Secret Scotland

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LNT – Russell Hobbs flat element kettle revisited

I covered what I THEN thought was the repair of an ancient Russell Hobbs Millennium kettle I had owned from new out-of-the-box, but which had never worked reliably from day one.

Why my new kettle NEVER worked properly

Once I rewired it and replaced the offending ‘boil switch’ I though the job was done.

But, I still thought it didn’t work ‘First Time, Every Time’, however, I attributed this to imagination.

I was wrong!

Despite the obvious failure of the ‘boil switch’, it seems this kettle held a second, equally destructive deeper fault.

Like most expensive kettles, this Russell Hobbs was fitted with over-temperature switches to kill the power if it boiled dry, or some idiot turned it on with no water in it. Unusually, it has TWO.

While I did make the filling/empty mistake a few times, I usually caught the slip (as this noisy kettle didn’t make the usual noises), and got into the habit of checking.

I assumed I had ‘Got it wrong’ one day when it didn’t boil, and I found very little water inside. Normally, the thermal switches reset when they cool, and you just carry on, but on this occasion it was completely dead. I assumed (wrongly) one or both switches had tripped and not reset.

I didn’t have any similar switches lying around, so just bought the cheapest kettle from Asda, assuming I could pull the part from that (at around £5 this is cheaper than buying just a switch online!).

That didn’t actually work out as planned – these supermarket plastic kettles are now so cheap they don’t have any safety features. Look at these pics…

First, just looking inside, plastic kettle should really have a metal plate at the bottom, to help dissipate heat if the automatic switch fails and they boil dry.

I was amazed to see this is no longer fitted. You can guess what happens if this boils dry, or you don’t fill it.

Asda Kettle Inside - no metal plate below element

Asda Kettle Inside – no metal plate below element

Things got worse when I went to dismantle it and collect the thermal switch I expected to find.

There wasn’t one – or apparently any sort of thermal cut-out to disconnect the power in the event of overheating.

I stopped short of dismantling the element, which connects directly to the power in the corded base, as it might have a thermal fuse inside, but since I wasn’t going to be cannibalising this new kettle after all, I wasn’t going to ruin it either.

There could well be a fusible link in there – I just don’t know. I have my doubts, as I’ve dismantled some very similar element bases, and they just go straight from those contacts to the element.

I’m amazed UK regulations allow this. It’s the sort of omission I expect to find inside Chinese home market goods, not export items.

Maybe the mains fuse (in the plug) is expected to blow if the element overheats with no water cooling it?

The two yellow wires go to power indicator fitted to the switch.

Asda Kettle Wiring - no obvious thermal cur-out

Asda Kettle Wiring – no obvious thermal cur-out

Oh well – back to the old Russell Hobbs, which I decided to investigate as I had started dismantling it in anticipation of repair.

This turned out to show my thoughts were ENTIRELY wrong, and it revealed the second ‘out-of-the-box’ failure it had come with.

I pulled the base of the kettle, and quickly found BOTH of the thermal cut-outs were perfect fine, as was the switch I’d fitted last time.

I checked all the wiring, which was fine, leaving only the flat element as the only part that could have been at fault and open circuit, but it looked perfect, as it was completely visible and I could see all the tracks were perfect, with no ‘blown’ or damaged spots to be seen.

I was puzzled now…

The element looked OK.

The wiring had checked out as continuous from the mains input to where it met the element, and all the switches were working perfectly on test.

That left only ONE possibility – was the wiring actually connecting to the element?

A plastic moulding covered the actual interface.

Stripping that out and removing the element revealed the cause.

The wiring did not connect directly to the element, but was terminated in a spring-loaded contact that was forced against the metal surface of the element.

A totally daft idea for a relative high current connection, with the inevitable result that one of them had failed, probably from the first time the kettle was ever used! Recall my first post noted that this kettle only worked two or three times before becoming intermittent and unreliable.

This is inevitable if there is any dirt, a poor or oxidised surface, or the spring fails for any reason to press the contact points together securely.

You can see from this pic that while one contact is still good, the other had completely burnt away, and it’s a wonder it ever worked.

Russell Hobbs Millennium Flat Element Burnt Connector

Russell Hobbs Millennium Flat Element Burnt Connector

Obviously, I can’t even attempt a repair – there’s nothing left to repair.

As everything else is fine, I will try permanently fixing the wire. Soldering should work in this case as the base can’t get about 100°C (unless the kettle is boiled dry or empty), but that substrate below the printed element track is at least 1 mm steel, so heating to make the connection will need care.

Another job for when I get around to it.

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13/04/2019 Posted by | Civilian, photography | , , , , | Leave a comment

Why my new kettle NEVER worked properly

A long, long time ago (years) I picked up what was then a new type of Russell Hobbs jug kettle at a clearance sale. As a new gimmick, these were vastly overpriced at the time, so I wouldn’t have been buying otherwise.

The novel feature was a flat element in the base, meaning there was no sign of the element if you looked inside, unlike a normal kettle, where the element was always obvious inside the body.

It was just a spare, so was only used a handful of times, but shoved in a box as it was unreliable, and would not turn on reliably.

I needed another kettle recently, so dug it out, but found it was completely useless, and would not turn on at all.

Since it had not even been used a dozen time, I wanted to know why.

I had suspected the base, this being a ‘cordless’ type, but when I dismantled this, and the base of the kettle, the connectors were found to be perfect, with no faults.

This only left the ‘boil switch’, mounted at the top of the jug handle, so more dismantling was needed.

But it was worth the effort, as the ‘boil switch’ was the culprit.

This pic shows the state of the moving contact of the switch, which has been overheated due to arcing, softening the metal, and rendering the switch useless. All the surrounding metal is blackened/discoloured from the heat. Bear in mind, this switch saw less than a dozen uses in its life to this point.

Cooked Contact

Cooked Contact

The next pic shows the same contact in place.

The contact is in the enhanced section of the pic, at top right.

The contact arm should be straight, not bent as seen here, and the black L-shaped lever should push the contacts open when the kettle boils. But, as can be seen here, the overheating cause the straight contact arm to lose its strength, soften, and just bend, rendering it useless. It just stayed where it was when the L-shaped lever moved away from it, so the contacts did not close and provide power to the element.

Failed Thermal Switch

Failed Thermal Switch

I’m guessing either the contacts were set too close together in the factory, so arced excessively due to lack of clearance, or, moisture was trapped between them when the kettle boiled and water vapour got into the switch, bridged the contacts, and again led to arcing and overheating.

It would be nice to drop a replacement part in, and have the kettle working, but the various ‘safety’ regulations seem to have made the supply of such parts virtually non-existent, so I’m not even going to waste time trying.

I’ll just alter the wiring, and have a plain cordless kettle that needs to be operated manually.

23/07/2018 Posted by | Civilian, photography | , , , | Leave a comment

   

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