Ground bar UFC.pdf

UFC 3-575-01

1 July 2012

Change 1 October 1, 2021

CHAPTER 2 STATIC ELECTRICITY PROTECTION

2-1 STATIC GROUNDING AND BONDING REQUIREMENTS.

Identify hazardous classified locations in accordance with NFPA 70. Provide grounding and bonding for these areas in accordance with NFPA 77 to support the intended operations.

Include a listing of hazardous materials, containers, and operating units in the design, and indicate fixed operating equipment locations on the drawings. Identify portable and movable equipment requiring static electricity grounding distinctively by location and with type of grounding method each location requires.

\1\ 2-1.1 Bonding and Grounding Conductors.

Bonding and grounding conductors must be sturdy enough to withstand mechanical damage and must not be smaller than 6 AWG copper. For added flexibility, use braided cable or flexible bonding straps for static grounds on portable or movable equipment. Install at least two separate braided cables or flexible bonding straps on portable or movable equipment such as doors, hinged shelves, or tables, for redundancy. Flexible cables or straps have a shorter life than solid copper, especially since they must be replaced once 50% of the strands are broken.

Conductors are typically uninsulated. Apply bonding for other facilities in accordance with NFPA 70 and NFPA 780. Before securing any bond, prepare for electrical continuity by removing any paint, oil, dirt, or rust on contact surfaces. If factory coatings are removed by chemicals used in the preparation process, that coating must be reapplied to protect against corrosion. A resistance reading of one ohm or less is required across bonds, to indicate continuity. /1/

2-1.2 Connections.

Do not connect static grounds above grade to:

• Electrical equipment grounding systems.

• Telecommunications systems grounds.

• Gas, steam, oil, hydraulic, hot water or airlines.

• Sprinkler systems.

• Any component of the lightning protection system (LPS).

• \1\ Down conductors. /1/

These systems must be interconnected below grade. As an exception to performing the calculations required by NFPA 780, the 6 foot (1.83 m) bonding requirement allowed by UL 96A may be used. The preferred method for reducing the potential for side-flash is to increase the separation distance between the static ground and the six items above, so that a bond is not required. The minimum size of the bonding conductor is 6 AWG copper.

Change 1 October 1, 2021

\1\ A static ground should never be bonded to a down conductor. It should be bonded to the building power system ground either at the service ground rod or at the main distribution panel or motor control center where the neutral bus bar and ground bus bar are bonded together.

Static bonds must be bonded only to component paths designed for static dissipation. /1/

2-1.3 Static Bus Bars.

A static bus typically consists of 2 inch x ¼ inch (51 mm x 6 mm) copper bars installed on the interior wall of the facility, as shown in Figure 2-1. Static bus bars must be used only for static grounding. Bus bars, especially those used in the telecommunications industry, may come with insulators, if specified when ordering. Static bus bars must be isolated from other grounding subsystems as much as possible and must be isolated when used for ordnance grounding and from lightning protection down conductors including steel columns used as the down conductor. The grounding system for the static bus bars is typically connected to the building grounding system by running at floor level on the interior until it can be routed to the exterior to the single point facility ground rod or be bonded to a ground rod and the ground rod bonded to the ground ring electrode. This configuration will allow the static bus bar to be grounded even if the ground ring electrode is broken or compromised, or requires replacement.

2-1.4 Resistance to Ground.

Current caused by static electricity is typically on the order of milliamperes. A resistance to ground of 10,000 ohms is more than adequate to bleed off normal static charges. All grounds used for static protection in DoD facilities, including those for aircraft and fuel tanks, must have a maximum resistance of 10,000 ohms. Any danger of electrical shock hazard caused by the 10,000 ohm value can be eliminated by proper bonding to other grounding media.

2-1.5 Ground Grab Bars.

Ground grab bars \1\ should /1/ be installed immediately outside entrance doors to operating buildings, rooms or structures where special hazards exist. A ground grab bar consists of a length of non-corroding conductive pipe or bar which is connected to the earth electrode system (EES).

Change 1 October 1, 2021

Figure 2-1 Static Bus Bar

2-2 GENERAL APPLICATIONS.

2-2.1 Conditions.

\1\ This UFC does not identify all applications where static electricity protection should be provided. The electrical designer must analyze suspected potential static electrical charges and address the conductive paths that could reasonably exist between them. The following