Browse Forums Lighting + Lighting Design 1 Oct 14, 2011 9:01 am I'm pleading for a bit of electrical help. I'm a little confused. We are half way through our new home build and it's time to supply our builder's sparky with our light fittings. We will have 6 downlights in our suspended concrete slab. After much consternation, we've elected to install 35W IRC halogens. (and hopefully later retrofit MR16 LEDs when the technology evolves.) Each downlight is individually switched. The sparky has already run low voltage wire from each slab canister to a common point in the house where the transformers will reside. The distances between transformer and slab canisters are between 3 and 10 metres. The builder has asked us to provide a separate transformer for each light, and has stated that we should provide them with iron-core transformers rather than electronic ones. It's my (limited) understanding that a good electronic tranny will run cooler and more efficiently than the older iron core equivalent. Is there a reason (perhaps the length of LV wire run between tranny and downlight?) that they want us to use iron core drivers? I'd really appreciete some help with this. Cheers, Avion. Re: Builder insists on iron core downlight transformers. Why 2Oct 14, 2011 9:34 am Hi I had a feeling it would be because of the radio-frequency interference generated by the high-frequency switching in an electronic transformer. It took some digging to confirm my suspicion, but I found it at http://www.paulmann.de/?Land_ID=1&Sprache_ID=2&1Menu_ID=90&Anwendung_ID=6&FAQAction=wwwshow&FAQKategorie_Int_ID=30 Quote: 17.Question: Why must the cables on the low-voltage sides of electronic transformers not exceed 2 m? Answer: Longer cables can cause the following problems: Radio-frequency interferences would increase because the low voltage cables act as transmitting antennas. The high operating frequency provokes the so-called SKIN-EFFECT. That means that not the full cable cross-section can be used for the transmission of current. The current density near the surface of the conductor is greater than that at its core. So if the cable is longer, the voltage drop is much higher and consequently the light is darker. Using a star connection (transformer in the center), 4 m can be supplied. If this is not sufficient, a 50 Hz inductive transformer can be used. Re: Builder insists on iron core downlight transformers. Why 3Oct 15, 2011 8:23 am Ahh, that's great info Paul. That makes sense then. With our long LV cable runs we might have very dim lights (and unwatchable TV! thanks to RF noise). Thanks heaps for taking the time to dig that up. By the way, I had a look at your blog. What a spectacular spot to live! Stunning! Builder insists on iron core downlight transformers. Why? 4Oct 15, 2011 7:51 pm Thanks. We can't wait to get settled. It looks like we will be in in January Hi SouthiMonk, can I please ask if you have had Terramater Coastal blackbutt hybrid installed in your home, and if so, are you happy with the flooring? I was going to… 1 4157 Versaloc is a mortarless besser block system that still needs a properly engineered footing. If you just do a 400x200 footing it will fail in time. At 17m long you need it… 1 22330 We have a Victorian style ripple iron fence out the front that has some moulded timber capping. Probably 15+ years old and has cracked and splintered in parts...not really… 0 2585 |