Lighting System - Junction Box Preferences

[Foot_Sore]

Due to a flooding incident we are renovating the living room. Ceilings have been ripped out and floor above is next! Gives a great opportunity to install some new lighting. Living room is on the large size at 8m by 6m and the lighting design includes 11 ceiling mounted fittings, one 5A Lamp socket, and 4 wall lights. Some lights to wash the walls, some task lighting, and some general lighting. All LED (bulbs checked for dimmability)

The lighting will be marshalled into 4 zones for control by either Lutron QS or Futronix P400.

The intention is to home run all 16 cables to a marshalling box to allow changes to the 4 zones of lighting at a later date (and ensures all joints are accessible at fitting/marshalling box).

I have previously installed a 12 Channel Futronix system. For this I used two boxes with Choc blocks to take some 28 lighting cables to marshall all the wiring. Neutrals & Earth commoned through Choc blocks.

Question 1: With some 16 lighting cables, 4 switched cables and a power cable what should I use to marshall and connect the cables.

Option 1 - Large plastic box, choc block with connecting cables to connect up the zones with multiple cables into a chock block. Terminal map would be done and left on front of box.

Option 2 - Wago Box for each zone (4), and one to split the incoming power to the four zones. So five Wago junction boxes in total. The most would be 6 cables (4-lights, switch and power) into Wago box so within spec. Each box could be labelled for zone.

Option 3 - Something else?


Question 2: Do I still need to allow 100W per fitting for load calculation in case some numpty puts in a light they can no longer buy in a fitting that it won't fit in and isn't rated for 100W anyway. So 20 lights on circuit (living + conservatory) 2000W = 8.33A, currently has a 6A MCB, is that OK. More than enough for planned lighting load which would be only 120W.

1.5mm cable is OK for 3600W/15A so am I OK on 1.5mm to the marshalling point. It is a short run to the CU so 2.5mm is no problem, would this be better or pointless?

All help appreciated. Just want to make sure I am making best use of latest connections and being as future electrician friendly as possible (one day I will move and an electrician will need to work out what I have done).

Regards
Dave

 

[flameport]

With that many cables, these would be a tidy and manageable solution: http://www.cablecraft.co.uk/connect/din-rail-mounted-terminals-accessories.html

100W per fitting is obsolete and left over from the days of a single pendant in each room. Use whatever the actual lights are rated for.

2.5mm will make terminating the wires far more difficult and is totally unnecessary. 1.5mm could be used, but it's still oversized. 1.0mm would be the usual choice.

 

[ban-all-sheds]

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Question 1: ...
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Question 2: ...
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Question 3: Do I really need 11 ceiling lights, i.e. about one every 2m?

No.

 

[Foot_Sore]

100W per fitting is obsolete and left over from the days of a single pendant in each room. Use whatever the actual lights are rated for.

Great I thought I had heard it was outdated but wanted to be sure.

2.5mm will make terminating the wires far more difficult and is totally unnecessary. 1.5mm could be used, but it's still oversized. 1.0mm would be the usual choice.

Was only going to do 2.5mm from CU to marshalling point then 1.5mm from there on. Could get 1.0mm but have always used 1.5mm on lighting circuits and I have a roll that should finish this job. Will see if I can get 1.0mm

With that many cables, these would be a tidy and manageable solution: http://www.cablecraft.co.uk/connect/din-rail-mounted-terminals-accessories.html

The Din Rail stuff looks great (if a little harder to get to grip with) and I am guessing avoids the need for little loop connectors as required with chock blocks. I presume the cross connects allow multiple connections to be common-ed together to connect the lighting cables. The earth box seem to do this automatically. More research required.

Had found DIN rail mounts for Wago 8-block connectors and thought that would be neater in a single box than 5 standard Wago boxes.

Thanks for the pointer.

Dave

 

[flameport]

If you already have 1.5mm then may as well use it.

1.0mm is rated for 16A if surface clipped, or 8A if surrounded by thermal insulation, therefore no problem using it with a 6A MCB even if installed in the worst conditions.

 

[Foot_Sore]

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Question 1: ...
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Question 2: ...
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Question 3: Do I really need 11 ceiling lights, i.e. about one every 2m?

No.

Mmmm OK it seems excessive but using LEDs with custom picked low wattages. The room is 8m*6m so 48m2. 11 lights is 1 light per 4m2 but they don't really work like that

Decorative Lighting - lower wattages and likely dimmed (2-4W LED)
Fireplace - 2 targeted spots
Window 1 - 1 targeted spots to wash light down curtains
Window 2/bench seat - 2 targeted spots to wash light down curtains
Window 3/french doors - 2 targeted spots to wash light down curtains
Book case - 1 targeted spot
2 tiny spots on driver in an alcove/shelf unit

Task Lighting (6W LED)
2 spots over 2 sofas for reading
1 spot over mainly empty second half of room for kids playing board games

General Lighting
4 wall lights - do not ask what they cost - I was nearly sick
5A floor socket for table lamp

The lighting controller will deliver/control lighting according to requirements. This includes dimming. Lighting for different tasks TV watching, reading, entertaining and autopsies (all on full)

It is a bit more high end than a couple of ceiling roses!

Sorry
Dave

 

[Foot_Sore]

If you already have 1.5mm then may as well use it.

1.0mm is rated for 16A if surface clipped, or 8A if surrounded by thermal insulation, therefore no problem using it with a 6A MCB even if installed in the worst conditions.

Room will likely have insulation (sound) above plaster board. But if 1.0mm still OK for 8A then I might go for it. I have a lot of connections to make. If it makes the job easier and more importantly neater then great.

Dave

 

[Foot_Sore]

OK - I have read up on the DIN rail terminals and struggling with choices, there are just so many of them. Single, Double, Triple linked, no linked.

I could put in triples so all three connections (L/N/E) for each light are on a single terminal. Thinking this could be really neat with some combed mini trunking inside the box to deliver each cable to the right terminals. Linking all the earths/neutrals with a 30 bank cross connector. The lives linked with relevant 2/3/4 and 10 connectors.

Alternatively use doubles for L/N and earth terminals for all the finals.

Finally use singles and use beige for all the lives, blue for all the Neutrals and Green/Yellow Earth terminals. This would be some 51 terminals (17*3) but still only 25cm or so.

The latter might be easier to understand but more a rats nest for changes as would need longer unsheathed cables inside the box. The former keeps each cable to a single terminal.

Any comments.

It is quite hard to work out what cross connectors go with which terminal, especially on web, the downloadable catalogue is based around each product rather than product type (e.g. all 2.5mm RKD range together rather than all end plates together). Rang the manufacturer for help and the nice call taker could give me prices but admitted to knowing nothing about how they worked or what cross connector goes with what terminal.

The wago stuff is easier to work out what I want but the DIN rail stuff looks like it could be done much neater.

Thanks for the help.

Dave

 

[333rocky333]

http://www.surewire.co.uk/products/...-switch-junction-boxes/products-and-benefits/

 

[bernardgreen]

The surewire panels have ONE switch controlling all the lights. You will need one surewire panel for each switch.

DIN rail connectors in a suitable and accessible housing do provide the most flexible way to connect lamps and switches at the time of installation. If they are all grouped together then, at the cost of more cable, there is the ability to easily make alterations when the original lighting plans are foune to be less then perfection.

Untitled

• bernardgreen
• 26 Mar 2015
• 3

This controls 12 lamps with the lamps wired to the tops of the DIN rail terminals. The lower terminals connect to the switches. In this the switches are the blue relays controlled by the PCB but could be ordinary switches wire using twin and earth.

 

[Foot_Sore]

I had already looked at the surewire box but ruled them out as they bring cables flat from every side (not pretty), I would need a number of them, and they would be less workable than even a chock block solution. Which still has its merits on the cost side.

I like the look of the DIN rails so will be ordering some. Just need to decide on the single/double/triple terminals.

Cheers
Dave

 

[SimonH2]

With DIN rail terminals, you can either wire along one side with short bits of wire, or you can use commoning bars which screw into the tops of the terminals and create a number of commoned terminals. Given that you are planning 16 lamps and 4 circuits I'd be inclined to do it something like this along the rail :
L,N,E in & loop out : 2 earth terminals (also acts as stop end), 2 terminals commoned and labelled N, 4 terminals commoned and labelled L
Switch drops : 2 of the L terminals from the above line will supply power to the switch drop(s), then 4 terminals for the switch returns*, then another few earth terminals.
Light circuits : You need 16 live terminals, 16 earths, and 16 neutrals. I'd be inclined to do them something like 4 E, 4 L, 8 N (commoned block), 4 L, 8 E, 4 L, 8N, 4 L, 4 E
Wire all your fixed wiring to either the top, or to the bottom - all one side. On the other side, link the groups of neutrals together (a length of wire from the in/loop N block to the first lights N block, then to the second lights N block. You don't need to link the earths that they are linked via the DIN rail. Then link the switch returns to the light outputs they are to control. When you want to change the mapping between switches and lights, you just change the links between live terminals.

That's a lot of terminals, and will need a fairly large box. You may find it beneficial to split it into 2 rails parallel along two sides of the box - you don't need much room between the rows of terminals, and you will need to link the two rails with an earth link.
You can reduce the number of E and N terminals by wiring to both sides, but it's something of a bodge. You can also bodge by putting more than one wire into a terminal - but again a purist will "frown" at that.

* You might want to make each switch circuit a block of 2 teminals with commoning bar to ease linking.