Tea urn randomly trips RCD!

[zigg]

Hi guys. I have a Burco 20l tea urn that I use in my shed. I was given it a few weeks ago, so it will be no great loss if I bin it. To begin with, it worked perfectly, had no trouble boiling a couple of gallons of water. Next time I plugged it in, it tripped the rcd before I even switched it on! Out came my meter, and I got continuity between earth and neutral.
I took the base off to check the wiring inside and everything looked ok, no loose or unattached wires, no water to be seen. Tried with my meter again, but couldn't get any continuity this time, so plugged it back in, and everything worked! Started to boil some water....all went well until...phhht!....rcd tripped again!
Off came the base again. This time I pulled each connector off in turn, sprayed with WD40, even inside the control switch....(the only bit with any moving parts!) put it back together, and boiled some more water....no probs. A couple of days later, got partway through a boil and......rcd tripped again!
As I said, I got it for nothing, and this is my last attempt at trying to solve the problem before tossing it. I just would like to find out what the problem is. It can't be anything complicated, 'cos it isn't a complicated bit of machinery!
I'm not an electrician by any stretch of the imagination, just know the very basics.
If anyone could throw some light onto this problem, I'd be very grateful. Thanks.

 

[bernardgreen]

Intermittant fault in the element is the most likely fault. Or abraided insulation allowing a wire to contact the metal work, missing grommit where wire goes through a hole in metal ?

 

[JohnD]

IME, when PAT testing, the faults to earth are overwhelmingly in watery appliances, such as kettles, tea urns, fishtank heaters, steam irons. The same with non-portables such as washing machines and immersion heaters.

Quite likely there is a fault in the element allowing water in. Maybe it had time to dry out before your first use. Oven elements, once failed, often absorb enough moisture into the mineral packing to trip the RCD, but are OK if they are used often enough to stay dry.

It could also be a water leak dripping onto the switch contacts, say, but you seem to have ruled that out by inspection.

If you can take the connectors off the element, test that alone. I don't know what a new element would cost.

There may also be an accumulation of small faults, so there could be a background leakage which is under the RCD tripping current, and the urn pushes it (or not) over the limit. This is common in outbuildings that may be a bit damp. Especially outdoor lighting exposed to rain, so the tripping may be worse in wet or humid weather.

 

[zigg]

Thanks for the replies. I've decided it's not worth bothering with any more, it had very bad limescale inside, too, so, I've just returned from the tip!......
p.s. I've got another, bigger one that works well, so I'm not without one.

 

[ban-all-sheds]

Making beer, or crystal meth?

 

[zigg]

Hehehe......let's say beer...........

 

[stillp]

I once developed an automated test chamber for load cells, running off a commodore PET (this was in the early 80s...). About once a week the system would crash, losing our test results, so I put a recording 'scope on the mains and found bursts of 400kHz interference at random intervals. Had the DNO round, and they put our factory on a tapping of the transformer separate from the one the heavier industries were on. Problem continued... about the 5th visit from the DNO, they said it must be caused by something in the factory, but we only had soldering irons, lights, an electric typewriter... oh, and the tea urn in the canteen. Anyone need three guesses?

 

[zigg]

 

[mwatsonxx]

zigg, you can legally buy stills (£150ish), as long as you don't use them.

 

[ericmark]

I expect not used as a still, but mashing the grain, as said the mineral insulation in the element is hygroscopic it will draw in water if the seal is damaged, new elements are cheap and easy to fit, also any high powered item can cause a RCD to trip due to an earth - neutral fault on anything else plugged in, it may be the boiler is not at fault.

I used a boiler as a still on the Falklands to produce distilled water for lead acid batteries, found running from 110 volt instead of 230 volt worked well, genital enough for water to condense, some one did not realise it was for distilled water and destroyed it, so I order a proper still to replace it. Found the deionising plants useless batteries failing all the time, simple distilled water is best.

Since you can brew to 21% ABV without a still, the idea of a still is crazy for alcohol, simply no need.

 

[securespark]

genital enough for water to condense

 

[EFLImpudence]

It sometimes pіsses out of mine.

 

[ericmark]

Darn spell checker, missed that one. Hope you had a laugh anyway.

 

[EFLImpudence]

 

[zigg]