Non-Metallic Conduit Troubles??

[Mike01]

Type DB-60 was submitted instead of EB-35 due to the fact it holds up better during the construction and installation process resulting is less wated and damaged ducts, however what is the difference between DB-60 and EB-35 I understand the wall thickness is different, the DB references NEMA TC 6, and the EB-35 NEMA TC 8? What is the difference these conduits are specified to be in a duct bank is it ok to put DB-60 in a concrete encased duct bank?. Everything I have seen indicates this ad direct burry where the EB states encasement burial? Also I noticed it is only rated for 90? wire installation what if you have primary cabling specified (rated) at 105?C what type of conduit is Required then? PVC 40 (I could not find the max. temp. for PCV sched 40 or 80) does anyone know where I can find this? In that installation than neither DB-60 or EB-35 would be acceptable? Than what would be? Just looking for some other opinions? Thanks.

 

[don_resqcapt19]

I don't think that you can use either DB-60 or EB-35 if this is an NEC application. I believe that the code compliant PVC conduit (Article 352) has the maximum permitted conductor temperature marked on it.

 

[barclayd]

Carlon's catalog lists the temperature rating, etc. They're both good for 90C.
There's a problem with Article 352 as applied to EB/DB. 352 allows 'RNC' to be installed exposed, in walls, etc., but EB/DB is expressly designed for underground applications.
Talk to your AHJ - we've got miles of it here - it's good stuff.
It meets NEMA & ASTM standards.
See Article 100 - "Listed".
db

 

[dnem]

'07 UL Whitebook page 103+104 says about PVC: "Unless marked for higher temperature, rigid nonmetalic conduit is intended for use with wire rated 75?C or less including where it is encased in concrete within buildings and where ambient temperature is 50?C or less. . Where encased in concrete in trenches outside of buildings it is suitable for use with wires rated 90?C or less."

 

[Bob NH]

'07 UL Whitebook page 103+104 says about PVC: "Unless marked for higher temperature, rigid nonmetalic conduit is intended for use with wire rated 75?C or less including where it is encased in concrete within buildings and where ambient temperature is 50?C or less. . Where encased in concrete in trenches outside of buildings it is suitable for use with wires rated 90?C or less."

The Whitebook quote is not consistent with the NEC requirement.

NEC 2005 - 352.12(E) states that the temperature limitation is based on conductors or cables OPERATING at a temperature higher than the RNC listed operating temperature. The italicized exception below the 352.12(E) requirement reinforces the point that the temperature that applies is the temperature at which the conductor is being OPERATED; not the temperature limitation printed on the insulation of the conductor.

 

[Mike01]

Wht type?

Wht type?

Ok the conduti is lised for 90 degree (pvc sched 40, 80, EB-35, and DB) where installing conductors in a ductbank outdoors what type of conduit do you typically use? we are utilizing 15Kv cable @ 105 degree however the normal operating condition will not operate near 90 degrees however under a single contingency outage (multiple utility primaries on site tied togerther thru a tie scheme) the conductors could operate at a high temperature for a short period of time (less than 24 hours) with this condition what type of conduit would you specify for and outdoor underground concrete encased duct bank?

 

[Mike01]

Construction

Construction

So how do you build a primary duct bank with 105 degree cable?

 

[dnem]

Unless marked for higher temperature, rigid nonmetalic conduit is intended for use with wire rated 75?C or less including where it is encased in concrete within buildings and where ambient temperature is 50?C or less. . Where encased in concrete in trenches outside of buildings it is suitable for use with wires rated 90?C or less.

The Whitebook quote is not consistent with the NEC requirement.

NEC 2005 - 352.12(E) states that the temperature limitation is based on conductors or cables OPERATING at a temperature higher than the RNC listed operating temperature. The italicized exception below the 352.12(E) requirement reinforces the point that the temperature that applies is the temperature at which the conductor is being OPERATED; not the temperature limitation printed on the insulation of the conductor.

I agree.

UL should read:
"Unless marked for higher temperature, rigid nonmetalic conduit is intended for use with circuit(s), feeder(s), or service(s) rated 75?C or less including where it is encased in concrete within buildings and where ambient temperature is 50?C or less. . Where encased in concrete in trenches outside of buildings it is suitable for use with circuit(s), feeder(s), or service(s) rated 90?C or less."

PS Did you ever notice that UL doesn't cooperate with NEC use of the word "conductor" ? . UL always uses the word "wire".