help with old style head

Dean Williams · Jun 26, 2013

Hi folks
testing an old victorian townhouse today and found the DNO cutout as shown in the photo. the make is Asco, never seen one this old before.
it appears to be TNC-S (the first way is not used). At the head with test leads connected to line and neutral/earth linked i measured 0.20 ohms, which is acceptable but at the DB i measured 4.50, it seems there's no earth cable from link to DB. there's no bonding in the house either main, supplementary or otherwise.
anyone else found this. I'm guessing it was rewired in mid 60s due to style of wylex DB.

[ElectriciansForums.net] help with old style head

telectrix · Jun 26, 2013

your first thing is to get DNO to replace that head. it's free. ask them for pme.

Dean Williams · Jun 26, 2013

what puzzled me also is that there was a DNO sticker on the DB dated 2009 where they've fitted new tails and a 60947-3 switch!

telectrix · Jun 26, 2013

nothing about the antics of DNOs is puzzling. they make up the rules as they go along up until friday lunch time. then anything goes as long as they can knock off on time.

Dean Williams · Jun 26, 2013

also the head itself isnt earthed!

Richard Burns · Jun 26, 2013

From the age of the head I would have expected a TNS system, but it looks like there is no earth so is there an earth rod elsewhere?
Is there any sign of an old earth connection from the incoming sheath?
It is possible it was a fused line and neutral at one point and the neutral was redirected when the tails were changed.

Dean Williams · Jun 26, 2013

i thought it was tncs because of the little green box at the side of the big one. its the same make and age as the big one. thought there might have been a connection between the lead sheath and neutral. can't find a rod anywhere, maybe it was/is connected to water main?

Burnt Fingers · Jun 26, 2013

I saw exactly the same head in Harrogate the other day - Line was fused at "something amps" - Electrician could not get it out without fear of breaking it and the N was just a link (or a high current fuse lol). earth was on lead sheathing TNS and beautifully educational as you dont see many TNS here. DNO after eighty phone calls are going to replace it though.

Engineer54 · Jun 27, 2013

Dean Williams said:
i thought it was tncs because of the little green box at the side of the big one. its the same make and age as the big one. thought there might have been a connection between the lead sheath and neutral. can't find a rod anywhere, maybe it was/is connected to water main?

The cut-out may well have been adapted to cater originally for a 2 phase + N!! When this Cut -Out was being installed, i doubt very much if anyone would have heard of PME/TNC-S.

Where is the earth linked to the neutral that you talked about testing, as i can't see any main earthing conductor leaving this cut-out???

thomas-1981 · Jun 27, 2013

what puzzled me also is that there was a DNO sticker on the DB dated 2009 where they've fitted new tails and a 60947-3 switch!

So why have you opened up the cut out? I can see bitumen leaking below the fuse carrier, was this still soft? Could be a slack connection. Call the DNO ASAP.

Dean Williams · Jun 28, 2013

It was only held shut with a cable tie. I opened it to find out what earthing system it is . the bitumen is solid by the way.

Engineer54 · Jun 28, 2013

thomas-1981 said:
So why have you opened up the cut out? I can see bitumen leaking below the fuse carrier, was this still soft? Could be a slack connection. Call the DNO ASAP.

That's not leaking, that's roughly the expected bitumen pitch level you would see in one of these older pitch filled cut-out heads...

Burnt Fingers · Jun 28, 2013

The Harrogate one was held closed with the seal and wire. A cable tie would have been a great improvement.

onions1066 · Jun 28, 2013

With a title like that this thread had so much potential.......... I think I got the wrong end of the stick.

help with old style head

Dean Williams

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telectrix

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Dean Williams

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telectrix

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Dean Williams

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Richard Burns

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Dean Williams

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Burnt Fingers

Engineer54

thomas-1981

Dean Williams

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Engineer54

Burnt Fingers

onions1066

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