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Re: Retrofitting results

PostPosted: Sun Aug 05, 2012 7:19 pm
by zzsstt
I can't find any high bays on eBay for under $200-$300 (I thought I'd have a look to see what they were!). Given that normally an LED high bay sells for >$300, I'd question the quality of anything at the $100 mark. But then 30W is a very low powered high bay!

In terms of LED vs. T5, firstly it is probably wise to reduce the "marketing" numbers for an LED by 20%, my experience has been that they rarely meet the paper claims and the cheaper they are the greater the deficit. I see no reason to believe that a cheap high bay will be more accurate in it's claims!

A T5 without a reflector will indeed radiate light at 360 degrees. This can produce a significant reduction in light, although that depends on the nature of the area being illuminated. My "playroom" has a white painted drywall ceiling, and linear T5's produce a beautifully even light in half of it, whilst circular pattern reflector MR16's LED's (trapeze lights, I was in a retro mood!) create distinct variations, together with darker corners and ceiling in the other half. My other small workshop has T8's without reflectors, but the unlined ceiling does tend to absorb a fair amount of light. However once again the remaining light is very evenly distributed.

With high bays the light is largely reflected downwards, though as the reflector dulls (especially the cheaper ones that dull quite quickly) this advantage is lost. The beam angle is, as you mention, very important - I know of one high bay on a >10m ceiling that has had its reflector removed because it created a circle of brightness with no light outside it! An 80degree bean angle will only illuminate a circle of about 7m diameter at 4m high - and all that light is coming straight down, so you tend to create a shadow right where you want to see (if looking down!).

For a small area like a 10x12 shed, seriously consider lining the ceiling (if you haven't already) and painting it white. For my toyroom, with a lined cathedral ceiling, I installed 4 x single tube 28W T5's (no reflectors), plus 4 x double tubed (2x28W) T5s in an area 7m wide by 8m long (the "playing with cars" half). They are switched so allow the single tubes to operate independently, so I have 3 levels of light available - 112W, 224W or 336W - i.e. single tubes, double tubes or everything. For most jobs I only need the single tubes - 112W. Now that's a bit more w/m^2 than you're looking at, but they are a reliable, quality light that cost very little and for which I can get new tubes at Bunnings - or even LED tubes, should I get adventurous! They give a very even light, no harsh shadows (white walls and ceiling). And because I lined the walls and ceiling I have an insulated "shed" that is cool in summer and warm in winter (and I have a wood burner!). The other half has trapezed MR16 LEDs. They produce a very different light, far more architectural but less evenly distributed, and that suits the purpose of the room.

Obviously it depends on usage. In my small workshop (100m^2) I have no lining and the T8's get swallowed by the gloom to some extent, but portable LED floodlights and a 50% opening (100% sliding area) north facing door counteract that. And for fixing tractors and farm machinery a lining is probably more trouble than it's worth! But tubes with reflectors would be an improvement.

If you stick to your existing plan, if the 3m section is divided off by a wall consider rotating the T5's by 90degrees - most of their output is at +/-90degrees to their length, so in your diagram you risk getting 3 bands of light with darker sections between them.

Re: Retrofitting results

PostPosted: Sun Aug 05, 2012 7:35 pm
by Smurf1976
zzsstt wrote:5/ Work out how much time the lights will acutally be on. There is no point in spending thousands of dollars on LED highbays that save 30% (whatever) on power bills, if they'll only be on for a few hours a month!

A principle that is all too often overlooked regarding energy efficiency in general.

For example, 5 years ago I needed to buy a TV (since I didn't have a working TV). The energy guzzling plasma that I bought cost $1500, versus $2600 for an LCD equivalent at the time. Obviously those figures have changed now, but spending $1100 in order to get something that uses 250W instead of 350W just didn't stack up economically, environmentally or in any other way.

The only reason to buy an LCD at the time, apart from if you just wanted one, would be if your electricity supply was physically limited (eg off-grid) such that there were reasons to save energy beyond cost and environmental considerations. But under any other circumstance you could save more money, or more CO2, by doing something else with the $1100 price difference.

So far as the garage lighting is concerned, at present I have older T8 fluorescent tubes, 8 x 36 W in total. For the 100 or so hours per year that they are used, there's just no point in worrying about them. Left alone, they'll probably sit there for the next few decades without attention, and the energy cost is pretty much irrelevant at that level of use.

Likewise the old T12 tube that's in the bathroom above the mirror - for the amount of time its used, it's just not worth worrying about. Sure, I could take out the 20W tube and put an 18W in the same fitting since they're a direct replacement. But to be perfectly honest, what's the point in worrying about 2 watts used for a few minutes per day? The cost and environmental effects of manufacturing the new tube would exceed any benefits of saving such a trivial amount of power, hence I'll leave it alone unless it wears out and actually needs replacing.

Obviously all that would be very different if I was running the lights 24/7 in a factory, or even just 9 to 5 in an office, in which case retrofitting something more efficient would make sense. Likewise it might have been worth worrying about the TV if it was in commercial usage rather than the few hours a week that I watch it.

The same principle applies to just about everything but often gets lost in discussion on the subject.

Re: Retrofitting results

PostPosted: Sun Aug 05, 2012 8:39 pm
by offgridQLD (not has some 35w units for $120 US but your looking at $40 to post it. I did see some for $100although I looked at hundreds of web pages so might not have been on ebay. All the same they would be china brand LED's. I have had real hit and miss results with cheep led lights. I purchased some bike lights about two years ago that are incredible and as good as lights costing 5 - 10 times as much. That said a have ended up with some that are now my daughters toys :lol: Its a risk that's why I thought perhaps just buy one as an experiment.

I wasn't planing to line the shed at least not at first. it's not out of the question down the track if I feel the need. The colorbond has a reasonably light backing. Almost the same as shale grey. I know this as I put down a shale grey roof with for a friends house a few weeks ago and we had to to look carefully for the faint code print to know what side was the front of back. That said not as reflective as a white or as flat as a painted plaster wall .

That's a good idea about running the batons the other way around to save shadow dead spots. There isn't a dividing wall between the two sections but there could be down the track if I am that way inclined. Actually all the battens could be swung around the other way . I was thinking of hanging the lights on drop chains in the 7-12m section as the roof slopes up to 5m high.

My usage would be usually from 7pm - 11pm . Not every day of the week but reasonably often during summer when the nights are a pleasant temp. That said we have excessive pv output in summer anyhow. 1.3kwh for the night if I had all the lights on its not that bad I guess even if i had to put 4 rows in.


Re: Retrofitting results

PostPosted: Sun Aug 05, 2012 9:30 pm
by zzsstt
offgridQLD wrote: That said not as reflective as a white or as flat as a painted plaster wall .

There's no reason why you shouldn't just mount a "bare" T5 luminaire on a 500mm x 1200mm piece of white painted scrap plywood - not as good as a lined ceiling or a luminaire with a reflector, but cheap! It would probably get you a bit more light by recovering some of the 30% that is going completely the wrong way!