Rule 10-906 Bonding Conductor Connection to Circuits and Equipment
(1) The bonding conductor or bonding jumper shall be attached to circuits, conduits, cabinets, equipment, and the like, which are to be bonded, by means of lugs, pressure wire connector clamps, or other equally substantial means.
(2) Connections that depend upon solder shall not be used.
(3) The bonding conductor shall be secured to every metal box by means of a bonding screw, which shall be used for no other purpose.
(4) The bonding conductor shall be brought into every nonmetallic outlet box in such a manner that it can be connected to any fitting or device which may require bonding to ground.
(5) Equipment shall be so installed that if the connections between the branch circuit and the internal conductors pass through an access cover, the bonding connection shall remain continuous when the cover is removed.
(6) A bonding jumper shall be installed to connect the bonding conductor to the grounding terminal of a receptacle and in such a manner that disconnection or removal of the receptacle will not interfere with, or interrupt, grounding continuity.
(7) In the case of metallically enclosed systems where the grounding path is provided by the metal enclosure, a bonding jumper shall be installed to bond the grounding
terminal of the receptacle to the enclosure.
(8) Notwithstanding Subrules (6) and (7), the bonding jumper, in the case of receptacles having grounding terminals isolated from the mounting strap required for special equipment, shall be permitted to be extended directly back to the distribution panel.
(9) Notwithstanding Rule 10-808, electronic equipment rated to operate at a supply voltage not exceeding 150 volts-to-ground and which requires a separate bonding conductor shall be permitted to be bonded to ground by an insulated conductor extending directly back to the distribution panel, provided that:
(a) The separate bonding conductor is enclosed in the same raceway or cable containing the circuit conductors throughout the length of that cable or raceway; and
(b) The separate bonding conductor is sized not less than that given in Table 16 for each leg of the run, determined by the size of the overcurrent protection for the circuit conductors; and
(c) The bonding requirements of Rules 10-302 and 10-400 are met.
Rationale for Rule 10-906.
When we lose a circuit conductor connection, we know immediately because the light goes off or the electrical equipment stops, or perhaps a fault occurs and a fuse or circuit breaker operates. When we lose a bonding conductor, we do not know until there is a fault, and at that time the loss of the bond may result in serious damage, shock, or fire. We have therefore taken every precaution to install the bonding conductor in such a way that it will not be accidentally or inadvertently disconnected. We make the connection of the bonding conductor by secure methods that do not depend on solder, and we fasten it with a screw or device that is used for no other purpose. We make sure that the bond is present and properly connected at every point at which it could be required and interconnected in such a manner that it will not be disconnected if a receptacle or other device is removed. We take care that the bond will remain continuous even if it is connected to or run through removable covers, and we do not depend on the mounting screw of a receptacle as a bonding connection.
In Subrule (8) we have permitted a separation between the bonding of the outlet box and the ground connection to a receptacle intended for use with electrical equipment that may be sensitive to power disturbances such as noise and voltage spikes carried over the bonding system. Voltage spikes, which are usually caused by the switching of large loads, can damage such electronic equipment as computers or corrupt the computer software, causing system shutdown and loss of data. This is also the rationale of Subrule (9), which applies not just to the bonding conductors to receptacles that supply data processing and similar equipment but to the bonding conductors for any circuit operating at not more than 150 V that supplies such equipment. In both these cases we have permitted a separate and dedicated bonding conductor to be run from the sensitive electrical equipment, directly back to the distribution panelboard.
Intent for Rule 10-906.
When we connect a bonding conductor, we wish to provide as secure a connection as possible. We do this by
(a) using only positive connection methods;
(b) making a connection that does not depend on solder (we can accept solder if the connection is secure and then soldered; under the Part II Standards, a wire that passes through a hole and is bent is considered to be secure);
(c) using a dedicated ground screw in each outlet box (ie, a screw that is used for no other purpose);
(d) bringing the bonding conductor into every outlet box, whether it is metal or nonmetallic, and securing it so that it is available for the bonding of any device installed there;
(e) installing the bond in such a way that the removal of a cover will not break the bonding circuit, even when the cover has the circuit conductors running through it (this will usually require a jumper running with the circuit conductors or between the cover and the enclosure);
(f) connecting the bonding conductor in any box in such a way that the removal of a device will not interrupt the bonding circuit;
(g) providing a bonding conductor from the outlet box to a receptacle if the bonding of the system depends on metal conduit; or
(h) permitting two separate bonding systems to exist, one for the raceway and one for the receptacle or other outlet connection, where, because of the possibility of damage to data processing equipment or to computer programs, a dedicated insulated bonding conductor is used.
Intent for Rule 10-906(8).
For receptacles, removal of the bonding jumper is permitted in accordance with Subrule 10-906(8), where the voltage-to-ground does not exceed 150 volts-to- ground, the receptacle is supplying sensitive electronic equipment, and the conditions of Subrule (9)(a), (b) and (c) are met.
Intent for Rule 10-906(9)
(see Figures 10-906(a) and (b)).
This Subrule is intended to permit insulated bonding conductors, serving a receptacle or hard wired equipment, to pass through panelboards, extending back to the main distribution switchboard and connected to the case or grounding bus at that point in the main distribution switchboard. The Subrule does not permit the separate bonding conductor to pass through the main distribution switchboard to a separate grounding electrode.
In this case, Subrule (9) applies to insulated bonding conductors that are used as the sole bonding means for exposed metal parts on sensitive electrical (electronic) equipment, and only in systems operating at voltages-to-ground of 150 V or less.
Tony Moscioni
Electrical Inspector
Electrical Safety Authority
