Burnt out switches

[Penney]

A plumber has installed a 8.3kw heating boiler pulling 35a which is being fed from a 6mm . it has burnt two 45a cooker switches already. Why. Rewiring to 10mm will be hard as tenants just moved in. Owner going mad ! Cable is running above ceiling near downlighters and poss insulation. Also could be bunched. What are my options. Help.

 

[telectrix]

first check cable run and calclulate if 6mm will cope with 35A. clipped direct is 47A so you have a certain derating to play with. second, are the switches good quality and are the terminations good? at a push, you could do away with the switch and use the MCB for isolation.

 

[alanl]

Poor quality switches, and / or poor quality fitting of the switch.
Buy a switch that has 2 screws for each terminal, you'll get a good connection then, and hopefully it wont happen again.

 

[ruston]

How has the cable stood up to the heat damage too.

 

[Octopus]

Poor switches (cheap) and poor installation.

Is this a wall switch or a pull cord switch?

 

[Farmelectrics]

the cable is ok

 

[Midwest]

Firstly, blame the plumber who installed heating boiler, without reference to the design of the electrical supply cable. Who installed the 6m cable or was it an existing cable (looking to blame someone else). Then present the options to the home owner, with the blame not apportioned to you.

 

[Midwest]

Sounds like the cable terminations have suffered thermal damage, and need cutting back before connecting up new isolator?

 

[DPG]

Firstly, blame the plumber who installed heating boiler, without reference to the design of the electrical supply cable. Who installed the 6m cable or was it an existing cable (looking to blame someone else). Then present the options to the home owner, with the blame not apportioned to you.

We don't know that it needs 10mm cable do we? Daz

 

[Midwest]

True, but it's not looking good though, OP mentioned his concern about insulation. Even with just 100mm that pops it down to 34a.

 

[snowhead]

Is the switch being used to isolate the heater whilst on full load?

 

[telectrix]

that could bugger it. why not fit a 100A Wylex isolator.

https://www.tlc-direct.co.uk/Produc...=adwords&kw=&gclid=CL-A-bu6sckCFSQTwwodm78Flg

 

[DPG]

that could bugger it.

Very well described Tel. I like that. I shall look that reference up in BS7671 forthwith. Daz

 

[Octopus]

that could bugger it. why not fit a 100A Wylex isolator.

https://www.tlc-direct.co.uk/Produc...=adwords&kw=&gclid=CL-A-bu6sckCFSQTwwodm78Flg

Hum.... nice feature on the wall .... NOT.

Surprised you can say bugger on here!

 

[telectrix]

look in definitions for bugger". maybe not in BS7671, you might find it in the Vatican Priests' handbook.

 

[DPG]

Can we all stop saying 'bugger' please. It's not on. Daz

 

[snowhead]

I'm thinking one of these, it'd last 3 times as long before total replacement..

Mem Exel 63A Switch fuse 3 phase isolator / disconnector with 63A fuses | eBay

 

[davesparks]

I've seen it happen a few times where the first switch has a loose connection causing it to burn out.
Then a muppet comes along to replace the switch but doesn't cut the burnt bit of conductor off and it causes another overheated connection