Conduit Spacing

[QES]

what is min. conduit spacing for 4" conduit in concrete?

 

[mdshunk]

What type of application? Could be zero.

 

[charlie b]

I believe the minimum is 4 inches, center to center. :wink: :smile:

Now, if you wish to ask about ampacity, that is another matter.

 

[QES]

right now I have it 4" conduit to conduit, I guess Iam ok then.

 

[infinity]

I believe the minimum is 4 inches, center to center. :wink: :smile:

That would make it a 3.5" conduit.

 

[charlie b]

That would make it a 3.5" conduit.

How do you figure that? Am I wrong in believing that when you say "four inch conduit," you are speaking of the outside diameter?

 

[iwire]

4" Conduit is approximately 4.5" OD.

The ID changes dependent on the type, RMC, IMC, PVC 40 or 80 etc.

 

[charlie b]

Thanks, Bob. I guess I need to hit myself over the head with a 1.5" by 3.5" board. If I can't find one of those, I'll just use a 2x4. :grin:

 

[LarryFine]

Am I wrong in believing that when you say "four inch conduit," you are speaking of the outside diameter?

Yes. Conduits are specified by inside (i.e., usable) diameter.

It would be impossible to space 4" conduits at 4" on center.

 

[iwire]

Thanks, Bob. I guess I need to hit myself over the head with a 1.5" by 3.5" board. If I can't find one of those, I'll just use a 2x4. :grin:

When my wife and I watch the DIY shows she is always surprised by trade weirdness like that. :grin:

There is a box hanger for stud walls it is called an H-23.

I don't know what the H stands for but the 23 means it fits both 2x3" and 2x4" stud walls which of course measure 1.5" x 2.5" and 1.5" x 3.5". :grin:



The nice thing about the pipe sizes is for example a 4" connector or hanger can fit and be listed for both thin-wall (EMT) or RMC as the ODs are the almost the same.

 

[iwire]

Yes. Conduits are specified by inside (i.e., usable) diameter.

They are really not specified by any 'real' measurement.

4" RMC, EMT PVC....none of them will measure '4"' ID or OD.

For example 4" schedule 80 PVC has an ID of 3.786" but 4" EMTs ID is 4.334".

 

[infinity]

The OD on conduit is pretty constant for all trade sized of 2 1/2" and above. Typical strut straps will fit all conduits above 2". For 1/2" through 2" some straps will fit both rigid and EMT some won't. On 2 1/2" and above many EMT fittings will also fit rigid conduit as well.

 

[Jim W in Tampa]

i have about 800 feet of whats called 3 inch emt.Its not even close to 3 id or od

 

[infinity]

i have about 800 feet of whats called 3 inch emt.Its not even close to 3 id or od

If it's truly 3" EMT than it should be larger than 3" both ID and OD.

 

[RUWired]

what is min. conduit spacing for 4" conduit in concrete?

The minimum would be what the spec call for.The chairs we use for 4" pvc creates a 3" space @ 7-1/2" centers.
Rick