Double insulated cooker hood trips RCD

[ARW]

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.

[Huge]

OK, thanks.

[The Natural Philosopher]

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.

[Peter Parry]

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?

[The Natural Philosopher]

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

[Graham Nye]

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.

[ARW]

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!

[The Natural Philosopher]

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

[Andy Burns]

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

[Huge]

*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.

[charles]

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).

[Huge]

Not that I wopuld compare myself in any way, shape or form to Barnes-Wallis, but yes, that's the kind of thing that happens.

[The Natural Philosopher]

I was a close neighbour back in the 50s.

Walked past his house on the way to skool..

[Fredxx]

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

[charles]

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

[John Rumm]

Which means you have eliminated one possible cause of problems.

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

[Huge]

It's an intermittent fault. It just means I haven't measured it when the fault is present.

[John Rumm]

[big snip]

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!

[tabbypurr]

too true for my liking

NT

[Huge]

[70 lines snipped]

My sympathies. :o)