Dear All,

I am trying to tidy up the kitchen wiring prior to fitting a new set
of units and worktops. As I have a large number of fused spurs
(boiler, washing machine, fridge, dishwasher, hob, extractor, 2*lights
under units) I was hoping to tidy up the array of single FCU switches.
I had planned to use dual metal back boxes but was wondering if anyone
knows of a supplier of dual FCU switch plates?

This would be wired into the ring main and allow two fused spurs in a
neat and tidy fashion.

I have looked on the BES, TLC etc www pages with no luck.

thanks

Ian

On 8 Sep 2003 00:39:57 -0700, (Ian) wrote:

Dear All,

I am trying to tidy up the kitchen wiring prior to fitting a new set
of units and worktops. As I have a large number of fused spurs
(boiler, washing machine, fridge, dishwasher, hob, extractor, 2*lights
under units) I was hoping to tidy up the array of single FCU switches.
I had planned to use dual metal back boxes but was wondering if anyone
knows of a supplier of dual FCU switch plates?

This would be wired into the ring main and allow two fused spurs in a
neat and tidy fashion.

I have looked on the BES, TLC etc www pages with no luck.

thanks

Ian

A good solution to this would be to use grid system components, then
you can build what you want. There are several brands, but MK have
the most comprehensive range that I've seen.

Basically you buy the back box, and then a frame for the appropriate
number of modules. The modules click into place and then there is a
front plate that fits over this. Face plates are in the usual white
plastic or metal patterns.

There are double pole switches (20A), neon indicators and fuses. For
a double FCU, you would need as a minimum a four module plate, which
is the width of a double socket. This would need two switches and
two fuses. If you wanted neons as well then it would be a six module
plate which is three above three and slightly larger.

You can order labelled switches if you want to be fancy.

Electrical wholesalers have this stuff and I've also seen it B&Q.



..andy

To email, substitute .nospam with .gl

I was hoping to tidy up the array of single FCU switches.
I had planned to use dual metal back boxes but was wondering
if anyone knows of a supplier of dual FCU switch plates?

You could do what I did and use a grid switch. I used a 3 module type that
is the size of a double socket (4 module would also fit a double socket
space). I used only 20A DP switches, running to an unswitched socket behind
the appliance. There is no fuse in the switch. It is safe to do this, even
on a 32A circuit, provided that the runs of 2.5mm aren't too long. This is
because overcurrent protection can be assumed to be provided by the 13A fuse
in the plug top. The 20A switch is protected because of this. If the 2.5mm
spur isn't too long, then earth loop impedence will be fine too. This is
required so that the 32A breaker can be used for short circuit protection
for the cable up to the socket.

Christian.

snip info from Andy and Christian on grid switches

Thanks Andy and Christian,

The grid system looks very useful for my needs, but I have difficulty
visualising the terminals on the DP and fuse modules. I have
downloaded the MK grid pdf file from TLC (I found them once I know
what to look for) but despite all the useful info and pictures not one
view from the rear of the modules.

I currently have the ring main going into the unswitched side of a
single FCU
and then continuing into another FCU (unwsitched side) and then a
double socket and then a third FCU (unswitched side) before returning
to the ring. So the single metal boxes containing the FCU each have
3*2.5mm2 cables (ring *2 and cable to hidden unswitched socket), these
are a little cramped. These
faceplates are all mounted together touching each other in a
horizontal line.

Am I correct in assuming that the 20A DP switch has two input
terminals and two output terminals? Earth wires all connected to the
grid frame?

And that the 13A fuse module has two screw terminals?

I assume that I would make the ring main up by using links between
modules?

sorry about the extra questions.

thanks

Ian

On 8 Sep 2003 06:46:46 -0700, (Ian) wrote:

snip info from Andy and Christian on grid switches

Thanks Andy and Christian,

The grid system looks very useful for my needs, but I have difficulty
visualising the terminals on the DP and fuse modules. I have
downloaded the MK grid pdf file from TLC (I found them once I know
what to look for) but despite all the useful info and pictures not one
view from the rear of the modules.

I currently have the ring main going into the unswitched side of a
single FCU
and then continuing into another FCU (unwsitched side) and then a
double socket and then a third FCU (unswitched side) before returning
to the ring. So the single metal boxes containing the FCU each have
3*2.5mm2 cables (ring *2 and cable to hidden unswitched socket), these
are a little cramped. These
faceplates are all mounted together touching each other in a
horizontal line.

You can get deep boxes for grid plates which will give you more room.
It doesn't really matter about the order that you wire the circuit as
long as you make only one spur and wire the rest as part of the ring.

Within the grid box you only need to run single conductors.

Am I correct in assuming that the 20A DP switch has two input
terminals and two output terminals?

Yes they do.


Earth wires all connected to the
grid frame?

Probably easiest. There is also an earth terminal on the box which
you connect to the frame as well. You can run all earths to the box
and a single to the frame if it's easier. Obviously sleeve all the
earths.


And that the 13A fuse module has two screw terminals?

Yes.


I assume that I would make the ring main up by using links between
modules?

Exactly.


sorry about the extra questions.

No problem.


thanks

Ian

..andy

To email, substitute .nospam with .gl

Am I correct in assuming that the 20A DP switch has two input
terminals and two output terminals? Earth wires all connected to the
grid frame?

Yes.

And that the 13A fuse module has two screw terminals?

Yes, but you don't need the fuse module. The plug top is already fused,
provided you don't attempt to hard wire the appliance flexes directly into
the grid switch. The design absolutely relies on there being a 13A fuse in
the system, however. This can be either the plug top and an unswitched
socket, or a unswitched fused connection unit to terminate the appliance
flex. The former is cheaper and more flexible, provided it can be located
where it won't be used for portable appliances. (i.e. under the worktop or
behind integrated appliances).

Your main issue will be ensuring that the ring is not overloaded or made
lopsided. With mine, this is not an issue as the whole lot is fed from a 6mm
radial on its own 32A circuit. If you have a dishwasher, washing machine and
tumble dryer off a single point on the ring, you may find that calculations
show the ring is overloaded, especially if it isn't near the mid point. You
would certainly have to consider refraining from using too many appliances
at once, especially if you have kettles, microwaves and built in ovens or
dual fuel cookers on the circuit.

The terminals aren't huge on the DP switch modules. I couldn't run 2 6mm
cables to them, so they are each fed with a separate 2.5mm cable to a nearby
junction box where the 6mm terminates. Again, these short sections of 2.5mm
are protected against overcurrent by the 13A fuse in the plug top and short
circuit by measured low earth loop impedence (no RCD in the system).

Christian.