PVC conduit under concrete and section 352.12(D)

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Adnan Hasan

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PVC conduit; 25 mm diameter, 1.8 wall thickness, 25 meters runway, was installed under concrete layer (screed) of 50 mm thickness on the roof. The temperature in summer is more than 55 and in winter around 5 degree Celsius.
Section 352.12(D) not permit to install PVC conduit if temperature in excess of 50 degree Celsius (122 Fahrenheit).
Question: is there any exception to the code if the installation of PVC conduit is covered by concrete layer of 50 mm thickness as described above? the concrete (roof) is subjected to direct sun light.
many thanks for help..
 
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Good question, the conduit is not directly within the air so the ambient temperature of the air above the concrete may not be the same as the temperature of the concrete where the PVC is installed. If the PVC were directly in the center of the concrete then the ambient temperature on the underside of the concrete would have an equal affect on the temperature of the conduit in the middle. If the PVC were near the bottom of the concrete then it's temperature would be nearer to the underside ambient air temperature.

I would assume that the color of the roof would play a part too. A highly reflective color would yield a lower surface temperature of the concrete when exposed to sunlight.
 
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If the center of the pvc conduit has a temperature that
exceeds the 122 degree F. amount, ...either the
conductors would have to be derated [ probably not
an option in your application ], ...or for the conductors
to actually be rated for the high temps., or for some
type of coating to be applied to the concrete lower the
surface temps. [ i.e. - something reflects the sunlight ,
or significantly blocks the sunlight - as **infinity**
mentioned ].

Is your application for some type of airport runway ?

: - :
 
There is no exception to part 352.12(D) of the code. You have 2" of concrete over a 1" pvc conduit , does the 1" pvc conduit ever come up through the concrete and get exposed to sunlight? What is the conduit for?
 
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Adnan Hasan said:
PVC conduit; 25 mm diameter, 1.8 wall thickness, 25 meters runway, was installed under concrete layer (screed) of 50 mm thickness on the roof. The temperature in summer is more than 55 and in winter around 5 degree Celsius.
Section 352.12(D) not permit to install PVC conduit if temperature in excess of 50 degree Celsius (122 Fahrenheit).
Question: is there any exception to the code if the installation of PVC conduit is covered by concrete layer of 50 mm thickness as described above? the concrete (roof) is subjected to direct sun light.
many thanks for help..
Click to expand...

2" of concrete isn't gonna change the temperature of the conduit much.
you say under, as in not embedded in the pour? the roof of a hospital,
so it's underneath the roof?

if it's embedded in the pour, i'd say it's not compliant. however, if its
on a rooftop helipad, can you run EMT under the roof? all we are talking
about is less than 100' of emt, and the labor and profanities necessary
to install it, of course. :happyyes:
 
Fulthrotl said:
2" of concrete isn't gonna change the temperature of the conduit much.
you say under, as in not embedded in the pour? the roof of a hospital,
so it's underneath the roof?
Click to expand...
the concrete roof is covered by 2" concrete layer (screed) and 1" PVC conduit is in between the roof and screed so its not embedded in the pour so its underneath the screed.

Fulthrotl said:
can you run EMT under the roof? all we are talking
about is less than 100' of emt, and the labor and profanities necessary
to install it, of course. :happyyes:
Click to expand...
it might be a violation to the code 358.12(3) using EMT :? I'm not sure
 
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