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 MIL-HDBK-419A
1.11.2.4.2 Grounding Procedure. Each stand-alone equipment is deployed with at least one ground rod. If the
total number of equipments within the enclosure are small enough and can be positioned such that the ground
rod for each can be used without compromising grounding integrity, then existing low resistance facilities or a
single driven ground rod per equipment may be used (reference 1.11.2.2.2.1) to ground collocated equipments.
Where large numbers of equipments are housed within an enclosure for which the individual grounding procedure
is not reasonable, a simple earth electrode subsystem should be deployed around the enclosure. The size of the
ground system and the number of attached rods needed to achieve the required ground resistance should be
determined according to 1.11.1.3.3. In deployment areas requiring additional lightning/EMP protection
measures described in 1.11.1.1.2 shall be incorporated.
1.11.2.5 Collocated Shelters.
1.11.2.5.1 General Description. Collocated shelters are transportable metallic shelters that share common
signal and/or power cables and are classified in two general categories; those located within 8 meters
(26.5 feet) of one another and those located greater than 8 meters (26.5 feet) from one another (see
Figure l-100). Collocated shelter configurations are typical of an equipment system that must be housed in
multiple shelters. Grounding requirements for collocated shelters are required to provide personnel and
equipment protection from the effects of lightning power faults and to provide a reference for signal grounds.
Particular consideration must be given to collocated shelters receiving power from the same power source or
communicating over inter-shelter signal cables. The need to establish an all encompassing shelter grounding
system for collocated shelters situated more than eight meters apart should be a function of ground resistance
measurements taken at each shelter site. The ground system of each shelter should be interconnected as shown
in Figure l-100 using two bare 1/0 AWG copper cables. If noise or other undesirable effects are produced as a
result of these higher ground resistance differences, the system having the higher resistance can be reduced by
use of chemical treatment or enhancement described in 1.11.1.3.4 or Section 2.9 of Volume I.
1.11.2.5.2 Grounding Procedure.
1.11.2.5.2.1 Power Ground. Shelters powered by a single, common power source should have all grounded
conductors (neutrals) grounded to one point at the generator. Where several power generators are connected in
parallel, the power neutrals of the generators should be interconnected and grounded at a single point. For
collocated shelters not sharing a common source but supplied by individual power sources, all neutrals may be
bonded together and grounded at one point. The equipment shelters should share a common earth electrode
subsystem if they are located within 8 meters (26.5 feet) of each other:
1.11.2.5.2.2 Signal Ground. Collocated shelters less than 8 meters (26.5 feet) with interfacing communications
cables should have the signal grounding conductors bonded to a common earth electrode subsystem (see
1.11.1.3.3). This provides all interfacing shelters with a common signal reference plane.
1.11.2.5.2.3 Fault Protection Subsystem. Intra-shelter green wire equipment grounding conductors should be
grounded at the power entrance panel of each shelter via the earth electrode subsystem.
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