Conduit Body Radius 1

[peebee]

I have a project under construction where twinax control wiring is being pulled into 1" EMT or IMT. The minimum bending radius of the wire as specified by the manufacturer is 3.5". Our contractor has installed conduit bodies all over the place in the conduit, and I am afraid that the maximum radius they will achieve is less than 3.5". Does anyone have any information on conduit body radii? I've contacted a few major manufacturers and have not been able to receive any verbal, let alone written, information on this issue.

 

[BJC]

Both the Crouse Hines and Appleton catalogs have dimensional data on all the conduit bodies they make. You can draw them to scale and see if the wire minimum bending radius will fit into the various conduit bodies.
On one projcet I had a complete collection of Condulets and Sealtite fittings that were sawn in half to demonstrate to the owner that they were good ( or in many cases not good).
In your case I don't think it sounds good.
Even if the cable fits in the fitting without exceeding the minimum bending radius check what happens if the wire is pulled out and back in the opening on the fitting. Generally the cover has to be 4 times as long as the minimum bending radius to get the "bite" back into the fitting without exceeding the MBR.

 

[busbar]

Rework is never fun, but there are 'mogul' conduit bodies down to 1 inch raceway size, like:

http://www.appletonelec.com/PDF/master_cat_005rev2/15mogel_unilets.pdf

The “UB” seems to be for extremes. Used succesfully for picky comm engineers on copper-sheathed PIC cable.

Pinched coax/twinax can degrade into a poor performer.

 

[jbartos]

Suggestion: When it comes to control wiring, may there be any way to circumvent your twinax control wiring requirement/specification? Normally, control conductors are more liberal to apply than power cables/conductors.

 

[peebee]

Thanks, busbar, I did come across that Appleton cut sheet. The problem with that is it's only for LB and UB fittings, no LR or LL fittings, and I'm under the impression that LR/LL's typically have a smaller radius. After a few calls to Appleton, I finally got a hold of their engineering drawings, which indicate that fittings of 2.5", 3" or 3.5" will be required for the 3.5" radius, depending on exact fitting & cover material & manufacture (cast, stamped, etc.), and configuration (LL, LB).

Jbartos, I'm not sure what you mean by circumvent the specification, please elaborate. 3.5" is the minimum we can do with this twinax, otherwise the signal "leaks" from the cable similar to fiber optics. Twinax or fiber will be required due to the distances involved (appr. 2500 feet).

It's all besides the point now, anyway, as the contractor consulted with his communications guy and has decided to replace all conduit bodies with weatherproof boxes. At least we caught this prior to cable installation.

 

[jbartos]

Suggestion: Visit

http://www.agere.com/long_haul_backbone/docs/TN02023.pdf

etc. for fiber bends

 

[BJC]

peebee
If the contractor is going to use standard fittings your still in trouble.
Pulling wire into and out of an opening requires a length of 4 times the MBR. Form C condultets will need an opening 4x the MBR or 14". An LB will need to have an opening of 3x or 10.5" LLs and LRs won't work at all except maby in the "mogul" sizes.

 

[resqcapt19]

If you are going to use "oversized" conduit bodies to get the required bending radius, you will have to provide independent support of the conduit body. Look at 314.23(E) in the 2002 code or 370-23(e) in the 99 code.
Don