LEDs not lighting with V-Com dimmer

Tomdhu · Monday at 9:34 AM

I wanted to convert 5 halogen down lights with new LED fittings and got these from TLC https://www.tlc-direct.co.uk/Products/CLH2CSPW.htm together with a Varilight V-COM as per recommendations.
Installed it all but the LEDs would not light up - even though I programmed the switch with 3 ON/OFF presses etc etc etc.
I then removed one LED and replaced it with one old halogen fitting. The dimmer controlled that one halogen fine but none of the LEDs.

Any suggestions on what I should try next?

brianmoooore · Monday at 10:16 AM

Welcome to the black art of LED dimming. Only thing I can suggest is that these LEDs require trailing edge dimming, not leading.

DefyG · Monday at 3:21 PM

What rating is the V-Com (VA/W)?
It sounds like you may need to set the boost limit higher - programming issue?

Tomdhu · Monday at 4:13 PM

I specifically asked TLC-Direct as to which dimmer to use and they said V-Com

DefyG said:
What rating is the V-Com (VA/W)?
It sounds like you may need to set the boost limit higher - programming issue?

The rating is 0 to 100W

brianmoooore · Monday at 4:52 PM

Tomdhu said:
I specifically asked TLC-Direct as to which dimmer to use and they said V-Com

The datasheet for the fitting states DM298FP, which is trailing edge.

DefyG · Monday at 6:52 PM

Think you were ill advised by TLC, looks like it is the wrong dimmer, try the V-Pro dimmer.

Tomdhu · Monday at 7:14 PM

brianmoooore said:
The datasheet for the fitting states DM298FP, which is trailing edge.

Many thanks for the guidance. I just wonder why the TLC guy missed that.

As the dimmer I want is in a faceplate with two others, I reckon I will need the DM298GRID rather than DM298FP which is a single faceplate switch.

brianmoooore · Monday at 7:23 PM

Tomdhu said:
Many thanks for the guidance. I just wonder why the TLC guy missed that.

Because the staff at TLC are sellers of cardboard boxes, not electricians. There's a notice to that effect above most electrical wholesaler's trade counters.

Avo Mk8 · Monday at 8:02 PM

Tomdhu said:
Many thanks for the guidance. I just wonder why the TLC guy missed that.

And maybe motivated by the fact TLC don't stock Colingwood dimmers, but they do V-COM/PRO

brianmoooore · Monday at 8:19 PM

Doesn't have to be that Colingwood dimmer, but is does need to be trailing edge.

Pretty Mouth · Monday at 9:04 PM

Tomdhu said:
Installed it all but the LEDs would not light up - even though I programmed the switch with 3 ON/OFF presses etc etc etc.
I then removed one LED and replaced it with one old halogen fitting. The dimmer controlled that one halogen fine but none of the LEDs.

Hmmm, I would have expected some sign of life from these, even with an incompatible dimmer. Did the old halogen fittings take MR16 bulbs, or GU10? Just wondering if there's a 12V transformer hidden in the ceiling space somewhere.

brianmoooore · Monday at 9:08 PM

Pretty Mouth said:
. Did the old halogen fittings take MR16 bulbs, or GU10? Just wondering if there's a 12V transformer hidden in the ceiling space somewhere.

I thought of that, and discounted it because the OP said it worked with one of the old lamps back in, but reading the OP again, that actually proves nothing, so you may well be onto something.

Pretty Mouth · Monday at 9:10 PM

brianmoooore said:
The datasheet for the fitting states DM298FP, which is trailing edge.

Surprisingly, the instructions actually specify a Varilight V-Com dimmer as suitable

Pretty Mouth · Monday at 9:12 PM

brianmoooore said:
I thought of that, and discounted it because the OP said it worked with one of the old lamps back in, but reading the OP again, that actually proves nothing, so you may well be onto something.

I read that as 'only the halogen lit up' but you could be right. @Tomdhu , could you clarify please?

Tomdhu · Monday at 9:19 PM

Pretty Mouth said:
Hmmm, I would have expected some sign of life from these, even with an incompatible dimmer. Did the old halogen fittings take MR16 bulbs, or GU10? Just wondering if there's a 12V transformer hidden in the ceiling space somewhere.

Wow!! I reckon you cracked it.!
I just checked the old halogens and they are 12v MR16. What threw me was that wiring to each was grey T&E and when I pulled each one out, there was no sign of a transformer. Also, all the other downlights in the kitchen and hall were 230volt. It's late now so I will do some checks tomorrow with a multi meter just to double check.Much appreciated PM.