Duct Bank Design Guide

Minimum of 1 bag of dye per 1yd of concrete.

Duct bank design guide.

This section summarizes the design criteria for underground exterior electrical distribution systems. Top of conduit conduit bank. Use bell adapters where conduits enter manholes. Reinforcement of concrete is not required.

B concrete encased ductbanks in all other areas. Lengths of secondary duct banks shall be minimized to limit pulling distances and electrical losses. Design all underground electrical raceways and duct banks for seismic zone 2. Duct banks is 3 feet below grade measured to top of ductbank.

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. The minimum allowable concrete duct compressive strength is 5 000 psi at 28 days. 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. 30 for secondary minimum 36 for primary minimum 48 maximum 10.

Electrical engineers designing electrical duct banks must understand the soil s thermal properties and the effects it will have on the overall installation. Where elbows are required to transition from horizontal to vertical for stub ups use rigid steel conduit sweep elbows. 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. Use schedule 40 rigid pvc.

Service entrance mv and lv duct banks are to be concrete encased. 3 inches between ducts and exterior envelope wall between 2 inches ducts for like services and 4 inches between power and signal ducts. In order to properly size the duct bank the following factors must be considered and evaluated. Minimum space between ducts.

Any secondary duct lengths. System design and performance requirements 1. 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.