Ceiling downlights

[argg35]

No doubt a regular subject but help required.

Moved in a year ago and inherited the previous owner's son's DIY bedroom electrics!

Bedroom currently has 2 sets of 3 LV downlights (instead of a ceiling rose) attached to a single dimmer. One transformer has now packed up (and I found a discarded transformer (also unusable) in the loft amongst the wiring) so probably a recurring problem.

All light fittings need replacing so I am looking to use 6 mains halogen (50WGU10) with 1.5mm twin and earth cable and a 400W dimmer.

Questions:
1. Am I best to connect all together as one chain or split the supply into 2 (as at present)?

2. Junction box or would cable block connectors be OK?

3 The current switch live supply does not appear to be marked. Am I safe to assume the current connection to the live input on the transformer is the switch live or should I check with a circuit tester. i.e. adopt the "mark what went where" approach

4. Think I understand the wiring and I understand to keep the earth connected but does it just terminate at the last fitting?

5. My biggest concern is the heat. This is in the loft and there is new thick insulation everywhere. I presume best not to lay insulation back over the wiring and fittings. Would boarding laid over the rafters with insulation laid back over the top be OK? Problem is newish house so rubbish rafters only about 2in high. Are there heat shields available?

Reply in words of one syllable please - you can guess I'm far from being an expert.

 

[plugwash]

All light fittings need replacing so I am looking to use 6 mains halogen (50WGU10) with 1.5mm twin and earth cable and a 400W dimmer.

you'll probablly get away with a 400W dimmer but it may be better to go for something a bit bigger (say a 500W or 600W). Mains halogens are quite hard on dimmers

1. Am I best to connect all together as one chain or split the supply into 2 (as at present)?

either arrangement is fine just use whichever is easier to wire

2. Junction box or would cable block connectors be OK?

use a junction box or enclose the terminal block in a chockbox

3 The current switch live supply does not appear to be marked. Am I safe to assume the current connection to the live input on the transformer is the switch live or should I check with a circuit tester. i.e. adopt the "mark what went where" approach

you won't cause any problems with your new lights if you end up with live and neutral reversed but it might be an idea to test anyway.

4. Think I understand the wiring and I understand to keep the earth connected but does it just terminate at the last fitting?

yeah assuming the fittings are double insulated it should just be connected through (you can use chock block for this) and end at the last fitting)

5. My biggest concern is the heat. This is in the loft and there is new thick insulation everywhere. I presume best not to lay insulation back over the wiring and fittings. Would boarding laid over the rafters with insulation laid back over the top be OK? Problem is newish house so rubbish rafters only about 2in high. Are there heat shields available?

most sparkys just leave gaps in the insulation.

the approved method for new builds is to build a large box around the lights (read the manufacturers minimum clearances then add a fairly generous margin over that) and then insulate over the top of this box.

there are fire hoods but theese are to stop fire spread not to do anything about normal operating heat. if its only a loft above you don't need theese

 

[delmel]

Although I am no fan of mains downlights, you should ensure no insulation is close to them, if you wish to board over generally 100mm depth min should be left between ceing and boarding. Also you have to downrate the dimmers for mains fittings. The percentage seems to differ from every manufacturer 25-50%

 

[Steve]

I prefer mains downlights as they give a clearer, crisper light and theres no need to mess about with transformers!

 

[dabaldie]

mains downlight are a good way of heating the room too!
I made the mistake of fitting them in the kitchen,.... spose i dont need a hot plate anymore!

 

[delmel]

I prefer mains downlights as they give a clearer, crisper light and theres no need to mess about with transformers!

Crafty you have that wrong low voltage give the clearer crisper and brighter output by a huge ammount.

 

[Steve]

delmel, i was talking halogens there, maybe i should justify my statement. we had 20w 12V halogens in our bathroom, replaced with 50w 240v halogens. Much clearer and brighter, but i suppose this is expected with higher wattage bulbs . oh well. still, less aggro with transformers!

 

[delmel]

That would be expected comparing 20w and changing for 50w. Compare lumen 4 lumen outout Low volt is more than twice the effeciency against mains. Also its only cheap crappy transformers you have major problems with. Stick with known brands should have little issue. Mode, IBL, Huco, Aurora also pretty good if you go for there better ones.

 

[Steve]

ah well i got mine from a shed you see, so i got what i paid for