Duct Bank Design Guide

Service entrance mv and lv duct banks are to be concrete encased.

Duct bank design guide.

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. Minimum of 1 bag of dye per 1yd of concrete. Electrical engineers designing electrical duct banks must understand the soil s thermal properties and the effects it will have on the overall installation. In order to properly size the duct bank the following factors must be considered and evaluated.

Reinforcement of concrete is not required. B concrete encased ductbanks in all other areas. Use bell adapters where conduits enter manholes. Any secondary duct lengths.

Lengths of secondary duct banks shall be minimized to limit pulling distances and electrical losses. Where elbows are required to transition from horizontal to vertical for stub ups use rigid steel conduit sweep elbows. Duct banks is 3 feet below grade measured to top of ductbank. System design and performance requirements 1.

Use schedule 40 rigid pvc. Backfill evenly around duct with clean dry earth and mechanically tamp in 12 lifts. 30 for secondary minimum 36 for primary minimum 48 maximum 10. The minimum allowable concrete duct compressive strength is 5 000 psi at 28 days.

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. Design all underground electrical raceways and duct banks for seismic zone 2. Contractor shall have class a 17 license for minimum of 2 years prior to work. Top of conduit conduit bank.

Minimum space between ducts. 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. This section summarizes the design criteria for underground exterior electrical distribution systems.