3 inches between ducts and exterior envelope wall between 2 inches ducts for like services and 4 inches between power and signal ducts.
Duct bank design guide.
Concrete shall be red dyed utilizing red dye mixed into the concrete for a minimum of 5 minutes prior to pouring.
Use walls of trench to form side walls of duct bank where soil is self supporting and concrete envelope can be poured without soil inclusions.
Any secondary duct lengths.
System design and performance requirements 1.
Use bell adapters where conduits enter manholes.
Where elbows are required to transition from horizontal to vertical for stub ups use rigid steel conduit sweep elbows.
Reinforcement of concrete is not required.
Duct banks are to terminate in a service entrance switchboard or switchgear within 5 of entering the building or are to remain in concrete and painted red until terminated in a service entrance rated disconnect.
Top of conduit conduit bank.
Electrical engineers designing electrical duct banks must understand the soil s thermal properties and the effects it will have on the overall installation.
Backfill evenly around duct with clean dry earth and mechanically tamp in 12 lifts.
B concrete encased ductbanks in all other areas.
Minimum space between ducts.
Contractor shall have class a 17 license for minimum of 2 years prior to work.
30 for secondary minimum 36 for primary minimum 48 maximum 10.
Underground concrete encased electric conduit duct banks shall consist of type db 60 polyvinyl chloride pvc conduit rated for 90 c cable and meeting nema standard tc 6 and astm f 512 for underground applications.
Ductwork standard design we can see from the velocity colour scale and the streamlines that in the design on the left the inlet air directly strikes the sharp turns that are present in the system which causes an increase in the static pressure.
Lengths of secondary duct banks shall be minimized to limit pulling distances and electrical losses.
Duct banks is 3 feet below grade measured to top of ductbank.
In order to properly size the duct bank the following factors must be considered and evaluated.
Service entrance mv and lv duct banks are to be concrete encased.
Use schedule 40 rigid pvc.
Design all underground electrical raceways and duct banks for seismic zone 2.
