Fan on Timer Install with Downlights

[Rob1982]

Before I ask the question its best you guys know some details:

About Me:

I’m a 25 year old IT technician who has had no experience of any electrical installations previous to the one I am currently doing. I have copies of BS 7671:2001 and BS 7671:2001 (2004) which I’ve been reading through over the past few months.

The Project:

I bought a 1950’s ex council flat back in March which had surface mounted cabling/accessories and existing vulcanised cabling left in walls and ceilings. I’m about half way through doing a complete reinstall of the entire electrical system.

Current Situation:

I have pulled down all the ceilings and removed all the existing cabling and accessories.

I’ve cut channels in walls/plaster and notches in the reinforced concrete beams above old ceiling for cable runs.

I’ve fitted all knock out boxes to walls and have run most of the cabling for power, lighting, TV, network and supplementary earth bonding.

I’m currently getting ready for the first fix inspection to be done by an electrical contractor on behalf of the council to get my work approved. I have been in regular contact with the contractor through the installation to make sure Im complying with the regs.


Question:

I have 4 12v down lights (plus 4 small junction boxes) that I will be putting in the bathroom and also have a fan with a timer. I will have a pull cord light switch inside the bathroom and a 3 pole isolator on the other side of the bathroom wall in one of the bedrooms.

I want the fan to turn on with the lights and to remain on for 15 minutes or so after the lights have been turned off.

I’d like to know how to connect everything up so that it will work the way I want it to. At the moment I have some 4 core cable going from the fan location to a box on the other side of the bathroom wall which will hold the isolator. I also have the cables from the lighting ring coming in both sides of the room.

Thanks in advance for any help guys!

 

[securespark]

I have copies of BS 7671:2001 and BS 7671:2001 (2004) which I’ve been reading through over the past few months.

You need BS 7671:2008....

I’ve cut.....notches in the reinforced concrete beams above old ceiling for cable runs.

You sure that's safe? Have you consulted a structural engineer?
[/quote]

Why have you got the loop (it's not a ring btw...at least, I hope not ) at the 3 pole isolator?

 

[Rob1982]

I know BS 7671:2001 and BS 7671:2001 (2004) are out of date but i made my application went they were still current. The contractor will also still let me have a split comsumer unit.

the reinforced beams are covered in clinker which iv cut into, not the concrete itself.

 

[Rob1982]

Why have you got the loop (it's not a ring btw...at least, I hope not ) at the 3 pole isolator?

whats the difference in the wiring of a loop and a ring?

the loop doesnt go directly to the 3 pole isolator[/quote]

 

[skenk]

At the isolator you need live, switched live, and neutral - if you have looped in at the switch then you can get these 3 from the switch. If you have looped in at the light, or likely in this case the first junction box, then you can get them all from here. Use the 3-core and earth, with the switched live sleeved in brown and the third core sleeved in blue (for neutral) to take these 3 to the isolator. Then connect the 3 poles of the isolator to the fan using the existing 3-core and earth you have installed. A timer fan will have 3 terminals (+earth possibly) - live, switched live and neutral.

Loop in refers to lighting circuits were you take the permanent live from the CU to the first light/switch, then the next light/switch, then the next . . . .

A ring circuit is when you take the live from the CU to the first outlet, then the next, then the next . . . <i>and finally from the last outlet back to the CU,</i> thus making a ring.

You don't wire lighting circuits as a ring . . . i don't know why, you just don't . . . it's not the way we do things here i guess, i suppose the (relative) complexity of lighting circuits don't lend themselves to it.

 

[Rob1982]

Thanks for the reply skenk but to honest i still dont fully understand!

Below is a plan of my bathroom (hopefully) and how the cabling has been done so you can see the current situation abd what needs to be done.

Just to be absolutely clear on whats what:

blue lines - walls
black lines - 1.5 T&E
purple - doors and windows
brown - 3 core + earth
yellow - beams and the notches cut into them

Untitled

• Rob1982
• 22 Jul 2008
• 1

If someone could explain in laymans terms what needs doing id really appreciate it!

 

[ColJack]

it's going to get awfully cosy in that pullcord...

take the "loop in" and "loop out" to the switch..

take a 3C+E from the switch to the fan isolator
take a T+E from the switch to the lights..

if you can fit a double pole switch it makes life easier..

put the brown from the loop in, loop out and 3C+E in the L ( feed ) terminal of the switch, the blue ( grey sleeved blue of the 3+E ) from the same into the N ( feed ).
then the brown of the T+E and the black ( sleeved brown ) core of the 3C+E into the L ( load ) terminal of the switch, and the neutral of the T+E into the N ( load )..

if you don't have a double pole switch then all 4 neutrals go in a terminal block..

alternatively you can do the same with a JB ( small enough to pull out through the light hole ) at the first light..
brown from loop in, out, swich and 3C+E in terminal 1.
blues from loop in, out and grey sleeved blue from 3C+E into terminal 2
blue ( sleeved brown ) from switch and black ( sleeved brown ) into terminal 3.

lights then connect to terminals 2 and 3 ( N and L respectively )

 

[Rob1982]

thanks for the detailed response coljack.

Since i already have a single pole pull cord and a few mini JBs i will probably do that method.

When you say for example "black ( sleeved brown )" do you mean i need to put a brown sleeve over the wire before it goes into the terminal like you would with a green/yellow sleeve for the earth wire?

 

[ColJack]

yes, this is to indicate that it's a live or switch wire, and not a neutral..

you can buy twin brown cable for switch drops but no one usually bothers unless they're doing a whole estate or large install..

 

[breezer]

There is a drawing in the stciky

 

[Rob1982]

Ok, thanks for clarification on that.

breezer, could you point me in the direction of the picture in the sticky that relates to my issue?

 

[breezer]

ok ,so it only has one light, all you have to do is add 3 more, i could have done a drawing, but how may "extra lights" 1,2,3, 4, 5..........