2 heads are better than 1?

Pretty Mouth · Jun 26, 2021

Came across this recently, haven't seen it before. External meter cupboard serving a ground floor maisonette. Early 1960s I'd say (there was no CPC on the lighting circuit, which was wired in PVC pirelli sheathed singles).

I'm guessing that at some point in the distant past the supply was due to be replaced, and the new and old supplies were joined for continuity of supply at switchover. Non contact volt stick suggests both fuses are still live, but obviously take that with a pinch of salt. Can anyone shed any light?

Dustydazzler · Jun 26, 2021

Interesting

I don’t think I have ever seen a spur off 1 cut out (presuming the original cutout) to feed another cut out like that before

nice find

timhoward · Jun 26, 2021

Very interesting. If both are live it gets a bit interesting regarding fault protection.
It couldn’t be that one of them is a lower fuse and outgoing to somewhere else, surely?!

I’m still trying to work out earthing and what’s going with the henleys on the left.
A good photo, hours of pondering material!

timhoward · Jun 26, 2021

Could top one just have links in, and this is a very wacky and strange way to do a looped supply?
Maybe something unmetered like a row of lamp posts or bus shelter?

Lucien Nunes · Jun 26, 2021

Agree that one surely must be outgoing. There's no reason on a domestic supply to do anything special to avoid interruption during a changeover.

Pretty Mouth said:
Non contact volt stick suggests both fuses are still live, but obviously take that with a pinch of salt.

No reason to pinch any salt. If your Voltstick is working properly and you know how to use it, they are a reliable and useful tool. The reason people say they are inherently unreliable is that they don't understand how they work and what they detect, therefore misinterpret the indications.

If both carriers contain a fuse then they will both be live because they are connected together. You can discover the configuration by clamping the cable and changing the load on the local meter. If the current in the link cable changes by the same amount, the top one is the supply,. If it doesn't change, the bottom one is the supply, If it changes by a fraction of the load change in a repeatable way, both are energised supplies.

snowhead · Jun 26, 2021

I would say that these were Local Authority built and the (reverse fed) cut out on the left is an unmetered but assessed supply to external lighting, posts or on walls on walkways.

Looks like the single green, lower left goes down to the sheath on the lower incoming supply cable.

Additional info which may or may not be usefull.
A friend recently bought a ground floor maisonette.
Outside there is a larger external meter box with 2 cutouts and 2 meters, 1 up 1 down.

The supply from meter to upstairs originally went though into the lower Maisonette then up a service void to above.
This has been cut off and an SWA runs up the outside.

The gas was the same, upstairs ran into the lower then up.
This now has a pipe up the outside.

This is one of 8 and has external lighting fed via a meter in another external box, all 8 split the bill between them.
These were privately built in the 70's.

Mikegh · Jun 26, 2021

Lucien Nunes said:
Agree that one surely must be outgoing. There's no reason on a domestic supply to do anything special to avoid interruption during a changeover.

No reason to pinch any salt. If your Voltstick is working properly and you know how to use it, they are a reliable and useful tool. The reason people say they are inherently unreliable is that they don't understand how they work and what they detect, therefore misinterpret the indications.

If both carriers contain a fuse then they will both be live because they are connected together. You can discover the configuration by clamping the cable and changing the load on the local meter. If the current in the link cable changes by the same amount, the top one is the supply,. If it doesn't change, the bottom one is the supply, If it changes by a fraction of the load change in a repeatable way, both are energised supplies.

Agree about the voltstick, an electricians best friend tbh

First item in my armoury for troubleshooting and checking for live/dead especially at sealed cabinets

I keep 2 in my back pocket

Pretty Mouth · Jun 26, 2021

Thanks for the replies. I hadn't entertained the idea that i was looking at 'one in, one out', but of course that would make sense. I have to go back there briefly on Thursday, so will have a closer look, and try to work out the configuration as per @Lucien Nunes 's instructions.

Lucien Nunes said:
No reason to pinch any salt. If your Voltstick is working properly and you know how to use it, they are a reliable and useful tool. The reason people say they are inherently unreliable is that they don't understand how they work and what they detect, therefore misinterpret the indications.

This was me, until a very short while ago. Have just been reading up on them here:

How does a Volt Stick work?

A detailed explanation of the technology behind non-contact voltage testers - Volt Sticks; how do they work and when false readings might occur.

voltstick.com

Very useful indeed. Particularly when you lift floorboards and you're faced with a dozen cables, and you need to identify which one belongs to a particular circuit.

Mikegh · Jun 26, 2021

Pretty Mouth said:
Thanks for the replies. I hadn't entertained the idea that i was looking at 'one in, one out', but of course that would make sense. I have to go back there briefly on Thursday, so will have a closer look, and try to work out the configuration as per @Lucien Nunes 's instructions.

This was me, until a very short while ago. Have just been reading up on them here:

How does a Volt Stick work?

A detailed explanation of the technology behind non-contact voltage testers - Volt Sticks; how do they work and when false readings might occur.

voltstick.com

Very useful indeed. Particularly when you lift floorboards and you're faced with a dozen cables, and you need to identify which one belongs to a particular circuit.

Also you can't 'prove' dead with a voltstick

But at the same time proving dead with a 2-wire tester assumes there is actually a reference(N/E) for the 2-wire voltage tester

Lucien Nunes · Jun 30, 2021

An important point that many people miss. A Voltstick can reliably indicate that something is live even when the best available reference for a 2-lead tester is not trustworthy.

UNG · Jun 30, 2021

With the great debate over the reliability neon screwdrivers and volt sticks I find one of these very useful for single point testing

loz2754 · Jun 30, 2021

The new Megger MET1000 can also be used as a single point contact voltage indicator. Can be quite useful.

timhoward · Jun 30, 2021

My two pole fluke t110 puts a light on even without the reference connected so behaves a bit like a one pole in that regard.
I also have a older martindale vt7 one pole contact tester and agree it’s very useful, it claims to indicate 50v or higher.
(I was surprised to find that a water pipe to a shower made it light dimly last night so need to find out what that’s all about, probably induction and no bonding but worth checking!)

Mikegh · Jun 30, 2021

UNG said:
With the great debate over the reliability neon screwdrivers and volt sticks I find one of these very useful for single point testing

I'll be getting one of these
I take it they work well

UNG · Jun 30, 2021

Mikegh said:
I'll be getting one of these
I take it they work well

Yes a very useful piece of kit, a word of warning though the tip is very sharp if you drop I don't recommend trying to catch it I ended up with the tip stuck in the side of my hand

nicebutdim · Jun 30, 2021

UNG said:
Yes a very useful piece of kit, a word of warning though the tip is very sharp if you drop I don't recommend trying to catch it I ended up with the tip stuck in the side of my hand

I have one from back when they were named EPF30 and that tip is still as sharp as it ever was.