"Andy Hall" wrote in message
...
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?

I would assume so.

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"

That was general statement, not saying run a ring in the garage. Although,
no reason why you can't.

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.

Not if you take it directly after the meter it is not. What you are saying
is that all homes would have again breaker between the meter and the CU.
No need as the CU has one.

"Andy Hall" wrote in message
...
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.

If taken off the CU yes. If not taken from the house CU, you need to size
correctly.

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.

That is what you said not me.

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.

But they go through main RCD which may be less than the total of the mcb's,
which protects the main cables.

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.

It must protect the cables that feed it.

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

Irrelevant.

You are confused.

On Mon, 25 Jul 2005 17:18:10 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message
.. .
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?

I would assume so.


Never "assume" with electricity. Everything should be properly
planned and carried out. You really haven't understood the issue
here.

The only places for hacksaws are to cut SWA cable and bus bars in
consumer units.



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"

That was general statement, not saying run a ring in the garage. Although,
no reason why you can't.

Rather pointless. The correct way, if it is a detached building is
with SWA of appropriate size run as a radial circuit.




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.

Not if you take it directly after the meter it is not. What you are saying
is that all homes would have again breaker between the meter and the CU.
No need as the CU has one.


You are very confused.

The two most appropriate solutions, both run as a radial circuit are

a) Suitable breaker in CU of correct rating for garage power
requirement and cable used to feed that from the house

b) As above but with suitable breaker separate to CU fed directly from
a point after the meter and before the CU

Do stick to selling compression fittings - you can't get into too much
trouble that way.



--

..andy

To email, substitute .nospam with .gl

On Mon, 25 Jul 2005 17:22:37 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message
.. .
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.

If taken off the CU yes. If not taken from the house CU, you need to size
correctly.

The cable needs to be sized correctly under *all* circumstances.



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.

But they go through main RCD which may be less than the total of the mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.




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.

It must protect the cables that feed it.

Wrong. Cables are *not* protected by CUs or any other element at the
load end of the cable.




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

Irrelevant.

You are confused.

Go and read the IEE On site Guide or Whitfield's Electrician's Guide.

You can find much of the latter on the TLC web site.




--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 17:22:37 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message
.. .
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.

If taken off the CU yes. If not taken from the house CU, you need to size
correctly.

The cable needs to be sized correctly under *all* circumstances.



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.

But they go through main RCD which may be less than the total of the
mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.

No. The cables form the meter, after the main fuse.

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.

It must protect the cables that feed it.

Wrong. Cables are *not* protected by CUs or any other element at the
load end of the cable.

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

Irrelevant.

You are confused.

Go and read the IEE On site Guide or Whitfield's Electrician's Guide.

You can find much of the latter on the TLC web site.

You are still confused.

On Mon, 25 Jul 2005 18:24:40 +0100, "Doctor Drivel"
wrote:


But they go through main RCD which may be less than the total of the
mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.

No. The cables form the meter, after the main fuse.

The meter tails are protected by the electricity supplier's main fuse,
not the MCBs in the CU.




--

..andy

To email, substitute .nospam with .gl

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 18:24:40 +0100, "Doctor Drivel"
wrote:


But they go through main RCD which may be less than the total of the
mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.

No. The cables form the meter, after the main fuse.

The meter tails are protected by the electricity supplier's main fuse,
not the MCBs in the CU.

An that same fuse would protect the cable to the garage CU, if the supply
was taken this way. It's main protection would be the main breakers and
collective breakers on the garage CU.

In article ws.net,
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.

[snip dangerous advice from Drivel]

--
*Don't sweat the petty things and don't pet the sweaty things.

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

In article ws.net,
Doctor Drivel wrote:
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,

[snip dangerous advice from Drivel]

--
*Microsoft broke Volkswagen's record: They only made 21.4 million bugs.

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

In article ws.net,
Doctor Drivel wrote:
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.

[snip dangerous advice from Drivel]

--
*Why can't women put on mascara with their mouth closed?

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

On Mon, 25 Jul 2005 19:30:34 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message
.. .
On Mon, 25 Jul 2005 18:24:40 +0100, "Doctor Drivel"
wrote:


But they go through main RCD which may be less than the total of the
mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.

No. The cables form the meter, after the main fuse.

The meter tails are protected by the electricity supplier's main fuse,
not the MCBs in the CU.

An that same fuse would protect the cable to the garage CU, if the supply
was taken this way. It's main protection would be the main breakers and
collective breakers on the garage CU.


Crap.

The delivery capacity of the supply with the main fuse is vastly
larger than the current carrying capacity of a cable that would be
used to run a supply to a garage.

The cables *downstream* of the garage CU are protected by the MCBs
installed therein.





--

..andy

To email, substitute .nospam with .gl

In article ws.net,
Doctor Drivel wrote:
1) Your proposal was that the garage CU and MCBs therein protects the
cable. It doesn't.

It does

[snip dangerous advice from Drivel]

--
*Forget about World Peace...Visualize using your turn signal.

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

In article s.net,
Doctor Drivel wrote:
The garage CU total protection should not allow loads above the supply
cable capacity.

Dangerous advice from Drivel again. This person should not be allowed on a
DIY group.

--
*They call it PMS because Mad Cow Disease was already taken.

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

In article s.net,
Doctor Drivel wrote:
But they go through main RCD which may be less than the total of the
mcb's, which protects the main cables.

Drivel hasn't a clue about this and shouldn't be allowed on a DIY group.

--
*Speak softly and carry a cellular phone *

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

In article ,
FreddieLIVES wrote:
Just a bit of advice to see if I am on the right track.

Please ignore all the dangerous 'advice' Drivel has posted as he hasn't a
clue, and should be barred from posting on such things.

--
*Any connection between your reality and mine is purely coincidental

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

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 19:30:34 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message
.. .
On Mon, 25 Jul 2005 18:24:40 +0100, "Doctor Drivel"
wrote:


But they go through main RCD which may be less than the total of
the
mcb's,
which protects the main cables.

The MCBs do *not* protect the main cables. That is done by the
electricity supplier's fuse.

No. The cables form the meter, after the main fuse.

The meter tails are protected by the electricity supplier's main fuse,
not the MCBs in the CU.

An that same fuse would protect the cable to the garage CU, if the supply
was taken this way. It's main protection would be the main breakers and
collective breakers on the garage CU.

Crap.

The delivery capacity of the supply with the main fuse is vastly
larger than the current carrying capacity of a cable that would be
used to run a supply to a garage.

The cables *downstream* of the garage CU are protected by the MCBs
installed therein.

And the MCBs also prevent a large load on the supply cable.

If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply cable.
Get it? Think about it. Nah, don't think, it is fatal.

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

[snip

snip more drunken babble

"Dave Plowman (News)" wrote in message
...
In article s.net,
Doctor Drivel wrote:
The garage CU total protection should not allow loads above the supply
cable capacity.

Dangerous advice

This pillock want the supply cable to be too small. Some mothers.....

"Dave Plowman (News)" wrote in message
...
In article s.net,
Doctor Drivel wrote:
But they go through main RCD which may be less than the total of the
mcb's, which protects the main cables.

Snip garbage. This one encouraged people not to service gas boilers because
he never did it for 18 years. Some mothers.....

"Dave Plowman (News)" wrote in message
...
In article ,
FreddieLIVES wrote:
Just a bit of advice to see if I am on the right track.

Please ignore .....

....the drivel from Plowman (alias Richard Cranium)

On Mon, 25 Jul 2005 20:24:44 +0100, "Doctor Drivel"
wrote:


"Andy Hall" wrote in message


The meter tails are protected by the electricity supplier's main fuse,
not the MCBs in the CU.

An that same fuse would protect the cable to the garage CU, if the supply
was taken this way. It's main protection would be the main breakers and
collective breakers on the garage CU.

Crap.

The delivery capacity of the supply with the main fuse is vastly
larger than the current carrying capacity of a cable that would be
used to run a supply to a garage.

The cables *downstream* of the garage CU are protected by the MCBs
installed therein.

And the MCBs also prevent a large load on the supply cable.

That is not their purpose. What would happen if the cable from the
house to the garage were shorted, and as you are suggesting, the only
protection were the electricity supplier main fuse.



If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply cable.

They do not protect the supply cable against a short before the MCBs.
Their purpose is to protect downstream...



--

..andy

To email, substitute .nospam with .gl

In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

--
Andrew Gabriel

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

That is normal and the average domestic installation. What protects the
cable from the meter to the CU is the main fuse.

If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply
cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

I haven't given any advise. The only thing I said was take an MCB off the
main CU and run three single cores through a conduit to a garage CU. Quite
normal.

In article ws.net,
"Doctor Drivel" writes:

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

That is normal and the average domestic installation. What protects the
cable from the meter to the CU is the main fuse.

The supplier's cutout protects a couple of metres of 25mm²
tails. Suppliers don't allow their cutout to protect any
more than around 3 metres of tails.

If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

I haven't given any advise. The only thing I said was take an MCB off the
main CU and run three single cores through a conduit to a garage CU.

which is not at all what you're suggesting in articles
eenews.net
eenews.net
reenews.net
reenews.net
reenews.net

--
Andrew Gabriel

On Mon, 25 Jul 2005 22:05:43 +0100, "Doctor Drivel"
wrote:


"Andrew Gabriel" wrote in message
. ..
In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

That is normal and the average domestic installation. What protects the
cable from the meter to the CU is the main fuse.

In the case of the main house CU, yes.

In the case of a garage one some metres away additional protection at
an appropriate and lower current rating is required.



If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply
cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

I haven't given any advise. The only thing I said was take an MCB off the
main CU and run three single cores through a conduit to a garage CU. Quite
normal.


SWA is more appropriate and you have been doling out all kinds of
misinformation as usual.





--

..andy

To email, substitute .nospam with .gl

Doctor Drivel wrote:

And the MCBs also prevent a large load on the supply cable.

You seem to have a fundamental misconception of the purpose of the
overcurrent devices (MCBs). They are for protection of the downstream
circuits *only*, explicitly *not* the upstream supply. It is the
function of a protective device at the *origin* of the supply to be
responsible for the protection of this sub main.

Hence overcurrent devices at the substation protect the cable runs to
the houses. The main fuse protects the cable runs to the CU and guards
against faults in the CUs themselves (unless they are more than two
meters from the fuse in which case an additional switchfuse should be
inserted). The MCBs in the CUs protects the cables in the house wiring,
and also performs the function of disconnection in the case of certain
fault conditions.

So in the same way that your 100A main supply fuse can not protect the
main cable (which will be supplying several properties), your MCBs can
not protect the meter tails since the maximum potential load of all
circuits combined will exceed the main fuse capacity. Also you may have
more than one CU.

If the garage CU has a 30A ring and A lighting circuit, then the supply
cable should be rated more than 35A. Then the MCBs protect the supply cable.
Get it? Think about it. Nah, don't think, it is fatal.

You are missing the point. Consider these situations:

Detached garage with two circuits: 6A lighting, and 32A sockets.
Sub main cable to garage CU rated for 40A nominal capacity.
Cable fed directly from a junction box that splits the tails from the
meter.
Supply rated for 100A, TN-C earthing.

Your garage catches fire. It melts the garage CU and results in a L-N
short on the sub main cable. What happens?

Since there is no suitably sized protection for the sub main cable at
its origin, the cable may burst into flames. What was a fire in your
garage is now a fire in the house as well.

You are digging in the garden and manage to stick a spade into the
cable. You cause a phase earth short. Lets say that the cable does not
burst into flames this time, but the main electricity companies fuse
blows taking out all circuits in the entire property and technically
requiring the assistance of the electricity company to come and fix the
fuse - which won't do because your knackered cable and spade are still
wired in, and there is no isolation for them.

--
Cheers,

John.

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

In article ws.net,
Doctor Drivel wrote:
Doctor Drivel wrote:
The garage CU total protection should not allow loads above the
supply cable capacity.

Dangerous advice

This pillock want the supply cable to be too small. Some mothers.....

[snip more dangerous advice from a drunken Drivel]

--
*When did my wild oats turn to prunes and all bran?

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

In article ws.net,
Doctor Drivel wrote:
"Dave Plowman (News)" wrote in message
...
In article s.net,
Doctor Drivel wrote:
But they go through main RCD which may be less than the total of the
mcb's, which protects the main cables.

Snip garbage.

You've just quoted one of your posts.

[snip dangerous advice from Drivel]

--
*Where there's a will, I want to be in it.

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

In article ws.net,
Doctor Drivel wrote:

Please ignore .....

Best bit of advice.

Ignore dangerous advice from Drivel.

--
*Time is what keeps everything from happening at once.

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

In article ws.net,
Doctor Drivel wrote:
But not a fault in the cable or CU.

That is normal and the average domestic installation.

[snip dangerous advice from a drunken Evil]

--
*Of course I'm against sin; I'm against anything that I'm too old to enjoy.

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

"Dave Plowman (News)" wrote in message
...
In article ws.net,
Doctor Drivel wrote:
Doctor Drivel wrote:
The garage CU total protection should not allow loads above the
supply cable capacity.

Dangerous advice

This pillock want the supply cable to be too small. Some mothers.....

"Dave Plowman (News)" wrote in message
...
In article ws.net,
Doctor Drivel wrote:
"Dave Plowman (News)" wrote in message
...
In article s.net,
Doctor Drivel wrote:
But they go through main RCD which may be less than the total of the
mcb's, which protects the main cables.

A dangerous man.

Snip garbage

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

Please ignore .....

This man is dangerous, take no notice of him.

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

But not a fault in the cable or CU.

That is normal and the average domestic installation.

The Hibernian has come home drunk after tossing the odd electric caber.

"Andy Hall" wrote in message
...
On Mon, 25 Jul 2005 22:05:43 +0100, "Doctor Drivel"
wrote:


"Andrew Gabriel" wrote in message
. ..
In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

That is normal and the average domestic installation. What protects the
cable from the meter to the CU is the main fuse.

In the case of the main house CU, yes.

In the case of a garage one some metres away additional protection at
an appropriate and lower current rating is required.

Can you cite this please. The breakers on the garage CU woud protect it.

If the garage CU has a 30A ring and A lighting circuit, then the
supply
cable should be rated more than 35A. Then the MCBs protect the supply
cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

I haven't given any advise. The only thing I said was take an MCB off
the
main CU and run three single cores through a conduit to a garage CU.
Quite
normal.

SWA is more appropriate and you have been doling out all kinds of
misinformation as usual.

No misinformation whatsoever. Conduit is also used. SWA looks naff,
conduit looks neat. You are confused.

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:

"Andrew Gabriel" wrote in message
.. .
In article ws.net,
"Doctor Drivel" writes:

And the MCBs also prevent a large load on the supply cable.

But not a fault in the cable or CU.

That is normal and the average domestic installation. What protects
the
cable from the meter to the CU is the main fuse.

The supplier's cutout protects a couple of metres of 25mm²
tails. Suppliers don't allow their cutout to protect any
more than around 3 metres of tails.

If the garage CU has a 30A ring and A lighting circuit, then the
supply
cable should be rated more than 35A. Then the MCBs protect the supply
cable.
Get it? Think about it. Nah, don't think, it is fatal.

Your advice sure is.

I haven't given any advise. The only thing I said was take an MCB off
the
main CU and run three single cores through a conduit to a garage CU.

which is not at all what you're suggesting in articles
eenews.net
eenews.net
reenews.net
reenews.net
reenews.net

I am not suggesting anything other than what I just said. That is making a
point with a man who doesn't know very much at all.

Doctor Drivel wrote:

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.

"Back to the CU with its own MCB" is a very different proposition.

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.

Plenty to choose from:

314-01-01 & 314-01-02 tripping of the house socket circuit RCD, or
opening of the FCU fuse will result in loss of supply to unrelated
circuits. I.e. lights in the garage (both cases), and socket circuit in
the house (second case).

You need to stay on the right side of 413-02-09, and 413-02-10 and meet
the required disconnection times. This requires attention to the total
earth fault loop impeadance in the outbuilding. Depending on the
distance it may not be possible. (on a 13A fuse you have about 2.5 ohms
to play with and under 1 ohm on a 40A feed - including the suppliers
earth impedance which might already exceed the allowable amount). If you
can't manage that then you *must* use a TT style setup and regs
412-02-18 to 413-02-20 now apply.

If you are exporting the house earth on a TN-C-S system then all of
547-03 (supplimentary bonding) applies. This may not be possible in some
types og garage - and is likely to be a PITA in most.

We have the requirement to not include fixed point loads on general
purpose ring final circuits, the general requirement to not do things
that are contrary to standard practice etc (CBA to find the numbers for
those).

All the above from the 16th edition.

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.

Then that is what should be done. You only have to build it once - you
have to live with it every day.

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.

Note here that the 15A fuse is actually larger than the 13A head end
fuse - hence no discrimination - this is just sloppy design. It also
renders the local CUs fuse pointless.

If you are going to stoop to this level, you may as well skip having the
garage CU altogether, wire the incoming feed into a socket, and add
another FCU to take off the lighting feed.

A 100A breaker was also fitted in the MEM.

What would be the point of that? Or do you in fact mean it had an
incomer switch rated at 100A?

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.

MCBs and RCDs do very different things. An RCD will not trip on
overcurrent. A MCB will not trip on earth leakage.

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

You think?



--
Cheers,

John.

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Doctor Drivel wrote:

This pillock want the supply cable to be too small. Some mothers.....

So what are you suggesting for a 100A main supply? 35mm sq singles out
to the garage? At over five quid a meter each, just to save having a
switch fuse at the head end.

--
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:

This pillock want the supply cable to be too small. Some mothers.....

So what are you suggesting for a 100A main supply?

No.

On Tue, 26 Jul 2005 00:03:05 +0100, "Doctor Drivel"
wrote:


"Andrew Gabriel" wrote in message

which is not at all what you're suggesting in articles
eenews.net
eenews.net
reenews.net
reenews.net
reenews.net

I am not suggesting anything other than what I just said. That is making a
point with a man who doesn't know very much at all.

If you don't know very much at all about something, as has been
pointed out (so glad you realise the error of your ways), why do you
persist in peddling incorrect and dangerous information?



--

..andy

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