cable size for low voltage lights

[stanna]

Eh Up!

Ok brickie requires advice.

Putting approx 12 mini downlights in ceiling using 20w G4 capsule bulbs.

Cut out is only 25mm diameter so access to tranny is not possible after fitting. I am putting this circuit on 1.5mm T&E and hope for it to be dimmable.

Problem is access to trannys (no jokes please) so it would make sense to place them in one location but i believe this gives rise to problems ie voltage drop.


What size cable could i use, if its feasable with the correct trannys, to connect lamp to tranny max distance 4 metres apart.

If i use bigger cable between tranny and lamp will this affect the 1.5mm T&E for the normal circuit ie from switch to tranny.

Is this possible?

Cheers

Stanna

 

[ban-all-sheds]

Putting approx 12 mini downlights in ceiling using 20w G4 capsule bulbs.

You do know that you ought to be able to light an entire floor of the average house with 240W of lighting, if you choose the appropriate type?

Cut out is only 25mm diameter so access to tranny is not possible after fitting. I am putting this circuit on 1.5mm T&E and hope for it to be dimmable.

No use hoping - you need to ensure that the power supplies are dimmable and that if they are you match the type of dimming the dimmer does (leading-edge or trailing-edge) to what the power supplies need.

Problem is access to trannys (no jokes please) so it would make sense to place them in one location but i believe this gives rise to problems ie voltage drop.

Not necessarily problems, but a factor to take account of when designing the circuit.

You must also make sure that all the cables on the ELV side are the same, or almost the same, length, or the lamps will be different brightnesses.

What size cable could i use, if its feasable with the correct trannys, to connect lamp to tranny max distance 4 metres apart.

http://www.tlc-direct.co.uk/Technical/Lighting/VoltageDrop.html

If i use bigger cable between tranny and lamp will this affect the 1.5mm T&E for the normal circuit ie from switch to tranny.

No.

Also, don't forget that if this is in a bathroom or kitchen in England or Wales it's notifiable

 

[stanna]

Cheers Ban All

The reason for this is that i wanted the smallest lamps and holder i could and the shallowest as they are going in a vaulted ceiling. I only have around 40mm (inc plasterboard) of depth to play with or risk hitting the Kingspan and the type im looking at only have a depth of 25-35mm.

They are only G4 bulbs so figure i will need plenty of them to cast a little light on the room (if you think not please advise). Room is approx 5m x 3m

Which is the best kind of dimmer ie most reliable?

Based on the link to the cable calculator (im assuming that the load box means per lamp ie 20 watt rather than all added together) i get a calc of !.0mm if my lengths are 4 metres.

Is this correct?

So can i use ordinary 1.0mm T&E or 1.5mm to suit the rest of circuit?

The downlights im looking at are these


http://www.mr-resistor.co.uk/item.aspx?g=8&t=64&r=641&i=2331&a=

or these

http://www.oceanlighting.co.uk/rece...-87043-denis-light-starlight-modern-11618.htm

Thanks very much for the help mate.

 

[ban-all-sheds]

They are only G4 bulbs so figure i will need plenty of them to cast a little light on the room (if you think not please advise).

I think you will need a lot of them.

Which is why you shouldn't use them.

Room is approx 5m x 3m

240W to light that is ridiculous.

Which is the best kind of dimmer ie most reliable?

A reputable make.

Based on the link to the cable calculator (im assuming that the load box means per lamp ie 20 watt rather than all added together) i get a calc of !.0mm if my lengths are 4 metres.

Is this correct?

Yes.

So can i use ordinary 1.0mm T&E or 1.5mm to suit the rest of circuit?

If it will fit.

The rest of the circuit is irrelevant - that's on the LV not the ELV side of the transformers, and sized according to different criteria. If these were 50W lamps 10m from the transformers you'd need 4mm² cable on the ELV side, but the LV lighting circuit would still only need to be 1mm².

 

[stanna]

Ok Thanks

I understand your point on 240 w to light the room and i was hping to use these as an accent light rather than main. I will be placing lights under the wall units to light the counter tops and a pendant for the centre island.

Ive ordered one of the lights i provided a link to for a look at what it gives out. Cant really get an idea when their in a showroom surrounded by 300 other lights.

I'd welcome any recommendation for a solution to this if you have any ideas.

Ta V much

 

[ban-all-sheds]

Put a small cornice around the base of the vaulted ceiling and use it to conceal cold-cathode lighting?

 

[stanna]

Thanks for your help.

Looks like a re-think on my part.