As I need to rewire my new house I thought I'd take the opportunity to add
some home automation ... however there are so many options and all the good
ones (star network with DIN based switching) seem too expensive for me just
now. So how difficult is it to convert from ring to star?
Would it be possible to:
-Run the ring to sockets and switches in conduit through plaster initially
If / when budget, time etc allow use of c-bus or similar
For a socket
-draw-out ring cable from conduit leading to socket
-use a junction box in under floor cavity to make ring continuous
-drop star-cable into socket
For a light
- using existing ceiling rose / junction box in under floor cavity to
continue light ring
- connect light fitting to star-wired DIN-Dimmer
- draw-out live/switched live cable to switch from conduit
- drop in c-bus control cable to switch box
I understand that in the recent regulations junction boxes are frowned on,
but they must be used for lighting circuits and if running a garage circuit
from a consumer unit (or are you expected to run SWA cable through the house
too). So if these are acceptable is the above use of junction boxes OK???
Junction boxes must be 'accessable', a term which is as open to
interpretation as the rest of regs. General opinion seems to be that
a junction box under floor-boards, especially with fitted carpet or
wood block is not accessable.
Apparently vibrations occur at mains frequency and this can cause the
screws to loosen because electricians, unlike other engineers, haven't
discovered self locking screws or screw locking compound yet :-)
Regulation 526-04-01 refers to accessability of junction blocks
An NICEIC recommendation says
"However, connections required by regulation 526-04-01 to be sccessible
should NOT generally be located under a floor where a carpet is likely
to be laid. A fitted carpet can effectivley render connections beneath
the floor inaccessible because of objections from the occupier to the
carpet being lifted, or difficulties in finding the access trap."
But it does seem to be a widely ignored reccomendation.
Ignored yes, I cannot see how to wire a light which doesn't have its own
rose without it being concealed?
For sockets does this mean that if I used some big chocolate block at the
back of the socket box and ran an additional star-wired cable down the
conduit that would be OK?
For a double 13A socket I assume 1.5mm cable would be fine?
526-04-01 relates to "Accessibility of connections" in general and not
just junction boxes. Access to junction boxes is not normally required
for testing and inspection (or for any other reason during the life of
most installations), and I suggest that NICEIC's interpretation of the
regulation is a little over the top for most cases.
Work that requires access to such a junction box will normally involve
ripping up the floor anyway.
Well you could use one of these and put the new fitting over it.
Alternatively if you cannot get access through the floor you can
always cut a hole in the ceiling. There is usually a way if you think
about it long enough.
You must put a warning label on the socket outlet or the socket box.
Anybody removing the socket could assume that the terminal blocks
belonged to the same circuit as the radial cable.
Using crimps and a proper crimp tool would, in my opinion, be a better
option for joining the ring as they take up less space in the socket
That depends on several factors such as the cable length and the
rating of its protecting MCB, to mention but two of them. Generally a
larger size of cable (2.5mm to 6.0mm) would be used.
It's tricky to convert power circuits properly. Also most of the
systems I have seen or installed control very few socket outlets
directly. You will almost certainly still need a number of
uncontrolled sockets to plug in such things as a vacuum cleaner.
Where appliances are to be switched in this way it's much better to
wire them using radial (star) circuits in the first place. You can
initially connect them into appropriate MCBs at the consumer unit and
add any control units later.
This allows you to wire the ring circuit in the usual way and to make
all the usual load calculations.
Switches are not normally on a ring. You will also find that conduit
does not fit in the depth of most plaster - so be prepared to dig into
the walls as well.
Yes. However if such sockets were wired as radials anyway then you
would only need to add a control unit at an appropriate place.
Why not run the cable for the light fitting and light switch to where
you eventually intend to locate the DIN system boxes. You can then
make all the connections there and it will save you pulling up the
I don't know who told you this but they are wrong.
Junction boxes can be used anywhere as long as they are appropriately
rated, and the connections made correctly.
SWA cable does not fit into junction boxes in any case.
Wire as star originally and then add controls - that is an excellent and
simple solution :) Not sure why I didn't think of that :-s
The hurdle now is to work out which sockets should be star-wired.
For sockets I am thinking 1 socket near curtains for automated opening, 1
for AV equipment that would sit on standby. And more for lights.
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