spot lights

[uslesscol]

I have recently installed 9x50watt dimmable halogen downlights transformer free i also changed the dimmer switch to a 500watt the lights worked fine for 3 days now they wont dim they stay full on why?

 

[plugwash]

most likely the dimmer wasn't suitable for nearly 500W of halogen. the ratings quoted are usually only for gls lamps.

halogens run hot, this means that for a given hot resistance the cold resistance is lower and therefore the inrush current is higher. and i'm pretty sure its the inrush current that causes most of the stress on a dimmers triac.

old rule of thumb for halogens was the rating of the dimmer should be double the rating of the lamps but this is probablly being more conserative than actually nessacery. the dimmer manufacturer should be able to tell you the needed derating factor.

 

[Adam_151]

Yeah, triac in the dimmer has overheated and 'stuck' on, triacs seem to have somewhat of a habbit of failing on, resolution is to replace the dimmer, paying attention to plugwashs comments about de-rating it for a halogen load

 

[baldelectrician]

try getting a danlers dimmer or a varilight dimmer-

varilight do a 1000w one which will do, i think it doesn't have to be derated for mains halogen

PS watch the lamps if they are unbranded swap them for branded ones whichshould be internally fused.

try osram, phillips or sylvania as they are good.