On Fri, 18 Sep 2009 06:35:30 -0700 (PDT), "js.b1"
wrote:

Go buy John Whitfield electrical guide.
BS7671 OnSiteGuide is a good reference, not a guide.


Is stripped T&E a realistic option for a small job?
If so, does the earth wire have to be sheathed throughout it's length?

No.
- Singles (6491X) have thicker insulation than FTE
- Earth MUST be sheathed throughout its length


Does oval marry up with the surface mounted
back boxes in a similar way to conduit?

No.
- For surface sockets use round conduit or mini-trunking.
- Round conduit suits "warehouse bare brick" or looks odd.

Options...
- Run FTE in mini-trunking between surface backboxes
- Sink FTE into wall in ZONE between sunk backboxes w/grommets, cover
the plaster cutout cutout with flat wooden bead until redecorated

The latter is much prettier and "lower profile" than mini-trunking
which is a ghastly abomination even in d-line.



In general.
- Capping & Oval require sheathed cable (Flat Twin & Earth, FTE).
- Round Conduit can use singles (6491X) or sheathed cable (Flat Twin &
Earth, FTE).

- With oval fit a grommet to the backbox, butt the oval up against the
grommet
- With plastic round conduit fit female bushes into the backbox, slide
the conduit into the bushes
- With steel round conduit you need proper Die (£25) & Bender (Hilmor
£250)

- Conduit must be installed prior to cable draw in (so enforcing the
rule that if someone got the damn stuff in then when it goes time for
replacement someone else can get it out and back in again!)
- Conduit must be continuous where Singles (6491X) are used, you can't
stop the conduit short and use a grommet

Plastic conduit is only sometimes used in domestic, 20-25mm oval is
flatter.
Steel conduit is very rarely used in domestic re expensive tools &
labour.

You can buy 20mm oval-to-round adapters, MK do them.
- Trading Depot might list them, £0.80-1.00 each
- Cable only passes easily through them one way
- Ok for oval-in-plaster-to-round-in-stud-wall-cavity runs


If you need to run a cable outside a Zone.
1 - Consider if a wiring accessory can be added to create a Zone.
2 - Use BS8436 cable such as Prysmian Flexishield or Earthshield

The problem with BS8436 is £120-180 for 1.5-2.5mm/100m.

Example of where BS8436 is useful:
- Light switch below chimney, no-where else to fit it
- a) BS8436 b) MK Echo (£180) c) Occupancy PIR (£50 + £50 for spare)
- Option a) is best because a switch is more reliable

Example of where BS8436 is useful:
- Room has sloping ceiling so no 150mm HORIZONTAL zone, solid floor
- BS8436 is a lot simpler than wiring accesory route-markers
everywhere

TLC are not carrying BS8436 (I asked, they asked NICEIC). No-one else
does.
Surprised, because "25m" would be a low risk investment for someone to
carry.

OP questions indicate he needs to read John Whitfield's book. Go to
Amazon UK.


Thanks, that's a lot of very good advice.
--
Kind regards,
Geoff Mills