Low Voltage Halogen ceiling lights.

[obeaston]

Just fitted two ten bulb low voltage ceiling lights with 20w Halogen bulbs.
One normal switch and one dimmer switch.
Old fittings had 5 40w bulbs each so wattage and dimmer should be ok

When switching on, all bulbs are ok, then a few seconds they dim, flicker and a humming noise is heard from both fittings - it's driving us nuts.

One fitting has a loose arm where the earth is connected - possible cause

These DAR lights look great, but when fitted one bulb on one fitting didn't work, live wire not fitted in connector in factory and other fitting has the loose arms as previously mentioned - German/Chinese quality control sucks

Any advice greatfully received.
Thanks guys.

 

[Adam_151]

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Old fittings had 5 40w bulbs each so wattage and dimmer should be ok

Erm... not quite

The rule of thumb when dimming TH lamps is that the dimmer should be rated for at least twice the connected TH load (unless dimmer manufacturer states that nameplate rating can be taken be assumed to have already been corrected for TH lamps)

The reason is due to the higher temperature they run at, which results in a lower cold lamp resistance, which puts more stress on the dimmer.

Secondly, do you actually mean LV? or ELV?

If the later, then the ELV source needs to be suitable for dimming, and even if it is, it'll still present a load thats reactive as opposed to simply resistive, and the dimmer needs to be capable of switching reactive as well as resistive loads!

 

[obeaston]

Thanks Adam 151,
The manufacturer states they are dimmable with a trailing edge type dimmer.
What trailing edge means,Ihave no idea.
The dimmer is 400w rated - should I them buy a 800w dimmer switch

Instructions only refer to self-sheilded low voltage tungston halogen lamps.

Thanks for any input.