Overload protection omission

[tester11]

Hi folks, not posted in a while but I have been having a few interesting discussions about this one !!!

I have come across a cooker connection outlet which is wired in 6mm and supplied via 45a dp sw and a 32a MCB

Now in this outlet I have an oven at 3kw wired in 2.5mm HOFR and a sparker for the hob wired in 1mm flex.

Guy from work reckons this is a C1 as the 2 cables are not rated to 32 amps. I disagree with him, While I think it is bad practice and would probably fit dual box with 2 s skts or spurs.

My take on it though is it could probably be coded c3 due to the fact that the oven and sparker will not draw anymore load than what they are rated at and the cables supplying them are adequate for that load hence overload protection may be omitted. As long as my circuit complies with fault protection requirements, it is not best practice and I would improve but would it warrant a C2 or C1!! And an unsatisfactory EICR ?? In my opinion no. But I have heard a few different opinions on this one !!!

 

[Octopus]

What you describe is NOT a C1 - a C1 is danger NOW.... i.e live components that can be touched.

Could be a C2 BUT you can reduce the CSA of a cable and as long as the cable is less than 2 meters - so no code.

If I did the EICR, I would probably comment on the set up to CMA

 

[bigspark17]

Yes i agree with @Murdoch. I would c3 it on the observations sheet.

 

[tester11]

Yeah I am of the same opinion. Defo not C1 or C2!!!

 

[westward10]

Does the ignition circuit cable incorporate a cpc. Have you considered short circuit protection between line/neutral, I would personally C2 this.

 

[westward10]

You also need to consider the 2.5 and 1.0 connected to the same terminal.

 

[tester11]

Does the ignition circuit cable incorporate a cpc. Have you considered short circuit protection between line/neutral, I would personally C2 this.

There is a CPC in the sparker cable yeah, with regards to l/n short circuit is that going to be an issue over 2m of cable ? I am no an engineer so not sure, but is the situation any different from a 2.5mm spurred of a ring on a 32a MCB ? This could easily be more than 2m long ?

 

[westward10]

You need to consider the magnitude of fault current on the 1.0 cpc regardless of cable length. Conductor csa should be selected so it can withstand fault current with no adverse effects.

 

[Ian1981]

What is this 2 meter rule?
I'm aware of fault protection and overload protection being placed on the load side at a maximum Of 3 meters when there is a reduced ccc or reduction in CSA and 2 other considerations required but not sure on this 2 meters?

 

[bigspark17]

You need to consider the magnitude of fault current on the 1.0 cpc regardless of cable length. Conductor csa should be selected so it can withstand fault current with no adverse effects.

If max zs is achieved and theres no visual thermal damage i dont see how you can c2 this

 

[westward10]

If max zs is achieved and theres no visual thermal damage i dont see how you can c2 this

The cpc must be capable of carrying fault current without suffering thermal damage, Zs is irrelevant.

 

[Ian1981]

Would be time to do everyone's favourite adiabatic equation to see if the thermal constraints of the 1.0mm are adequate for a32amp mcb.
Or if the let through energy is Less than the formula K2S2 => I2t
Bit of a chew on really

 

[Wilko]

With no sign of damage I would C3 it, on the basis that it would work, once at least.

 

[telectrix]

C 2 ½

 

[soms]

Had a quick look in the BYB. The '3m rule' is to do with reg 433.2.2.
Something for me to read in a bit more detail and compare against fault protection requirements sometime.

 

[Ian1981]

Had a quick look in the BYB. The '3m rule' is to do with reg 433.2.2.
Something for me to read in a bit more detail and compare against fault protection requirements sometime.

The '3 meter rule as it were comes with 2 other stipulations so all 3 have to be met to comply not just the fact it's under 3 meters and fault/overload protection still needs to be installed after the '3 meters' protecting the load side

 

[westward10]

Aside from it not being provided with suitable circuit protection I find it difficult to believe it is actually correctly restrained at the outlet plate.

 

[Ian1981]

Aside from it not being provided with suitable circuit protection I find it difficult to believe it is actually correctly restrained at the outlet plate.

imagine trying to get 1.0mm flex into 45amp cooker outlet terminals

 

[Lucien Nunes]

It's not only the flex you can see - how do you know what kind of wiring is inside between the input and the internal fuse? The hob manufacturers will have considered this when stipulating the required protection and I doubt the their instructions permit fusing at 32A. You only have to take the MI into account, but you would be hard pressed to justify ignoring their recommended max S/C protection.

 

[westward10]

imagine trying to get 1.0mm flex into 45amp cooker outlet terminals

Just strip back a meter of copper and fold it over thirty times