Grounding System

TM 11-5895-878-14&P

box.

These grounds are jumpered common and

b. Black Alarm System. The black alarm system is

extended to the building ground systems buried

similar to the red system (a above). The major/minor

externally. The three grounds are the shield, DC, AC

panel is mounted in bay 1.21 (fig. 1-7). In addition, the

grounds.

.AU/CCU and station clock alarms are connected into

a. AC Ground.

The AC ground is extended

the system.

throughout the TCF where it serves the AC ground

requirements as well as bonding all the iron work within

2-21. Grounding System

the site to common.

Grounding systems are connected separately to the red

b. Shield Ground. The shield ground is extended

and black equipment and circuits (fig. FO-9). Each

to both the VF and DC IDF's, where it is commonly used

grounding system consists of three separate and

to terminate the shields or armor of cables.

isolated grounds. The shield and DC systems are tied

together only at the station ground box. Each ground

c. DC Ground. The DC ground runs from the

provides a fixed ground reference for the various

ground box to the power supplies and distribution

equipments and systems within the building. The

boards, where it is distributed to power boxes and alarm

grounds are isolated from one another to minimize

panels throughout the site.

ground current loops and, therefore, reduce unequal

ground potentials throughout the site. Each ground

cable is tied to a separate isolated ground bar within the

2-61