K8MHZ
Senior Member
- Occupation
- Electrician
It's more common that not to spray the cut surfaces on the jobs I have been on.
This is good stuff
Violation? 314.23 F or Luminiare hung by conduit (with "reinforcement")
- Thread starter xguard
- Start date
- Status
It's more common that not to spray the cut surfaces on the jobs I have been on.
This is good stuff
It's more common that not to spray the cut surfaces on the jobs I have been on.
This is good stuff
That's what we use.
- Location
- Massachusetts
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
Even if without it the limit on length of unsupported raceway is violated?Its hindering it in the fact it is ugly and unneeded.
- Location
- Massachusetts
Yes.
Carultch
Senior Member
- Location
- Massachusetts
I agree. Even if the strut was made with aluminum that is self-resistant to excessive corrosion, it still is modified in a way that would ruin the structural integrity. The folded shape gives it its resistance to bending. Cut through the sidewalls, and now it is just an 1/8" thick piece of metal, with a stress point nearby.
I don't think it's either.
I think he bent the tabs of the strut strap so it will grab.
mivey
Senior Member
Yes but we don't cut it and bend it backwards like that at the cut point since that is not its intended use. We usually have our shop manufacture a bracket with proper welded seams and paint it as well.
I also get to see what wind does to hardware when causing oscillations. Adding a rusty cut and bent-backwards piece of metal is a potential point of failure.
mivey
Senior Member
What is the length of that pipe? Would that fixture be whipping excessively in a storm or on a windy day?Its hindering it in the fact it is ugly and unneeded.
- Location
- Massachusetts
Well how much wind are we designing for?
An F5?
If that is RMC or IMC I would have no problem hanging that fixture without that extra brace.
mivey
Senior Member
Nah, just F4.
Carultch
Senior Member
- Location
- Massachusetts
The building code design standard is usually the maximum 3-second gust wind speed that is statistically expected to occur not more than once within 50 years, for a building of standard occupancy category II.
K8MHZ
Senior Member
- Occupation
- Electrician
Actually, the brace increases the wind load. It also increases the weight on the RMC without adding any benefit. It looks like the RMC is supporting the brace, not the other way around.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
It may be adding rigidity to the right angle runs it triangulated, but it is not clear whether it does anything for the bending moment at the point where the vertical conduit leaves the strut structure.
mivey
Senior Member
As added offset weight, it is a force vector not directed through the attachment point so it is clear that it adds to the bending moment. It does add rigidity (until it slips or fails) to the right angle, much like a shelving bracket.
add: forgot to look at picture first. I forgot the strut was attached below the last clamp so it will transfer some of the vertical load below the clamp. If I was at my desk, a force diagram with some approximate calcs would be interesting but I'm mobile.
Last edited:
K8MHZ
Senior Member
- Occupation
- Electrician
Looking at the strut clamps and the way they were hacked to fit, won't they be the weak link?
If there is enough force to bend the RMC, do you think the cheesy bent strut strap is going to make a hill of beans worth of difference?
Like I said before, it looks like the conduit is supporting the brace, not the other way around.
- Location
- Placerville, CA, USA
- Occupation
- Retired PV System Designer
The force on the strut is all in compression except for a very short portion at the ends, while most of the load on the RMC is bending moment.
The axial compression strength of the piece if strut is more than adequate.
The axial compression strength of the piece if strut is more than adequate.
mivey
Senior Member
A calc with some general assumptions would be revealing but it would have to be later. My phone calculator and a napkin just won't do it for me.
Add: Not real sure what they did with the clamps. They may wind up slipping.
K8MHZ
Senior Member
- Occupation
- Electrician
Technically, those straps are conduit hangars, not clamps, correct?
I doubt the strut bracket was installed for anything else but to be a stiffener.
I don't need an engineering degree to know that if I jumped up with all 225 lb's of me and grabbed onto the fixture that most likely the top strut strap on the horizontal run would slip, that is until the strut slid horizontally until it hit the 90 degree bend above the fixture, then the lower verticle strut strap would slip until the bracket ran into other lower strut strap on the strut rack. At this point I would have bent the upper 90d elbow furthest from the fixtures but would probably still be able to support all my weight off of it as long as the threads didn't pull out of the fixture hub.
The same scenario above without the bracket in play would have a little different outcome. I'd jump up and grab onto the fixture and the 90d elbow furthest from the fixture would immediately bend in half althought it would still probably support my weight,,,,, the biggest problem is that when that happens the conduit would have cut into the wires and if I hung there until the photocell called for the lights to come on,,, it would short out at the bend,,,,,burn the 1/2" rigid in half and I'd go crashing to the ground in a firey decent.
Just saying..
JAP>
I don't need an engineering degree to know that if I jumped up with all 225 lb's of me and grabbed onto the fixture that most likely the top strut strap on the horizontal run would slip, that is until the strut slid horizontally until it hit the 90 degree bend above the fixture, then the lower verticle strut strap would slip until the bracket ran into other lower strut strap on the strut rack. At this point I would have bent the upper 90d elbow furthest from the fixtures but would probably still be able to support all my weight off of it as long as the threads didn't pull out of the fixture hub.
The same scenario above without the bracket in play would have a little different outcome. I'd jump up and grab onto the fixture and the 90d elbow furthest from the fixture would immediately bend in half althought it would still probably support my weight,,,,, the biggest problem is that when that happens the conduit would have cut into the wires and if I hung there until the photocell called for the lights to come on,,, it would short out at the bend,,,,,burn the 1/2" rigid in half and I'd go crashing to the ground in a firey decent.
Just saying..
JAP>
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