ChronoMonkeyX OP t1_itv2dm8 wrote on October 26, 2022 at 2:59 PM

Reply to comment by paulgraz in Question about fluorescent light fixture replacement: how much light do I need? by ChronoMonkeyX

The goal is get rid of old generic(and cracked and yellowing) fixture for something nicer since we are remodeling the kitchen, and to switch to LEDs for power consumption. I'd say the amount of light before was fine, I don't need more and don't think I want much less.

I'd be perfectly happy with the standard LED box replacements, but it's my mother's kitchen and my sister isn't going to settle for a new plain box light.

When I saw the old bulbs are 2600 lumens each, I started to worry about the kitchen being dim.

blahblahblah123pp t1_ityc5ve wrote on October 27, 2022 at 5:08 AM

If you get an LED panel the rated lumens are what actually come out of the fixture into the room. Since fluorescent bulbs can be placed in any fixture they’re rated on what comes out of the tube, not the fixture itself. Depending on what fixture you have the effective output could theoretically be anywhere from 0-100%. At my company we tend to use 50% of the total rated output of fluorescent tube fixtures as a basis for LED panel selection. This is because fluorescent tubes are omnidirectional, so you tend to lose a lot of light going sideways/upward into the fixture itself. In this case it would be 2600x4/2=5200 lumen LED panel. Now from there we do one test fixture and use meters to do an actual comparison, but it’s a good starting point if you wanna keep things easy. LED panels also tend to have a much wider projection, so it’ll seem like the entire room gets lit evenly vs the spotlighting effects you have from recessed fixtures.

ChronoMonkeyX OP t1_itz3sle wrote on October 27, 2022 at 11:15 AM

Thank you, I suspected the full 10,400 was unlikely because of the shape of the fluorescent tube, but wasn't sure what kind of estimate to use. 10,000 lumens of LED light would be insane in a kitchen.

blahblahblah123pp t1_itz8d2r wrote on October 27, 2022 at 12:01 PM

Yeah, it’s part of what helps the “efficiency” of LED lights. I’m using quotes because the portion of the energy savings that comes from what I was talking about in my last message isn’t actually in the LED tech itself, but in the fact that it’s directional. Even LED tubes only have light shooting in one direction (at least all the ones we use) so it’s very important to orient them in the right direction or you won’t be getting the light where you want it (i.e. in the recessed ceiling fixtures the light could just end up going straight up into the ceiling instead of down in the room).