Can I use 1 transformer for multiple lights?

[mk2phil]

Hi there,

I'm planning on mounting 8 20w Low Voltage lights in my ceiling, with the first light being approx 3-4 metres away from the last light. Can I simply buy a single transformer - eg one thats rated at 160w - and use this to feed the first light and then daisy chain the remaining 7 ?

Or should I buy a 20-60w transformer for each light. The problem I see with this is that as I'm using 20w bulbs, will that be suitable for a 20-60w transformer which seems to be the smallest I can find.

As a side note, I'd like to be able to dim them if needed - will this be possible or should I look at using 35w bulbs instead that I'll be able to dim when required?

Many thanks for any help

 

[mikhailfaradayski]

Are you looking for something like this:-

http://www.tlc-direct.co.uk/Products/LTYT250.html

 

[mikhailfaradayski]

Oh dear, i seem to have overlooked the grave errors in your ways.
Im sure there will be other points of view coming shortly.

 

[Steve]

mk2phil, anythings possible with enough money thrown at it.

The recommendation is one transformer per lamp.

I must point out though, that the easiest lamps to dim are mains voltage, as you dont have to worry about matching a dimmer with the transformers. Mains voltage has other advantages too - you can easily swap them for CFLs (energy saving and much better light) and LED (+energy saving and improving technology) lamps.

A 20-60w transformer means it will power between 20 and 60 watts of lamps. If you attach a 20w lamp, you can still dim it (if its dimmable). But the whole dimming transformers business is a minefield of trouble. I wouldnt.

 

[mikhailfaradayski]

HI Steve,

Not taking issue, but can you clarify the 'recommendation' that it should be 1tx for 1lamp.

 

[electronicsuk]

I must point out though, that the easiest lamps to dim are mains voltage, as you dont have to worry about matching a dimmer with the transformers. Mains voltage has other advantages too - you can easily swap them for CFLs (energy saving and much better light) and LED (+energy saving and improving technology) lamps.

It should also be pointed out that extra low voltage LED lamps are still relatively common, and mains voltage downlight reflector lamps usually have an absolutely terrible light output in comparison to their 12v counterparts.

 

[Steve]

It should also be pointed out that extra low voltage LED lamps are still relatively common

Indeed, but they cause havoc with the transformers minimum load requirements.

 

[mikhailfaradayski]

HI Steve,

Did you look at the link i posted earlier? -Works from 0W up.

Can you clarify where you got the 1 tx for 1 lamp recommendation from?

 

[Steve]

Did you look at the link i posted earlier? -Works from 0W up.

Oops.

Can you clarify where you got the 1 tx for 1 lamp recommendation from?

Yes, for future maintenance. When a Tx fails, you dont want to be pulling every downlighter down to find it. If theres one above every light, its obvious where the failed one is!

 

[mikhailfaradayski]

Sorry, i understand you reason for saying that WRT maintenance, but there is no 'recommendation' by any authority that im aware of that says it should be like that.

It would mean that DIY shops selling kits of 1 tx and 3lamps are no good. It would also mean that tx manufacturers would not make txs with sufficient capacity for several lamps.

 

[Taylortwocities]

The big problem with one transformer for all the lights is volt drop.

If, as the OP suggested, he has one xfrmr

and use this to feed the first light and then daisy chain the remaining 7 ?

Then the lamps will get dimmer as you get further from the transformer, even with fairly hefty cable.

If you must use 12v lamps and transformers, the best solution would be to use three 60VA transformers.
Each transformer would power 3 lights (two in the last case). If you use the same length cable from each transformer to the lights then volt drop is not so much of an issue.

 

[electronicsuk]

Can you clarify where you got the 1 tx for 1 lamp recommendation from?

Yes, for future maintenance. When a Tx fails, you dont want to be pulling every downlighter down to find it. If theres one above every light, its obvious where the failed one is!

I agree this makes sense, although equally it seems that ELV downlights often come packaged with very cheap transformers prone to failing. The best option is one transformer per light with good quality TXs, but I'd sooner have one high quality transformer powering multiple lights than multiple cheap ones.

 

[RF Lighting]

Can you clarify where you got the 1 tx for 1 lamp recommendation from?

Probably from me, as that is what I recommend.

 

[electronicsuk]

Can you clarify where you got the 1 tx for 1 lamp recommendation from?

Probably from me, as that is what I recommend.

Listen to that man, he

downlights!

 

[Steve]