Rmc conduit support

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dburney

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Location
Brooklet ga usa
I have a pvc underground changing to rmc comeing out the ground going to a meter can my question is should the rmc be supported between the ground and meter can. Their is no support on the conduit unless the consider the ground the support and should it be supported within 18" of the can or 3' and where can I find this in the code book
 
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kwired

kwired

Electron manager
Location
NE Nebraska
dburney said:
I have a pvc underground changing to rmc comeing out the ground going to a meter can my question is should the rmc be supported between the ground and meter can. Their is no support on the conduit unless the consider the ground the support and should it be supported within 18" of the can or 3' and where can I find this in the code book
Click to expand...
344.30 is where to look.

I sure hope the earth is considered support, or else how would one support the underground portion of the run?
 
don_resqcapt19

don_resqcapt19

Moderator
Staff member
Location
Illinois
Occupation
retired electrician
The most common reason for a expansion joint in this type of application is 300.5(J) and the length of conduit between the earth and the enclosure does not enter into the issue.

As far as support, I see the earth as a support, but an additional support is needed within 18" of the enclosure.
 
C

Carultch

Senior Member
Location
Massachusetts
don_resqcapt19 said:
The most common reason for a expansion joint in this type of application is 300.5(J) and the length of conduit between the earth and the enclosure does not enter into the issue.

As far as support, I see the earth as a support, but an additional support is needed within 18" of the enclosure.
Click to expand...

Where does 18" come from?
 
kwired

kwired

Electron manager
Location
NE Nebraska
There is also 344.30(A)(2):

Fastening shall be permitted to be increased to a distance of 1.5 m (5 ft) where structural members do not readily permit fastening within 900 mm (3 ft).
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Wouldn't normally apply on the side of a building, but is there if the conditions present themselves.
 
kwired

kwired

Electron manager
Location
NE Nebraska
edward said:
For 2008 344.30 (C)

For 2011 that requirement was removed.
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I think that was a change thrown in at that time that got removed.

IIRC the general rule was still requiring first support within 3 feet, but if you had at least 18 inches but less then 3 feet they were still wanting additional support besides the ends of the raceway.

I still remember an inspector giving an CEU class on 2008 NEC code changes pointing out he thought if you had a 3 foot length of 4 inch RMC between two cabinets with no additional supports other then at the terminations - it likely wasn't going to go anywhere unless the cabinets go with it.
 
C

Carultch

Senior Member
Location
Massachusetts
edward said:
For 2008 344.30 (C)

For 2011 that requirement was removed.
Click to expand...

The 18" was for a nipple that connects two adjacent enclosures.

I think in most applications where you accommodate ground movement with an expansion fitting, you need close to 18" for an expansion fitting to fit. And it is difficult to fit a strap onto an expansion fitting.
 
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