halogen lamps 8 x 12v 20w fade out after 20 mins on dimmer

[robhanlon]

Hi

I have a light fitting with 8 bulbs which are halogen 12v 20 w. they have been working on a 250w 1 way dimmer for a few years completely ok. but recently the bulbs started to blow if all 8 were in and now the lights fade out after being turned on for 20 mins or so.

i thought it was the dimmer switch so replaced it with the same rated dimmer but no joy.

the transformer in the light is a doughnut shaped Braun 50VA. I assume it can work with a dimmer switch as it has previously? Do I need a low voltage dimmer switch to work with the light fitting?

Any help much appreciated.

cheers Rob

 

[electronicsuk]

If the information you have provided is correct then it's surprising you get any light at all. You have a total load of ~160VA, and the transformer is only good for 50VA.

I'm a little suspect that there may be more than one transformer or you've made a mistake, as I don't think it would support that load at all, never mind over a period of 20 minutes. As you mention it being 'doughtnut shaped' I assume it's a toroidal transformer, so there probably wont be any electronic limiting, but the load on it must certainly be dragging the supply voltage down a long way below 12v.

 

[robhanlon]

hi matthew

i've checked the transformer in the light fitting and it has this printed on the side

Braun TCI 50VA mod 147160 50/60hz taz60 C class b

i'm sure it should be fine for the 8 bulbs as it's all in it's state as bought from Habitat.

does the above info help at all?

Cheers Rob

 

[TicklyT]

For a purely resistive load, 1 VA = 1 Watt.

Incandescent lamps are, for all practical purposes, resistive loads.

A 50 VA transformer would happily run up to 10 X 5 Watt lamps (= 50 Watts)

8 X 20 Watt lamps = 160 Watts.

Can anyone else smell burning transformer windings?

 

[Softus]

Braun TCI 50VA mod 147160 50/60hz taz60 C class b

i'm sure it should be fine for the 8 bulbs as it's all in it's state as bought from Habitat.

does the above info help at all?

You asked for assistance, you were given it, and you ignored it!

In what way do you think a 50 Watt transformer can handle a load of 160 Watts?

If the bulbs are 12V G4 capsules, for example, then you can buy those in 5W, 10W, and 20W packages. If over the years you've gradually been replacing 5W bulbs with 20W ones, then the light fitting is no longer in the state in which you bought it from Habitat.

 

[robhanlon]

Tickly T - thanks for your help. It makes sense as this problem has only happened since I had tenants for last year whilst I was travelling. They must have been putting in 20w bulbs to replace 5w bulbs. I'll swap them over to se what happens.

Softus - no need to be rude - I haven't ignored any advice. get a life.

 

[Softus]

If the information you have provided is correct then it's surprising you get any light at all. You have a total load of ~160VA, and the transformer is only good for 50VA.

i'm sure it should be fine for the 8 bulbs as it's all in it's state as bought from Habitat.

In what way is that not ignoring electronicsuk's advice?

Then, after my post, you suddenly understood:

It makes sense as this problem has only happened since I had tenants for last year whilst I was travelling. They must have been putting in 20w bulbs to replace 5w bulbs.

No sh*t, Sherlock.

Softus - no need to be rude - I haven't ignored any advice. get a life.

You ignored electronicsuk and thanked TickyT. I don't require any thanks, but you could at least thank electronicsuk for getting it right first time.

I'll swap them over to se what happens.

I wouldn't waste my money on new bulbs. The toroidal transformer has failed, and you won't be able to find a replacement without trawling the back streets of Bejing, so you'll need an entire new fitting.

Like it or loathe it - the advice you get on this site is correct. If you want to be treated like a VIP then you need to behave like one. "get a life" isn't the kind of comment that will open locked doors, although it's an attitude that's commonplace with particularly stupid landlords. We see a lot of those here.

 

[sm1thson]

to test if the transformer has been fried you could run it with just 2 20w bulbs, if it is fine put all 5w bulbs in.

 

[robhanlon]

thanks ALL for your help.

softus - not sure where your attitude comes from though.

yes i had tenants for 1 year living in my flat but that doesn't make me a typical landlord! i'm just trying to work out what the hell is wrong with my light fitting/dimmer. i don't know a lot about electronics hence writing a post. that's why this forum seems to work - people with the right knowledge helping people without. i think you have too much time on your hands to rant the way you do.

 

[robhanlon]

it seems to work with 2 x 20w bulbs so hopefully the transformer is ok. thanks for the suggestion.

looks like i won't have to trawl around beijing after all.....

 

[Softus]

Putting this anomoly:

i'm sure it should be fine for the 8 bulbs as it's all in it's state as bought from Habitat.

... aside, it appears, based on the claim that the transformer still works, I reached the wrong conclusion, therefore I apologise to all concerned.