Lengthy Suspended Luminaires and swing

[ZSIM]

Looking to learn, what is the maximum length of aircraft cable you would use to install a light fixture to suspend from a ceiling? So that it wouldn’t cause swing from say a dock door opening and wind coming in.

I have a small installation where the plans call for a few lithonia IBG to be installed in a portion of a 40 ft warehouse. The plans suggest installing the lights at 25 feet above finish floor. That would basically be 15 feet of aircraft cable.

I was always under the impression that would be too long to suspend a luminaire for a couple reasons, but in this case because they would probably swing.

Lithonia does offer though a 20 foot aircraft cable wire for suspension, so it does seem like it’s commercially viable.

So just looking for people’s thoughts on if they should be raised up with a higher lumen package, or if this is common / acceptable installation?

Any pitfalls to watch out for if I do suspend them 15 feet down?

 

[hbiss]

I don't think it would make any difference what the suspended length is, if there is something to cause it to move it's going to sway. Only thing I could think of is some diagonal cables off each end to stabilize it.

-Hal

 

[LarryFine]

Would it be worth it to use three cables per light?

 

[ZSIM]

Have either of you installed luminaires suspended at those lengths?

 

[LarryFine]

Have either of you installed luminaires suspended at those lengths?

By conduit, not cable.

 

[Little Bill]

What is a lithonia IBG?

 

[cadpoint]

I'm sorry it just seems so wrong to drop floating lights in an aircraft hanger...
I've never seen anything hanging as you've described. The minimum Lum is 50 but usually closer to 100 and can be easily achieved with LED's
I googled a few angles but everything goes into deep double speak with the FAA requirements even with a Hanger!

The Lithonia IBG looks like an exterior grade 2 X 4 on steroids.

 

[ZSIM]

What is a lithonia IBG?

It’s a large, high lumen warehouse light from acuity/Lithonia lighting.

 

[ZSIM]

I'm sorry it just seems so wrong to drop floating lights in an aircraft hanger...
I've never seen anything hanging as you've described. The minimum Lum is 50 but usually closer to 100 and can be easily achieved with LED's
I googled a few angles but everything goes into deep double speak with the FAA requirements even with a Hanger!

The Lithonia IBG looks like an exterior grade 2 X 4 on steroids.

I think you read that wrong. It Is not being installed in an “aircraft hanger”. The suspension of the luminaire is using “aircraft cable”. Not sure why they call it that but it’s just very thick hanging wire you could probably tow a truck with.

The building is just a plain warehouse, and the drawings say to use 20ft aircraft cable supplied by the Lithonia.

 

[qcroanoke]

the drawings say to use 20ft aircraft cable supplied by the Lithonia.

And that is what I would do.

 

[cadpoint]

I lost that argument, LOL What's aircraft Cable? I got hung up on that.... Excuse me.

I'm in the game now!

Lets argue aircraft cable: Is the installer determining the length drops and their going to be crimping
the ends in the field? Now one has to consider the securing mechanic's behind the loop eye to the structural members,
then loop and crimp the light loop?

They make a real nice LED 3/4 shaded conical that lights up and down, and it's hung at the ceiling.

 

[Kansas Mountain]

Submit an RFI requesting a more stable suspension, like allthread (maybe in tandem with unistrut for surface mounting the fixture). If request is denied, not your problem at that point.

 

[hillbilly1]

If that’s what the engineer calls for, and Lithonia makes a product specifically for that use, I don’t think it’s your problem. They are probably trying to be green, and use less energy by having the lights closer, while trying to make the lights forklift resistant. (Good luck) LOL!

 

[infinity]

You're not the designer you're the installer, I would just install it as designed. If the client is unhappy with the movement then they'll need to find a way to mitigate it after it's all installed.

 

[cadpoint]

JMO
I'm sorry this install still bothers me! I also sense the same from others here!

The best you could do to CYA and design standard lengths looped cable ends and include some rated carabiner to attach to lights and structure!
I'm sure you could find some light manufacturer references and cable manufacturers that can supply numbers.

The real problem with dropping lights in this design will be either now busy to the eye, or why are you giving up so much space in a
warehouse of all things. It is certainly a premium space around these parts.

 

[hillbilly1]

Unfortunately, we don’t know what the tenant is warehousing, and may not have tall racks, or racks at all. It may just be what’s available in that area.

 

[Tulsa Electrician]

When your done and if there is an issue. It can be resolved with and X and Y ( lateral & longitudinal) approach on the cabling system. Using an X Y quadrant it will reduce if not virtually element the issue. Very similar to seismic cable bracing.
One difference is the angles.
One item I have done is to install you hanger cables at an angle from zero. This will add load to the cable so a factor must be added to weight calculation based on its angle.
An example would a three foot fixture cable hung at a five or six foot spaced perlin. Depending on cable length you get an angle. This angle is weight multiplier for the load that the cable and fasteners can handle or there load rating.
I have hung these types in an industrial setting. And have had good success. Where we had machines with vertical fans the X Y solved the sway issue.
We formed an X Y Quadrant over that area.
Supper simple to do. Span small cable and attach to the fixtures down cable.
Add an additional X with a long Y span. This will take some harmonic sway from the cable spans.

 

[synchro]

You might compromise and suspend it by conduit partway and by cable the rest of the way, using for example:

https://www.gordonelectricsupply.com/p/Garvin-Sc-75-4Sq-Swivel-Fix-Hanger/6252595?text=garvin+sc75
https://www.gordonelectricsupply.com/p/Garvin-54C75-3-4-Fixture-Hanger/6254745
https://www.gordonelectricsupply.com/p/Appleton-Fhlf-75-3-4-Fixture-Hook/5736762

 

[James L]

Have either of you installed luminaires suspended at those lengths?

I've never hung single luminaires at a length like that, but I've installed linear strips from 28 feet, hanging at 12 feet.

Airline cables in the box were something like 5 feet long. Replacements from the manufacturer were 20 feet long, and we hung off strut which spanned across bar joists.

Granted, we didn't have wind blowing through, but the manufacturer supplied cable was used in that case, and I would use it in your scenario

 

[ZSIM]

Thank you all for the feedback.

I have a call in with our distributor Monday. If I find anything useful to add I’ll post it here.