Dimmer, Downlights and Transformer woes ;-(

[Banbert]

Hi, I am currently most of the way through a double garage conversion (pics and info in this threaD HERE) and although I am very much a newbie at DIY its not going too bad due to help and guidance from others in the know.

Biggest issue I have is wth the LV down lighting and I wondered if someone could help me fault find this or give me their opinion.

I have 2 x 2 gang dimmer switches (Crabtree 2G 2 Way 250 Watt)

Each switch is connected directly to a LV transformer (Halolite 100-210VA 240V)

Connected to the 4 Transformers I have 3 of these lamps each with a 50 watt bulb in it, except on one transformer I have 4 lamps, again with 50 watt bulbs (Low Voltage Adjustable Halogen Downlight)

I followed all the instructions on how to wire them up, kept the cables under 2 meters and same length from each transformer to each light etc and it was really pleasing when they all switched on and dimmed back and forth really nicely... least it was until the first one went out (which was the one with 4 lamps on it) after being on for about 1 hours then a few hours later a second one stopped working (on the different switch unit, so different power going into it and diff switch altogether) then a third one went a short time after this.

Swapping transformers round lead me to believe that the transformers were at fault but after getting all 4 new transformers yesterday I fitted 3 of them and found they didnt work, except on the one position that was left working previously.... I took the time and tried all the transformers on that position and they worked, I tried them on the other positions on the switch and they didnt work.

This is all leading me to believe that the dimmers are knacked, buts whats killing my dimmers and what can I do about it ?

When I bought the stuff from screwfix I found the lights first and then worked my way back with what it recommended to pair with them in the hope of avaoiding any incompatability issues but it doesnt seem to have made any difference.

Any help is greatly appreciated, I dont have hair to pull out but if I did it would be coming out in lumps right now !



My immediate plan is to get some cheap standard switches to test in place of the dimmers to see if thats whats killing em.

[hornydragon]

hmm something is odd our wiring is not what i would i use or cal standard normally each lamp hasits own tramsformer, you need to add 10% to the lamp load for the dimmer to cater for the transformer (this works when its 1 trans per lamp) this sort http://www.screwfix.com/prods/48058/...r-20-60VA-240V

[Banbert]

So using those single light transformers you would cable them to each switch in a series, so 3 or 4 transformers linked to each other in my case from the switch..... rather than what I have which is 3 or 4 lights on each transformer ?

Isnt the load on the switches going to be the same though ?

I went to focus tonight to to get some basic switches (just switches rather than dimmers) to swap out the dimmers and try and identify the issue and whilst I was there I looked at all the dimmers they have and they seemed to vary quite a bit, maybe the ones I have just arent meaty enough for this application ?

[dolph]

I'd look for some dimmers specifically designed to work with LV lighting like the Varilight touch dimmers which supposedly don't need de-rating either (and come in at 400W anyway)

[Banbert]

Cheers guys, I think your spot on about the meatyness of the dimmers.

I went to focus tonight and picked up some cheap £3 2G 2W switches and hey presto everything works! Whilst I was there I also opened up a few boxes and read the different instructions and ratings that came with each and theres definitely dimmers and theres DIMMERS it would seem.

Mine are rated to 250 and that appears to not be enough so I will look now for some 400, plus I am also thinking about touch and remote control ones ...... there goes the budget again !

Thanks for the advice so far, happy to hear anything from others if they want to contribute their own thoughts.

[Banbert]

I spoke to the people at Halolight (Aurora) today and they had some info to add to this issue.

The technical person there reckons that 250Wa switches should be fine and that going to 400w may give me an issue with flickering when I try to do dim them, he reckons the issue is more like that the switches that I am using are more suited to Trailing Edge dimming rather than Leading Edge dimming, he then went on to explain the difference about the electricty wave and how one works one way and the other another way but at this point he was losing me a bit.

It does however tie up with quite a few things I have read on the 1stopelectrics website where they state the suitability of the dimmers for different transformers and many of them state suitability for leading edge and trailing edge....... pretty steep learning curve this aint it

[hornydragon]

leaidng and trailing edge could be the issue but when i looked at the transformer spec it did say both i think i can never remember which way round it is either...

[Banbert]

These are the ones I have bought from 1stopelectrical, so 300w instead of 250w and they actually say they are leading edge and designed for the sort of transformers and lights that I have, so hopefully they will do the job.

https://www.1stopelectrics.com/product/IDCP302S/

Thanks again for the help guys.

[Goochie]

I know you've gone for Crabtree dimmers already but it may be worth noting that Scolmore (Click Lighting) do a range of dimmers and with theirs, you can chop and change the dimmer module part on the back of the plate. For example, you could have a 2 gang 2 way plate with 1 250W dimmer and another 400W dimmer. All their dimmer modules are suitable for mains and low voltage.

I think most of the lighting manufacturers use leading edge dimmers by the way, but I did once hear that trailing edge dimmers should operate both leading and trailing edge transformers - how true this is though, I dont know.