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[zebb]

hi folks , my kitchen has 15 spot lights sunken into the cieling and they run on transformers , 3 lights to 1 transformer, they have been installed for 10 years now and occassionally are switching themselves on and off due to the transformers overheating with age i presume , now i can easily buy new transformers and solve this however i recently bought 12 spotlights for another room which work from the lighting ring without the use of a transformer, so my question is do the lights with the transformers use more electricity than the lights on the lighting ring mains, or do they use less electricity ?which setup will be more efficient energy wise ?

[ericmark]

In theory using an inverter (transformer) means the voltage is corrected meaning the lamps are brighter plus the element is thicker so they last longer. However in practice unless in an area with huge voltage fluctuations the GU10 and GZ10 low voltage (230v) versions work better than the extra low voltage (12v) lamps and have the added advantage that:-
1) Can't fit wrong type GZ10 bulb will not fit a GU10 holder so less likely to overheat fitting.
2) They will take cold cathode (florescent) lamps.
3) There is no inverter to burn out as it seems often when lamps blow they take inverter with them.
4) The holders seem better able to take heat.
So unless the location requires SELV as with some locations in a bathroom I would used GU10.
However there are more angles of light available with the ELV versions and also more precise colours so where one is lighting pictures which is really what the lamps are for one can select the angle required to give best light.
To light a room the spot lights are completely useless as typically to get the same spread as with more conventional lighting one would need so many it would look like a planetarium. However fitting 2D lighting which is today likely the best general lighting which looks reasonable assuming one would not want a florescent tube in a living room can leave areas where one wants to read a little on dark side so adding a few spots can redress the problem of dark areas.
However as to power used this becomes complex as running a tungsten lamp hotter means it gives out more light per watt and since one can run an inverter controlled lamp hotter than direct connection bulb it means in spite of the heat from the inverter they are slightly more efficient. But although both types can use LED lamps, some inverters have a minimum wattage so can't use them. Also it is easy to exceed the power of the inverter as many designed for lamps under 50W which seems to be around the standard size some being designed for as little as 10W. There are 75W versions which will likely overload most inverters. With the old transformers (very heavy) there is no advantage.
The "energy saving" (assuming you don't want the heat) lamps both LED and Cold cathode are slightly longer than the tungsten version and one has to select the lamp holders with care to ensure they look right with the longer lamp.
It is unlikely in the winter that the so called energy saving lamps save any energy. Because the heat from a tungsten lamp is radiated heat it heats the body rather than the air so air changes do not get rid of the heat. To be in the comfort zone likely the room air temperature can be 2 degrees colder with tungsten lighting than with discharge lighting (energy saving) so the only saving is because gas costs less then electricity per Joule.
Banning tungsten lighting in unheated areas makes sense but not in heated areas. Of course in the South of France where air conditioning is used they will save energy but not in UK.
However most of our houses are fitted with ceiling roses as standard and these are rated at 5/6 amp so in the main because the lighting power is daisy chained through these the maximum size of fuse/MCB/RCBO for lighting is 6 amp. That's approx 1380W and builders have for many years based it on 100W per fitting. So 13 fittings can be used from one supply and in general that will cover the whole house. In later years mainly for safety it has been split into two upstairs and downstairs but fitting 50W spot lamps can very easy exceed to total power available for lighting.
I think we all have to change the lighting and I have removed the two single lamps in my living room and first used two three lamp units with 40W bulbs so just slightly over at 120W per fitting. But as energy saving lamps came in these were swapped for five bulb units and now I have 10 times 8W bulbs in the room so under half of the power originally used. However there are also three lamps plugged into the sockets so no real saving.
Main reason is maintenance as a florescent tube lasts so long. On my landing I was changing a bulb at least once a month until I fitted an 18W florescent battery backed unit and I have just fitted a new lamp after 18 years and first one was second hand in first place. The 10 energy saving bulbs had two blow with in first years but since then no more have needed renewing and again it was a weekly chore to renew bulbs. Kitchen does not seem to far too well tubes only last about two years each.
Bedroom has one GU10 tungsten and one GU10 cold cathode above bed for reading again tungsten has been renewed many times cold cathode is original. Did try to get second but would not fit in holder so gave to my daughter.
So my total lighting power is well below original but it was not done to save money but so I was not continually changing lamps. But you still need to count up when adding lamps to make sure you don't exceed the 1380W max per circuit.

[zebb]

thanks for the reply eric it was much appreciated, I eventually went for the cheaper option and bought 5 new transformers 35w-105w halolite from screwfix priced at just over £8 each, they are much slimmer and lighter than the old ones that were from wickes , the wickes ones seemed to be much better quallity but after 10 years have served well , now I fitted the new ones and the downlights don't seem to be as bright as they were with the wickes transformers, in fact they are a good bit dimmer and quite noticable, any idea why this is ? I just seem to be a little dissapointed with the outcome . zebb

[ericmark]

As I said old units were just transformers and any over or under voltage on the supply would be reflected on the transformer output. New units are inverters and the input voltage has very little effect on output voltage the internals correct to output voltage.

[ericmark]

Further to first reply the inverters you have bought have a minimum output of 35W so with three lamps on each you have to have at least 15W lamps which means you can't move to energy saving lamps. I would not have used extra low voltage well I would not have used 15 stop lights in a kitchen. To my mind the kitchen gets too hot and anything to reduce the heat in a kitchen is a bonus. So I use florescent lights and an induction hob so as much as possible the energy used in the kitchen goes into the food not the room.

I am completely against gas as it produces loads of moisture and heat and means one has to run huge fans to extract the moisture and heat which are just not required with electric. Plus of course all the dangers of a naked flame and complete lack of control where ovens have gas mark X rather than degrees. Plus all the auto shut down features found on a modern induction hob are missing.

To use spots to light special areas is OK but never whole kitchen. Assuming you are using 35W lamps (any bigger and it would overload inverters) that's over 500W or 2.3A your kitchen must be like an oven?

[zebb]

thanks for the reply eric , my kitchen is quite big , 5m x 5m , 3 x 35w bulbs to 1 transformer , i may change all next year to low energy downlights at 11w each when i have a bit more cash, cheers zebb