And now for something different

Hey, it’s electric!

Today we have a crappy Chinese Tea Kettle to take apart and see what makes it not tick. This is an Ovente model #GK83R bought less than a year ago. It randomly refuses to heat and smells of molten plastic.

As expected, the product label does not even list UL/ETL or anything remotely resembling safety certification.

Look ma, no safeties

Let’s start with the base to make sure power actually gets in.

Power base

Looks pretty good from this side, except for some signs of melting

Looks pretty good from this side, except for some signs of melting

The Line terminal looks pretty beat up

At least ground wire is connected..

At least ground wire is connected..

Taking kettle apart

Now on to the actual kettle.To take things apart, we take out four the screws on the bottomAll screws out

then pry two clips under the handle’s plastic insert from the top:

Two clips are hiding under the top

Two clips are hiding under the top

And finally remove it:

Handle cover

Handle cover. Note the two clips on the left

Handle cover off

Remove one more screw under the wires and the whole glass carafe  can be maneuvred off the kettle:

Note screw hiding under the wires

Power switch looks reasonable:

Power switch. Line in on the bottom, heater and LEDs lines out on top

Power switch. Line in on the bottom, heater and LEDs (white)  lines out on top

And this is how they drive these fancy blue LEDs:

Run it through a power resistor, she'll be allright

Run it through a power resistor, she’ll be allright

12k 5W

12k 5W

The base holds a light pipe with two blue LEDs in it:

Light guide

Led details

Now on to the actual heating element that’s bonded to the glass:

Bottom view

Bottom view

Heater element and associated wiring

Heater element and associated wiring

Power receptacle

Power receptacle removed. Signs of melted plastic abound

Taking power receptacle off, reveals the thermal switch housing with even more melted plastic.

A bit melted in here

 

Seeing how the chance of finding replacement parts is fairly slim, we might as well proceed to destructive disassembly to learn how things used to work:

Hot plate side of the thermal cutoff assembly

The two white actuators are depressed when installed. One by the base, another by a bimetallic sensing plate that changes geometry when heated:

Inside thermal cutoff. Does not look repairable

And finally let’s take a look at the power switch and the boiling detection:

Switch with actuator removed

Familiar bimetallic thermostat pushes on a reset pin when heated by steam

A plastic chamber directs steam to a bimetallic thermostat. Once it reaches trip temperature, the metal disk snaps and pushes switch reset pin in, shutting the kettle off.

Schematic diagram:

It’s an “interesting” design. From safety point of view it is done reasonably well, with two series thermal switches and grounded frame. The LEDs are driven in series through a large resistor, though the way the are reverse biased on every other AC cycle is a bint cringe-worthy. Why not stick them in parallel and back to back so that one is always forward biased at any given time? As it is, they are most likely just getting away with it thanks to a large series resistance limiting reverse breakdown current. Plus it’s easier to wire- probably a non-trivial consideration for cheap volume build product.

Schematic

Conclusion:

This teardown started as a quest to find out why the kettle is not working. It appears the weak design of power inlet and thermal switches resulted in way more heat being seen by parts than expected, melting thinngs and disconnecting Line circuit. Not much is fixable here, so the kettle is getting dismantled and sorted into recyclable parts and e-waste. Oh well, now we know what to look for in a new one. And don’t forget those safety certs!

 

2 thoughts on “And now for something different

  1. You should report this product to UL, CPSC, and/or the FTC.
    This device obviously shouldn’t be sold on the market … :/

Leave a Reply

Your email address will not be published. Required fields are marked *