UK switch burnt every few months

lugluglug · Oct 4, 2022

9kw deep fryer, a cooker switch, stop working every few months,
I found the fryer use thin flex cable (see picture 3), it was burnt, the power supply cable are much thicker and it has no problem.
The fryer thin flex cable was just plugged into the switch, no lug,
Am I right? I guess it can be the thin copper flex cable are not contacted properly with the switch, that's why it overheated,
If I soldering the thin flex cable or use a lug ( see pic), it can improved?

Many thanks

Lucien Nunes · Oct 4, 2022

What size is the fryer flex?
Unless the connection was badly made or the flex is too small, it is likely that the heat is coming from the switch contacts and the heavy supply cable did a better job of conducting it away.
Ferrules might help to make a better connection to the flex. Do not solder (tin) the end, this makes it look neat but causes a bad connection as the solder is soft and creeps out leaving the terminal loose.
Consider using a better, heavier duty switch, that is not run so close to its maximum rating.

davesparks · Oct 4, 2022

Have you removed the damaged section of cable each time and made the connections to good clean copper?

If you've been connecting to the heat damaged cable each time then that will be causing the overheating of the new switch terminals.

lugluglug · Oct 4, 2022

Lucien Nunes said:
What size is the fryer flex?
Unless the connection was badly made or the flex is too small, it is likely that the heat is coming from the switch contacts and the heavy supply cable did a better job of conducting it away.
Ferrules might help to make a better connection to the flex. Do not solder (tin) the end, this makes it look neat but causes a bad connection as the solder is soft and creeps out leaving the terminal loose.
Consider using a better, heavier duty switch, that is not run so close to its maximum rating.

Thanks for your advice, the flex cable from fryer is not small, it could be about 3mm, I will try ferrules then.

lugluglug · Oct 4, 2022

davesparks said:
Have you removed the damaged section of cable each time and made the connections to good clean copper?

If you've been connecting to the heat damaged cable each time then that will be causing the overheating of the new switch terminals.

Sure, good advice, this has been done by others, but today I was helping, and I cut off some burnt cable, the flex cable copper wire are dark instead of copper colour now, but the cable was not long enough, so next time I will try to drag the cable and redo it.

davesparks · Oct 4, 2022

lugluglug said:
Sure, good advice, this has been done by others, but today I was helping, and I cut off some burnt cable, the flex cable copper wire are dark instead of copper colour now, but the cable was not long enough, so next time I will try to drag the cable and redo it.

If it is dark and not copper coloured then you are likely to have made a poor connection and created another fire risk.