30A junction box question

[steve1811uk]

I want to repair a damaged cable using a 30A 3 terminal 4x6mm sq MK junction box.

The damaged cable is 6 mm sq protected by a 32A MCB feeding a 5kW double oven.

Is this acceptable or not? I know that the total load current will not exceed 22A in use. But a fault current could exceed 30A (the junction box rating). Not sure about the rules for junction boxes. All help appreciated. Steve.

 

[mo2]

32Amcb 30A JB, I don't think so.


http://www.tlc-direct.co.uk/Products/AAJB60.html

 

[davy_owen_88]

30A junction boxes are the standard rating from when rewirable fuses were more common. MCB's react quicker so they replaced the 30A fuse wire with a 32A MCB.

The only junction box above 30A is 60A and that is overkill, you'll be fine with a 30A.

Davy

 

[sparkyspike]

What if someone decides to upgrade the oven and seeing the circuit is in 6mm uprates to a 40A breaker. They won't necessarily know that there is a 30A JB in the circuit!

 

[davy_owen_88]

JB's should be accessible and before upgrading the CPD the whole circuit should be inspected to make sure it is safe to do so, but I do see your point, some people are idiots

For a cooker circuit I would suggest replacing the cable entirely anyway but if this isn't an option ensure the junction box is accessible and leave a note at the CU stating a 30A junction box is in use on the cooker circuit, or just fit the 60A JB.

Davy

 

[ricicle]

'Bout time someone made a 45A JB

 

[steve1811uk]

Thanks for the comments. I do see your points. The cable in question is in fact damaged within 4 inches of the CU and I will make the Junction box visible. I would replace the cable if it were easy enough to do but it is in plaster without any slack. I could replace the MCB with a 25A one if that would help.

 

[securespark]

With all due respect, I don't feel mo2's comments are valid.

If that were true, you would not be able to use a 5A junction box (or connector blocks or accessory) on a 6A circuit, or 15A connector blocks on a 16A circuit etc...