Phenolic material used in cutouts etc, i.e. Bakelite.

[ericmark]

A rather long YouTube video

but it raises issues, where the cutout is in doors. What is the point of metal consumer units when we have next to them Phenolic material used for the DNO head.

 

[JohnW2]

A rather long YouTube video .....] but it raises issues, where the cutout is in doors. What is the point of metal consumer units when we have next to them Phenolic material used for the DNO head.

Interesting - but have you ever seen a case of "phenolic degradation" in relation to anything electrical?

 

[SUNRAY]

Interesting - but have you ever seen a case of "phenolic degradation" in relation to anything electrical?

I have encountered damage looking much like those shown but have always attributed the overheating to bad connexions or underrated components... It does make me wonder if my faultfinding is faulty.

 

[JohnW2]

I have encountered damage looking much like those shown but have always attributed the overheating to bad connexions or underrated components... It does make me wonder if my faultfinding is faulty.

Maybe, but maybe your fault finding was not faulty!

 

[SUNRAY]

Maybe, but maybe your fault finding was not faulty!

I suspect you comment is not faulty either

 

[SUNRAY]

Interesting - but have you ever seen a case of "phenolic degradation" in relation to anything electrical?

I did discover that perspex is not an insulator at 400W of Band II.

 

[ericmark]

Maybe, but maybe your fault finding was not faulty!

This was the main point made in the talk, have we blamed the wrong thing on failures? I do remember when cars had a distributor, and problems with tracking on the distributor cap, and when I could not get a replacement, how drilling a hole through the track would keep it going for a time.

As far as plastic consumer units go, I think the problem was due to the terminal not being forced open with some makes, and the MCB pressing against the bus bar rather than being clamped, also some simply not being torqued up.

I attended one home, where the phones were not working as they should. It turned out a consumer unit had been ordered, and the supplier had put the MCB's in the CU, so one item needed to be carried to the van, but the electrician has assumed that it had come populated, so did not check terminals which he had not connected to, and all the bus bar connections were loose, yes it does say test all terminals are torqued up, but can also see why the electrician never checked them. Lucky no damage, torqued them all up, and phones worked without a problem.

As to if faults like this would be found in an EICR, not sure, I know the "service of a batching plant" was in the main testing each terminal torqued up, but with a metal frame, more likely to vibrate loose.

I have also seen poorly finished screws causing a problem, they were tight in the thread, so the torque screwdriver did not tighten them enough, would have likely felt it with a standard screwdriver, but the torque screwdriver masked the problem. And once heated up and cooled, then the screw was loose, so electrician blamed, well suppose he should have tested the terminal first, but also should be a factory test as well. He lost his job over that, maybe a good thing, as he has a degree now and working as an electrical engineer.

But I do not rely on torque screwdrivers any more.

 

[JohnW2]

I did discover that perspex is not an insulator at 400W of Band II.

Do you mean that it does not stop RF getting through it? If so, I would have thought that was true of most 'plastics', isn't it?

 

[SUNRAY]

Do you mean that it does not stop RF getting through it? If so, I would have thought that was true of most 'plastics', isn't it?

No, the Pi tank filter was built on Perspex (the real thing) and it tracked across from 'hot' to a mounting screw, I'd say well over an inch.

 

[JohnW2]

This was the main point made in the talk, have we blamed the wrong thing on failures?

Yes, but I was really making the opposite point to that - that maybe we (including Sunray) have been 'blaming the right thing' (overheating) in most cases and that it may be that, in most cases, it is attribution of damage to 'phenolic degradation' that is 'wrong'.

But I do not rely on torque screwdrivers any more.

It seems pretty odd, but I have never relied on them since I discovered how 'loose' (as judged by a hand and screwdriver!) MCB terminals were when tightened to the recommended torque!

 

[mattylad]

Our very own JW (Flameport) in that video and sadly Paul Skerm passed at a great loss to the electrical industry.

Phenolic is an amazing material that has lasted a very long time, but like everything it can only last so long until problems arise.
The modern replacement (plastic) won't (IMO) even last a fraction of how long that stuff lasted.

 

[JohnW2]

No, the Pi tank filter was built on Perspex (the real thing) and it tracked across from 'hot' to a mounting screw, I'd say well over an inch.

That's odd - I've done that countless times. However, I imagine that 'tracking across' is rather different from 'being electrically conducted through' a material - are you sure that there was not something, like 'grease' (maybe from a finger) on the surface of the Perspex?

In terms of 'electrical conduction through it', the dielectric strength of Perspex is something like 15 kV/mm.

 

[JohnW2]

Phenolic is an amazing material that has lasted a very long time, but like everything it can only last so long until problems arise. The modern replacement (plastic) won't (IMO) even last a fraction of how long that stuff lasted.

Probably true, but I suspect that the urea-formaldehyde resins used for most electrical accessories might last 'for ever' unless they are abused!