Oven cable melted cable and casing - can't work out why

[SashaWu]

When two things touch, only a very tiny area of material makes contact - the rest of the surface is separated by a thin film of air / grease / tarnish. An electrical connection needs a minimum cross-section of copper-to-copper contact to carry the current, just like a cable needs a minimum cross section. When you clamp a terminal tightly, it squeezes out air and moisture and dirt as the metal cold-flows into position. Only once that has happened is the contact area large enough to carry the current involved here.

Oh - I had no idea about that at all. Thank you very much for your help.

 

[marconi]

duplicate post

 

[marconi]

You have also, I think, not recognised that the terminal type requires a fork termination to be made, whereby the strands of each live conductors are separated to form two similar prongs, which are then inserted left and right of the nut and bolt, thereby maximising the amount of surface area in electrical contact. You have simply inserted to one side of the nut and bolt.

 

[marconi]

It needs to be a good connection because at 30Amps around 200 million million million electrons are passing (actually drifting) through it every second.

 

[HandySparks]

You have also, I think, not recognised that the terminal type requires a fork termination to be made, whereby the strands of each live conductors are separated to form two similar prongs, which are then inserted left and right of the nut and bolt, thereby maximising the amount of surface area in electrical contact. You have simply inserted to one side of the nut and bolt.

These terminals typically have a plastic shroud with one access hole per terminal for the conductor. They're not very good. You just have to do them up as tight as you dare without stripping the thread.

 

[MFS Electrical]

The connection was insecure and of high resistance; the heat has melted the plastic housing and probably allowed the terminal to short-circuit to the metal casing. It's not clear whether your side of the connection was at fault or the internal one(s) hence Marconi's question. From the pattern of burning, I think it's your connection.

Common causes are crossed threads - the nut feels tight but isn't clamping the cable or cable not in position so that it creeps out from under the washer. Did you give it a good tug-test after fitting?

I agree and you can’t beat a good tug test