8 way grid plate and back box

[Chri5]

From what I can find out the box for 8 way (sunk) has 3 x 25mm knockouts to the base. So 3 x 25mm conduits for vertical drops.

What I need to feed in and out of 8 grid back box.

Ovens x 2 (13 amp each)
1 x 4mm radial circuit 32 amp in daisy chained from supply side of grid switch Oven 1 and Oven 2
2 x 2.5mm out to 2 unswitched single sockets under counter for oven plugs.

2 x 2.5mm ring circuit in / out

The ring to be looped in and out of 5 grid switches

1 x 1.5mm to 3 amp high level fused spur for hood extractor

1 x 1.5mm to 3 amp high level fused spur for wall extractor

1 x 1.5mm to 3 amp under counter fused spur for gas hob

1 x 2.5mm to 1 x unswitched single socket for washer unit

1 x grid fuse 3 amp feeding to grid switch for under wall unit LED strip, so 1.5mm out of back box.

Questions

Will a grid switch supply side take 2 x 4mm terminations

Would 3 x 25mm conduits have space for 1 x 4mm, 5 x 2.5mm and 4 x 1.5mm

 

[flameport]

2x4mm in a single terminal - not going to happen.
All those circuits in the conduits - perhaps if they are all in singles, if T+E then no way.

A ring looped in/out of 5 grid switches is also the wrong design.

 

[holmslaw]

..

 

[Taylortwocities]

2x4mm in a single terminal - not going to happen.
.

You should check your facts. The terminal capacity of the MK Grid swuitches is:
4 x 1mm2, 4 x 1.5mm2, 4 x 1mm2, 3 x 2.5mm2,
2 x 4mm2, 1 x 6mm2

So two 4mm² is provided for.

The grid back box has a large oval access hole at the back. So cable entry can be there. Stand grid box off the background with a ½inch batten and clip the cables down the wall.

It is a lot too much in that box though.

 

[RF Lighting]

2x4mm in a single terminal - not going to happen.

 

[Chri5]

What a ridiculous waste of money.

As you may have worked out it's to reduce above counter isolation via various separate boxes to a single central bank of switches.

Component cost is about £70 against £50 of above counter switches, numerous box chops and then the time the tiler would take to tile round the boxes.

It might be a bit too designer, but you blasting the idea as a waste of money is simply wrong- after taking the centralised v individual boxes (and the other extra works that requires) it would be the most economical method.

A ring looped in/out of 5 grid switches is also the wrong design.

Please qualify, how else should it be done if you wanted X number of same ring circuit feeds switched in a grid system ?

You should check your facts. The terminal capacity of the MK Grid switches is:
4 x 1mm2, 4 x 1.5mm2, 4 x 1mm2, 3 x 2.5mm2,
2 x 4mm2, 1 x 6mm2

So two 4mm² is provided for.

It is a lot too much in that box though.

Thanks ToTC.

Could you qualify your comment in bold. Do you mean that (in simple terms) the volume of cables + the switches and grid frames just haven't got the room ?

Obviously you understand my reason for asking, but when you get 12 / 18 /24 w units surely the same would happen (even with 1.5mm TE)?

The box is 133 x 133 x 40 for 6 or 8 way

It appears that it will take 4 x 25mm conduits (previously thought it was 3). MK catalogue states 4 ko's- the picture shows 3

So that would help with the cable entry / congestion.

 

[plugwash]

2x4mm in a single terminal - not going to happen.
All those circuits in the conduits - perhaps if they are all in singles, if T+E then no way.

A ring looped in/out of 5 grid switches is also the wrong design.

As long as the ring only serves the grid switches I don't see anything wrong with it electrically. Since the load will be very close to the middle the ring will be well balanced.

 

[1john]

For the demand stated it would appear that a 20A designated radial would suffice.

 

[Taylortwocities]

It appears that it will take 4 x 25mm conduits (previously thought it was 3). MK catalogue states 4 ko's- the picture shows 3 icon_confused.gif

It has 4 x 20mm and 4 x 25mm knockouts. 3 at top and bottom and one on each side.

I was only voicing my concern over the amount of wiring in that smallish space. You'll be needing to wire up line and neutral, so it will be busy in there!

Probably best to ignore Holmslaw - he can't get advanced things like Grid switches where he lives

 

[jaysean1]

I hope the guy knows he has to fit fuse module too with all the DP switches

 

[electronicsuk]

I hope the guy knows he has to fit fuse module too with all the DP switches

It's debatable whether or not this would be required when the switch feeds only a single 13A socket, as it's not a far cry from a spur from a ring final circuit, and the load is limited by the fuse in the 13A plugtop.

I personally wouldn't like to see it without fuses fitted, which seems like another reason to feed the whole lot from a 20A radial instead. It also means one less cable to fit in the conduit.

 

[Chri5]

I hope the guy knows he has to fit fuse module too with all the DP switches

Jay re read the 1st post, where fans req 3mm contact seperation (per MI guides) plain fused spurs will be provided at high level.

The hob coexists with the oven housing's so that will be a plain fused spur. Which will be in the same service panel as the oven sockets

The washer, and 2 oven will each have 13 amp plugs so access to 3 x single sockets required. Which will be via service panels.

For everyday use, and the main pint of isolation for those items would be at the grid.

Grids are part designed for bespoke work, and the principle is simply to comply with isolation requirements (immediate, without having to hunt about and within a short distance of the appliance) and to avoid clutter along a 9m counter area (u shape 4m + 3m + 2m).

I hate bursts of 12 sockets / fuse spurs / switches every 400mm above counter nearly as much as BAS hates downlights of the touch type.

What I might do is break the grids down and cover the ovens and fans on one quad plate, and the other items on a quad plate at different ends of the area.

Still not sure....... hey I'll go and dream up another idea, it's way past bed time.

 

[Taylortwocities]

At least with quads you can use 47mm double boxes.
More room for the spaghetti!

 

[holmslaw]

..

 

[RF Lighting]

It's a horrible way to do it though.

I have the little lablled grid switches in my kitchen and they're fantastic.

If i want to turn my dishwasher off to service it why should I have to isolate the entire kitchen? I could just turn the circuit breaker off to do that.

I use mine more as functional switches than I do as isolaters.