Strain relief in vertical conduit runs

[dancase]

We're going to be replacing the incandescent obstruction lighting on three 55 year old radio towers with new LED obstruction light fixtures. The project will involve stripping out all of the old, brittle, braided-insulation wiring and replacing it with new conductors better suited to the application.

The existing 1" rigid conduit is in remarkably good condition, and we'll be re-using it for the new system. We will be running one #10 and up to four #12's in that conduit, depending on height (there are four levels of lights, and unlike the old installation each level will be wired on a separate conductor to allow remote monitoring of the light status). My issue here is how to best provide vertical support for these conductors. In a new installation, there are special junction boxes designed specifically for tower lighting that have strain relief means built in. In this case, it appears that there was no strain relief used in the original installation, and if there was it wasn't on the construction drawings.

What would be the best means of providing strain relief for these conductors? I've seen strain relief devices like the O-Z/Gedney cable supports that mount to conduit nipples, but I haven't found anything as yet that fits 1" rigid. I'm leary of braided-wire grips when using multiple individual conductors -- seems like it would be easy for one of then to slip loose. I keep thinking I've seen something on the order of a neoprene drive-in plug with holes that is made for just this situation, but I haven't found anything yet.

And, of course, whatever we use has to be easy enough for a guy to work with while hanging from the side of a tower.

Any ideas?

D.

 

[charlie]

Re: Strain relief in vertical conduit runs

I don't know, can someone help?

 

[dancase]

Re: Strain relief in vertical conduit runs

As it turns out, there are versions of the Kellums grips that will work for wire bundles, if thay are installed correctly. One version actually hangs on the lip of the male conduit end.

But, it really doesn't matter. The old conduit only has boxes at the light locations, which makes them about 125 feet apart. Current code requires my conductors to be supported at intervals not less than 100 feet. Crud. We're gonna have to pull down and replace the conduit, too.

Oh, welll... we'll survive.

D.

 

[mdshunk]

Re: Strain relief in vertical conduit runs

Originally posted by dancase:
The old conduit only has boxes at the light locations, which makes them about 125 feet apart. Current code requires my conductors to be supported at intervals not less than 100 feet. Crud. We're gonna have to pull down and replace the conduit, too.

I'd be asking the AHJ for an exception on that and use the Kellems grips at the 125' intervals. We're talking about darned little weight here, and the extra 25' I can't see hurting much. Call me crazy, but I think that an exception would be easy to get on this one.

 

[dancase]

Re: Strain relief in vertical conduit runs

Originally posted by mdshunk:
I'd be asking the AHJ for an exception on that and use the Kellems grips at the 125' intervals. We're talking about darned little weight here, and the extra 25' I can't see hurting much. Call me crazy, but I think that an exception would be easy to get on this one.

In reality, this job isn't subject to inspection. It's in a locale where there's a remarkable lack of such things -- I recently built an 800' tower and transmitter site not far away, and the only local/state permits I needed through the entire process were a Flood Plain Permit (my access road crossed a flood plain) and a driveway permit (to have a new access road off of the main highway). No building permits, no inspections of any kind (other than the guy who checked to make sure I used the right size pipe under the driveway). State law requires all electrical work to meet current NEC, but in this particular county there's no requirement for inspection. A $900K facility covering about 20 acres!

As a company (owners of the facility, not contractors), we have a strict rule of 100% compliance will all applicable laws, rules, and codes. It's a strict zero-tolerance policy, and sometimes I'd rather face the feds than our internal auditors.

Thanks!

D.