Page 1 of 2 12 LastLast
Results 1 to 15 of 21

Thread: Shop lighting - Number of fixtures insane!

  1. #1
    Join Date
    Mar 2003
    Location
    Vermont
    Posts
    341

    Shop lighting - Number of fixtures insane!

    I read through Jack Lindsey's article in the section on shop lighting, and ran through a bunch of calculations, and it has managed to completely confuse and annoy me. This is what I have, that I plugged into his simple formula:

    800 sf shop (approx. 24 x36), 10' ceiling, walls and ceiling painted white. 100 foot-candles at work surface.
    Assuming 40% of fixture lumens gets to work surface, 800 sf x 100 fc = 80,000 lumens required / 0.4 = 200,000 fixture lumens required.

    I planned on using a Commercial Electric LED shop light from Home Depot (SKU 1000532467) which claims 3600 lumens. If I plug that into the formula, I get 56 (!) fixtures required. Fifty-six. No way. Even if I made a reasonable assumption that 60% of the usable lumens are reaching the work surface, I'm at 133,333 lumens which is still 37 fixtures. I can hang the lights a lot lower but that tends to ruin the purpose of the 10' ceilings.

    What's wrong with this picture? Where are my assumptions or calculations way off here? I read on other forums about people allegedly lighting their huge pole barn shop with a half-dozen fixtures and being able to conduct neurosurgery, so what gives?
    Jon Endres
    Killing Trees Since 1983

  2. #2
    Hi John,

    I'm not at home to run any calcs but no doubt 37 fixtures is waaay too many. The last shop I wired (as a licensed electrician) was also 24 x 36 with a 12' ceiling. I installed (6) 8' T-5 High Output fluorescent, four 54 watt lamps in each fixture, and it was one of the brightest shops I've ever seen. The fixture came from HD and were about $70 each and the lamps were about $5 each for a total cost of $540 for materials, and the labor was minimal compared to installing many more cheap fixtures to get the same lumens. Here's the link to the fixture:

    http://www.homedepot.com/p/Lithonia-...10PS/202516724

    That owner wanted 4100K lamps which I thought looked just a bit blue but still gave good color rendering. I personally prefer Philips Alto 3500K lamps as the color rendering is decent for the price point.


    Mike

    Edit: Oh yeah, that fixture/lamp combo put out about 19,000 lumens per fixture.
    Last edited by Mike Jungers; 05-24-2016 at 5:01 PM.

  3. #3
    Join Date
    Mar 2006
    Location
    SoCal
    Posts
    21,695
    Blog Entries
    1
    My shop is about 20 x 30 and I have 18 twin lamp fixtures at about 9 feet. There are still areas where I need task lighting. Lighting a work area is not like lighting a living area. Very good illumination is required over a large area.
    Take me to the hotel - Baggage gone, oh well . . .

  4. #4
    Join Date
    Dec 2008
    Location
    South Central Pennsylvania, USA
    Posts
    761
    Well, my first thought was that considering that his sample calculation has more s.f. (1500) and his fixtures have less lumens (2800) and he comes up with only 27 fixtures, I was going to guess something went wrong with your calculations...

    Then I realized that he is using 4 lamps per fixture (2800 lumens x 4) I was…

    My 1000 s.f. metalworking shop with 11’ ceilings, light grey walls, and galvanized metal ceiling (so, less reflective than the white walls and white ceilings) has three bays each with three 8’ double bulb T12HO fixtures. The bulbs are 8600 lumens each, so that is 155,000 lumens total - and that is BRIGHT! Now, he has half again as much space (1500 s.f.), but he has more reflectivity and is still saying he needs twice as much light (300,000 lumens). Figuring my lumens for 1500 s.f. would be the equivalent of only 232,500 lumens.

    Again, my shop is BRIGHT!

    Now, your shop is a bit smaller than mine, but to get the same level of light as my T12 fixtures you’d be using five of your fixtures therefore 9 x 5 = 45. So maybe your 37 isn’t too far off?

  5. #5
    Join Date
    Jun 2010
    Location
    Upland, CA
    Posts
    1,343
    Those LED Linkable lights are TASK LIGHTING, not shop lighting. They have a pull chain!

    They are only 3500 lumens. Their intended use is to add one or two over a workbench or other work area to add extra light right at the work. Probably hanging no more than 4' above the bench, likely more like 30-36" above the bench. Buying those to light a workshop would be like a trucking company sending someone out to buy a big truck and they come back with 37 scooters.

    I have Lithonia lights over my home workbench but want it at 11' to light the benches and surrounding area. I use a 17,700 lumen 6x32wT8. These are also from HD: http://www.homedepot.com/p/Lithonia-...-MVH/202193185

    3 of those do a decent job of lighting up that 6' x 32' area. As an experiment I used an extra Lithonia LED light to replace the middle one as that is the area where there isn't a bench. This is to let me turn on only that light as I come and go and then add the others when I'm doing real work. The one I added is this one from HD: http://www.homedepot.com/p/Lithonia-...L-MV/203812710
    It is only 11,200 lumens but is good enough and will probably be happier going on/off 25 times a day with the occupancy sensor.

    Here is the graphics to show this:
    #1 is a two bulb 4' shoplight similar to the one you were picking. It is 2x2800 lumen lights so 5600 lumen fixture although super low end florescent not likely to be getting all the light where you want it due to poor reflectors, etc. Still needing 48 or them to get 100fc at 30" table height:

    24x36-100fc-#1.jpg

    #2 is the fixtures I'm using. 9 getting 130fc at 30" bench height. Not sure you want to use that exact fixture on a 10' ceiling and they can't be surface mounted anyway:

    24x36-100fc-#2.jpg
    Last edited by Greg R Bradley; 05-24-2016 at 6:18 PM.

  6. #6
    Join Date
    Mar 2003
    Location
    SE PA - Central Bucks County
    Posts
    60,552
    My shop is ~22x30 and I have 14 fixtures; 12 of which are LED at this point. It's like working next to the sun...

    My fixtures are either LED fixtures or LED replacement tubes, all from Costco. (Feit)
    --

    The most expensive tool is the one you buy "cheaply" and often...

  7. #7
    Join Date
    Jul 2008
    Location
    Courtenay BC Canada
    Posts
    2,747
    Building a new shop.. I had the lighting done by a lighting person. (ALA) ..

    Shop is 27 x 37 .. has 13 foot ceilings at the peak .. it spec'd .. 6 x 6 tube T-5 HO .. 5000 Lumens per tube.. or 180,000 lumens total plus 4 x T-8 Twin Tube over the bench, for another 24,000 lumens and a 2 tube flourescent at 6000 lumens directly over the table saw.

    So 960 sf shop .. will have 210,000 lumens. 2 switches so I can turn 1/2 of them off for normal use.

  8. #8
    Jon - The article was written specifically for luminaires utilizing fluorescent sources and is not intended to apply to luminaires using LED's. This is explained in the second and third paragraphs of the article.

    The Standards for fluorescent lamps and ballasts are consistent throughout industry thus the operating characteristics of fluorescent systems are well known, and can be applied to a broad cross section of commercially available products. LED lamps and drivers simply don't enjoy the same consistency. Lamps and drivers must be compatible but this is not necessarily true in all cases. There may be wide variations in lamp life and lamp lumen depreciation between driver and lamp systems, and I believe we have a ways to go before I am comfortable in presenting a simplified calculation method.

    If you want to use LED's I suggest you contact the luminaire manufacturer for their recommended light loss factor (LLF) and coefficient of utilization (CU), and ask if the LLF includes a dirt depreciation factor. If it does simply multiply the CU by the LLF and substitute that value for the 50% factor I use. If it does not, multiply that value by 0.80 and then apply that value.

    Hope this helps.
    Last edited by Jack Lindsey; 05-25-2016 at 1:00 PM. Reason: add info on CU

  9. #9
    Join Date
    Mar 2003
    Location
    Vermont
    Posts
    341
    Thanks for all the responses. I'm beginning to think that putting LED fixtures in the shop, maybe not the best idea? T8 tubes aren't going away anytime soon. If I go with a 48", 4-bulb low-bay industrial shop light, I think I can reduce my fixture count and my upfront costs.
    Jon Endres
    Killing Trees Since 1983

  10. #10
    Join Date
    Oct 2006
    Location
    Bloomington, IL
    Posts
    6,014
    I definitely know that "bright as the sun" means different things to different people so take my desired lighting as it is only right for me and my shop.
    My numbers:
    64X40X16 shed
    6 bulb T5HO ~3A ea - 30000 lumens spcd ea (no idea if that number is right - these are just 2X4 with specular reflectors from Cors Lighting seller on Ebay - Howard fixtures and bulbs so nothing fancy)
    The formula above - 2560X100/.4/30000=21.3

    I put in 18 fixtures so far, just under the trusses so pretty much at 16', on four 3-way switched 20amp lighting only circuits. Fellas, it is flat out amazing light. No kidding. Come by and I will demo for you.
    I spaced mine north to south in four rows in a 5, 4, 4, 5 spacing with the odd rows having the extra light in the woodworking bench area and the other extra light over the 1340 metal lathe and kneemill area in the metalworking area.

    My advice is put in the circuits for what you could/should get too and add to your lighting as you can afford it.

    For anyone building a new shop, consider planning for separate circuits and switches if possible so you can choose which sections of light you want.. Also pay attention to garage door placement and what they cover if you work where they are open and plan that light accordingly. Also when you are running light circuits consider some above bench potential area tool circuits. Also consider a wifi access point outlet, any fan outlets you might need, garage door opener outlets and if any of those you might want switched. Also in ceiling speakers if you want music in ceiling. Sorry for OT OP.
    Last edited by Mike Heidrick; 05-25-2016 at 9:50 AM.
    Glad its my shop I am responsible for - I only have to make me happy.

  11. #11
    Join Date
    Jun 2010
    Location
    Upland, CA
    Posts
    1,343
    Jack's input is really excellent as always.

    Nothing wrong with LEDs except two big problems that make it tough to choose wisely. One, the manufacturers are mostly new and they make some lousy fixtures and then exaggerate the specs to the point of being silly. Two, most people think LED will somehow be really bright and use very little electricity, which doesn't work out well all the time. Most people are happy with a change to LED because the fixtures are new instead of some magic improvement in technology. LED fixtures are simply fabulous for some applications. Just choose wisely.

    Am I understanding correctly that you have a white flat ceiling at 10' and that you wish to surface mount your fixtures?

  12. #12
    Join Date
    Feb 2008
    Location
    E TN, near Knoxville
    Posts
    11,649
    Quote Originally Posted by Rick Fisher View Post
    Building a new shop.. I had the lighting done by a lighting person. ... .. it spec'd .. 6 x 6 tube T-5 HO .. 5000 Lumens per tube..
    So 960 sf shop .. will have 210,000 lumens. 2 switches so I can turn 1/2 of them off for normal use.
    My shop lighting was designed by a non-professional, me. I am extremely happy with the result. I use the same T5 HO bulbs in 4-bulb fixtures, rated at 5000 lumens per bulb (measured by an independent laboratory at about 4700+). I use about 24x32' of my 24x62 building for the general shop and have eight 4-bulb fixtures in that end of the building.

    When all the fixtures bulbs are on a couple of visitors have joked that they need sunglasses. I also used the feature built into the electronic ballasts to light just 1/2 of the bulbs in each fixture with the main switch with an extra switch to turn on the other half when needed. This, in my opinion, is a perfect solution to the shop lighting issue.

    I put my fixtures in "zones", each with a separate main and extra light switch. I mount the extra switches higher on the wall above the main switch. The different zones are so I can avoid turning on all the light when I don't need it - I have areas for woodturning, main shop, wood storage, etc. (Most fixtures are on 3-way switches so I can control everything from the entrance way if needed.) Nearly all of the time just two bulbs in each fixture are enough light. On rare occasions with detailed work the extra light is a huge benefit.

    I also installed several switched outlets at the lathe, bandsaw, and machine shop area for plug-in task lighting - this is better than using an outlet strip or turning on several task lights one at a time.

    Another thing I did which I can highly recommend: I wired a string of lower-wattage LED and CFL fixtures from one end of the building to another, all switched from any of three entrances. This gives me more than enough light to move through the shop to to access tools and materials without turning on the main lights.

    A couple of safety things: having lights on more than one breaker would be good in the rare event that a lighting breaker is tripped. Even better - I added a set of cheap battery-powered safety/exit lights wired into the building power.

    When designing lighting be careful if your table saw has a polished, reflective surface. A poorly placed bright light could cause undesirable glare. I guess sanding the top to a satin finish would help.

    One note about the T5 fixtures. Those with four bulbs in parallel are wired so the outer two are off unless turned on by the extra switch. This is fine. I also have some that are 8' long with two rows of two bulbs each. These come wired internally so the extra switch controls two bulbs on one end so 4' of the fixture is dark. This is not fine. Before mounting them I took them apart and moved the bulb connectors so the lighted pairs are the entire 8' length of the fixtures for a more even lighting.

    JKJ

  13. #13
    Join Date
    Jun 2010
    Location
    Upland, CA
    Posts
    1,343
    Yes, "brighter than the sun" is badly misleading.

    If you look at the lighting displays at the consumer stores like HD and Lowes, you are mostly looking AT the light, which is completely different than working under it at the intended install height with other lights hooked up in your install grid. Big difference. High color temperature lights will look "whiter" and will be judged brighter even if they aren't. Irritating colors like cheap florescents and LED with poor CRI will be judged brighter even though they are harder to work under, etc. UV is irritating, not useful.

    Our QA lab at one of my businesses was lit to 400fc at the work surface. Nobody ever complained about being too bright because it was useful light.

    I have an old T5 fixture lighting a narrow corner of my home shop. It seems really bright because it has two T5 bulbs 1/2" apart and it's mounted at 8'. It seems too bright but when you try to work under it you would not think so. Another narrow corner has a 4xT5HO fixture. It has really useful light underneath but isn't glaring because you can't see the bulbs directly unless you stand under it and look straight up.

    12' is a typical minimum for my 6x32T8 fixtures. Mike's 6xT5HO fixtures at 16' is a typical minimum for those. They will have more light coming out of a smaller area.
    Last edited by Greg R Bradley; 05-25-2016 at 10:23 AM. Reason: spelling error changing meaning completely - replaced "can" with "can't"

  14. #14
    Join Date
    Oct 2006
    Location
    Bloomington, IL
    Posts
    6,014
    As always thank you to Jack and Greg and the rest of you very smart individuals in helping me get to where my shop is lit today. Your info is awesome!
    Glad its my shop I am responsible for - I only have to make me happy.

  15. #15
    [QUOTE=Greg R Bradley;2568610]Yes, "brighter than the sun" is badly misleading.

    If you look at the lighting displays at the consumer stores like HD and Lowes, you are mostly looking AT the light, which is completely different than working under it at the intended install height with other lights hooked up in your install grid. Big difference. High color temperature lights will look "whiter" and will be judged brighter even if they aren't. Irritating colors like cheap florescents and LED with poor CRI will be judged brighter even though they are harder to work under, etc. UV is irritating, not useful.

    Our QA lab at one of my businesses was lit to 400fc at the work surface. Nobody ever complained about being too bright because it was useful light.


    Thanks for pointing this out, Greg. Since you brought up the topic of perception versus reality I'll add the fact that for a small diameter light source (think T-5) to produce the same light output as a larger diameter source (think T-8 orT-12) it must have a higher luminance per unit area. This is commonly misconceived as the smaller source producing more light. It doesn't but it does look brighter.

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •