Loft conversion - consumer unit

Hi,
I have been told the electrics in the loft have to be on their own consumer unit. Fine I suppose - except they now say it will be sited on the ground floor next to the existing CU, which has plenty of spare capacity. Is it definitely a requirement for a separate CU? Seems bizarre.
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Geoff wrote:

Have you been told on what specific grounds a new one is required? The only thing I can think of is that there's some something to do with your scenario which maybe you don't even know about which means it might be needed? Can't imagine what though.
David
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On Mon, 03 Dec 2007 08:53:17 GMT, Lobster
[snip]

No, I shall have to enquire with the BCO,
Regards.
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Geoff wrote:

There's no such requirement. What age is the existing CU? Might it be that components for it are no longer available?
--
Andy

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On 3 Dec,

Or so the BCO can sign it off under prat P without getting involved with the rest of the wiring.
--
B Thumbs
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snipped-for-privacy@privacy.net wrote:

I don't see how that follows, assuming that the existing circuits on the CU aren't being modified. The EIC can cover the new circuits only (and report any observations made on the old). In any case adequacy of the existing supply, meter tails, earthing and bonding will need to be checked and if necessary upgraded to ensure compliance of the new work. Adding a second CU might also require adding a isolator (switch-disconnector) in order to meet the requirement for a single main switch [460-01-02].
--
Andy

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On Mon, 03 Dec 2007 09:40:06 +0000, Andy Wade

Seems different folk, different tales. Spoke to the BCO and he confirmed providing the existing CU has the capacity, there is no such requirement.
As an aside, 2 smoke detectors run on mains power are required and must be on a separate circuit. Can each be taken off a different light circuit or must they be standalone circuits just for the detectors?
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Geoff wrote:

Either - pros and cons of each. It was discussed here very recently actually: http://tinyurl.com/3yjg59 (or <http://groups.google.co.uk/group/uk.d-i-y/browse_thread/thread/6673e81fc8df4566/c57b3e2d5ea5c27f?hl=en&lnk=st&q=# )
David
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Lobster wrote:

But, just to be clear, if they are interlinked they *must* both be on the *same* circuit (otherwise the linking would interconnect two circuits, which is forbidden).
--
Andy

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Andy Wade wrote:

and if they do not have a battery backup, then the circuit must be dedicated to the alarms and not power any other devices.
--
Cheers,

John.

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John Rumm wrote:

The OSG (p56) says they must have battery backup and that supply from a local, regularly used lighting circuit is OK. (It goes on to say that they shouldn't be fed via a 30 mA RCD - that'll have to be re-written soon, methinks.)
--
Andy

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Andy Wade wrote:

Which while not exactly conflicting with the building regs (other than the "must have battery backup" bit), only covers one of the options they present.
From B1:
"Power supplies 1.17 The power supply for a smoke alarm system should be derived from the dwelling's mains electricity supply. The mains supply to the smoke alarm(s) should comprise a single independent circuit at the dwellings main distribution board (consumer unit). If the smoke alarm installation does not include a stand-by power supply, no other electrical equipment should be connected to this circuit (apart from a dedicated monitoring device installed to indicate failure of the mains supply to the smoke alarms - see below).
1.18 A smoke alarm, or smoke alarm system, that includes a standby power supply or supplies, can operate during mains failure. It can therefore be connected to a regularly-used local lighting circuit. This has the advantage that the circuit is unlikely to be disconnected for any prolonged period. "

Or insist they must be wired in MICC etc?
--
Cheers,

John.

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John Rumm wrote:

[snip]
Thanks for all that (which I see is reproduced in the EGBR).

B1-1.20 (2000 version) and the EGBR says that the non-use of an RCD is only "preferable" and that any RCD should not also protect sockets for outdoor portable equipment. All quite sensible and an obvious case for an RCBO in a TT system or in 17th edition land.
B1-1.20 (2006 version) just says that the electrical installation should comply with Approved Doc. P, which is about as vague as it comes. In fact the 2006 version of AD-P refers you back to the 2000 version of B1 - what a mess.
--
Andy

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Geoff wrote:

I have never heard this stated as a general case before....

Unless yours is for some reason unacceptable - but that seems odd.
Many loft conversions end up having power taken by extending the existing upstairs circuits (since these are often lightly loaded).
--
Cheers,

John.

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On Mon, 03 Dec 2007 08:49:56 +0000 someone who may be Geoff

It would help if you stated:-
1) who told you this
2) on what grounds they claimed this
Without this information further speculation is pointless.
--
David Hansen, Edinburgh
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On Mon, 03 Dec 2007 18:31:06 +0000 someone who may be David Hansen

No reply yet. I suspect a troll.
--
David Hansen, Edinburgh
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