Conduit under Aircraft Hangar slab

[Platinum]

If I wanted to run PVC under the hangar slab, is it really required to be concrete encased?

501.10(A)(1)(a) Exception states 2" concrete encased for the PVC, but then goes on and says the concrete encasement can be omitted if you comply with 514.8 Excep 2 AND 515.8(A).

In the Handbook there is a explanation section on this: "These provisions are for specific occupanceies where there has been considerable experience with underground nonmettallic conduit." What does that mean?:?

Thanks for any feedback.

-Keith

 

[rbalex]

If I wanted to run PVC under the hangar slab, is it really required to be concrete encased?
...

Yes

...
501.10(A)(1)(a) Exception states 2" concrete encased for the PVC, but then goes on and says the concrete encasement can be omitted if you comply with 514.8 Excep 2 AND 515.8(A).
...

You probably got to Section 501.10(A)(1)(a) from Section 513.8. Article 514 and 515 Exceptions don't apply.

...
In the Handbook there is a explanation section on this: "These provisions are for specific occupanceies where there has been considerable experience with underground nonmettallic conduit." What does that mean?
...

Start with Article 510. Basically, Articles 511 to 516 reflect experiences of several Technical Committees different from Code Making Panel 14.

 

[Platinum]

Hey Bob,

Yes, started my journey at 513.8(A) which brings me to 501.10(A)(1)(a).

So the concrete encasement can be omitted IF we comply with 514 (Motor Fuel Dispensing Facilities) and 515 (Bulk Storage Plants).
Since we are an aircraft hangar, this exceptions don't apply and we have to concrete encase the PVC conduits.


Apreciate your help.

-Keith

 

[Platinum]

I basically developed an underground conduit detail that displays 2 methods for doing this:
1- Using PVC coated RGS conduit under the hangar slab and using PVC coated RGS elbows (easiest way to do it i think).
2- Using PVC conduit with 2" concrete encasement. Also using RVC coated RGS elbows and RGS conduit the last portion of the run going up to the device.


I guess this is a separate question along the similar topic: What do you do when you have a 400Hz underground line?
If I want to use PVC conduit concrete encased, but what do you do about the final part of the run where it sweeps up....the final portion (2ft) has to be RGS conduit per 501.10(A)(1)(a)?
It's only 2ft or so of ferrous conduit......it shouldnt affect the 400Hz cable too much?

 

[rbalex]

I basically developed an underground conduit detail that displays 2 methods for doing this:
1- Using PVC coated RGS conduit under the hangar slab and using PVC coated RGS elbows (easiest way to do it i think).
2- Using PVC conduit with 2" concrete encasement. Also using RVC coated RGS elbows and RGS conduit the last portion of the run going up to the device.

Either is fine. Check your economics though.

...
I guess this is a separate question along the similar topic: What do you do when you have a 400Hz underground line?
If I want to use PVC conduit concrete encased, but what do you do about the final part of the run where it sweeps up....the final portion (2ft) has to be RGS conduit per 501.10(A)(1)(a)?
It's only 2ft or so of ferrous conduit......it shouldnt affect the 400Hz cable too much?

Depending on the cable/conductor design and overall circuit design, it shouldn't affect the cable at all. It would only be affected if there is a current path for the circuit outside the raceway.

 

[Platinum]

Thanks Bob.

 

[masterinbama]

What do you do when you have a 400Hz underground line?

Asphalt coated aluminum sweeps.