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 Topic Title: Lighting Design 2 Topic Summary: Created On: 30 January 2013 08:46 AM Status: Post and Reply Linear : Threading : Single : Branch
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 30 January 2013 08:46 AM Richard64 Posts: 231 Joined: 15 October 2009 I'm trying to work out an energy saving calculation of 28w 2D lamps against 14w LED. I assume that due to the ballast etc, the 2Ds draw more than 28w. The manufacturer's site has it's own calculator, comparing 35w against 13w. Is this reasonable, or just sales BS? 30 January 2013 09:29 AM AJJewsbury Posts: 13117 Joined: 13 August 2003 I assume that due to the ballast etc, the 2Ds draw more than 28w. With conventional magnetic ballasts, certainly. With HF electronic ballasts, my experience is that they run the lamp somewhat more efficiently with the lamp being supplied with a little less power (for the same or better light output) than conventional setups, with the result that lamp + ballast together take about the nominal rating of the lamp alone. - Andy. 30 January 2013 09:36 AM OMS Posts: 20647 Joined: 23 March 2004 Be a bit careful of just comparing operating watts - different lamp types in similar looking fittings often have significantly different light output ratios (ie how much of the lamp lumens actually gets out the box). To do the comparison, you really need to be looking at: luminaire-lumens per circuit-watt Essentially the metric looks at how much useable light out compared to the power in. You need lumens as well as watts to make a comparison. Regards OMS ------------------------- Let the wind blow you, across a big floor. 30 January 2013 09:52 AM impvan Posts: 912 Joined: 07 September 2005 In comparing 2D with LED replacements, I'd be sceptical of ANY manufacturers comparisons. You want to know the lumens output, and be sure you're comparing them at the same colour temperature - eg if you're replacing warmwhite 2D make sure you compare the output with warmwhite LED! ~ the manufacturer will usually compare against coolwhite LED to get higher figures. You also need to consider that the 2D LEDs have zero light going sideways or backwards. Where I've fitted them to luminaires with prismatic covers, the difference hasn't been too bad, but with diffuse covers it's had a queer effect on the light distribution. At the cheaper end of the scale there's a marked difference in the colours of white which doesn't look good when you've a number of lights in a row.... Also consider reliability. I've fitted perhaps a hundred LED lights of various types and had quite a lot of failures; I must have fitted a thousand HF fluorescent ballasts over the years with a much lower failure rate. As regards the energy consumption, Andy's correct about electronic ballasts. 30 January 2013 10:33 AM Richard64 Posts: 231 Joined: 15 October 2009 Thank you for your replies. Most of the work I'm carrying out is for direct replacements, not new installs. So, as long as the output is sufficient, that should be OK. I just wanted to give an idea of energy saving. And to be honest, with the guarantees available 50 000 hours, the benefits are more in reduced maintenance and the convenience of having all the lights working at the same time :-)
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