Hello strangers,,

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..

Get ready to dig in... Watts are Watts are Watts.

A 50 watt bulb will consume 50 watts no matter what the voltage is. The low voltage setup might consume a little more power then the 110 volt unit due to loses in the transformer.

Better bring some salt for that 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.

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?


Alan

If you mean the dicros then I disagree.

briselec,
Web prices UK. Good Quality items.

12V 20W/50W halogen dich 2000 hrs £1.20ea
12V 50W OSRAM " " 4000 hrs £2.25ea
12v 50W ? " " 10000 hrs £4.25ea
240 v 50W OSRAM " " 2000 hrs £2.95ea
240 v 50w economy " " 2000 hrs £1.95ea

None of the h. d. bulbs from this supplier were less than 2000 hrs life claimed.

GLS 240v 100W tungsten 1000hrs £0.16ea

My experience with these is nil, but the makers are claiming at least twice the life of a tungsten bulb. Mind you, at 7 to 25 times the price, they aren't exactly economic!

Alan

edit phantom voltages twice!








[This message has been edited by Alan Belson (edited 01-28-2006).]

[This message has been edited by Alan Belson (edited 01-28-2006).]

They don't handle unclean power as well as normal lamps. In an installation where there are lot of voltage spikes and dips you will find they blow very quickly.

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).]

Thankyou guys

i will be eating the pie in the morning with the obligatory vending machine coffee..

Paul, eating pie in the morning aint that bad and vending machine coffee is still better than instant.

You're right about the ECN still being the best place to get answers though.