Hi all,

Just a bit of advice to see if I am on the right track.

New external garage (not attached to the house) and I would like to
wire it up for lights and a couple of applicances(fridge+spin dryer) +
usual garden stuff.

The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

In the garage, feed into a smaller CU with an RCD and the necessary
MCB's required for the various circuits.

The supply earthing system in the house is TN-C-S (PME) so I assume I
will have to put an earthing rod in garage somewhere.

Does that sound ok?

Any advice is much appreciated.

TIA

Steve

In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.

--
*Why isn't 11 pronounced onety one? *

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.

Then split the tails from the meter to the consumer unit with Henley blocks
and install a completely separate isolator switch for the out-house /
garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth system
at the out-house end of the installation to protect the whole lot.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected by
the new spike at the out-house. This prevents any interaction from the new
out-house supply interfering on your house installation.

The new isolator switch should only have some kind of safety breaker device
to protect the supply cable in the event of damage or short circuit along
its length. The new CU in the out-house will take care of everything else
connected to the new supply.

On Sun, 24 Jul 2005 15:35:50 GMT, "BigWallop"
wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.

Then split the tails from the meter to the consumer unit with Henley blocks
and install a completely separate isolator switch for the out-house /
garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth system
at the out-house end of the installation to protect the whole lot.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected by
the new spike at the out-house. This prevents any interaction from the new
out-house supply interfering on your house installation.

The new isolator switch should only have some kind of safety breaker device
to protect the supply cable in the event of damage or short circuit along
its length. The new CU in the out-house will take care of everything else
connected to the new supply.


Would the isolator switch be in the garage end of the SWA or the House
End?

"FreddieLIVES" wrote in message
...
On Sun, 24 Jul 2005 15:35:50 GMT, "BigWallop"
wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /
garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth
system
at the out-house end of the installation to protect the whole lot.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected
by
the new spike at the out-house. This prevents any interaction from the
new
out-house supply interfering on your house installation.

The new isolator switch should only have some kind of safety breaker
device
to protect the supply cable in the event of damage or short circuit along
its length. The new CU in the out-house will take care of everything
else
connected to the new supply.


Would the isolator switch be in the garage end of the SWA or the House
End?


The house end. All you're doing is supplying directly from the house meter
to a new separate isolator switch that controls the out-house. The new
isolator switch will also house the safety breaker device that protects the
new SWA cable run and also keeps it separated from any protective device
used for the house. This way, any fault occurring in the SWA or the
out-house will not interfere with the house at all.

"FreddieLIVES" wrote in message
...
Hi all,

Just a bit of advice to see if I am on the right track.

New external garage (not attached to the house) and I would like to
wire it up for lights and a couple of applicances(fridge+spin dryer) +
usual garden stuff.

The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

In the garage, feed into a smaller CU with an RCD and the necessary
MCB's required for the various circuits.

The supply earthing system in the house is TN-C-S (PME) so I assume I
will have to put an earthing rod in garage somewhere.

Does that sound ok?

Any advice is much appreciated.

Sounds fine.

"BigWallop" wrote in message
k...

"FreddieLIVES" wrote in message
...
On Sun, 24 Jul 2005 15:35:50 GMT, "BigWallop"
wrote:


"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /
garage. Using Steel Wire Armoured cable will let you connect
everything
securely at both ends, and also allow for a completely separate earth
system
at the out-house end of the installation to protect the whole lot.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is
protected
by
the new spike at the out-house. This prevents any interaction from the
new
out-house supply interfering on your house installation.

The new isolator switch should only have some kind of safety breaker
device
to protect the supply cable in the event of damage or short circuit
along
its length. The new CU in the out-house will take care of everything
else
connected to the new supply.


Would the isolator switch be in the garage end of the SWA or the House
End?


The house end. All you're doing is supplying directly from the house
meter
to a new separate isolator switch that controls the out-house. The new
isolator switch will also house the safety breaker device that protects
the
new SWA cable run and also keeps it separated from any protective device
used for the house. This way, any fault occurring in the SWA or the
out-house will not interfere with the house at all.

This sounds like overkill for someone who just wants power to run the odd
light and socket in the garage.

If the garage is run as a workshop then what you say is the way. But I
would presume overkill in this case. The original proposal sound fine.

In some new properties they run the garage off the downstairs ring, which is
off the main CU RCD, and then having a garage CU in the garage, with a fuse
as main protection for the garage.

In article ws.net,
Doctor Drivel wrote:
Sounds fine.

You'd use TW&E in conduit?

Figures.

--
*Everybody lies, but it doesn't matter since nobody listens.

Dave Plowman London SW
To e-mail, change noise into sound.

"Dave Plowman (News)" wrote in message
...
In article ws.net,
Doctor Drivel wrote:
Sounds fine.

You'd use TW&E in conduit?

If it is cheap enough yes. If it is internal cable then putting it in
conduit will protect it, and make the job look neater. Conduit looks far
neater than external cable.

You could use single cores.

In message ,
"Dave Plowman (News)" wrote:

In article ws.net,
Doctor Drivel wrote:
Sounds fine.

You'd use TW&E in conduit?

Figures.


The only issue with T&E in conduit -v- SWA (note that the proposed
route is above ground level) is the possible loop impedance of the earth
path if you intend to export the earth.

Hwyl!

M.

--
Martin Angove: http://www.tridwr.demon.co.uk/
Two free issues: http://www.livtech.co.uk/ Living With Technology
.... Television is so dull that children are doing their homework.

"BigWallop" wrote in message
. uk...

"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

Easier to use SWA cable. 6mm 2 core is 1.50 + vat per metre from TLC.


Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /
garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth
system
at the out-house end of the installation to protect the whole lot.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected
by
the new spike at the out-house. This prevents any interaction from the
new
out-house supply interfering on your house installation.

Exactly what do you think will happen if the length of SWA from the house to
the out-house suffers an earth fault? The chances are an outside earth
electrode will struggle to meet a low enough earth impedance to give a rapid
disconnection from the supply since you have conveniently glossed over the
overcurrent protection provided at the supply end.



The new isolator switch should only have some kind of safety breaker
device
to protect the supply cable in the event of damage or short circuit along
its length. The new CU in the out-house will take care of everything else
connected to the new supply.

If your technical advice is limited to stating "some kind of safety breaker
device" I suggest you should refrain from giving it. Do you have any
electrical qualifications at all?


To the OP I would suggest you obtain a copy of the On Site Guide to the
wiring regulations, study it and armed with a little more knowledge be in a
position to ask again.
I missed your original post so I can't make definitive answers.

This is a copy of the original post again, just for you.


Hi all,

Just a bit of advice to see if I am on the right track.

New external garage (not attached to the house) and I would like to
wire it up for lights and a couple of applicances(fridge+spin dryer) +
usual garden stuff.

The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

In the garage, feed into a smaller CU with an RCD and the necessary
MCB's required for the various circuits.

The supply earthing system in the house is TN-C-S (PME) so I assume I
will have to put an earthing rod in garage somewhere.

Does that sound ok?

Any advice is much appreciated.

TIA

Steve

In article ws.net,
Doctor Drivel wrote:
Sounds fine.

You'd use TW&E in conduit?

If it is cheap enough yes.

Few would have a drum of 6mm lying around, unlike 2.5mm.

If it is internal cable then putting it in conduit will protect it, and
make the job look neater. Conduit looks far neater than external cable.

Neater than SWA? I don't think so. SWA can be paged to look as neat as
your skills. Plastic conduit not. Of course I could make a decent job
using steel conduit since I have a bender, but knowing your pipe working
skills I doubt you could even with the correct tools. Which you wouldn't
have.

You could use single cores.

TLC prices give 6mm singles at 40p per metre. Add in the cost of the
conduit - and the hassle - and 6mm twin SWA at 1.50 a metre is the cost
effective answer as well as being the correct way to do the job.

--
*Welcome to **** Creek - sorry, we're out of paddles*

Dave Plowman London SW
To e-mail, change noise into sound.

"Martin Angove" wrote in message
...
In message ,
"Dave Plowman (News)" wrote:

In article ws.net,
Doctor Drivel wrote:
Sounds fine.

You'd use TW&E in conduit?

Figures.

The only issue with T&E in conduit -v- SWA (note that the proposed
route is above ground level) is the possible loop impedance of the earth
path if you intend to export the earth.

As long as the conduit is for external use, and fitted properly so any water
that happens to enter, is naturally drained out, and the MCBs are sized
properly, it is sound. Personally I would use separate conductors (single
wires for Live, Neutral and Earth). The more air around them the better.

"Dave Plowman (News)" wrote in message
...
In article ws.net,
Doctor Drivel wrote:

Sounds fine.

You'd use TW&E in conduit?

If it is cheap enough yes.

Few would have a drum

snip drivel

If it is internal cable then putting it in conduit will protect it, and
make the job look neater. Conduit looks far neater than external
cable.

Neater than SWA? I don't think so.

SWA looks crap.

snip drivel

In article ws.net,
Doctor Drivel wrote:
The only issue with T&E in conduit -v- SWA (note that the proposed
route is above ground level) is the possible loop impedance of the
earth path if you intend to export the earth.

As long

[snip dangerous and misleading advice}

--
*Pentium wise, pen and paper foolish *

Dave Plowman London SW
To e-mail, change noise into sound.

In article ws.net,
Doctor Drivel wrote:
Neater than SWA? I don't think so.

SWA looks crap.

What, round plastic covered black cable looks crap compared to conduit?

Do you know what SWA is?

Stick to giving misleading advice about boilers. It's what you're best at.

--
*The average person falls asleep in seven minutes *

Dave Plowman London SW
To e-mail, change noise into sound.

BigWallop wrote:

Then split the tails from the meter to the consumer unit with Henley blocks
and install a completely separate isolator switch for the out-house /

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent protection
for the SWA.

garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth system
at the out-house end of the installation to protect the whole lot.

Not only that, but with a PME system in the house you would have to
ensure that the equipotential zone is maintained in all the garrage
(i.e. all metalwork bonded etc). Hence why it is usually simpler to make
the garrage a TT system.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected by
the new spike at the out-house. This prevents any interaction from the new
out-house supply interfering on your house installation.


The new isolator switch should only have some kind of safety breaker device
to protect the supply cable in the event of damage or short circuit along
its length. The new CU in the out-house will take care of everything else
connected to the new supply.

I would suggets a slight modification here....

Do the earthing the other way arround. i.e. connect the earth to the
armour at the house end, and then isolate it by using a plastic clad CU
in the garrage. Otherwise you will be relying on the earth spike to to
try and sink enough fault current to clear any phase (live) to earth
fault on the cable. There is very little chance that the earth spike
fault loop impedance will be low enough to do this, and you will end up
needing a RCD at the head end of the cable.

--
Cheers,

John.

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

Doctor Drivel wrote:

If the garage is run as a workshop then what you say is the way. But I
would presume overkill in this case. The original proposal sound fine.

The original proposal does not deal with the issues of extending the
equipotential zone into the garage - this may or may not be easy / desired.

In some new properties they run the garage off the downstairs ring, which is
off the main CU RCD, and then having a garage CU in the garage, with a fuse
as main protection for the garage.

Don't do this as it is very poor practice, is unlikely to comply with
current regulations.


--
Cheers,

John.

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

FreddieLIVES wrote:

New external garage (not attached to the house) and I would like to
wire it up for lights and a couple of applicances(fridge+spin dryer) +
usual garden stuff.

The plan is to take a feed from the non-RCD side of the CU in the
house to the garage using 6mm T&E at high above ground level (in
conduit) with it's own MCB in the House CU.

T&E is a right pain to feed through conduit - more so when it is a thick
cable like 6mm^2. I would be tempted to use HiTuf or SWA - probably
cheaper as well.

In the garage, feed into a smaller CU with an RCD and the necessary
MCB's required for the various circuits.

You will need to take care here with sizing the MCBs so that you still
achieve discrimination between the MCBs in the garage, and the one in
the house. Otherwise a large overload on a socket circuit in the garage
could trip the MCB at the head end rather than the one in the local CU
and hence plunge you into darkness.

Using a HRC fuse carrier in place of the MCB at the head end would
likely solve this issue.

The supply earthing system in the house is TN-C-S (PME) so I assume I
will have to put an earthing rod in garage somewhere.

Unless you want to get into extending the equipotential zone in the
house to the garage as well this would be wise.

Does that sound ok?

Mostly ;-)



--
Cheers,

John.

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

"John Rumm" wrote in message
...
BigWallop wrote:

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent protection
for the SWA.

garage. Using Steel Wire Armoured cable will let you connect everything
securely at both ends, and also allow for a completely separate earth
system
at the out-house end of the installation to protect the whole lot.

Not only that, but with a PME system in the house you would have to
ensure that the equipotential zone is maintained in all the garrage
(i.e. all metalwork bonded etc). Hence why it is usually simpler to make
the garrage a TT system.

This is done by only supplying the new isolator switch with a Live and
Neutral feed, and leave out the earth bonding totally so it is protected
by
the new spike at the out-house. This prevents any interaction from the
new
out-house supply interfering on your house installation.


The new isolator switch should only have some kind of safety breaker
device
to protect the supply cable in the event of damage or short circuit
along
its length. The new CU in the out-house will take care of everything
else
connected to the new supply.

I would suggets a slight modification here....

Do the earthing the other way arround. i.e. connect the earth to the
armour at the house end, and then isolate it by using a plastic clad CU
in the garrage. Otherwise you will be relying on the earth spike to to
try and sink enough fault current to clear any phase (live) to earth
fault on the cable. There is very little chance that the earth spike
fault loop impedance will be low enough to do this, and you will end up
needing a RCD at the head end of the cable.

Cheers,

John.


If the safety breaker used in the new isolator switch is of an RCD design,
then the housings can be metal clad at both ends of the new sub-mains
supply. There is no need to insulate using things made of plastic in
between the new consumer unit and old installation. The OP (FreddieLives)
should know what types of safety breaker devices to use on this type of
sub-mains installation or he shouldn't be touching it at all, in my opinion.

A new earth spike at the out-house would protect both the new SWA supply and
the garage CU without interfering with the existing house system. The only
connections made inside the house would be the tails and Henley blocks from
the meter to a new isolator switch with a properly rated safety breaker
device in-built.

The earth fault loop impedance would not have to bring the new installation
to the same potential as the house, as the new supply and garage
installation would become a totally separate entity from everything around
it. So there would be no need to install equipotential bonding or insulated
anything between all parts of the old and new systems. The new earth spike
at the garage would be between the sub-mains cable and the out-house
consumer unit, and would mean a more secure method of fault detection for
all of the new system. If done properly, then the SWA cable and new
consumer unit and wiring system in the out-house would share the same earth
fault protection between them.

Nothing over complicated in it, and all safe.

"John" wrote in message
...

"BigWallop" wrote in message
. uk...

snipped

If your technical advice is limited to stating "some kind of safety
breaker
device" I suggest you should refrain from giving it. Do you have any
electrical qualifications at all?


And you not fully understanding my reply, shows that you have? Anyone
asking the type of question that is being asked in this instance, should
already know how to design safety into the type of sub-mains supply layout I
have given. If they don't, then they shouldn't be touching it at all in my
opinion.

I don't know what type of loading is being applied to this installation, so
I have also not given any advice on the gauge of cable to be used. I have
only advised on a style of cable suitable for this type of installation.
Does this also mean I don't have any qualification on this type of works? I
have also not supplied any techincal details on the earth fault loop design,
and only advised on a suitable position for it to placed. So I take it, in
your view, this also means I'm not qualified?

I'm not holding the hand of the person that is attempting this project, so I
can't say anything more technical than give advice on how I think the layout
should be made and without over complicating the whole thing. So this makes
me un-qualified to make suppositions on how the final design should take
into account the loadings they wish to apply, or on the safety devices they
must use in their final design. I'm not doing the job for them, so I'm
un-qualified to give any more advice on the works unseen.

If you think you can give anymore advice on this unseen project by using
your telepathic skills, then by all means go ahead. If you know more than I
do about the loadings that the OP will be applying to this new sub-mains
installation, then do not hesitate to continue to tell them which specific
products they must use.

If you are as much in the dark about the full details as everyone else is,
then shut the hell up and don't cast aspersions on people you know nothing
about. Now **** off little boy, before you make me angry. I do not have to
deem myself to you, or any other, on my personal qualifications or skills.

"Dave Plowman (News)" wrote in message
...
In article ws.net,
Doctor Drivel wrote:
The only issue with T&E in conduit -v- SWA (note that the proposed
route is above ground level) is the possible loop impedance of the
earth path if you intend to export the earth.

As long

This Pillock thinks conduit is dangerous, yet leaves his boiler unserviced
for 18 years. Some mothers......

"John Rumm" wrote in message
...
BigWallop wrote:

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent protection
for the SWA.

Of course there is. The garage CU will have over current protection for
each circuit. The total load of the garage CU should not exceed the limits
of the SWA cable.

"John Rumm" wrote in message
...
Doctor Drivel wrote:

If the garage is run as a workshop then what you say is the way. But I
would presume overkill in this case. The original proposal sound fine.

The original proposal does not deal with the issues of extending the
equipotential zone into the garage - this may or may not be easy /
desired.

In some new properties they run the garage off the downstairs ring,
which is
off the main CU RCD, and then having a garage CU in the garage, with a
fuse
as main protection for the garage.

Don't do this as it is very poor practice, is unlikely to comply with
current regulations.

I don't like it, but it is done, ana safe, within regs, and I have seen a
number of them on new houses. An unswitched spur is inserted into the
downstairs ring on an outside wall, then an armoured cable out through the
wall to the garage.

On Mon, 25 Jul 2005 10:27:58 +0100, "Doctor Drivel"
wrote:


"John Rumm" wrote in message
...
BigWallop wrote:

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent protection
for the SWA.

Of course there is. The garage CU will have over current protection for
each circuit. The total load of the garage CU should not exceed the limits
of the SWA cable.


Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.

Stick to hacksawing plastic pipes. At least you are reasonably
unlikely to cause death through electrocution or fire.



--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 10:27:58 +0100, "Doctor Drivel"
wrote:


"John Rumm" wrote in message
...
BigWallop wrote:

Then split the tails from the meter to the consumer unit with Henley
blocks
and install a completely separate isolator switch for the out-house /

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent
protection
for the SWA.

Of course there is. The garage CU will have over current protection for
each circuit. The total load of the garage CU should not exceed the
limits
of the SWA cable.

Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.

What crap. The ring has an over-current mcb, so the ring CANNOT be run more
than what the cables on the ring is rated. If it exceed supply capacity the
mcb trips in. Boy are you dumb.

...Lord Hall doesn't know, a man who has no clue
...he has no clue about the things which are known to me and you

...24/7 he is vacant within his head
...no knoweldge, reason, logic, this must be said

...drivel and babble just comes so
...relentless, incoherrent in its flow

...it's time take no notice of this hot head babbling fool
...just laugh and smile and thank the Lord you are sane and cool

OC prtoection for the cable has to be at source - you 'fuse down' to
protect the cable....the individual cct protection in the garage is to
protect the devices plugged in - not the cable to the house.

On Mon, 25 Jul 2005 11:08:29 +0100, "Doctor Drivel"
wrote:


Of course there is. The garage CU will have over current protection for
each circuit. The total load of the garage CU should not exceed the
limits
of the SWA cable.

Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.

What crap. The ring has an over-current mcb, so the ring CANNOT be run more
than what the cables on the ring is rated. If it exceed supply capacity the
mcb trips in. Boy are you dumb.


1) Your proposal was that the garage CU and MCBs therein protects the
cable. It doesn't.

2) Are you proposing running a ring to the garage now?


The correct way is to install a separate circuit from the main house
CU or main supply with correct circuit breaker fitted to it.

A poorer practice alternative is to run from a ring circuit but via a
suitable overload protection.

25 Yorkshire elbows please.



--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 11:08:29 +0100, "Doctor Drivel"
wrote:


Of course there is. The garage CU will have over current protection
for
each circuit. The total load of the garage CU should not exceed the
limits
of the SWA cable.

Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.

What crap. The ring has an over-current mcb, so the ring CANNOT be run
more
than what the cables on the ring is rated. If it exceed supply capacity
the
mcb trips in. Boy are you dumb.


1) Your proposal was that the garage CU and MCBs therein protects the
cable. It doesn't.

It does if the main garage CU isolating switch is rated under the supply
cable rating. Which I drew cautioned.

2) Are you proposing running a ring to the garage now?

You are making things up again.

The correct way is to install a separate circuit from the main house
CU or main supply with correct circuit breaker fitted to it.

For light use yes. One was proposing a separate supply after the meter.
That may be OK for heavy use, and easier for separate metering.

A poorer practice alternative is
to run from a ring circuit but via a
suitable overload protection.

I mentioned that. Boy are you slow.

On Mon, 25 Jul 2005 11:49:12 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message


1) Your proposal was that the garage CU and MCBs therein protects the
cable. It doesn't.

It does if the main garage CU isolating switch is rated under the supply
cable rating. Which I drew cautioned.

It does not.

What happens if the cable is shorted before the garage CU?




2) Are you proposing running a ring to the garage now?

You are making things up again.


It's what you said


The correct way is to install a separate circuit from the main house
CU or main supply with correct circuit breaker fitted to it.

For light use yes. One was proposing a separate supply after the meter.
That may be OK for heavy use, and easier for separate metering.


It's good practice anyway.




--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 11:49:12 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message


1) Your proposal was that the garage CU and MCBs therein protects the
cable. It doesn't.

It does if the main garage CU isolating switch is rated under the supply
cable rating. Which I drew cautioned.

It does not.

What happens if the cable is shorted before the garage CU?

The same thing that happens if the cable is shorted before the CU of the
house.

2) Are you proposing running a ring to the garage now?

You are making things up again.

It's what you said

I never. But there is no reason not to if the mcb in the garge CU is rated
accordingly.

The correct way is to install a separate circuit from the main house
CU or main supply with correct circuit breaker fitted to it.

For light use yes. One was proposing a separate supply after the meter.
That may be OK for heavy use, and easier for separate metering.

It's good practice anyway.

What is?

On Mon, 25 Jul 2005 12:48:38 +0100, "Doctor Drivel"
wrote:


It does if the main garage CU isolating switch is rated under the supply
cable rating. Which I drew cautioned.

It does not.

What happens if the cable is shorted before the garage CU?

The same thing that happens if the cable is shorted before the CU of the
house.

The main electricity supplier fuse goes?




2) Are you proposing running a ring to the garage now?

You are making things up again.

It's what you said

I never. But there is no reason not to if the mcb in the garge CU is rated
accordingly.

You said, and I quote:

"The ring has an over-current mcb, so the ring CANNOT be run more
than what the cables on the ring is rated. If it exceed supply
capacity the mcb trips in"




The correct way is to install a separate circuit from the main house
CU or main supply with correct circuit breaker fitted to it.

For light use yes. One was proposing a separate supply after the meter.
That may be OK for heavy use, and easier for separate metering.

It's good practice anyway.

What is?

Installing a separate ciruit with a breaker providing overcurrent
protection for the cable to the garage.



--

..andy

To email, substitute .nospam with .gl

Doctor Drivel wrote:

I don't like it, but it is done,

I Don't dispute that...

ana safe,

Not immediatly dangerours unless issues relating to the extension of the
equipotential zone are not also followed, but not as good as if done
correctly.

within regs,

Nope. We have had this discussion before. If you insist I can quote
chapter and verse of the regulations is falls foul of.

and I have seen a
number of them on new houses. An unswitched spur is inserted into the
downstairs ring on an outside wall, then an armoured cable out through the
wall to the garage.

If you were dealing with an attached garage that is effectively part of
the house (i.e inside connecting door etc) then there is nothing
stopping you extending the socket ringl final circuit into the garage,
and the downstairs lighting circuit likewise. No need for the FCU.

If you are talking about a detached building then it is a lash up for
various reasons.

--
Cheers,

John.

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

BigWallop wrote:

If the safety breaker used in the new isolator switch is of an RCD design,

"safety breaker" is a non standard term. I would suggest that if you are
going to offer advice in this area you be a little more specific with
your terminology, since subtle misunderstandings can make big differences.

then the housings can be metal clad at both ends of the new sub-mains
supply. There is no need to insulate using things made of plastic in
between the new consumer unit and old installation.

You need to decide if the garage is going to be part of the PME system
with associated implications, or a standalone TT system. If it is TT
then you do not want any connectivity between house earth and the TT
earth. Hence the need for an insulated CU (or a metal clad one and
insulating glands etc). You seem to be advocating some mixture of both.

? The OP (FreddieLives)
should know what types of safety breaker devices to use on this type of
sub-mains installation or he shouldn't be touching it at all, in my opinion.

Wow!, what a cop out. What is the point in posting half the solution,
and expecting the OP to guess which bits you missed out?

A new earth spike at the out-house would protect both the new SWA supply and
the garage CU without interfering with the existing house system. The only

Note sure what you mean by "interfering with the existing house system"
in this case. Could you clarify?

connections made inside the house would be the tails and Henley blocks from
the meter to a new isolator switch with a properly rated safety breaker
device in-built.

An isolator switch is just that. It includes no overcurrent protection.
Unless you mean a switchfuse, or a CU, in which case it is better to be
specific I would suggest.

The earth fault loop impedance would not have to bring the new installation
to the same potential as the house, as the new supply and garage

Woa, there boy! Your speaking bollox. What has earth fault loop
impedance go to do with bringing "the new installation to the same
potential as the house"?

installation would become a totally separate entity from everything around
it. So there would be no need to install equipotential bonding or insulated
anything between all parts of the old and new systems.

Again - you need one or the other. If separated (i.e. TT) in the
outbuilding then don't join the earths. If part of the PME system, then
do the required bonding.

The new earth spike at the garage would be between the sub-mains cable and the
out-house consumer unit,

What do you mean by "between"?


--
Cheers,

John.

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

Doctor Drivel wrote:

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent protection
for the SWA.

Of course there is. The garage CU will have over current protection for
each circuit. The total load of the garage CU should not exceed the limits
of the SWA cable.


Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.


What crap. The ring has an over-current mcb, so the ring CANNOT be run more
than what the cables on the ring is rated. If it exceed supply capacity the
mcb trips in.

Since the only "ring" here is presumably one in the outbuilding, then
you are correct (allthough not relevent). The MCB for that circuit will
protect the cables of the circuit. However we are not talking about that
cicruit, but the sub main feed to the CU that supplies it. The
overcurrent protection is needed for this to cope with two eventualities:

Firstly when the total load of the garage CU (i.e. all circuits
combined) exceeds the sub main cable capacity, and secondly, when a
fault affects the sub main cable before the garage CU (i.e. damage to
the cable itself or a fire in the garage etc).

Boy are you dumb.

Those in glass houses ought not throw stones....


--
Cheers,

John.

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

"John Rumm" wrote in message
...
Doctor Drivel wrote:

I don't like it, but it is done,

I Don't dispute that...

and safe,

Not immediatly dangerours unless issues relating to the extension of the
equipotential zone are not also followed, but not as good as if done
correctly.

within regs,

Nope. We have had this discussion before.

I saw it and questioned it, and was assured it was fully within. No
electrical man has countered when presented. Mopst say back top the CU and
its own mcb, but apart from that the same, as these garages were just spured
off a ring.

f you insist I can quote
chapter and verse of the regulations is falls foul of.

Please do, and tell when the reg came about. 3-core cable was taken to the
garages from a switchless spur, with 13 A fuse off the downstairs ring.

and I have seen a
number of them on new houses. An unswitched spur is inserted into the
downstairs ring on an outside wall, then an armoured cable out through
the
wall to the garage.

If you were dealing with an attached garage that is effectively part of
the house (i.e inside connecting door etc) then there is nothing
stopping you extending the socket ringl final circuit into the garage,
and the downstairs lighting circuit likewise. No need for the FCU.

If you are talking about a detached building then it is a lash up for
various reasons.

It was the most convenient point of take off. Otherwise the cable had to go
an extra 20 - 30 foot and enter the building via the mains cable duct to the
CU, or a separte duct. One light and one double socket in the garage,
pretty standard. The garage CU was a MEM Numera 2000 with two fuses, not
mcb's, of 5A and 15A. A 100A breaker was also fitted in the MEM.
Protection in the garage is via the fuses alone, as I can't see that 100A
main garage CU breaker does anything, being off a 30A RCD'd house ring. The
RCD would cut in before the fuses had a chance to blow.

So the fuse in MEM, the fuse in the switchless spur, the mcb at the CU and
the RCD. Then the Plugtop fuse as well when using an appliance. Seems well
protected

"John Rumm" wrote in message
...
Doctor Drivel wrote:

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent
protection
for the SWA.

Of course there is. The garage CU will have over current protection
for
each circuit. The total load of the garage CU should not exceed the
limits
of the SWA cable.


Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.


What crap. The ring has an over-current mcb, so the ring CANNOT be run
more
than what the cables on the ring is rated. If it exceed supply capacity
the
mcb trips in.

Since the only "ring" here is presumably one in the outbuilding, then
you are correct (allthough not relevent). The MCB for that circuit will
protect the cables of the circuit. However we are not talking about that
cicruit, but the sub main feed to the CU that supplies it. The
overcurrent protection is needed for this to cope with two eventualities:

Firstly when the total load of the garage CU (i.e. all circuits
combined) exceeds the sub main cable capacity, and secondly, when a
fault affects the sub main cable before the garage CU (i.e. damage to
the cable itself or a fire in the garage etc).

Boy are you dumb.

Those in glass houses ought not throw stones....

I thought of you.

The cable from the meter to the garage CU should be sized to suit. Obvious.
The garage CU total protection should not allow loads above the supply cable
capacity. This is the same for the main house supply cable and CU.

Lord Hall was on about rings quite often exceeding the load capacity and
getting away with it. That is nonsense. The rings two cables are rated
above the mcb on that circuit. So they cannot be exceeded.

On Mon, 25 Jul 2005 14:20:19 +0100, "Doctor Drivel"
wrote:



The cable from the meter to the garage CU should be sized to suit. Obvious.
The garage CU total protection should not allow loads above the supply cable
capacity. This is the same for the main house supply cable and CU.

You have it the wrong way round.

The house end circuit breaker should not allow loads over the cable
carrying capacity.





Lord Hall was on about rings quite often exceeding the load capacity and
getting away with it. That is nonsense.

What you have said is nonsense.

What I said is that it is common practice for the sum of the circuits
and breakers protecting them installed in a CU to exceed the capacity
of the circuit feeding said CU. This is one of the principles of
diversity.

The only exception is that the CU itself must not have the principles
of diversity applied to it.


The rings two cables are rated
above the mcb on that circuit. So they cannot be exceeded.


Irrelevant.




--

..andy

To email, substitute .nospam with .gl

"Doctor Drivel" wrote in message
enews.net...

"John Rumm" wrote in message
...
Doctor Drivel wrote:

Might be worth pointing out that this ought to be a switch fuse unit
rather than just a switch - otherwise you have no overcurrent
protection
for the SWA.

Of course there is. The garage CU will have over current protection
for
each circuit. The total load of the garage CU should not exceed the
limits
of the SWA cable.


Dangerous nonsense.

1) The overcurrent protection for a length of cable needs to be at the
supply end.

2) It is normal for the total potential load of a set of circuits on a
CU to exceed the supply capacity - common practice in house main CUs
for example.


What crap. The ring has an over-current mcb, so the ring CANNOT be
run
more
than what the cables on the ring is rated. If it exceed supply
capacity
the
mcb trips in.

Since the only "ring" here is presumably one in the outbuilding, then
you are correct (allthough not relevent). The MCB for that circuit will
protect the cables of the circuit. However we are not talking about that
cicruit, but the sub main feed to the CU that supplies it. The
overcurrent protection is needed for this to cope with two
eventualities:

Firstly when the total load of the garage CU (i.e. all circuits
combined) exceeds the sub main cable capacity, and secondly, when a
fault affects the sub main cable before the garage CU (i.e. damage to
the cable itself or a fire in the garage etc).

Boy are you dumb.

Those in glass houses ought not throw stones....

I thought of you.

The cable from the meter to the garage CU should be sized to suit.
Obvious.
The garage CU total protection should not allow loads above the supply
cable
capacity. This is the same for the main house supply cable and CU.

Lord Hall was on about rings quite often exceeding the load capacity and
getting away with it. That is nonsense. The rings two cables are rated
above the mcb on that circuit. So they cannot be exceeded.


Two 2.5 mm csa' cables make a total cross sectional area of 5 mm. The
breaker normally used on a ring final circuit is 30 (32) Amps rated. This
current rating is to high for a cable of cross sectional area of 5 mm.
Specially so if the ring final circuit is rather long. It is called
diversity and takes into account that not all points on the ring final
circuit will be used at full load at all times. So you are telling us this
can't be done?

The diversity guide also applies to the mains supply conductors, but these
must be protected separately at their source by their own automatic breaker
devices. This ensures that the supply is broken in the event of a fault on
the supply. The mains conductors can not rely on the breaker devices in the
consumer unit that they supply.