Washing machine on extension

[SUNRAY]

I've never seen on like that, as a top ring, our rings were metal slabs, apart from the grill, which used bare wire. To rewire them, you didn't 'stretch as you went' - you measured the length with string, then stretched the element to match the string length, so it was nice and even once in it's slot.

Yes the string was my method too.
That sort of arrangement used to exist in in ceramic/glass topped hobs but more recently it's rigid elements.

 

[JohnW2]

Yep I like to think I know all that. and have identified oferload of one end of a ring several times, one was blatantly predictable, the house owner had added a socket in his garage almost beside the CU, a 32A socket for the welder which he used a lot making wrought iron products.

As I said, even that ought not to harm any of the ring final cable. A welder is presumably not going to draw large currents for long periods of time and, as I said, Method C 2.5mm² cable is deemed to be able to safely carry about 39A for an hour, and appreciably more than that for shorter periods.

My first test was current clamp at MCB which at the time showed well over 32A and a very high percentage of that on one leg.

... as above, 2.5mm² can carry a lot of current for relatively short periods without coming to harm.

Kind Regards, John

 

[SUNRAY]

As I said, even that ought not to harm any of the ring final cable. A welder is presumably not going to draw large currents for long periods of time and, as I said, Method C 2.5mm² cable is deemed to be able to safely carry about 39A for an hour, and appreciably more than that for shorter periods.

That cable was well cooked but don't forget that was added to the ring, not the only load, also it may have easily been one of the circuits I've found with an oversized OCPD.

... as above, 2.5mm² can carry a lot of current for relatively short periods without coming to harm.

Kind Regards, John

This one showed slight evidence of heating at the clips on the vertical run where the insulation could be seen to have sagged slightly and settle on top of the clip.

 

[securespark]

I think that it must be very rare to see a domestic dryer or washer-dryer on a 'dedicated circuit'. I don't recall ever having seen that - have you?

Yeah, I've seen it a few times.

TD, WM, DW.

 

[JohnW2]

Yeah, I've seen it a few times.....TD, WM, DW.

Three separate 'dedicated' circuits, or two or three such appliances on the same 'non-dedicated' circuit?

In any event, even if the former, that's only a 'few times' - I suspect a tiny proportion of those domestic installations you've seen in which you've seen such appliances powered from (multi-socket) sockets circuits - is that the case?

Kind Regards, John

 

[JohnW2]

That cable was well cooked but don't forget that was added to the ring, not the only load, also it may have easily been one of the circuits I've found with an oversized OCPD.

Well, if the OCPD is 'oversized' (in relation to cable CSA), then it would be no surprise if the cable may, under some circumstances, get 'cooked'.

I don't know exactly what you would regard as constituting 'well cooked', but I would be surprised if Method C 2.5mm² cable protected by a B32 would get 'well cooked' (per my view of that term), no matter what loads were applied to the circuit.

Kind Regards, John

 

[SUNRAY]

Well, if the OCPD is 'oversized' (in relation to cable CSA), then it would be no surprise if the cable may, under some circumstances, get 'cooked'.

I don't know that it was, just mentioned it's not unknown.

I don't know exactly what you would regard as constituting 'well cooked', but I would be surprised if Method C 2.5mm² cable protected by a B32 would get 'well cooked' (per my view of that term), no matter what loads were applied to the circuit.

Kind Regards, John

To me overcooked means heated to the extent the insulation has significantly changed shape.
I'll try to see if I have pics on another laptop in a day or two.

 

[winston1]

True, but kettles are only on for very short periods of time. Don't forget that Method C 2.5mm² cable is deemed to be able to safely carry about 39A for one hour (and much higher currents for shorter periods), and even if the CCC of the cable (as installed) is the minimum allowed (20A) it is still deemed able to safely carry about 29A for an hour.

But you said:

Two (or more) 'large' loads connected close to one end of a ring can theoretically 'overload' the cable of the short leg of the ring, even if each of the loads is (legitimately) connected via a 13A plug.

Which contradicts. Two large loads being 2x13A.

 

[JohnW2]

But you said:

... Two (or more) 'large' loads connected close to one end of a ring can theoretically 'overload' the cable of the short leg of the ring, even if each of the loads is (legitimately) connected via a 13A plug.

Which contradicts.

No contradiction.

"Theoretical overloading" arises when the current through a cable exceeds its 'theoretical CCC' (i.e. as tabulated for relevant installation method and adjusted by any 'de-rating' factors) . However, as I wrote in the previous paragraph (which you seem to think is a contradiction) cables are deemed to be able to safely carry currents well above their "theoretical CCC" for substantial periods of time.

Two large loads being 2x13A.

What is your point/problem here? 2 x 13A loads 'could' (would) result in 'theoretical overload' of the short leg of a ring if the CCC of the cable were less than 26A (and CCC as low as 20A ia allowed for a ring final). "Two (or more)" 13A loads could result in such an overload even with a CCC of 27A.

Kind Regards, John

 

[JohnW2]

I don't know that it was, just mentioned it's not unknown.

I realise that, but was saying that if the OICPD were oversized, then that would be a different (additional)problem.

To me overcooked means heated to the extent the insulation has significantly changed shape.

Fair enough - but, as I said, I wouldn't really expect to see that with Method C 2.5mm² cable protected by a B32, regardless of what loads were applied. However, it sounds as if your experiences may differ.

Kind Regards, John

 

[winston1]

"Two (or more)" 13A loads could result in such an overload even with a CCC of 27A.

Kind Regards, John

Erm, isn't 26 less than 27?

 

[JohnW2]

Erm, isn't 26 less than 27?

It is. However (more than 2) x 13 is a lot greater than 27.

 

[Harry Bloomfield]

Erm, isn't 26 less than 27?

A ring has two ends, two cables, two directions of source.