Oven Wiring

[noel shelleyParticipant @noelshelley55608]

For ferrules use small bore thin wall copper pipe as we use on our models ? As for undersize  wire, Look at the cost of copper,manufacturers are using the thinnest they can get away with, reduces safety but it ups the profit. The issue of lead/solder flowing when cold check out the workings of the time delay fuses developed by MI-R for SOE during WW2. Noel.

[Speedy Builder5Participant @speedybuilder5]

Perhaps I am a bit dim, but shouldn’t there have been a local fuse and isolating switch at the outlet, or is this above the work surface and what got burnt up was below the w/surface ?

[noel shelleyParticipant @noelshelley55608]

The problem was resistive heating not overload or short circuit. A fuse would have been little help and an isolator  done nothing. It could be said that the wire acted as a fuse ? Noel.

[Robert Atkinson 2Participant @robertatkinson2]

Both the crabtree and MK are superior to the BG. They both use “cage clamps” to secure the conductor unlike the single point screw of the BG / Nexus.

Under no circumstances should mains flex screw connections be “tinned” with solder. As pointed out the solder cold flows resulting in loose connections eventually.
It also has two other issues,

The copper dissolves in the solder increaing the resistanceThe thansition from soldered to unsoldered is a stress raiser and can cause fatigue failures.

Robert.

[Wink HackmanParticipant @winkhackman25989]

Speaking as a retired sparky, I’d say that the ferrules are not necessary. Tighten up the terminals firmly on the wire, without tinning it.  A month later, tighten them again – stranded wire always loosens over time. BG outlets are so-so, Crabtree are good.  MK used to be top quality but some of their stuff is variable nowadays.

[VicParticipant @vic]

In spite of this incident, I have every faith in the electrician. He seemed very thorough and didn’t rush to do anything, quite the opposite. As he quoted before the work I wasn’t paying by how long he spent on the job. He also supplied all the relevant paperwork required. I’ll be using him again at some point in the future for another couple of jobs.

[Speedy Builder5]

On Speedy Builder5 Said:

Perhaps I am a bit dim, but shouldn’t there have been a local fuse and isolating switch at the outlet, or is this above the work surface and what got burnt up was below the w/surface ?

The isolator is indeed above the oven near the worktop, it’s combined with a switched 13A outlet. The burnt out wire was behind the cooker.

[Robert Atkinson 2]

On Robert Atkinson 2 Said:

Both the crabtree and MK are superior to the BG. They both use “cage clamps” to secure the conductor unlike the single point screw of the BG.

Yes, I noticed that, that’s why I bought it. It does seem to be a better design.

[EmgeeParticipant @emgee]

Vic

Does that mean you don’t need the ferrules ?
Twisting and folding back the wire to terminate will work well with clamp type terminals.

On checking the cable size by calculation using your quoted figures of 32 strands of 0.22mm diam the conductor is only 1.25mm, your final circuit supply protective device is a 20A type B mcb which means the flexible cable to the cooker does not have the required protection.

Changing the mcb for a 16A would go some way but still not provide protection to the 1.25mm flex so I am surprised the cooker manufacturer has not supplied a larger size flexible connector.

Emgee

[VicParticipant @vic]

Thanks for the offer, I’ll try it without the ferrules. My cable looks very much like this, which they say is 1.5. My cable, when twisted measured about 1.45.

[EmgeeParticipant @emgee]

Vic

The conductor size is not the diameter but the cross sectional area (csa) in mmsq of all of the strands,
so in your case 32 of 0.22mm diam using pixrsq the csa is 1.25mmsq.

Emgee

[Emgee]

On Emgee Said:

Vic

The conductor size is not the diameter but the cross sectional area (csa) in mmsq of all of the strands,
so in your case 32 of 0.22mm diam using pixrsq the csa is 1.25mmsq.

Emgee

Rather light for a nominal 16A rating, is it not ?

MichaelG.

[Dave HalfordParticipant @davehalford22513]

As it’s a NEFF he conductor sqmm will be moulded into the sheath along with the spec that the cable conforms to.

The fact that the part# includes 1.5 may point to the sqmm

Oven cable is designed to run at higher temps that plain PVC twin and earth that bleeds fluid @ over 60C.

[Michael GilliganParticipant @michaelgilligan61133]

Happy to accept your assurances, Dave

My comment was based on the measurement and calculation of two Engineers

… which probably only goes to show how difficult it is to do.

MichaelG.

[VicParticipant @vic]

This is the oven plug on the NEFF supplied cable. It is marked 16/250 which I strongly suspect is the cable rating?

[Emgee]

On Emgee Said:

Vic

The conductor size is not the diameter but the cross sectional area (csa) in mmsq of all of the strands,
so in your case 32 of 0.22mm diam using pixrsq the csa is 1.25mmsq.

Emgee

I figured it would be something like that, just giving you the approximate physical size of the cable in case it helped the calculation.

[Author]

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