wire routing for overhead lights in my shop

[rjacobs]

Looking for some advice/opinions on how to route the EMT and wiring to the lights I am planning to put into my shop.


Im strongly considering 10x of these 4' LED fixtures. 7200 x 10 / 700 = just north of 100FC's. I would be at 13' mounting height which is the max they recommend for these lights so I dont think I would actually get 100fc's at the ground. Plus, if my overhead doors are open I lose 4 lights basically... I'm probably at the limit of overkill.

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ANYWAY. I would mount them on the horizontal cross braces. Those braces are ~15' wide give or take. I would push them out as far as possible, so 10x total fixtures.

I have 2 thoughts on wire/conduit routing.
1: Center above the cross brace in EMT, j box at each, convert to MC to the fixtures.
2: Center below the cross brace in EMT, j box at each, EMT to each fixture.

I dont think cost wise I am really any different. Im buying 3x 500ft spools of #12 THHN to wire the whole shop with(probably wont be enough, but thats my starting point), so ill have the wire if I stick with EMT. Either way I need a j-box at each cross member. If I dont go "below" and use my THHN+EMT, then I need to buy like 50ft of 12-2 MC which is about 60 bucks...5 sticks of 1/2" EMT is about 35 bucks... So converting to MC is maybe 25 bucks more... I dont count fittings as both need fittings at j-box and lights so its sunk cost.

Im leaning towards "below" the cross brace and then staying with EMT to each fixture. This would allow me to run another piece of EMT "above" the cross brace to a few other circuits I have planned(2x lifts, 2x garage door openers) to keep things relatively clean without just having random *** EMT running all over the damn place.

Any other thoughts on how to run the wiring to look clean?

 

[u2slow]

I would probably run EMT up to a couple JBs.

How high is the ceiling? For a high ceiling, I would chain-hang the fixtures each with their own armoured-cable whip.

Otherwise you might want to use those angle braces for mounting.

 

[rjacobs]

I would probably run EMT up to a couple JBs.

How high is the ceiling? For a high ceiling, I would chain-hang the fixtures each with their own armoured-cable whip.

Otherwise you might want to use those angle braces for mounting.

those horizontal cross braces are basically exactly 13' from the floor. Like I said thats the lighting manufacturers max height recommendation on that light... then yea they would recommend high bay. My electrician buddy thats going to help me said he wouldnt do high bay fixtures in my shop as they would be far to bright being right at the limit. He "liked" my plan. Im "over" on the recommended FC's, but due to being at max ceiling height, that light will likely defuse a bit so should be ok.

Those angle braces from the wall to the ceiling arent 4' so not ideal... plus the last 2 on each side, no way to mount lights to them due to the garage door almost hitting them when you raise them. There is only about 1" of clearance, maybe less.

 

[bronc076]

The nice thing about flex to the light fixtures is if you decide they need repositioned a little you have that freedom. I'm putting switched outlets in my ceiling so I can swap fixtures, move fixtures, etc with little effort in the future.

id do emt to boxes, then a whip to the light fixtures.

 

[u2slow]

Those angle braces from the wall to the ceiling arent 4' so not ideal... plus the last 2 on each side, no way to mount lights to them due to the garage door almost hitting them when you raise them. There is only about 1" of clearance, maybe less.

Maybe put a runner-board or strut along the braces?

I have a 19.5' tall ceiling, and none of my lighting is above 8'. Mostly around the perimeter. I built an 8' shelf down one side of the shop and put LED strips on the edge.

Some day, eventually, I plan to throw in 4-6 UFO style highbays.

 

[dscheidt]

I'd use FMC instead of MC. There are EMT to FMC connectors, so you don't have to have a box at each fixture, just terminate the flex at the fixture and pull your wires. Also, get some 14 AWG thhn. Not only is it cheaper, it's easier to work with; easier to pull, easier to terminate on devices. You don't need your lights on 20A circuits, they're not carbon arc spotlights.

 

[rjacobs]

The nice thing about flex to the light fixtures is if you decide they need repositioned a little you have that freedom. I'm putting switched outlets in my ceiling so I can swap fixtures, move fixtures, etc with little effort in the future.

id do emt to boxes, then a whip to the light fixtures.

I dont have MUCH room to re-position. I was thinking of getting 12'(3x 4' fixtures) of lighting as that company makes a bridge kit to essentially make it 1 piece, but I think I came out like 150fc's of light which I believe is way to bright. I "think" the 2x 4' fixtures spread to edges of my horizontal roof brace will work out pretty well for overall lighting. I may run into the need for some kind of focus'd light, but I can deal with that later...

Maybe put a runner-board or strut along the braces?

I have a 19.5' tall ceiling, and none of my lighting is above 8'. Mostly around the perimeter. I built an 8' shelf down one side of the shop and put LED strips on the edge.

Some day, eventually, I plan to throw in 4-6 UFO style highbays.

that doesnt help me on the 2 on each side that are to tight to the overhead doors when they are open... that would actually make things worse.

Im just going by the max height of 13' that the lighting manufacturer says their fixtures are good to. I have read that real "high bay" lighting shouldnt ever be mounted below 14'. My electrician agreed.

I'd use FMC instead of MC. There are EMT to FMC connectors, so you don't have to have a box at each fixture, just terminate the flex at the fixture and pull your wires. Also, get some 14 AWG thhn. Not only is it cheaper, it's easier to work with; easier to pull, easier to terminate on devices. You don't need your lights on 20A circuits, they're not carbon arc spotlights.

I didnt know FMC existed... good call since ill already have a bunch of THHN wire. Im still on the fence on just running EMT out from j-boxes mounted in the center straight to the fixtures. I guess my thought on the j-box's is I need to split the wire run to 3 places(2x lights plus the next j-box down the way).

My city prohibits 14g in branch circuits...

 

[dscheidt]

My city prohibits 14g in branch circuits...

what city?

 

[Dagny]

I don't use a lot of 14 but thats a stupid law.

 

[rjacobs]

what city?

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8-31
#14 is prohibited in branch circuits...
ETA: I can guarantee its because we have a lot of home builders in the area trying to build things as cheap as possible... Im sure they would use #14 and then string 20+ outlets off of it all protected by a 15a breaker if they could to save 3c per foot of romex.

They have also basically eliminated the ability to use aluminum in feeder circuits until you get to some crazy size(250). We were going to run aluminum under ground to my shop, but had to run copper after reading the local amendments... so that cost another 500 bucks or so.

 

[Dagny]

I carry about 15 rolls of 12AWG in my stepvan just don't have room for more gauges.

 

[Dagny]

Nothing quite like a house wired to minimum code.

 

[goneracin]

I ran emt up out of the box to the truss. then just bent it to follow the truss. I ran 3 rows total (9 8' lights) lengthwise in my building
26X40
Im going to put some smaller lights near where i will put my bench and by where the lift will go in the back right corner

 

[u2slow]

that doesnt help me on the 2 on each side that are to tight to the overhead doors when they are open... that would actually make things worse.


My city prohibits 14g in branch circuits...

For a while I looked at hanging strips from the garage door tracks.

Always some funny rules... can't say I always follow the silly ones.
My jurisdiction prohibits 20A lighting circuits - in dwelling units. So check if your #14 restriction is for all building types.

 

[rjacobs]

I ran emt up out of the box to the truss. then just bent it to follow the truss. I ran 3 rows total (9 8' lights) lengthwise in my building
26X40
Im going to put some smaller lights near where i will put my bench and by where the lift will go in the back right corner

very clean... like it.

 

[BillK]

Cant help you with the location and wiring but take a good look at the fixture you linked to. It says it is "commercial" grade which sound good but commercial grade fixtures and tubes are not as good as residential grade ones when it comes to RFI. Make sure that it meets the FCC specs for RFI emissions. They will drive a radio crazy if they dont.

 

[rjacobs]

It says it is "commercial" grade which sound good but commercial grade fixtures and tubes are not as good as residential grade ones when it comes to RFI. Make sure that it meets the FCC specs for RFI emissions. They will drive a radio crazy if they dont.

Like an FM radio???? yea dont care about that.

I didnt even realize they were "commercial" grade...whatever that means honestly... I took a commercial grade dump this morning, ill label it in a box... LOL

The company is based just north of Austin, and their products are made in Mexico... Yea its not "Made in USA" but at least its not "made in China"... although I bet their LED chips are made in China... I have read a TON of good things about the company over on a big Facebook group.

 

[cybrdyke]

Im strongly considering 10x of these 4' LED fixtures. 7200 x 10 / 700 = just north of 100FC's. I would be at 13' mounting height which is the max they recommend for these lights so I dont think I would actually get 100fc's at the ground. Plus, if my overhead doors are open I lose 4 lights basically..

You're not understanding how foot-candles work. 10 of these fixtures wont give you anywhere near 100fc.
Dont shoot the messenger.
CD

 

[dave*99]

You're not understanding how foot-candles work. 10 of these fixtures wont give you anywhere near 100fc.
Dont shoot the messenger.
CD

I had the same thought.

 

[rjacobs]

You're not understanding how foot-candles work. 10 of these fixtures wont give you anywhere near 100fc.
Dont shoot the messenger.
CD

care to enlighten then if you understand it better than me?

Do I need to divide my number by 13 since they will be 13 feet away from the floor?

I've looked at a bunch of calculators and they all basically just do lumens/sq. ft. without taking anything else into consideration.

 

[dave*99]

I've looked at a bunch of calculators and they all basically just do lumens/sq. ft. without taking anything else into consideration.

Without a height factor, you can't determine illumination at the work plane from the emitted illumination. Lumens are emitted. Footcandles are observed illumination. If the calculators you are using do not evaluate height, your values will be off.

 

[cybrdyke]

^^^ What he said. Foot-candle calculations are not derived from the quantity of lumens of the light source, but from the quantity of lumens that are hitting the target, in your case, the floor. Any calculator that just does lumens/sq.ft. comes from someone who doesn't know what they're doing. Chalk it up under "it's on the internet, so it must be true".
So, if you have 10 x 720 lumen fixtures, you do not have 7200 lumens on your target. Some of those lumens will never hit your target. Some get absorbed into non-reflective surfaces, some get absorbed into dark colors, others just bounce around the room never getting to the target.
If it helps, think of it like this....
You have a 2' x 5' closet with an 8' ceiling and a 100 lumen light bulb. You have 10 lumens/sq.ft. Now what if your ceiling was 100' high? You still have 10 lumens/sq.ft. Do you think it will be the same brightness? Of course it wont. What if you had black walls? What if you had a carpeted floor? All of these things reduce foot-candles.
You're gonna be off by 30-50%. That said, you dont really need 100fc anyway. Most garages are lit to about 35fc. If you are planning to do work in there, you should shoot for 50 -70fc. That's really bright. For reference, a grocery store is typically 45-ish fc. School classrooms are 35-40-ish. If you need more than that, you should be using a task light.
Hope that helps explain a little bit.
CD

 

[strength_and_power]

Can you mount lights just under the door track ? That way it won’t matter if the door is open or closed.

In my lights, the company I bought mine from did a lighting layout based on dimensions I gave them. Their layout said I needed 6 lights. I ended up going with 14. 3 circuits, 2 switches per circuit. One switch controls 3 light in the row, other controls 2. My center was a bit different because of the HVLS fan and door, 1 light and 3 lights. Is it bright? Yup. Is it too bright? Nope.

 

[rjacobs]

Got my lights up today.

Ran EMT everywhere. Each "truss" got a j-box in the center with 3/4" EMT run from box to box plus down to the panel. Then 1/2" EMT from each j-box out to each light.

Prime Lights Bolt Gen 2 4ft frosted LED. I think each is 7200 lumens.

VERY happy with how everything came out and how much light it puts out.