Wire-wound or toroidal transformers and an LED dimmer?

SRJDIY · Post by **SRJDIY** » Fri May 14, 2021 5:03 pm

Apologies if this is a dumb question!

I need a new dimmer switch, and figured I may as well upgrade to one that's compatible with LED bulbs (the previous dimmer was used with halogen bulbs).

The Varilight V-Pro JQP401W seems to have good reviews. However, when checking the specifications I noticed it's not suitable for use with 'wire-wound or toroidal transformers'. I'm not sure whether I have one of these.

I've been doing some googling to see how I can find out, but I've not found anything useful, probably because I'm not even 100% sure if I have a transformer or what exactly it's for in this case.

Would anyone be able to help me out please? The switch looks perfect in every other respect; I just want to make sure I don't burn my house down by using it with the wrong transformer!

kellys_eye · Post by **kellys_eye** » Fri May 14, 2021 5:08 pm

If the original halogen bulbs are rated at 240V and NOT a lower voltage then you can use that dimmer with your LED bulbs.

Many halogen lights utilise a transformer to drop the AC mains voltage to 12V and it's this type of device that the dimmer won't work with. If your existing lights have a 'little box' associated with each one and that box is quite heavy then it is a 'wire-wound/toroidal' device.

SRJDIY · Post by **SRJDIY** » Sat May 15, 2021 1:08 pm

kellys_eye wrote: ↑Fri May 14, 2021 5:08 pm If the original halogen bulbs are rated at 240V and NOT a lower voltage then you can use that dimmer with your LED bulbs.

Many halogen lights utilise a transformer to drop the AC mains voltage to 12V and it's this type of device that the dimmer won't work with. If your existing lights have a 'little box' associated with each one and that box is quite heavy then it is a 'wire-wound/toroidal' device.

I'm not sure what the original bulb was rated at as it doesn't say on it and the box was thrown away a long time ago. It's just a regular lightbulb for a single-bulb ceiling light (i.e. not one of those mini spotlights). I also don't see a little box either on the bulb or the light itself (although I don't know what's hidden in the ceiling).

Someone-Else · Post by **Someone-Else** » Sat May 15, 2021 1:16 pm

Picture of the end of the lamp would be useful. (The end that "plugs in" and in focus would also be good)

SRJDIY · Post by **SRJDIY** » Sat May 15, 2021 3:09 pm

Someone-Else wrote: ↑Sat May 15, 2021 1:16 pm Picture of the end of the lamp would be useful. (The end that "plugs in" and in focus would also be good)

Here's the bulb and the socket. I've also noticed that on the glass end of the bulb it says "220-240v 100w". Does this mean that I'm good to go?

Someone-Else · Post by **Someone-Else** » Sat May 15, 2021 4:10 pm

That is a standard B22 fitting, so no transformer in your light, so as you would (did) say you are good to go. (With a LED lamp)

Hosepipe · Post by **Hosepipe** » Sat May 15, 2021 5:08 pm

The bulb in photo is 240V bayonet type fitting. It's unlikley to be dimmable, but could be. The only way to find out is a statement usually on the packing, but it could be stamped on the bulb.
Dimming LED lighting can be a problem as the dimmers will only work with certian types of LED's. It's best to buy the lights and dimmer from same supplier to make sure they match.
The little boxes are called drivers which are usually used on recesed lighting, it should state on the driver if they are dimmable and which type of dimmer to use.

Someone-Else · Post by **Someone-Else** » Sat May 15, 2021 5:40 pm

Hosepipe wrote: ↑Sat May 15, 2021 5:08 pmThe bulb in photo is 240V bayonet type fitting. It's unlikley to be dimmable

Are you sure about that? I would suggest you read the 3rd post again.

ericmark · Post by **ericmark** » Sun May 16, 2021 2:03 am

A halogen bulb can be dimmed, but it should not be dimmed, you need the old non quartz bulb to dim it, or LED. The whole idea of quartz is the envelope is so hot tungsten will not be deposited on the quartz, if run cool the quartz will go black and the bulb fail early. The old pearl tungsten bulb was OK to dim, it actually increased its life, but not quartz.

However I know many do dim the quartz bulb and just accept it will not last as long.