Burnt 6mm twin & earth

[BluSparx]

Been racking my brains all day and still can't figure out how a 6mm twin and earth has ended up burnt out as though having more current through than should the scenario

8.5kw/h electric shower
6mm2 t&e in trunking on wall
40a MCB with 30ma RCD Protected

The cable burnt at CU end and MCB has scorch marks

I cannot understand how the 8.5kw/h shower which pulls 36.95a at maximum heat protected by a 40amp breaker has scorch marks and the cable burnt, any ideas appreciated

 

[cagedanimal2010]

loose connection???

 

[Spudnik]

Loose connection.

 

[BluSparx]

That was my first thought but was in tight when i got there but hey new cable pulled and replaced MCB so all should be fine

 

[Spudnik]

The screw had probably seized and the cable welded itself in due to the heat build up, giving the impression that it was ok.

 

[BluSparx]

Cheers Jason, hadn't thought of that hopefully it is sorted now nice job for a callout on a sunday "i Smell burning from my fusebox"

 

[malcolmsanford]

Been racking my brains all day and still can't figure out how a 6mm twin and earth has ended up burnt out as though having more current through than should the scenario

8.5kw/h electric shower
6mm2 t&e in trunking on wall
40a MCB with 30ma RCD Protected

The cable burnt at CU end and MCB has scorch marks

I cannot understand how the 8.5kw/h shower which pulls 36.95a at maximum heat protected by a 40amp breaker has scorch marks and the cable burnt, any ideas appreciated

Your 6mm^ T+E erection method B is rated a 38 amps ................awfully close to that 37amp threshold, all you need is a semi loose connection, and you will start heating up. Change it to 10mm^ if it's in a trunking

 

[telectrix]

10mm is great if only the shower switches were designed for it!!! just had to replace a switch, 10mm cable, only one earth term . in switch, impossible to connect all strands, and this was a MK switch!!

 

[malcolmsanford]

10mm is great if only the shower switches were designed for it!!! just had to replace a switch, 10mm cable, only one earth term . in switch, impossible to connect all strands, and this was a MK switch!!

Was that a ceiling mounted double pole or wall mounted double pole?

 

[beaver74]

Your 6mm^ T+E erection method B is rated a 38 amps ................awfully close to that 37amp threshold, all you need is a semi loose connection, and you will start heating up. Change it to 10mm^ if it's in a trunking

beat me to it

 

[telectrix]

ceiling mounted pull switch. even the knock-out in the patress was too small to get outer sheths of 2x 10mm thru

 

[sjm]

For 10mm cable ceiling mounted pull switch I only fit the crabtree 50 amp switch. Perfectly designed for 10mm cable. Also when the cover is removed it removes the neon as well. Nice to see something designed with US in mind.