Basic Electrical Materials and Methods cont'd

DOE-HDBK-1132-99

Aluminum conduit is preferred in atmospheres where steel conduit is unsuitable;

for example, exposed conduit runs in damp or wet areas, such as cooling tower

areas. Copper-free aluminum conduit and fittings are preferred. Aluminum

conduit should not be used underground or be encased in concrete.

If dissimilar conduit materials are used, dielectric couplings should be

considered.

Steel conduits are recommended to route power cables to motors supplied from

variable-frequency controllers to minimize noise to and from adjacent circuits.

Variable-frequency controllers should be specified to include electrical filters.

In general, copper conductors are preferred for interior electrical systems, but

aluminum conductors, size No. 4 American wire gauge (AWG) and larger, may

be used where appropriate.

A minimum wire size of No. 12 AWG is recommended for lighting and receptacle

branch circuits. This recommendation is based on the branch circuit overcurrent

device rating of 20 amperes or less.

All receptacles with their power source, including UPS-critical circuits, should be

labeled. Electrical penetrations through a fire barrier should have an approved

fire barrier seal. Penetrations through confinements should be designed to

minimize leakage.

Each DOE facility should consider establishing a standard color-code system to

distinctly identify unground phase conductors by voltage level. The following

scheme is typical:

Color coding for 120/240V single-phase systems

Ungrounded conductor

Black

Ungrounded conductor

Red

II-25