Two dimmers on one circuit?

[mark_a]

Hello,

I am having a loft converted and plan to have two sets of LV halogen track lights installed to be controlled by two 2 gang 2-way dimmer switches at either end of the room. Could someone please confirm if this is technically possible as I searched this forum and there appears to be an issue with putting two dimmers on a single circuit?

Thanks

Mark

 

[breezer]

you miss read, miss understood.

you cant have 2 dimmers controlling the same light* theyinteract with each other


* you will need to use master / slave dimmers designed for the job, not ordainairy dimmers

 

[mark_a]

Thanks for the clarification. How about one dimmer at one end of the room and an ordinary two way switch at the other end (both 2 way), would that work?

 

[Steve]

Thanks for the clarification. How about one dimmer at one end of the room and an ordinary two way switch at the other end (both 2 way), would that work?

Yes.

But, If you use these:
http://www.tlc-direct.co.uk/Main_In...s_All/Wiring_Accessories~Dimmers_5/index.html
Get a master and slave, the master can be remote controlled with any remote control! I have some, they're great

 

[mark_a]

Thanks again, I will investigate and maybe have a rethink as I was planning on having 6x50w bulbs one one of the tracks.

 

[Space cat]

two sets of LV halogen track lights

That means transformers. Most of these things are not transformers at all and they aren't all suitable for dimming. On top of that, halogen lights aren't meant to run dim. The reason they are so much brighter than standard bulbs of the same power is that their filaments run hotter. (3200K instead of 2800K - I think!) Tungsten boils off the filament and condenses on the envelope, just as it does in normal bulbs only much faster. The halogen picks this up as metal halide. Now for the clever bit; back at the filament the halide breaks down and puts the tungsten back. It's a neat trick but, to make it work, the envelope has to be very hot indeed. If you run them dim it won't work. Not only will the halogen be unable to remove tungsten from the envelope; it can even erode the cool filament instead!

 

[Mike2007]

Hello,

I am having a loft converted and plan to have two sets of LV halogen track lights installed to be controlled by two 2 gang 2-way dimmer switches at either end of the room. Could someone please confirm if this is technically possible as I searched this forum and there appears to be an issue with putting two dimmers on a single circuit?

Thanks

Mark

This subject should be in "Sticky", as it keeps coming back to haunt you lot! I made the same mistake and others keep doing the same.

 

[Steve]

two sets of LV halogen track lights

That means transformers. Most of these things are not transformers at all and they aren't all suitable for dimming. On top of that, halogen lights aren't meant to run dim. The reason they are so much brighter than standard bulbs of the same power is that their filaments run hotter. (3200K instead of 2800K - I think!) Tungsten boils off the filament and condenses on the envelope, just as it does in normal bulbs only much faster. The halogen picks this up as metal halide. Now for the clever bit; back at the filament the halide breaks down and puts the tungsten back. It's a neat trick but, to make it work, the envelope has to be very hot indeed. If you run them dim it won't work. Not only will the halogen be unable to remove tungsten from the envelope; it can even erode the cool filament instead!

Space cat, you're nearly right, theres some errors in your logic.

1. Many light fittings you purchase at B&Q and BHS and other home stores, still come with toroidal wire-wound REAL transformers. These are NOT suitable for dimming, without the right equipment. You can tell this type of Tx as they are big and bulky, often round so they fit in a light fitting base.

2. The best type of transformer to dim is an electronic transformer, this is not a true transformer, as it uses fancy electronics to reduce the voltage. Most of these types of Txs are suitable for dimming, as the electronics have been specially put together to withstand it and give a smooth dimming curve. (The dimmer must also be suitable for use the the Tx)

3. Dimming halogens does shorten their life, however, there is a theory that running them at full belt for a few hours every so often will jump some of the tungsten back onto the lamp, however its still not as good as running full belt all the time. In practise many many people dim halogen lamps without noticeable ill effect.

 

[Space cat]

1. Many light fittings you purchase at B&Q and BHS and other home stores, still come with toroidal wire-wound REAL transformers. These are NOT suitable for dimming, without the right equipment. You can tell this type of Tx as they are big and bulky, often round so they fit in a light fitting base.

Thanks Steve. I didn't know that most of the switch mode PSU's sold as transformers were dimmable. I'd always assumed the opposite. I also forgot that a lot of dimmers don't like the inductance of a real transformer.

there is a theory that running them at full belt for a few hours every so often will jump some of the tungsten back onto the lamp

It will certainly remove the tungsten film from the envelope.