Underground conduit requirements
Underground conduit requirements
(OP)
Hello,
I have been debating with a fellow engineer the need to use a concrete encased duct bank, as opposed to just running PCV, packed in dirt, and covered with a 2" layer of concrete. A duct bank reduces conductor ampacity and costs a lot of money to build. I don't think it's necessary except in locations where damage is very likely. The code makes no mention of needing concrete encasement, even beneath road crossings.
When and why is a concrete duct bank a necessity?
EE
I have been debating with a fellow engineer the need to use a concrete encased duct bank, as opposed to just running PCV, packed in dirt, and covered with a 2" layer of concrete. A duct bank reduces conductor ampacity and costs a lot of money to build. I don't think it's necessary except in locations where damage is very likely. The code makes no mention of needing concrete encasement, even beneath road crossings.
When and why is a concrete duct bank a necessity?
EE





RE: Underground conduit requirements
Consider your soil conditions carefully. If your area has flooding or other factors present even rarely, PVC conduits in particular can float and move enough to damage your "duct bank", which could nullify any initial savings.
Still, I say this only as an experienced electrician (37 yrs), and can't refer you to any papers or studies to support my recommendations, although I'm sure some exist. I'm not in the IEEE anymore, but their IAS used to have such stuff.
.
Me wrong? I'm just fine-tuning my sarcasm!
RE: Underground conduit requirements
The duct bank is provided with manholes to facilitate cable run and the duct are big enough to accommodate a lot of cables for further development or as on the initially design the cable amount is unknown.
And –by-the-way-for a power station the entire electrical installation-equipment and cable and cable raceway represents less than 10% of the investment. It is more important to put the power
station in operation as soon as possible.
RE: Underground conduit requirements
Are direct buried cables a consideration in this instance?
GG
"I have not failed. I've just found 10,000 ways that won't work." Thomas Alva Edison (1847-1931)
RE: Underground conduit requirements
I saw four circuits leaving a substation underground with direct buried PVC. One conductor per conduit plus spare conduits.
The ditch was over twenty feet wide.
You don't always have that much space available.
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Underground conduit requirements
.
Me wrong? I'm just fine-tuning my sarcasm!
RE: Underground conduit requirements
Bill
--------------------
"Why not the best?"
Jimmy Carter
RE: Underground conduit requirements
EE
RE: Underground conduit requirements
RE: Underground conduit requirements
There is question as to the seismic performance of duct banks, particularly duct banks that have just enough rebar to be very rigid but not enough rebar to fully withstand the earthquake forces.