Another one to mull over....


NT



The CU, Consumer Unit or Fusebox provides overcurrent protection for
all a house's electical circuits. It usually contains a switch to
control all the circuits, and many also feature leakage current
protection with [[RCD]] or [[RCD|RCBO]]s.


==Split Load CU==
A split load CU has 2 halves with separate power switches. So some of
your wiring can be turned off while the rest stays on. So whatever may
happen with your electrical system, you don't need to turn it all off.
This enables you to have power in the event of a fault, and to have
power while working on the installation itself. (There are exceptions
of course, such as lightning strike or a major fire.)

Split load CUs are common today (especially with wiring compliant with
the 17th edition of the wiring [[regs]]), and can be recommended in
nearly all cases.


==Upgrades==
Its often assumed that, being newer, [[MCB]]s provide better safety
than [[fuse]]s, but the level of protection both provide is very
similar, and both have minor pros and cons.

The main ways in which CUs can be upgraded a
* Fitting a split load unit
* Elimination of touchable live parts, as found
** on many CUs when fuses are pulled,
** always live parts are common on pre-war fuseboxes, though these
aren't often seen now
* Incorporation of leakage protection
** with [[RCD]](s)
** with circuit discrimination using RCBOs
* Increasing the number of circuits rather than extending existing
ones
* Adding provision for a shower, cooker, or other high current load
* Providing a separate feed for an outbuilding
* Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
* Replacement of an inadequate, damaged or faulty CU
* Making an old installation look modern

===Upgrading CUs on TT installs===
A little care is required over earth leakage protection when replacing
a CU on a [[Earthing Types|TT install]], as a CU setup not
specifically suited to TT use is likely to leave the system dangerous.


==MCBs & Fuses==

===Ratings===
* Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
* Immersion heater: 15/16A
* Socket circuits, ring: 30A fuse, 32A MCB
* Socket circuits, radial: 20A
* Cooker, shower: Usually 45A or more
* Small loads: 2.5A, 5A, 6A.

For information on type B, C and D MCBs, see [[MCB]]

==Live parts==
A lot of fuseboxes/CUs are in use that expose the user to live parts
if fuses are pulled with the power on. Always turn power off before
pulling a [[fuse]].

===Working on the CU===
The switch in the CU is the main power switch for most houses. Thus
exposed wiring will be live when the CU cover is removed, even with
the switch off. Removing the main supply fuse before the meter solves
this, but is illlegal, but its common practice nonetheless. Power
companies have so far not objected to the practice, for an assortment
of legal, safety and financial reasons.

==Trips==
Tripping or repeated fuse blowing are normally caused by a fault
outside of the CU itself.
* RCD trips are usually caused by a faulty appliance or a less than
ideal installation design. See [[RCD]]
* [[MCB]] trips are most commonly caused by blowing filament bulbs.
Faulty appliances often also cause this.
* RCBO trips may be due to either of the causes above, since an RCBO
combines the functions of both MCB and RCD.

There are of course other possible causes of trips and blown fuses,
the above is just a pointer to the most likely.


==Brands==
Ashley

Contactum

MK

Wickes

Wylex
* Cheap & basic Wylex fuseboxes are very common in existing installs
* Fuses expose live parts if pulled with power on
* Overheating occasionally happens on high current circuit fuses
(greater than 30A)


==See Also==
* [[House Wiring for Beginners]]
* [[Rewiring Tips]]
* [[:Category:Electrical|Electrical articles]]
* [[Special:Allpages|Wiki Contents]]
* [[Special:Categories|Wiki Subject Categories]]


[[Category:Electrical]]

wrote:

Another one to mull over....

I think much of the intro and theory of this is already covered in the
intro for:

http://wiki.diyfaq.org.uk/index.php?..._consumer_unit

The CU, Consumer Unit or Fusebox provides overcurrent protection for
all a house's electical circuits. It usually contains a switch to

Always provides fault current protection, and usually (but not always)
provides overcurrent protection.

control all the circuits, and many also feature leakage current
protection with [[RCD]] or [[RCD|RCBO]]s.


==Split Load CU==
A split load CU has 2 halves with separate power switches. So some of

2 or more sections - 3 and 4 are now quite common.

your wiring can be turned off while the rest stays on. So whatever may
happen with your electrical system, you don't need to turn it all off.
This enables you to have power in the event of a fault, and to have
power while working on the installation itself. (There are exceptions
of course, such as lightning strike or a major fire.)

Split load CUs are common today (especially with wiring compliant with
the 17th edition of the wiring [[regs]]), and can be recommended in
nearly all cases.


==Upgrades==
Its often assumed that, being newer, [[MCB]]s provide better safety
than [[fuse]]s, but the level of protection both provide is very
similar, and both have minor pros and cons.

and some not so minor ones (like unprotected spurs when using imperial
spec T&E with re-wireable fuses).

http://wiki.diyfaq.org.uk/index.php?...f or_a_change




The main ways in which CUs can be upgraded a
* Fitting a split load unit
* Elimination of touchable live parts, as found
** on many CUs when fuses are pulled,
** always live parts are common on pre-war fuseboxes, though these
aren't often seen now
* Incorporation of leakage protection
** with [[RCD]](s)
** with circuit discrimination using RCBOs
* Increasing the number of circuits rather than extending existing
ones
* Adding provision for a shower, cooker, or other high current load
* Providing a separate feed for an outbuilding
* Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
* Replacement of an inadequate, damaged or faulty CU
* Making an old installation look modern

===Upgrading CUs on TT installs===
A little care is required over earth leakage protection when replacing
a CU on a [[Earthing Types|TT install]], as a CU setup not
specifically suited to TT use is likely to leave the system dangerous.

TT suitable is more down to what you fit in it (or before it) rather
than the CU itself. (having said that, one ought to use insulated CUs
for TT and not metal clad ones)

==MCBs & Fuses==

===Ratings===
* Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
* Immersion heater: 15/16A
* Socket circuits, ring: 30A fuse, 32A MCB
* Socket circuits, radial: 20A
* Cooker, shower: Usually 45A or more
* Small loads: 2.5A, 5A, 6A.

For information on type B, C and D MCBs, see [[MCB]]

==Live parts==
A lot of fuseboxes/CUs are in use that expose the user to live parts
if fuses are pulled with the power on. Always turn power off before
pulling a [[fuse]].

===Working on the CU===
The switch in the CU is the main power switch for most houses. Thus
exposed wiring will be live when the CU cover is removed, even with
the switch off. Removing the main supply fuse before the meter solves
this, but is illlegal, but its common practice nonetheless. Power
companies have so far not objected to the practice, for an assortment
of legal, safety and financial reasons.

==Trips==
Tripping or repeated fuse blowing are normally caused by a fault
outside of the CU itself.

I would be seriously worried if that were not the case!

* RCD trips are usually caused by a faulty appliance or a less than
ideal installation design. See [[RCD]]
* [[MCB]] trips are most commonly caused by blowing filament bulbs.
Faulty appliances often also cause this.

Never seen this - but it may be a phenomenon that only presents with
particularly stiff supplies.

* RCBO trips may be due to either of the causes above, since an RCBO
combines the functions of both MCB and RCD.

There are of course other possible causes of trips and blown fuses,
the above is just a pointer to the most likely.


I have a feeling it might be worth merging the front of this article
with that on the changing a CU one, and making it an intro to CUs article.

The changing a CU one could then just focus on the how and link to the
intro. This article could focus on the equipment specifics and also link
to the same into.


==Brands==
Ashley

Contactum

MK

Wickes

Wylex
* Cheap & basic Wylex fuseboxes are very common in existing installs
* Fuses expose live parts if pulled with power on
* Overheating occasionally happens on high current circuit fuses
(greater than 30A)



This section could be expanded into a quite substantial and useful "body
of experience" type article. I.e. not only the characteristics and
pros/cons of each CU brand, but also cover topics like
interchangeability of parts, and servicing older CUs where bespoke parts
are no longer available.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

John Rumm wrote:
wrote:

Another one to mull over....

I think much of the intro and theory of this is already covered in the
intro for:

http://wiki.diyfaq.org.uk/index.php?..._consumer_unit

Yes, a merge/resplit would be useful... maybe later.


The CU, Consumer Unit or Fusebox provides overcurrent protection for
all a house's electical circuits. It usually contains a switch to

Always provides fault current protection, and usually (but not always)
provides overcurrent protection.

fairy nuff

control all the circuits, and many also feature leakage current
protection with [[RCD]] or [[RCD|RCBO]]s.


==Split Load CU==
A split load CU has 2 halves with separate power switches. So some of

2 or more sections - 3 and 4 are now quite common.

your wiring can be turned off while the rest stays on. So whatever may
happen with your electrical system, you don't need to turn it all off.
This enables you to have power in the event of a fault, and to have
power while working on the installation itself. (There are exceptions
of course, such as lightning strike or a major fire.)

Split load CUs are common today (especially with wiring compliant with
the 17th edition of the wiring [[regs]]), and can be recommended in
nearly all cases.


==Upgrades==
Its often assumed that, being newer, [[MCB]]s provide better safety
than [[fuse]]s, but the level of protection both provide is very
similar, and both have minor pros and cons.

and some not so minor ones (like unprotected spurs when using imperial
spec T&E with re-wireable fuses).

http://wiki.diyfaq.org.uk/index.php?...f or_a_change




The main ways in which CUs can be upgraded a
* Fitting a split load unit
* Elimination of touchable live parts, as found
** on many CUs when fuses are pulled,
** always live parts are common on pre-war fuseboxes, though these
aren't often seen now
* Incorporation of leakage protection
** with [[RCD]](s)
** with circuit discrimination using RCBOs
* Increasing the number of circuits rather than extending existing
ones
* Adding provision for a shower, cooker, or other high current load
* Providing a separate feed for an outbuilding
* Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
* Replacement of an inadequate, damaged or faulty CU
* Making an old installation look modern

===Upgrading CUs on TT installs===
A little care is required over earth leakage protection when replacing
a CU on a [[Earthing Types|TT install]], as a CU setup not
specifically suited to TT use is likely to leave the system dangerous.

TT suitable is more down to what you fit in it (or before it) rather
than the CU itself. (having said that, one ought to use insulated CUs
for TT and not metal clad ones)

Hence why it says 'CU setup'. Some are unsuitable however you
configure them.


==MCBs & Fuses==

===Ratings===
* Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
* Immersion heater: 15/16A
* Socket circuits, ring: 30A fuse, 32A MCB
* Socket circuits, radial: 20A
* Cooker, shower: Usually 45A or more
* Small loads: 2.5A, 5A, 6A.

For information on type B, C and D MCBs, see [[MCB]]

==Live parts==
A lot of fuseboxes/CUs are in use that expose the user to live parts
if fuses are pulled with the power on. Always turn power off before
pulling a [[fuse]].

===Working on the CU===
The switch in the CU is the main power switch for most houses. Thus
exposed wiring will be live when the CU cover is removed, even with
the switch off. Removing the main supply fuse before the meter solves
this, but is illlegal, but its common practice nonetheless. Power
companies have so far not objected to the practice, for an assortment
of legal, safety and financial reasons.

==Trips==
Tripping or repeated fuse blowing are normally caused by a fault
outside of the CU itself.

I would be seriously worried if that were not the case!

RCDs fail


* RCD trips are usually caused by a faulty appliance or a less than
ideal installation design. See [[RCD]]
* [[MCB]] trips are most commonly caused by blowing filament bulbs.
Faulty appliances often also cause this.

Never seen this - but it may be a phenomenon that only presents with
particularly stiff supplies.

I'm surprised. A 30/32A MCB often blows quicker than a 13A fuse.


* RCBO trips may be due to either of the causes above, since an RCBO
combines the functions of both MCB and RCD.

There are of course other possible causes of trips and blown fuses,
the above is just a pointer to the most likely.


I have a feeling it might be worth merging the front of this article
with that on the changing a CU one, and making it an intro to CUs article.

The changing a CU one could then just focus on the how and link to the
intro. This article could focus on the equipment specifics and also link
to the same into.


==Brands==
Ashley

Contactum

MK

Wickes

Wylex
* Cheap & basic Wylex fuseboxes are very common in existing installs
* Fuses expose live parts if pulled with power on
* Overheating occasionally happens on high current circuit fuses
(greater than 30A)



This section could be expanded into a quite substantial and useful "body
of experience" type article. I.e. not only the characteristics and
pros/cons of each CU brand, but also cover topics like
interchangeability of parts, and servicing older CUs where bespoke parts
are no longer available.

Good point. Better to leave it there for the moment, until someone
decides to do that, or make it an almost empty article of its own?


NT

On 7 Mar, 06:44, John Rumm wrote:
wrote:
Another one to mull over....

I think much of the intro and theory of this is already covered in the
intro for:

http://wiki.diyfaq.org.uk/index.php?..._consumer_unit

The CU, Consumer Unit or Fusebox provides overcurrent protection for
all a house's electical circuits. It usually contains a switch to

Always provides fault current protection, and usually (but not always)
provides overcurrent protection.

control all the circuits, and many also feature leakage current
protection with [[RCD]] or [[RCD|RCBO]]s.

==Split Load CU==
A split load CU has 2 halves with separate power switches. So some of

2 or more sections - 3 and 4 are now quite common.

your wiring can be turned off while the rest stays on. So whatever may
happen with your electrical system, you don't need to turn it all off.
This enables you to have power in the event of a fault, and to have
power while working on the installation itself. (There are exceptions
of course, such as lightning strike or a major fire.)

Split load CUs are common today (especially with wiring compliant with
the 17th edition of the wiring [[regs]]), and can be recommended in
nearly all cases.

==Upgrades==
Its often assumed that, being newer, [[MCB]]s provide better safety
than [[fuse]]s, but the level of protection both provide is very
similar, and both have minor pros and cons.

and some not so minor ones (like unprotected spurs when using imperial
spec T&E with re-wireable fuses).

http://wiki.diyfaq.org.uk/index.php?...nsumer_unit#Re....





The main ways in which CUs can be upgraded a
* Fitting a split load unit
* Elimination of touchable live parts, as found
** on many CUs when fuses are pulled,
** always live parts are common on pre-war fuseboxes, though these
aren't often seen now
* Incorporation of leakage protection
** with [[RCD]](s)
** with circuit discrimination using RCBOs
* Increasing the number of circuits rather than extending existing
ones
* Adding provision for a shower, cooker, or other high current load
* Providing a separate feed for an outbuilding
* Replacement of 3kA retrofit MCBs with 6kA [[MCB]]s.
* Replacement of an inadequate, damaged or faulty CU
* Making an old installation look modern

===Upgrading CUs on TT installs===
A little care is required over earth leakage protection when replacing
a CU on a [[Earthing Types|TT install]], as a CU setup not
specifically suited to TT use is likely to leave the system dangerous.

TT suitable is more down to what you fit in it (or before it) rather
than the CU itself. (having said that, one ought to use insulated CUs
for TT and not metal clad ones)



==MCBs & Fuses==

===Ratings===
* Lighting: Usually 6A MCB or 5A fuse. 10A circuits are sometimes used
* Immersion heater: 15/16A
* Socket circuits, ring: 30A fuse, 32A MCB
* Socket circuits, radial: 20A
* Cooker, shower: Usually 45A or more
* Small loads: 2.5A, 5A, 6A.

For information on type B, C and D MCBs, see [[MCB]]

==Live parts==
A lot of fuseboxes/CUs are in use that expose the user to live parts
if fuses are pulled with the power on. Always turn power off before
pulling a [[fuse]].

===Working on the CU===
The switch in the CU is the main power switch for most houses. Thus
exposed wiring will be live when the CU cover is removed, even with
the switch off. Removing the main supply fuse before the meter solves
this, but is illlegal, but its common practice nonetheless. Power
companies have so far not objected to the practice, for an assortment
of legal, safety and financial reasons.

==Trips==
Tripping or repeated fuse blowing are normally caused by a fault
outside of the CU itself.

I would be seriously worried if that were not the case!

* RCD trips are usually caused by a faulty appliance or a less than
ideal installation design. See [[RCD]]
* [[MCB]] trips are most commonly caused by blowing filament bulbs.
Faulty appliances often also cause this.

Never seen this - but it may be a phenomenon that only presents with
particularly stiff supplies.

* RCBO trips may be due to either of the causes above, since an RCBO
combines the functions of both MCB and RCD.

There are of course other possible causes of trips and blown fuses,
the above is just a pointer to the most likely.

I have a feeling it might be worth merging the front of this article
with that on the changing a CU one, and making it an intro to CUs article..

The changing a CU one could then just focus on the how and link to the
intro. This article could focus on the equipment specifics and also link
to the same into.

==Brands==
Ashley

Contactum

MK

Wickes

Wylex
* Cheap & basic Wylex fuseboxes are very common in existing installs
* Fuses expose live parts if pulled with power on
* Overheating occasionally happens on high current circuit fuses
(greater than 30A)

This section could be expanded into a quite substantial and useful "body
of experience" type article. I.e. not only the characteristics and
pros/cons of each CU brand, but also cover topics like
interchangeability of parts, and servicing older CUs where bespoke parts
are no longer available.

--
Cheers,

John.

/================================================== ===============\
| * * * * *Internode Ltd - *http://www.internode.co.uk* * * * * *|
|-----------------------------------------------------------------|
| * * * *John Rumm - john(at)internode(dot)co(dot)uk * * * * * * *|
\================================================= ================/

John has I think picked up on the points I was concerned about.

The four that I noted was

your comment on split CU's (yes, 3 or 4 banks rather than just 2)
having separate power switches - this is incorrect as I have 3 split
CU's (one in the house and 1 in each outside area) and none have
separate switches.

You need to explain why TT earth requires a special CU - I'm not sure
that is correct either as my understanding is that as long as
everything is covered by an RCD/RCBO, nothing more is required.

Referring back to my first comment, somewhere near the end you mention
switching off the CU, but if it has several switches you should
indicate which one as you just say 'Switch off the CU...'

Beware of words like 'usually' - an RCD trip for instance is *always*
caused by a faulty device or faulty wiring, with the only unlikely
exception being a faulty RCD. I trust that the RCD article does
strongly advise a full investigation by a professional if the cause of
the tripping isn't immediately obvious.

Rob

Rob G wrote:
On 7 Mar, 06:44, John Rumm wrote:
wrote:

snip

John has I think picked up on the points I was concerned about.

The four that I noted was

your comment on split CU's (yes, 3 or 4 banks rather than just 2)
having separate power switches - this is incorrect as I have 3 split
CU's (one in the house and 1 in each outside area) and none have
separate switches.

then in what sense are they split? Or are you saying an RCD isnt a
switch?


You need to explain why TT earth requires a special CU - I'm not sure
that is correct either as my understanding is that as long as
everything is covered by an RCD/RCBO, nothing more is required.

Again it says 'CU setup'
An old Wylex fusebox with no rcd provision is not suitable to replace
a broken modern box
TT CUs should be plastic
And a single RCD only is not compliant


Referring back to my first comment, somewhere near the end you mention
switching off the CU, but if it has several switches you should
indicate which one as you just say 'Switch off the CU...'

Beware of words like 'usually' - an RCD trip for instance is *always*
caused by a faulty device or faulty wiring, with the only unlikely
exception being a faulty RCD.

So its not always


I trust that the RCD article does
strongly advise a full investigation by a professional if the cause of
the tripping isn't immediately obvious.

Perhaps you could explain why if you do it for yourself you'd become
incompetent.

FWIW most causes of RCD trips can be found perfectly safely by a
novice with £5 of equipment.


NT

wrote:

===Upgrading CUs on TT installs===
A little care is required over earth leakage protection when replacing
a CU on a [[Earthing Types|TT install]], as a CU setup not
specifically suited to TT use is likely to leave the system dangerous.
TT suitable is more down to what you fit in it (or before it) rather
than the CU itself. (having said that, one ought to use insulated CUs
for TT and not metal clad ones)

Hence why it says 'CU setup'. Some are unsuitable however you
configure them.


==Trips==
Tripping or repeated fuse blowing are normally caused by a fault
outside of the CU itself.
I would be seriously worried if that were not the case!

RCDs fail

Perhaps, but you were talking about fuses (and by association MCBs). A
fuse blowing repeatedly due to a fault within the CU would be worrying.

Never seen this - but it may be a phenomenon that only presents with
particularly stiff supplies.

Thinking about it - I have seen it once, but that was in a commercial
premises and not a domestic situation, (where the offending fault was a
pair of pliers across the supply inside a 4 way trailing lead!)

I'm surprised. A 30/32A MCB often blows quicker than a 13A fuse.

Only if there is sufficient fault current. Easy enough to achieve on a
lighting circuit, but not always so easy on a power circuit at the
appliance end of a flex (where you are going to need north of 160A to
get into the instant trip part of the curve on a type B MCB).

Having said that, we are talking about an event that is so rare for most
people as to be hardly worth mentioning. I am not sure if I have ever
needed to replace a 13A fuse in a plug. (More common if you have a
supply voltage on the high side I understand).

This section could be expanded into a quite substantial and useful "body
of experience" type article. I.e. not only the characteristics and
pros/cons of each CU brand, but also cover topics like
interchangeability of parts, and servicing older CUs where bespoke parts
are no longer available.

Good point. Better to leave it there for the moment, until someone
decides to do that, or make it an almost empty article of its own?

In the interest of attempting to avoid too much repetition, that is what
this article could be the practical advice on CUs one - pretty much all
of the other stuff is already included in the numerous other articles on
MCBs, Changing CUs, Basic Electrics etc.

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 7 Mar, 13:01, wrote:

snip

your comment on split CU's (yes, 3 or 4 banks rather than just 2)
having separate power switches - this is incorrect as I have 3 split
CU's (one in the house and 1 in each outside area) and none have
separate switches.

then in what sense are they split? Or are you saying an RCD isnt a
switch?

Hmm, OK that is correct in that case but I think that needs clarifying
as I would regard myself as competent (electronic engineer and several
full house re-wires) and if I'd followed that to the letter I would
have expected to find a further switch that looks like the incomer
isolator switch.

You need to explain why TT earth requires a special CU - I'm not sure
that is correct either as my understanding is that as long as
everything is covered by an RCD/RCBO, nothing more is required.

Again it says 'CU setup'
An old Wylex fusebox with no rcd provision is not suitable to replace
a broken modern box
TT CUs should be plastic
And a single RCD only is not compliant

Fine then add that I suggest.



Beware of words like 'usually' - an RCD trip for instance is *always*
caused by a faulty device or faulty wiring, with the only unlikely
exception being a faulty RCD.

So its not always

That's being pedantic as you know full well what I'm getting at.


I trust that the RCD article does
strongly advise a full investigation by a professional if the cause of
the tripping isn't immediately obvious.

Perhaps you could explain why if you do it for yourself you'd become
incompetent.

FWIW most causes of RCD trips can be found perfectly safely by a
novice with £5 of equipment.


Hmm, again. I'm not sure that the collective will agree with that.
How many times has there been a relatively basic electrical enquiry
here and someone like yourself or John R has made the point that if
the OP is asking such questions he shouldn't be anywhere near
electricity (actually usually said a little kinder !).

You know as well as I do that the common cause of an RCD trip is
detectable with the Mark 1 Eyeball - ie every time you switch on the
cooker, washing machine, dish washer, and so on, the RCD trips -
therefore it's that piece of equipment.

If it's not that then how is a novice with a £5 DVM from Maplin going
to locate the fault ? If he's a novice he won't really know about
DVM's and is equally unlikely to know about the niceties of house
wiring, nor I would be concerned, the dangers.

Hence my comment.

Rob

Can I add:

==Brands==
....

Contactum
* Beware the flimsy busbar cover

Hager
* Wider than usual range of MCBs and RCBOs, including double pole.
* Snappable busbar with good quality slip on sleeve makes live working safer
and allows custom split load configurations to be made
* MCBs and RCBOs comptable across the domestic plastic and inductrial metal
enclosures.
* Double pole (SPSN) and single pole devices may be mixed freely on a
standard single phase busbar (insulated busbar way on the neutral side and
flying lead for the neutral). Double pole devices are general double width.

MEM
* Expensive, but RCD "pods" are available for some of the MCBs allowing many
custom RCBOs to be constructed.
* Probably the only manufacturer listing a true double pole busbar carrying
both phase and neutral on a split comb arrangement, avoiding the need
for "flying neutrals".

Square-D
* Innovative enclosed and hidden busbar which allows devices to be clipped
in without removing the busbar from all devices.




Cheers

Tim

On Sat, 07 Mar 2009 22:40:11 +0000, Tim S wrote:

Can I add:

==Brands==
...
snip

I'm not too sure that it's a good idea comparing brands on something
like Wiki; it might start to appear that Wiki is 'pushing' a
particular make.
By all means point out factual differences (features etc.), but leave
out opinions...

--
Frank Erskine

Frank Erskine coughed up some electrons that declared:

On Sat, 07 Mar 2009 22:40:11 +0000, Tim S wrote:

Can I add:

==Brands==
...
snip

I'm not too sure that it's a good idea comparing brands on something
like Wiki; it might start to appear that Wiki is 'pushing' a
particular make.
By all means point out factual differences (features etc.), but leave
out opinions...


Fair enough. So remove the reference to Contactum then? I think the rest
were fairly matter of fact, but if you saw anything else, please do point
it out.

BTW - my obsession with double pole should be explained: I like it on
external circuits, though it's not generally required, except with a TT
system, in which case I *think* its is mandatory, though I'd have to check
that to find an explicit regulation.

I may be making my outside circuits TT, so I hedged my bets a bit - anyway,
having double pole isolation on shed and garden lights feels right IMHO,
whether it's required or not.

Cheers

Tim

wrote:

Another one to mull over....

Editable version now live:

http://wiki.diyfaq.org.uk/index.php?...Consumer_Units

Feel free to add your comments on any brand you have used...

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

On 7 Mar, 23:21, Tim S wrote:
Frank Erskine coughed up some electrons that declared:

On Sat, 07 Mar 2009 22:40:11 +0000, Tim S wrote:

Can I add:

==Brands==
...
snip

I'm not too sure that it's a good idea comparing brands on something
like Wiki; it might start to appear that Wiki is 'pushing' a
particular make.
By all means point out factual differences (features etc.), but leave
out opinions...

Fair enough. So remove the reference to Contactum then? I think the rest
were fairly matter of fact, but if you saw anything else, please do point
it out.

BTW - my obsession with double pole should be explained: I like it on
external circuits, though it's not generally required, except with a TT
system, in which case I *think* its is mandatory, though I'd have to check
that to find an explicit regulation.

I may be making my outside circuits TT, so I hedged my bets a bit - anyway,
having double pole isolation on shed and garden lights feels right IMHO,
whether it's required or not.

Cheers

Tim

Tim
My house is TT so I'm interested in what you are saying - but what has
to be 'double pole' ? And why?

And also, why are you making your outside circuits TT ? Is this to
avoid the voltage rise in the return to the CU with an inadequate CPC,
or questionable earthing in the casing if using SWA ? I assume that
the outside circuits are covered by an RCB at the point of use.

Thanks
Rob

John Rumm coughed up some electrons that declared:

wrote:

Another one to mull over....

Editable version now live:

http://wiki.diyfaq.org.uk/index.php?...Consumer_Units

Feel free to add your comments on any brand you have used...


Looks good John. I'm sure MK warrents some description as they are widely
used and sold. But having not personally touched on, I don't feel
qualified. Anyone?

Cheers

Tim

Rob G wrote:
On 7 Mar, 13:01, wrote:

snip

your comment on split CU's (yes, 3 or 4 banks rather than just 2)
having separate power switches - this is incorrect as I have 3 split
CU's (one in the house and 1 in each outside area) and none have
separate switches.

then in what sense are they split? Or are you saying an RCD isnt a
switch?

Hmm, OK that is correct in that case but I think that needs clarifying
as I would regard myself as competent (electronic engineer and several
full house re-wires) and if I'd followed that to the letter I would
have expected to find a further switch that looks like the incomer
isolator switch.

ok, hopefully its now clearer


You need to explain why TT earth requires a special CU - I'm not sure
that is correct either as my understanding is that as long as
everything is covered by an RCD/RCBO, nothing more is required.

Again it says 'CU setup'
An old Wylex fusebox with no rcd provision is not suitable to replace
a broken modern box
TT CUs should be plastic
And a single RCD only is not compliant

Fine then add that I suggest.

done


Beware of words like 'usually' - an RCD trip for instance is *always*
caused by a faulty device or faulty wiring, with the only unlikely
exception being a faulty RCD.

So its not always

That's being pedantic as you know full well what I'm getting at.

I'm not a mind reader.


I trust that the RCD article does
strongly advise a full investigation by a professional if the cause of
the tripping isn't immediately obvious.

Perhaps you could explain why if you do it for yourself you'd become
incompetent.

FWIW most causes of RCD trips can be found perfectly safely by a
novice with £5 of equipment.


Hmm, again. I'm not sure that the collective will agree with that.
How many times has there been a relatively basic electrical enquiry
here and someone like yourself or John R has made the point that if
the OP is asking such questions he shouldn't be anywhere near
electricity (actually usually said a little kinder !).

That's criticism of a signifcantly different scenario to using a
multimeter on all plug-in appliances to look for a leaky one. The
latter is very safe.


You know as well as I do that the common cause of an RCD trip is
detectable with the Mark 1 Eyeball - ie every time you switch on the
cooker, washing machine, dish washer, and so on, the RCD trips -
therefore it's that piece of equipment.

....if youre lucky. Often not.


If it's not that then how is a novice with a £5 DVM from Maplin going
to locate the fault ? If he's a novice he won't really know about
DVM's and is equally unlikely to know about the niceties of house
wiring, nor I would be concerned, the dangers.

as explained above. Plug-in appliances outnumber fixed ones. The one
fixed one that often causes RCD trips is the immersion heater, and
those pass so much leakage when they split that they leave little
doubt as to which appliance is faulty. Hence often a basic meter
applied to plug pins is enough.


NT

Tim S wrote:
Can I add:

==Brands==
...

Contactum
* Beware the flimsy busbar cover

Hager
* Wider than usual range of MCBs and RCBOs, including double pole.
* Snappable busbar with good quality slip on sleeve makes live working safer
and allows custom split load configurations to be made
* MCBs and RCBOs comptable across the domestic plastic and inductrial metal
enclosures.
* Double pole (SPSN) and single pole devices may be mixed freely on a
standard single phase busbar (insulated busbar way on the neutral side and
flying lead for the neutral). Double pole devices are general double width.

MEM
* Expensive, but RCD "pods" are available for some of the MCBs allowing many
custom RCBOs to be constructed.
* Probably the only manufacturer listing a true double pole busbar carrying
both phase and neutral on a split comb arrangement, avoiding the need
for "flying neutrals".

Square-D
* Innovative enclosed and hidden busbar which allows devices to be clipped
in without removing the busbar from all devices.




Cheers

Tim

great, cheers


NT

John Rumm wrote:
wrote:

Another one to mull over....

Editable version now live:

http://wiki.diyfaq.org.uk/index.php?...Consumer_Units

Feel free to add your comments on any brand you have used...


1. a lot of editing had already been done, so editing an already out
of date version live isnt really constructive.
2. the article already written is CU rather than Consumer Units.
Consumer unit and fusebox were going to be redirects to it. This makes
creating links in other articles way less work.
3. the shifting of material between CU and replacing a cu hasnt even
started, and discussion of it has been very limited so far.
4. Proposing and discussing edits here enables them to be discussed
and concensus reached rather than simply anyone editing any way on the
wiki with no discussion.

Now with 2 very divergent versions we have extra work to do, its going
to be alot easier not to do this next time.


NT

Rob G coughed up some electrons that declared:

Tim
My house is TT so I'm interested in what you are saying - but what has
to be 'double pole' ? And why?

Something I picked up on the IEE/IET forums. I'll see if I can locate
anything in the regs or OnSite tomorrow.

And also, why are you making your outside circuits TT ? Is this to
avoid the voltage rise in the return to the CU with an inadequate CPC,
or questionable earthing in the casing if using SWA ? I assume that
the outside circuits are covered by an RCB at the point of use.

It's more to do with the supplier's earth. Although EDF claim, in writing
that I have a TN-S system, it measures and looks more like a TN-C-S (which
is available as an upgrade in the area anyway, meaning there's a good
chance their records are wrong).

I've read various articles in the IEE's "Wiring Matters" magazine that say
the it's not desireable to export TN-C-S earths to outbuildings under
certain circumstances - but again, I'd have to go digging to see if I can
find out where exactly in the regulations it says that, if at all.
Certainly, it's better not to export TN-C-S earths to buildings with
supply-earthed metalwork, eg a steel garage or greenhouse.

Folklore says that odd faults (including on the supply network) can lead to
TN-C-S supply earths gaining significant potential above the local ground.
In a house, this doesn't matter much[1] as things are bonded so as to give
an equipotential zone or zones internally. But outside, this is less true
as it's much more likely that the use could be in contact with the ground.

[1] What happens with a ground floor bathroom with a concrete slab floor on
earth? Short of including a metal grid in the floor, bonded locally,
there's not much you can do about this.

I'll have RCBO protection back in the house CU. I haven't fully committed to
which design to use, and I won't be doing the outside for a while, but I
wanted to get a the RCBOs that gave me the most options.

If anyone can add any clarity to the above, I'd like to read it. In the
meantime, I'll have a dig around the red book.

Cheers

Tim

wrote:
John Rumm wrote:
wrote:

Another one to mull over....
Editable version now live:

http://wiki.diyfaq.org.uk/index.php?...Consumer_Units

Feel free to add your comments on any brand you have used...


1. a lot of editing had already been done, so editing an already out
of date version live isnt really constructive.

I uploaded and included the edits mentioned so far... (in the brands
section anyway - I left out the rest for the moment anyway, but it seems
easier to capture things like the interchangeability matrix in situ)

2. the article already written is CU rather than Consumer Units.
Consumer unit and fusebox were going to be redirects to it. This makes

I don't really like having abbreviations as article names - nothing to
stop you having CU and fusebox as redirects to it though. Failing that
once can always rename it if required.

3. the shifting of material between CU and replacing a cu hasnt even
started, and discussion of it has been very limited so far.

and?

4. Proposing and discussing edits here enables them to be discussed
and concensus reached rather than simply anyone editing any way on the
wiki with no discussion.

Tis what the talk page on the wiki is for as well...

most wikis seem to function ok without the backup of a newsgroup.

Now with 2 very divergent versions we have extra work to do, its going
to be alot easier not to do this next time.

You worry too much... ;-)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Tim S wrote:
Frank Erskine coughed up some electrons that declared:

On Sat, 07 Mar 2009 22:40:11 +0000, Tim S wrote:

Can I add:

==Brands==
...
snip

I'm not too sure that it's a good idea comparing brands on something
like Wiki; it might start to appear that Wiki is 'pushing' a
particular make.
By all means point out factual differences (features etc.), but leave
out opinions...


Fair enough. So remove the reference to Contactum then? I think the rest
were fairly matter of fact, but if you saw anything else, please do point
it out.

Having used lots of contactum, I thought I would fill that out a bit...

BTW - my obsession with double pole should be explained: I like it on

I take it you mean double pole RCBOs here?

external circuits, though it's not generally required, except with a TT
system, in which case I *think* its is mandatory, though I'd have to check
that to find an explicit regulation.

I may be making my outside circuits TT, so I hedged my bets a bit - anyway,
having double pole isolation on shed and garden lights feels right IMHO,
whether it's required or not.

You get that via the double pole switch or RCD ;-)

(then again I usually stick external stuff on a dedicated CU so it is
completely separate from the house one)

--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/

Tim S wrote:

I've read various articles in the IEE's "Wiring Matters" magazine that say
the it's not desireable to export TN-C-S earths to outbuildings under
certain circumstances - but again, I'd have to go digging to see if I can
find out where exactly in the regulations it says that, if at all.
Certainly, it's better not to export TN-C-S earths to buildings with
supply-earthed metalwork, eg a steel garage or greenhouse.

Yup, any time there is access to an independent local earth, or any
services that would typically be included in the equipotential zone.
With an exported TN-C-S earth, one would also have to export the
equipotential zone. That in itself can prove difficult in a practical
sense since the size mandated for the main bonding conductor may exceed
the CSA of the armour etc on your submain.

Folklore says that odd faults (including on the supply network) can lead to
TN-C-S supply earths gaining significant potential above the local ground.
In a house, this doesn't matter much[1] as things are bonded so as to give
an equipotential zone or zones internally. But outside, this is less true
as it's much more likely that the use could be in contact with the ground.

[1] What happens with a ground floor bathroom with a concrete slab floor on
earth? Short of including a metal grid in the floor, bonded locally,
there's not much you can do about this.

Chances are its tiled or has some other flooring which will act as an
insulator. Also the premise of PME is that there will be multiple
connections to earth on the suppliers PEN conductor, so the rise in
voltage ought to be constrained.

I'll have RCBO protection back in the house CU. I haven't fully committed to
which design to use, and I won't be doing the outside for a while, but I
wanted to get a the RCBOs that gave me the most options.

If anyone can add any clarity to the above, I'd like to read it. In the
meantime, I'll have a dig around the red book.

There is a section on exporting earths in the outside electrics article:
http://wiki.diyfaq.org.uk/index.php?...i ng_an_earth



--
Cheers,

John.

/================================================== ===============\
| Internode Ltd - http://www.internode.co.uk |
|-----------------------------------------------------------------|
| John Rumm - john(at)internode(dot)co(dot)uk |
\================================================= ================/