Rumm wrote:
On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:

[17 lines snipped]

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.


Great. So the consensus would appear to be no point in changing the
cooker hood because it's something else.

Fair enough. At the aesthetic cost of a bit of trunking I'll put it on a
non-RCD circuit and I'll wait until the next time to see if the real
culprit shows up.
At a no doubt inconvenient time.

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

No fault found. Put CU back together.

Which means you have eliminated one possible cause of problems.

Trips again the following day.

And still have another to find, although one less than previously! ;-)




--
Cheers,

John.

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

On 29/12/2017 15:28, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

[big snip]

Reassemble CU.

15mins for all that?

Na, 25 for all that ;-)

Although I played a variation of the game yesterday...

How long does it take to install a strap boss on a 110mm soil pipe and
connect up some 40mm waste pipe to it?

Well you start with wanting to cut a hole. Have hole saw the right size,
but this is all under a floor and between a couple of joists that also
have a large RSJ running between them, so there is no way to actually
get the drill in there far enough...

Try the angle drill - only has 10mm chuck, and hole saw arbour is 11mm.
Not only that, drill body will not go in the gap anyway.

Try small 10.8V drill - that will fit, but same chuck problem...

Swap chucks on 18V and 10.8V drill as a temporary measure? Nope, don't fit.

Thinks, aha, I bought an arbour for the smaller hole saws the other day,
I could "modify" that to fit the smaller chuck.

Stick it in the lathe, and turn down the 11mm hex shank to something
round that will fit the small chuck.

Then find the boss for the hole saw is smaller as well, and does not fit
the 52mm saw. Argggg

Look at online catalogs to see if anywhere local sells extension bars
that will fit the shank of the hole saw.

Look to see if there is a way of making an extension for the arbour.
Realise it has a hole all the way though it (for the pilot drill).
Contemplate drilling that out and tapping to take some threaded rod.

Engage lateral thought - hang on, you can move that pilot drill by
freeing a screw. What if you poke it out of the back? Oh look you could
grip that in a chuck - if only it were long enough to poke out the back
and the front at the same time! Swap out the pilot for a long 6mm bit -
slightly lose fit in the hole, but close enough.

Time to drill hole 2 mins. Time to get started at least 2 hours!

Now fit the boss, solvent weld in a reducer, hook up short bit of pipe
and 45 degree bend, and try to fit length that will connect to bath
waste. The work out you can't actually get it all assembled working form
just the ends, even if you could get the length of pipe in. Hack through
another 10 floor boards and lift them. Tit about for a bit and finally
hook up pipe.

Now pour a few litres of water down it to test and discover it leaks
slowly from the boss. Lean that the original soil pipe does not take to
solvent welding at all! It was a massive pain to get in place, and do
up. Its now much harder to get undone because now all the space is full
of waste pipe that is glued into it. Finally get it free, and butter the
back of it with "plumbers gold" sealant. now refit the whole thing which
is now even harder - laying face down on the floor, reaching round from
an adjacent space with head wedged under a loo.

Get it done. Drop screwdriver and torch into void in floor, and then
work out that void carries on for 9' or more almost down to the ground
floor. Get cable rods with magnetic pickup on, and retrieve torch and
screwdriver.

Re-test pipework - jobs a goodun, put off screwing down loads of floor
boards til the following day.

Realise after the fact, that due to a quirk of the building design, I
could have turned a corner with the waste pipe and installed the strap
boss a couple of feet to the right where there was far more space to
work on it!


--
Cheers,

John.

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

On Friday, 29 December 2017 15:28:20 UTC, Peter Parry wrote:
On Fri, 29 Dec 2017 12:20:28 +0000, John Rumm
wrote:

On 29/12/2017 11:41, Lee wrote:
On 29/12/2017 11:18, Huge wrote:
On 2017-12-29, Peter Parry wrote:

It would probably only take 15 mins to go through each circuit in the CU
and do a quick N to E resistance check...

(i.e. turn off MCB, disconnect circuit neutral(s) from bus bar, and
measure resistance to earth (of if you have an insulation resistance
tester measure N+L joined together to earth))

No chance :-

Excavate cupboard under stairs to find CU and get access.

Approach CU to remove cover.

Discover deranged plumber has at some time years ago run a pipe such
that you can easily undo 3 of the screws to remove the CU cover but
not the 4th.

Go to garage and make up a special screwdriver with 3 convoluted bends
and a sharp turn at the end so you can painfully slowly remove the
last screw 1/10th of a turn at the time. Spend 2hrs doing so.

Remove screw and discover the pipe, plus another you hadn't noticed,
prevent you from removing the CU cover even with all screws undone.
Spend an hour fiddling with every possible position to discover this.

Get long screwdriver and start levering pipes to get enough clearance
to remove cover.

Smell gas.

Hear gas

Discover small hole you have just made in gas pipe.

Shut off gas. Get issued with dire warnings about dinner (lack of).

Go to plumbing box to find you have 12 American standard gas fittings
which fit nothing, 6 x 3/4in and 8 x 1/2 inch neither of which fit
anything either.

Drive to Screwfix to get fittings and 4inches of pipe (minimum size
sold - 3m).

Bend pipe to fit in car.

Drive back and find 2.8m of bent pipe left over from when you last
needed 4in of pipe.

Get Blowlamp.

Go back to Screwfix to get gas for blowlamp.

Rework gas pipe to allow lid of CU to be removed.

Peer at CU to find Adam's apprentice fitted it and every screw on the
neutral commoning bar has the head snapped off.

Spend 4hrs trying without success to extract mangled screws.

Cut neutral wires at commoning bar.

Forget why you are under the stairs at 01:00 and go to sleep there
instead.

Go back to Scewfix to get screws and spare neutral bar, find non
there. Buy new CU instead.

Go home, discover remains of last consumer unit you forgot you had
bought the last time you needed spare bits.

Fit new neutral bar - discover Adam's Apprentice left no slack so
neutrals will now no longer reach neutral bar.

Rework and extend all neutrals.

Start testing, no fault found. Try again - find fault but it vanishes
as soon as it appears.

Spend several hours investigating and finding nothing consistent
until you realise fault comes back when someone walks along upstairs
landing. Start ripping up laminate floor you layed last month.

Find nail through cable. Repair

Jump up and down on floor. No fault.

Restore floor upstairs temporarily amongst loud cries of "If you leave
that lot there like that I'll get a man in to do it properly".

Reassemble CU.

15mins for all that?

too true for my liking


NT

"Huge" wrote in message
...
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.

Why can't you find it by measuring the leakage, then turn breakers
off in turn until it goes, then break that circuit in half chop method
until you find where its got the problem ? Nothing even remotely
like 2 years to find it.

Rod Speed wrote:

"Huge" wrote in message
...
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.

Why can't you find it by measuring the leakage, then turn breakers
off in turn until it goes, then break that circuit in half chop method
until you find where its got the problem ? Nothing even remotely
like 2 years to find it.

You clearly know not the joys of the intermittent fault.

--

Roger Hayter

"Roger Hayter" wrote in message
...
Rod Speed wrote:

"Huge" wrote in message
...
On 2017-12-29, Peter Parry wrote:

[18 lines snipped]

The hood may have little to do with it. It could be the result of a
Neutral to Earth fault anywhere in the house. This can cause a
leakage current just insufficient to trip the RCD. When the cooker
hood is switched on or speed changed there is enough (harmless)
inductive coupling to surrounding metalwork/cabling to trip the RCD.

A friend once had a house where plugging an extension lead in was
fine - but as soon as you walked out with it and put it on the grass
(with nothing plugged in) the RCD tripped. The fault was eventually
traced to a nail through the upstairs ring which bridged neutral and
earth.

Just to cheer your holiday up these faults can take ages to find.

Just to cheer you up even more, we've been trying to track down a
similar fault for 2 years now.

Why can't you find it by measuring the leakage, then turn breakers
off in turn until it goes, then break that circuit in half chop method
until you find where its got the problem ? Nothing even remotely
like 2 years to find it.

You clearly know not the joys of the intermittent fault.

You're wrong, as always.

All you have to do is keep checking that the fault is
still there and come back when it is again if its gone.

Rod Speed wrote:

"Roger Hayter" wrote in message
...
snip

You clearly know not the joys of the intermittent fault.

You're wrong, as always.

All you have to do is keep checking that the fault is
still there and come back when it is again if its gone.


OIC, I hadn't thought of that.

--

Roger Hayter

On 28/12/2017 21:35, Lee wrote:

At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

You shouldn't be doing electrical work at your age.

Bill

On 30/12/2017 19:23, Bill Wright wrote:
On 28/12/2017 21:35, Lee wrote:

At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

You shouldn't be doing electrical work at your age.

Bloody well should be. Or at least know how to reset a MCB or RCBO.


--
Adam

On 30/12/2017 19:23, Bill Wright wrote:
On 28/12/2017 21:35, Lee wrote:

At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

You shouldn't be doing electrical work at your age.

I think I probably started doing socket extensions at the age of ten ;-)


--
Cheers,

John.

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

On Saturday, 30 December 2017 23:43:00 UTC, John Rumm wrote:
On 30/12/2017 19:23, Bill Wright wrote:
On 28/12/2017 21:35, Lee wrote:

At ten years old I'm more than happy to swap it out, if it really is
the cause of the problem.

You shouldn't be doing electrical work at your age.

I think I probably started doing socket extensions at the age of ten ;-)

I put in whole socket & lighting systems at that age. Scary really.


NT