I’ve tried using dimmer switch, transformer, and LV down lights (ScrewFix bless’um) but they flicker and the switches buzz

Can anyone tell me what gear will work properly and where I can get it


Thanks
Dusty

either an unsuitable transformer or an undersized dimmer

how many lights do you have?
what power each are they?
what is the power rating of the transformer?
what is the power rating of the dimmer?
does the transformer explicitly say dimable?

Also - most dimmers have a MINIMUM rating as well as a MAXIMUM. If the dimmer states on rear side something like "60W to 400W" and  you stick in a 40W bulb, say, the net result is the bulb flickers.

RR

Go for a transformer which is rated top-side of the job and go for one transformer per light fitting.
Don't try to run more than one light off a single tranny.
You should ensure that the tranny is suitable for dimming and if you are using 20w lamps, then go for a 50va tranny for each fitting.

5 x 20w = 100w so your dimmer switch should be rated at this. Better still, go for a 250w one.

TT

Thanks, The_Trician

So if I decide to change the plan and fit 8 downlights, are you suggesting I buy 8 transformers

I'd like to stick with LV because I've heard they omit much less heat and you can fit more of them without installing separate circuits.  Is this true.

Thanks
Dusty

[quote author=Dusty  link=1092214325/0#8 date=1092324584]I'd like to stick with LV because I've heard they omit much less heat and you can fit more of them without installing separate circuits.  Is this true. [/quote]
Well - a 12V halogen of x watts is going to put out about the same amount of heat as a 230V x watt one.

And the current load on the 230V circuit will be slightly higher with the ELV lights, as you have transformer losses to consider.   And as the current on the 12V circuit is approx 20x higher than the same amount of mains lighting would be, those cables need to be thicker.

Lectrician 8)

May be the forum should conduct a debate/survey into which is best, mains or LV
You also mention in an earlier post to "oversize the dimmer".  The only dimmers I’ve ever seen are 400w.
That’s what I fitted the last time I installed a downlight and it buzzes and flickers like hell
Right now, I don’t know what I should fit, mains or LV.
Thanks
Dusty

agreed with the fire caps, not sure why people refer to them downlighters as LV unless there mains voltage, 12V is Extra Low Voltage (ELV) not LV.

when you dim ELV lights you allow for the load of the tranny not the bulb plus you must derate by 25%

so 10 50watt lamps on seperate 60 watt transformers = 600watts so dimmer must be at least 800 watts

with mains halogen lamps you must derate by 50% so 10 50 watt fittings = 500 watts so dimmer must be 1000 watts

[quote author=Lectrician  link=1092214325/0#11 date=1092329564]Dont like LV then BAS   [/quote]
No - I do like LV.   It's ELV that I don't like  


Quote:

This is to do with the lamp design, dichroic vs PAR, not the voltage, and you can get both types in mains lamps, so you have the choice.   In a ceiling, heat coming out forwards is not usually a problem, whereas a lot of heat going back into the luminaire might be, so this choice is a good thing...

Quote:

There's not a great deal of difference - if you didn't have both types next to each other to compare, then I don't think you'd ever look at a mains halogen and think "oo-err, that's not very white".   They are all a great deal better in this respect than traditional incandescents.

Quote:

Not always true. Different manufacturers at different price points quote different lives. In both cases it's a spread of lengths with a lot of overlap. Some mains halogens are longer lived than some 12V ones, and in a lot of cases the differences are so small that if you were concerned about them you'd not be using halogen lighting in the first place.

Additionally, dimming can be troublesome - you have to select an appropriate dimmer and you also have to ensure that the transformer is suitable for dimming - more complication, not less. And even then, there's a reasonable chance that the transformer will generate an annoying buzz when dimmed.

And good quality transformers are not cheap.

Finally - future proofing. LED lamps are getting better and cheaper all the time - they're already up to 20-30w equivalence, and the hugely increased life already more than compensates for their higher price. With mains luminaires you can just plug them in. With 12V ones you'll run into problems with underloaded transformers, as the actual consumption of these lamps is in the 1-2W range.

LV is below 1000v and I think ELV is below 50v but I'd have to look it up to be sure.

It becomes even more confusing when you consider that electronic equipment (eg television) voltages are referred to as LT,HT,and EHT. When it comes to cars the spark plug voltages roughly correspond to EHT in a tv yet are invariably referred to as HT.

Even us sparks break the rules and call them LV - slapped wrists

When i walk into a room, and someone says "can you stick a couple more downlights in", i can tell if they are LV or ELV without getting the steps out - the mains ones are a warmer colour.  Maybe its just me

I love the ELV, the dichroic reflector gives a great effect with a tinge of colour aswell.

[quote author=L.Spark  link=1092214325/15#23 date=1092528855]well that post I have to say was brilliant BAS. [/quote]
Is that another pun??  

yes, we dont have Millenium boy, or ChubbyRegsWise on our forum, well maby its a bit Chubby here, but mostly not so  

Shall we diet?  

Thats my thinking BaS  


when shall we start?  

bah!, chubby cleansing!