Some questions that I would appreciate some help with...

[jdwood]

Hey guys,

First post so please be gentle! Its on a subject that seems to be a bit of a taboo around here - downlights.

Id better set the scene...

I recently got the keys to my first home (a new build apartment) which I am doing a fair bit of work on before I move in, including multiroom audio and video distribution and changes to the lighting. It is quite a unique apartment as it is in a 3 storey building, but covers half of the top 2 stories and has its own front door on the ground floor. The ground floor is one apartment and then the top two floors are split in half to create two mirrored apartments. So at no point is there another dwelling above mine.

Does that make sense?!

Id better add a bit about myself aswell. I am not an electrician but I run all kinds of cables and do installations of various pieces of electronic equipment (including hardwiring) for a living. This is mostly done overseas in an environment where regulations dont apply so much, but I will avoid going into details about that.

Ok, the downlighters...

These will be fitted into a number of rooms, the ceiling construction is plasterboard onto wooden joists. I am using 230v sealed unit downlighters with 90minute fire rating. I will be replacing all the bulbs with 35w.

So the first question is, am I using suitable units and is this notifiable to the building regulators?

One of the rooms that I am intending to have the lights in is the kitchen. Obviously I cant terminate these myself but is it allowed for me to cut the holes, run the cable in and leave hanging for a qualified sparky to come in and terminate/test? How would you electricians feel about doing the job? Would you want to run the cable yourself?

There is also a bay window in the kitchen where I would like to have 2 LV lights on the same circuit as the under unit lights. Recessed lights are a no go so I have surface mounts. I have already cut the plaster and put some low profile trunking in place ready for these. Is this the correct way of doing it? I didnt like the idea of having the cables from the transformer plastered directly into the wall! I have already pulled in a 1.5mm2 T+E between the void were the transformer will be located and the switch for the under unit lights.

Also in the kitchen I have a wall mounted TV. To get power to this I was intending to have a fused spur at outlet height with flex running up to a backbox behind the TV. The flex would be protected in the wall cavity by flexible conduit and glanded into the backboxes. Is this adequate protection? And again, if I were to run the cable and leave ready to terminate would this be ok? Finally, on this part of my installation, does a double gang single socket with single fused spur exist (kind of like a cooker unit but 13A) or will I need to cut two separate single gang holes as I would like a socket outlet next to the fused spur.

Finally, there is a two-way circuit between the entrance hall and first floor landing. Is it possible to separate the entrance hall lights from the circuit to put them on there own switch? And is this possible using the existing wiring?

Oh, I did say finally, but ive just thought of something else! Could anyone suggest somewhere to get dimmer switches for two-way circuits? Am looking at single point dimmers and slave type setups aswell.

Sorry for the essay but any help/advice on the above will be hugely appreciated!

Many thanks

John

EDIT: Just to add, all materials would be provided by myself (light units, cable, earth sleeve, cable clips, MK faceplates, dry wall backboxes etc) so the electrician in theory would only need to terminate/test and nothing else. Again, is this something you electricians would be happy with?

 

[ban-all-sheds]

Id better add a bit about myself aswell. I am not an electrician but I run all kinds of cables and do installations of various pieces of electronic equipment (including hardwiring) for a living. This is mostly done overseas in an environment where regulations dont apply so much, but I will avoid going into details about that.

In that case you should read about the regulations here: //www.diynot.com/wiki/electrics:part_p, and you'd probably appreciate the technical info here:

http://www.kevinboone.com/domesticinstallations.html
http://www.kevinboone.com/cableselection_web.html

So the first question is, am I using suitable units

Not from an efficiency POV.

and is this notifiable to the building regulators?

In kitchens and bath/shower rooms it is.

One of the rooms that I am intending to have the lights in is the kitchen. Obviously I cant terminate these myself but is it allowed for me to cut the holes, run the cable in and leave hanging for a qualified sparky to come in and terminate/test? How would you electricians feel about doing the job? Would you want to run the cable yourself?

You need to find your electrician first, and ask him. He will have to sign documents to say that he designed it and he installed it, and that it complies with all the applicable wiring and building regulations, so it's how he feels that matters.

There is also a bay window in the kitchen where I would like to have 2 LV lights on the same circuit as the under unit lights. Recessed lights are a no go so I have surface mounts. I have already cut the plaster and put some low profile trunking in place ready for these. Is this the correct way of doing it?

Oval conduit would have been easier. And are the channels deep enough to allow a thick enough layer of plaster to avoid cracking?

I didnt like the idea of having the cables from the transformer plastered directly into the wall! I have already pulled in a 1.5mm2 T+E between the void were the transformer will be located and the switch for the under unit lights.

Did you do the voltage drop calculations to check that 1.5mm² is OK?

Also in the kitchen I have a wall mounted TV. To get power to this I was intending to have a fused spur at outlet height with flex running up to a backbox behind the TV. The flex would be protected in the wall cavity by flexible conduit and glanded into the backboxes.

Why are you using flex for permanent fixed cabling?

Is this adequate protection?

Yep. If there's insulation in the cavity you should do due diligence and confirm that the cable capacity is OK for that installation method.

And again, if I were to run the cable and leave ready to terminate would this be ok?

See above.

Finally, on this part of my installation, does a double gang single socket with single fused spur exist (kind of like a cooker unit but 13A) or will I need to cut two separate single gang holes as I would like a socket outlet next to the fused spur.

You'll never get them properly spaced - use a dual box:

Finally, there is a two-way circuit between the entrance hall and first floor landing. Is it possible to separate the entrance hall lights from the circuit to put them on there own switch? And is this possible using the existing wiring?

Do you mean you have lights in the entrance and the landing, both controlled by a single switch in each location? If so the answers to your questions are yes and no, respectively.

Oh, I did say finally, but ive just thought of something else! Could anyone suggest somewhere to get dimmer switches for two-way circuits? Am looking at single point dimmers and slave type setups aswell.

If you want to be able to control the dimming from multiple locations then master/slave or home automation (i.e. X10 or more modern equivalent) is the only way to go.

EDIT: Just to add, all materials would be provided by myself (light units, cable, earth sleeve, cable clips, MK faceplates, dry wall backboxes etc) so the electrician in theory would only need to terminate/test and nothing else. Again, is this something you electricians would be happy with?

Again see above, but also make this clear to the electrician since it may affect what he charges you.

 

[jdwood]

Thanks for taking the time to reply to all my queries. Ill do my responses in the same order.

1. Thanks for the links. Have looked at the Part P regulations a number of times in the past but having not done a specific course that covers them, not all the points are very clear!

2. You say that I am not using suitable units from an efficiency point of view... is that referring to downlighters in general or just this specific type of unit?

3. Am I right in thinking that notification to the building regulators is done by the electrician who completes the work?

4. Good point, which I didnt think of. I will leave the cable in place then he can use it as a draw if not happy terminating it. I will do the same with the others - cut the hole and put draws in place. He can then do his own stuff if not happy with the routes.

5. Oval conduit would not have been able to fit in I wouldnt have thought. The trunking is fairly low profile so there is about 7-10mm depth for plaster.

6. No, but I will do to make sure. I thought most lighting circuits went on 1.5mm2? I will still do it either way. The lights are only 10w G4 caps.

7. Its not a permanent installation as such. The flex will have an IEC on one end plugged directly into the TV. It will exit behind the TV (with the rest of the cables) through a double gang box with brush strip faceplate. If you imagine a fused spur with knock out for a flex, I basically want that but with the cable going from the back of the faceplate rather than coming out at the front. Does that make sense and more to the point, is it allowed?

8. Theres no insulation in the cavity, the cable is the one that came with the TV with the plug chopped off basically.

9. Will have a look into those backboxes but drywall ones would be easier. Looks like I will need to have two single gang holes. One for a socket, one for the fused spur and will just space them accordingly.

10. Yep, thats what I meant. Will look into the way its cabled and have a look at my options.

11. Have thought about X10 as an option but its all abit overkill really to just dim lights from two locations! Again, will look at the options and decide if its really worth it.


Thanks again for taking the time to respond. Has given me alot to think about but clarified a number of things also.

Cheers

John

 

[ban-all-sheds]

2. You say that I am not using suitable units from an efficiency point of view... is that referring to downlighters in general or just this specific type of unit?

In general. Next time you're in a house that has them, count them up. They'll almost certainly be 35 or 50W lamps, so try to imagine how brightly lit the room would be with 1/3rd to 1/2 the number of traditional 100W bulbs hanging down.

3. Am I right in thinking that notification to the building regulators is done by the electrician who completes the work?

Yup. Beforehand if he's not registered, afterwards if he is.

4. Good point, which I didnt think of. I will leave the cable in place then he can use it as a draw if not happy terminating it. I will do the same with the others - cut the hole and put draws in place. He can then do his own stuff if not happy with the routes.

Will that allow him to be happy that cable routes are satisfactory, that any joist holes are in the right places etc?

5. Oval conduit would not have been able to fit in I wouldnt have thought. The trunking is fairly low profile so there is about 7-10mm depth for plaster.

Oval conduit is shallower than trunking....

7-10mm sounds OK - check with the plasterers in the building forum

6. No, but I will do to make sure. I thought most lighting circuits went on 1.5mm2? I will still do it either way. The lights are only 10w G4 caps.

Sorry - I misread your original - I thought you were talking about the secondary cable - voltage drop bites much more readily with ELV lighting, as the currents are 20x higher for a given wattage.

7. Its not a permanent installation as such. The flex will have an IEC on one end plugged directly into the TV. It will exit behind the TV (with the rest of the cables) through a double gang box with brush strip faceplate. If you imagine a fused spur with knock out for a flex, I basically want that but with the cable going from the back of the faceplate rather than coming out at the front. Does that make sense and more to the point, is it allowed?

Why not just put a socket on the wall behind the TV?

8. Theres no insulation in the cavity, the cable is the one that came with the TV with the plug chopped off basically.

Or an FCU with flex outlet on the wall behind the TV?

Or an FCU supplying a flex outlet plate?