A Story of Repair (SoR): Electric Kettle

One or two weeks ago, during the day, the RCCD (residual-current circuit breaker) tripped.
The root cause was very unclear at first since no equipment was switched on or off during the event. Also the weather was quite humid and sticky after a thunderstorm, so that could be a factor as well.

By unplugging some usual suspects one at a time, we could trace it to the culprit. First I unplugged the coffee maker from the mains, but again the RCCD tripped after some minutes. Next the electric kettle was unplugged, and bingo! The RCCD did not trip again.

This Kettle, a Tristar HL-108B, has a base piece. This base did have my suspicion, since the inner wires became visible from where there should be a cable strain relief.

Opening the base required special spanner or ‘fork’ style screws. Somehow they want to discourage repair, but they are wrong. With a suitable long bit style drivers it was fairly easy to get access to the wire terminals.

The multimeter did not show any problems, but these kind of insulation current leakage problems can only be measured reliably with a proper insulation tester, aka ‘Megger’. I do not own one, nor wanted to invest one for repairing just a kettle. The cheapest-kind-of-reliable-ones would cost over 200 euro. The second hand market is not exactly flooded with such testers. I decided be just relying on the installed RCCD if my repair works or not.

After opening the base the damaged wire insulation was clearly visible. A few drops of water can easily cause a bridge to ground.

I could have just bodged in some heat shrink tubing over the wire, but decided against it since the wire ends looked kind of molten or had quite a bit of heat strain with usage. Also cutting the wires shorter to cut away the bad pieces was not an option, since the cord was quite short (1 meter at most) already. Making it impractical to use. Instead I decided to replace the cable with another bit longer cable I salvaged from older equipment. I keep a pile of those for these kind of repairs.

To replace the ring terminals, I took some measurements of those as well. The hole diameter is only about 3mm.

The base was further disassembled and cleaned with a bit of soapy water and properly dried. This just to eliminate any possible paths for any small leakage current over ‘kitchen-greased’ parts.

To crimp the terminals to the wires, I did need to invest in some crimp profiles or jaws for such non-insulated style connectors for the Knipex crimp-pliers I own. I did briefly look online for a cheaper and a locally available second hand alternative, but only a set of suitable 89 euro Knipex 97 52 14 pliers appeared in the quick search I did.

For 10 euros less I bought new jaws (Knipex 97 49 04) together with new ring terminals (Vogt Verbindungstechnik 3310A.67). These terminals are actually one or two millimeter too long for these jaws, so next time I’ll need to find better matching ones to the crimp pliers jaw width.

The outer cable mantle was removed with the Jokari Nr 16.

The inner wires were stripped to about half a centimeter bare copper.

The crimp tool was used to attach the terminals firmly to the wires.

Note the ring terminals had to be slightly cut back from 8mm outer diameter to 6mm to fit in the connection block.

All was assembled back, and success!