Conduit Support

[d_amp]

Where in the code book does it state, "Any conduit, less than 3' but greater than 18", requires a strap/support."

 

[augie47]

Your conduit supports are part of the Code in ***.30 with the *** referencing the type conduit.
Taking a guess, I think you are looking for 352.30(C) which discusses PVC conduit < and > 18"

 

[don_resqcapt19]

Where in the code book does it state, "Any conduit, less than 3' but greater than 18", requires a strap/support."

It only said that in the 2008 NEC. Previous and newer editions require the raceway to be supported no matter how short it is.

 

[augie47]

It only said that in the 2008 NEC. Previous and newer editions require the raceway to be supported no matter how short it is.

Thanks for being thorough. TN is still stuck in '08 and I sometimes forget to go back to the furture

 

[Carultch]

It only said that in the 2008 NEC. Previous and newer editions require the raceway to be supported no matter how short it is.

How am I supposed to put a strap on a close nipple, offset nipple, or chase nipple?

Obviously there is a practical consideration for cases when the conduit termination is a suitable support.

 

[infinity]

How am I supposed to put a strap on a close nipple, offset nipple, or chase nipple?

Obviously there is a practical consideration for cases when the conduit termination is a suitable support.

The NEC has waffled on this one for the past 8-10 years, once reducing the requirement to nipples over 18" and then going back. IMO it is dumb to require a strap on a 6" nipple between two enclosures when you can have up to 3' of unsupported EMT, RMC, etc. between the box and the first support.

 

[don_resqcapt19]

How am I supposed to put a strap on a close nipple, offset nipple, or chase nipple?

I have no idea, but that is what the code rules require. The CMP does not seem to understand what their rules actually mean, as this issue has been addressed with proposals a number of times and nothing has changed.

Obviously there is a practical consideration for cases when the conduit termination is a suitable support.

I submitted a public input for the 2017 to say that the conduit termination could be used as the required support where the conduit is 36" or less in length and it was rejected because conduit terminations are not supports.

 

[kwired]

The NEC has waffled on this one for the past 8-10 years, once reducing the requirement to nipples over 18" and then going back. IMO it is dumb to require a strap on a 6" nipple between two enclosures when you can have up to 3' of unsupported EMT, RMC, etc. between the box and the first support.

An observation - even pointed out by an inspector back when I was in a CEU class that was covering 2008 NEC, was that if you had two enclosures on the wall with a 4 inch GRC nipple between them (be it 6 inches long, 18 inches long, 36 inches long or even 48 inches long - if you placed a strap or clamp on that nipple, does it really support anything?

You can come in with a 8 pound hammer and start beating and the strap/clamp likely gives up long before there is any compromise to the 4 inch RMC.

 

[infinity]

An observation - even pointed out by an inspector back when I was in a CEU class that was covering 2008 NEC, was that if you had two enclosures on the wall with a 4 inch GRC nipple between them (be it 6 inches long, 18 inches long, 36 inches long or even 48 inches long - if you placed a strap or clamp on that nipple, does it really support anything?

You can come in with a 8 pound hammer and start beating and the strap/clamp likely gives up long before there is any compromise to the 4 inch RMC.

Yup that was my point. You could attach the strap with a plastic plug anchor and screw which wouldn't survive one hammer blow in your example but it would be code compliant.

 

[Carultch]

The NEC has waffled on this one for the past 8-10 years, once reducing the requirement to nipples over 18" and then going back. IMO it is dumb to require a strap on a 6" nipple between two enclosures when you can have up to 3' of unsupported EMT, RMC, etc. between the box and the first support.

The other issue I find, is cantilevering conduit that doesn't terminate on an enclosure.

There are applications, where conduit might terminate with a cord grip, or an end-bell, or a bushing, and have wiring enter/exit open air from the conduit. This might void its definition as a raceway system, rendering it to a "sleeve for protection", but it still is a legitimate concern about how to properly support conduit in such an application.

My strategy is to keep spans within the NEC's span rules, and to aim for no more than 35% of the NEC span rule or 3 ft for the cantilever (whichever is smaller). "35% of the span" comes from typical performance of a uniform loaded beam.