Conduit support requirements: Elbows, Sweeps, Flex Bends, and Bodies

[Carultch]

In each conduit type's article, the NEC specifies how far from a termination, and how far between supports, one must support the raceway. Easy for long straight runs, but bends make it more challenging to understand the rules.

How do these distances get measured, when the conduit changes direction in some form or another?

1. Is it an "as the crow flies" measurement across the chord of the bend? Or is it along the centerline arc length?
2. If ? Or should it have more localized support near the elbow on both legs?
3. If a straight run has an elbow on each side, and is only supported on the straight run, do typical straps secure it against rotation?
4. Are conduit bodies such as LB's considered part of the raceway system, or a termination of the raceway on both/all sides?

Examples:
A 4" conduit exits an enclosure, immediately elbows 90 degrees at standard radius/tangent, and then gets supported. As the crow flies, that is about 34" from support to termination, but along the length it is 41".

LFMC is used for an offset return. A total of 14 inches of raw material. The terminations are 11" apart, after the offset/return is formed, as measured directly. 12" is the cutoff for requiring an LFMC support, so is this under or over 12"?

A T-body is located between the first support and the termination onto a wireway enclosure. There is a 6" nipple on the enclosure side, and a straight run on the side toward the support. No support is on the 6" nipple, other than the connection to the T-body and the enclosure termination.

An elbow between straight runs is supported within 12" on the east leg, and on the north leg it isn't supported until 8'-0" away.

 

[Carultch]

See this attachment to illustrate the concept:

 

[luckylerado]

1. Is it an "as the crow flies" measurement across the chord of the bend? Or is it along the centerline arc length?

It is measured along the raceway. Not as the crow flies.

2. If ? Or should it have more localized support near the elbow on both legs?

I often receive specs that require additional straps / supports within 12" of a change of direction more than 15° but this is above and beyond NEC requirements.

3. If a straight run has an elbow on each side, and is only supported on the straight run, do typical straps secure it against rotation?

Not very well IMO except maybe a tight strut strap.

4. Are conduit bodies such as LB's considered part of the raceway system, or a termination of the raceway on both/all sides?

A termination point.

"EMT...securely fastened within 900 mm (3 ft)
of each outlet box, junction box, device box, cabinet, conduit
body, or other tubing termination...."

Examples:
A 4" conduit exits an enclosure, immediately elbows 90 degrees at standard radius/tangent, and then gets supported. As the crow flies, that is about 34" from support to termination, but along the length it is 41". Violation

LFMC is used for an offset return. A total of 14 inches of raw material. The terminations are 11" apart, after the offset/return is formed, as measured directly. 12" is the cutoff for requiring an LFMC support, so is this under or over 12"? Over and probably a pain in the butt to fish a tape through.

A T-body is located between the first support and the termination onto a wireway enclosure. There is a 6" nipple on the enclosure side, and a straight run on the side toward the support. No support is on the 6" nipple, other than the connection to the T-body and the enclosure termination. I do not find an exception for a 6" nipple but I would probably not use a strap unless it was flimsy.

An elbow between straight runs is supported within 12" on the east leg, and on the north leg it isn't supported until 8'-0" away.

10' apart along the raceway.