well if you have a question you need answering this is the place..
I am sure this has been posted before but i cant find any posts..
having a large discussion in the wholesalers this morning i may have made a bit of a fool of myself... we were arguing about the running costs of 12volt lv lamps in particular down lights.. i said they were cheaper to run than the equivalent in mains voltage ie 50watt gu10s.. the other chap said they are not,, can anyone help please, with maybe a link to support this. i might have to eat humble pie..
A 12v 50W halogen light will never be cheaper to run than a 50W mains bulb (if such a thing existed) because of transformer losses. 50W for the lamp and another 5-10W lost in the transformer. Allow 60W mains power for each 50W halogen bulb. Stick a bare 60W bulb in the middle of the same room and watch how much more it lights up. Downlights, whether 12 or 240V might be trendy, but they're downright ineffecient.
#144877 - 01/28/0603:45 AMRe: Low Voltage Dichrohics
Actually, halogen bulbs produce a greater % of light, with less % heat, than a conventional tungsten filament bulb, so they are more 'efficient' = more light for your dollar to the poco. Trouble is, we tend to fit more of them - dichroic bulbs are directional and can leave 'pools of darkness' unless used in numbers. They do also last longer. As to the humble pie, the transformer losses must make the 12v versions less efficient, but efficiency sells naff-all today, what we want is the "look". Quite right too, who wants to live in a cave?
Wood work but can't!
#144878 - 01/28/0608:20 AMRe: Low Voltage Dichrohics
Watts are watts are watts, so a 12V 50W bulb is going to use exactly the same amount of power at as a 24V 50W bulb, a 120V 50W, or a 240V 50W bulb. Better decide whether you like your crow rare or well-done, I'm afraid.
Whether the bulbs are more efficient (more luimens per watt) is another matter, but if they're the same wattage, they'll consume the same amount of power (with the 12V bulb drawing 20 times as much current as the 240V one). The losses in the xfmr have already been mentioned.
I remember a job two or three years ago where the homeowner had bought two sets of dichros to replace a couple of pendant lights in a hallway. They were those supposedly "trendy" types with three spots on a bar shaped like a lazy S. ("Bar lazy S" -- Sounds like we've strayed into cattle country! ).
The owner was convinced that because they were low-voltage spots ("and so neat and small too") that they would cost much less to run than the existing lights. I had to explain that with three 50W bulbs on each bar, there would be a total of 300 watts running (not to mention xfmr losses). The kicker was that the two existing pendants had already been fitted with 11 or 16W compact fluoros.
[This message has been edited by pauluk (edited 01-29-2006).]
#144882 - 01/29/0611:13 AMRe: Low Voltage Dichrohics