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Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]



 
 
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  #1  
Old October 27th 09, 01:50 PM posted to uk.d-i-y
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Posts: 59
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]

Hi,

I need to move 6 circuits from an old CU (which will be removed) to a new
one (which is already installed).

2 x ring main (32 Amp)
1 x Simple spur (15 Amp, to boiler and controls)
3 x lighting (5 Amp)

The problem is that I will need to extend the existing cabling by about 2
feet to the new CU.

I intend to use IMO DIN components / IP66 enclosure which I will install at
the location of the (old) CU.

My question arises from this pic I found (posted by Andy)
http://www.cucumber.demon.co.uk/cu1.jpg and concerns the ring main circuits:

QUESTION

Given that the CU and the DIN rail will be separated, should I extend the
ring circuits using 2 x 2.5mm T&E cables so they meet at the new CU? Or
is it valid to run single 4.0mm T&E from junction box to new CU (essentially
as in the picture)?


D


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  #2  
Old October 27th 09, 02:46 PM posted to uk.d-i-y
external usenet poster
 
Posts: 9,206
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]

In article ,
"Vortex4" writes:
Hi,

I need to move 6 circuits from an old CU (which will be removed) to a new
one (which is already installed).

2 x ring main (32 Amp)
1 x Simple spur (15 Amp, to boiler and controls)
3 x lighting (5 Amp)

The problem is that I will need to extend the existing cabling by about 2
feet to the new CU.

I intend to use IMO DIN components / IP66 enclosure which I will install at
the location of the (old) CU.

My question arises from this pic I found (posted by Andy)
http://www.cucumber.demon.co.uk/cu1.jpg and concerns the ring main circuits:

QUESTION

Given that the CU and the DIN rail will be separated, should I extend the
ring circuits using 2 x 2.5mm T&E cables so they meet at the new CU? Or
is it valid to run single 4.0mm T&E from junction box to new CU (essentially
as in the picture)?


You can use 4.0mm T&E (although I actually used 6mm, and that's going
to be better where you might have cable grouping, and it's more common).

One concern might be the single earth, whereas a ring has two separate
earth routes. However, what's not so obvious in the picture is that
all the DIN rail earth terminals also connect to the DIN rail, so
actually there are 4 paralleled earth connections from the DIN rail
back to the main earthing terminal. Were it not for this, I would
say that if you are using a single 4mm or 6mm T&E branch to a ring
circuit, I would add a second earth connection in parallel with the
integral earth in the T&E for redundancy.

The other suggestion I would make -- use one size larger DIN rail
terminal than you might think you need, particularly where multiple
conductors are being connected. When a DIN terminal says 2.5mm (or
whatever), it really means it - there's no spare space in the
terminal at all.

Also, it would have been easier if I'd used a larger box for making
the cable connections at the top.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  #3  
Old October 27th 09, 04:11 PM posted to uk.d-i-y
external usenet poster
 
Posts: 1,005
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]

Andrew Gabriel
wibbled on Tuesday 27 October 2009 13:46


One concern might be the single earth, whereas a ring has two separate
earth routes. However, what's not so obvious in the picture is that
all the DIN rail earth terminals also connect to the DIN rail, so
actually there are 4 paralleled earth connections from the DIN rail
back to the main earthing terminal. Were it not for this, I would
say that if you are using a single 4mm or 6mm T&E branch to a ring
circuit, I would add a second earth connection in parallel with the
integral earth in the T&E for redundancy.


Andrew,

How do you rate the electrical integrity of the DIN rail to earth clamp?

I have bought some RS terminals for my lighting junction boxes, and I was
considering relying on the DIN rail to common the earth terminals. Whilst
this appears to be the intention, do you consider it sufficient?

Cheers

Tim

BTW - to the OP:

The RS own brand DIN terminals are very well made and are one of the best
priced I could find.


--
Tim Watts

This space intentionally left blank...

  #4  
Old October 28th 09, 10:05 AM posted to uk.d-i-y
external usenet poster
 
Posts: 59
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]


"Andrew Gabriel" wrote in message
...
In article ,
"Vortex4" writes:
Hi,

I need to move 6 circuits from an old CU (which will be removed) to a
new
one (which is already installed).

2 x ring main (32 Amp)
1 x Simple spur (15 Amp, to boiler and controls)
3 x lighting (5 Amp)

The problem is that I will need to extend the existing cabling by about 2
feet to the new CU.

I intend to use IMO DIN components / IP66 enclosure which I will install
at
the location of the (old) CU.

My question arises from this pic I found (posted by Andy)
http://www.cucumber.demon.co.uk/cu1.jpg and concerns the ring main
circuits:

QUESTION

Given that the CU and the DIN rail will be separated, should I extend the
ring circuits using 2 x 2.5mm T&E cables so they meet at the new CU?
Or
is it valid to run single 4.0mm T&E from junction box to new CU
(essentially
as in the picture)?


You can use 4.0mm T&E (although I actually used 6mm, and that's going
to be better where you might have cable grouping, and it's more common).

One concern might be the single earth, whereas a ring has two separate
earth routes. However, what's not so obvious in the picture is that
all the DIN rail earth terminals also connect to the DIN rail, so
actually there are 4 paralleled earth connections from the DIN rail
back to the main earthing terminal. Were it not for this, I would
say that if you are using a single 4mm or 6mm T&E branch to a ring
circuit, I would add a second earth connection in parallel with the
integral earth in the T&E for redundancy.

The other suggestion I would make -- use one size larger DIN rail
terminal than you might think you need, particularly where multiple
conductors are being connected. When a DIN terminal says 2.5mm (or
whatever), it really means it - there's no spare space in the
terminal at all.

Also, it would have been easier if I'd used a larger box for making
the cable connections at the top.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]


Thanks for the input Andrew,

I had not considered the earth redundancy via the DIN rail.

D

  #5  
Old October 29th 09, 01:59 PM posted to uk.d-i-y
external usenet poster
 
Posts: 9,206
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]

In article ,
Tim W writes:
Andrew Gabriel
wibbled on Tuesday 27 October 2009 13:46


One concern might be the single earth, whereas a ring has two separate
earth routes. However, what's not so obvious in the picture is that
all the DIN rail earth terminals also connect to the DIN rail, so
actually there are 4 paralleled earth connections from the DIN rail
back to the main earthing terminal. Were it not for this, I would
say that if you are using a single 4mm or 6mm T&E branch to a ring
circuit, I would add a second earth connection in parallel with the
integral earth in the T&E for redundancy.


Andrew,

How do you rate the electrical integrity of the DIN rail to earth clamp?

I have bought some RS terminals for my lighting junction boxes, and I was
considering relying on the DIN rail to common the earth terminals. Whilst
this appears to be the intention, do you consider it sufficient?


I wouldn't rely on it without finding a suitable product spec
and/or BS/EN reference.

--
Andrew Gabriel
[email address is not usable -- followup in the newsgroup]
  #6  
Old October 29th 09, 02:11 PM posted to uk.d-i-y
external usenet poster
 
Posts: 1,005
Default Moving a Consumer Unit. Cable extension "best practice" question. [PING Andy Gabriel]

Andrew Gabriel
wibbled on Thursday 29 October 2009 12:59


How do you rate the electrical integrity of the DIN rail to earth clamp?

I have bought some RS terminals for my lighting junction boxes, and I was
considering relying on the DIN rail to common the earth terminals. Whilst
this appears to be the intention, do you consider it sufficient?


I wouldn't rely on it without finding a suitable product spec
and/or BS/EN reference.


Hmm. Suppose I'd better daisychain some link wires down one side. Wish I'd
saved the money and just used simple 30p yellow terminals

Unless there is a BS/EN reference. Any tips on how I might go about
searching for this - is there a BS for "Earthing Integrity"?

--
Tim Watts

This space intentionally left blank...

 




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