Expansion joints for rigid conduit

[mull982]

Can someone tell me what the expansion joint requirements are for rigid metallic conduit? Is there a reference in the NEC.

Is there an additional specific requirement for conduits on a rooftop?

How do most of you specify this expansion requirement in design drawings? Do you specify with a general note? Or is this really more of a contractor installation issue and not the responsibility of the engineer to specify on design drawings?

 

[augie47]

Take a look at 300.7(B)

 

[raider1]

Also keep in mind that the 2011 NEC has a new requirement for raceways that cross structural joints. (See 300.4(H))

If you are using PVC on a roof then you will also want to review 352.44.

Chris

 

[mull982]

Take a look at 300.7(B)

Thanks

Looking at 300.7(B) however it only seems to talk about the idea of thermal expansion and doesn't really give any guidance or requirements for expansion fittings?

Also on a sort of different note I had a question relating to the support for rigid metal conduit on a rooftop. Table 344.30(B)(2) gives the support requirements for RMC however 344.30(B)(1) says conduit should be supported every 10ft. If I have straight runs of 2-1/4" conduit can I support it every 16ft as listed in the table?