Heating element becomes a capacitor

My only thought is water ingress into the element. While the end of an element there may be a ceramic insulator, within the element the separation between the conductor and body is likely to be an oxide powder. It is possible that this has got wet.

One way of finding out is to place the assembly in an oven for an extended period of time, to hopefully drive out any moisture.

Sounds like its got a leak alright, if its really festered up all sorts of things could go wrong. Best chuck them both.

Brian

It's hygroscopic, so it will try hard to get wet.

You could confirm the element by disconnecting (and if necessary safely insulating) the element connections, and trying it again.

Another would be to run it on a non-RCD protected circuit, but I would fit a closely matching fuse for the power rating, and also beware that it might end up with a live chassis if you have multiple faults (and you know you have at least one fault already).

I used to have a T-shirt that showed a character connected up to a car battery, with lightning zaps everywhere, and sticking-out hair, and the slogan: "Sometimes I need a good jolt in the morning". This could be a replay of that T-shirt.

It could indeed, hence the warnings. Magnesium oxide insulated heating elements can sometimes leak in a way which is curable by running them for a short time. This was even allowed in the PAT test guidelines, if the leakage is initially found to be too high.

However, if the earth fault is something else, you might get a spectacular bang. Hence the suggestion to confirm the element is the cause of the leakage first by disconnecting it, and to fit a close rated fuse.

The insulation is powder in these elements.

NT

Methinks you have reinvented the wet cell. Dissimilar metals plus water gives a current.

Try your meter on the Volts or microamps range, you will see your "cell" discharging through the meter on current.

Disconnect from the mains first by the way.

Baking the element in an oven will drive out the moisture, then all you have to do is replace the solvent you currently use for espresso manufacture with a high grade olive or vegetable oil. This will extend the element life ad infinitum!

HN

I vaguely remember a short story (ISTR it was in a book with a title like _Southern Fried Stories_) about a card sharp who started getting shaky hands. He went to the big city to see a doctor, & got some kind of electric shock treatment that worked for a while, but didn't like the expense of going back every few months for more, so his friends started strapping him to a car distributor & cranking the starter for a few seconds.

How neat. Wouldn't it be great if this effect could be exploited for practical applications!

Sorry, I didn't understand the last part. Are you suggesting the element should have some kind of oil in it?

Daniele

Thanks to everyone for the advice. The I left it in the oven while cooking; there is already a great improvement. I can still see the effect I noted before, but it's much less.

Don't worry, it's just the boiler top-half and the embedded elements I'm busy with; I will reassemble it all later.

Daniele

He is saying make your coffee with oil instead of water - then it won't dissolve/leach out the powder...

Funnily enough, the other day I was reading about making a coffee cake (for example) having allowed the ground coffee to flavour the butter and or cream so as to extract flavours which are usually left behind by water/steam extraction methods.

But it is!

The dissimilar metals are usually selected to optimise the movement of electrons and the electrolyte is usually acidic.

If you turn an ignition key on in a vehicle, you are exploiting the effect.

Even further than that, change your coffee recipie so that you use a none conducting fluid. No problems with RCB's tripping, higher calorific input means less time in the mornings making toast & oatmeal and it might even taste nice.

If the idea fills you with shock & horror, just think of the first poor blighter that thought it might be a good idea to follow a civet cat around with a bucket!

HN

If that doesn't suffice, you can connect the element to the mains with nothing connected to its metal case, suspended by the mains wires, and switch off when it begins to glow very slightly. If that doesn't dry it out, nothing will.

NT

Joke.

Oh I see. The moisture got in there when I was descaling the boiler, not through normal use.

It's in the oven now, having a last bake.

Daniele

Did you descale the terminals or something?

If you got the area around the terminals wet then the element would happily absorb moisture should the seal be less than perfect. So your baking should do the trick nicely.

If the ingress was through a crack in the element then it's time to move toward soft drinks.

Should baking fail then maybe you could deep fry it in batter, there could be a market for it north of the border.

I would have been very tempted to remove the earth and run up the element, although I gather that there is a risk of a small explosion doing things this way. You have to get the timing right too otherwise the thing thinks it's a light bulb!

HN

Without a heat load, and I'm assuming this is to heat/boil water, I would expect a meltdown or very loud bang after a few minutes with a corresponding shower of white powder, well before any "glow"!!

So this is something I wouldn't recommend.

An idea I hadn't though of! One way of maintaining a high temperature within sensible bounds.

And hey, if you short it out with your tongue it will give you a belt or a batter. We could call it a belterry. It'll never catch on, you know. Newpfangled nonsense.

Well, that's not my experience. Normally they'll glow bright red for a minute or so before any failure. As soon as you see any glowing its more than hot enough to drive out any water and burn off any carbon deposits.

And there's nothing to go bang, its just a metal wire element in oxide powder in a metal tube. The worst failure I've seen arced and melted part of the outer tube, then popped a fuse.

NT