GU/GZ10 Mains Halogen and CBus Dimmers

Not sure if these are used in Oz, but we have a number of projects where the client want GU or GZ10 Mains Halogen downlights/spotlights etc.

On normal wall mounted dimmers we have to derate the dimmer by 50%, i.e. 4 x 50w Mains Halogen requires 400w Dimmer to control.

Is there any issues like this with the DIN Dimmer modules ?

We usually get the clients to have LV Halogen, but on this particular project the client has chosen surface GZ10 spots that are mounted off an oak beam.

I certainly dont want to try putting 4 to every single 1a channel if it causes a problem, and likewise dont want to quote twice the size for every circuit if not necessary.

Any help appreciated.




Dean.

 

Dean

for what it is worth I have two banks of 4 x 50w Gu10s and two banks of 3 x 50w Gu10s all running off 8channel 1amp dimmers and have had no problems in the past 18 months.

I am not a sparks so I can't comment on safety etc but it works fine.

Regds
Mick

 

Dean

Why do you need to derate? Are these not just standard incandecent lamps, albeit halogens?

 

Have a look at this thread.

http://www.cbusforums.com/forums/showthread.php?t=89&highlight=240v+halogen

 

Silly clients know best

gay dean, be sure to install those 240v halogens in a accessible area.you be forever there changing globes and listening to a client complain that the globes say 4000 hours on the box and they are always blowing after a couple of weeks.they create alot of heat that seems to affect globe life.Your local commercial light rep would be able to provide backing evidence.they are just not made for long hours of use.But thats only my 2 bobs worth.

 

Mick

Good to know you've had them working ok for that length of time - that puts my mind at rest.

DBuckley

Dont know why we derate, but all the big manufacturers in the UK - MK, MEM Home Automation tells us we have to, and from personal experience before this was made common knowledge i had a 250w dimmer fail twice which was controlling 4 x 50w Mains Halogen

Rohan

Thanks for that - confirms its ok - i only searched from GZ10 or GU10....

Nick

Unfortunately i'm very aware of the lamp problem. We moved from LV to Mains Halogen a number of years ago when philips were first pushing them. We were installing around 2500 fitting per year and the failure rate was appauling, either straight out the box, or after a short period of time.

What came to light is that the Mains Halogen manufacturers show a SUGGESTED lamp life i.e. 2.5k hours, rather the LV who give a guaranteed life of upto 5k hours. These fittings are actually going to be in a real git of a location off a couple of oak beams two storeys up. I'm currently actively looking for a similar fitting to that chosen that is available in LV. Problem is its going to need an integrated Transformer as its a surface fitting, and most of those i've come across dont dim



Dean.

 

A bit of info

Hi everyone,
I would like to provide some info on the issue of 240V vs 12V dichroic, or otherwise light sources. Having worked for a couple of years at Osram in the Tech department, I do know one or two things. Facts are as follows:

- the Mains Halogens behave exactly like incandescent lamps, except that lamp life is a bit better.

- lamp life of Mains halgens is only marginally better than incandescents, depending on the filament rating vs actual supply voltage at site.

- LV halogens are rated 4000 or 5000h average expected life, vs 1000 or 2000h for the mains voltage version.

- light output of the Mains version is no more than one third of it's LV counterpart .... think of replacement frequency here

- at the same time, dimming ANY filament type of lamps by only 5% will increase it's life by a factor 2.

- Cost of the Mains version vs LV version of dichroics is a factor 2 to 3 (in this country).

Looking at the above, it would make sense not to recommend such a light source (Mains), except for areas such as walk-in cubboards, pantry's, or any other short-run-time areas.

In summary, as regards the dimmer, the Mains version of whatever halogen or incandescent lamps you use, will allow you to utilise the full rated capacity of the dimmer (leading or trailing edge), only if you use LV versions must you heed the type and model of transformer used, and de-rate your dimmer in accordance with the schedule issued by Clipsal.

Hope this helps,

Regards
Thomas

 

Theres LV Out there

Dean
Have found crompton lighting have some good quality fittings with a electronic lv trani for each track head pretty reasonably priced . i have used these and found them to work great and this would solve all your problems

 

I have seen Mains Halogens used on conventional and C-bus dimmers in OZ and O/S since ~2000 never heard of any de-rating issues. Dimmer sees them as an incandescent type load (ie 0Ohms cold resistance rising rapidly as power flows). Interested to hear from any one who has details of why derating is required.