Original General Order 95 

Section VIII

Detailed Construction Requirements for Communication Lines
(Class C Circuits) 

87.4    Clearances

The clearances for conductors as specified in Rule 84.4 shall apply to cables and their messengers except where modified herein and shall be measured to the nearest surfaces of ,the cable and messenger assembly, including cable rings and messenger supports.

A.    Above Ground (see Rule 84.4-A)

B.    Above Railways And Trolley Lines

(1)    Which Transport Freight Cars: See Rule 84.4-B1.

(2)    Operated By Overhead Trolley: The clearances specified in Table 1, Case 2, Columns A and B are based upon a maximum trolley pole throw of 26 feet.

Messengers and cables may have clearances above the rails or running surfaces used by trolley cars or coaches less than the distance specified in Table 1, Case 2, Columns A and B (26 feet) for trolley-throw clearance, provided the messengers and cables are not less than 4 feet above the trolley contact conductor and are encased in wood boxing or moulding 1-inch or more in thickness for distances of at least 2 feet horizontally from the vertical plane of each trolley contact conductor.

Where railways operated by overhead trolleys transport freight cars, the provisions of Rule 84.4-B1 also apply.

C.    Between Conductors And Cables

The minimum horizontal and vertical clearances shall be those specified in Rule 38, Table 2, (see also, Rule 32.2-D) with the following modifications.

(1)    Cable Conductors: Insulated cables (including rubber-insulated single conductors, duplex, triplex, and paired conductors, whether single or grouped and whether with or without supporting messengers) are treated as single conductors and therefore no specified clearance is required between the individual conductors which comprise them. The clearance of 3 inches required by Table 2, Case 15, Column C, likewise does not apply between different cables.

(2)    Between Separate Cables: The horizontal separation of 3 inches specified in Table 2, Case 15, Column C, is not intended to apply between separate cables on crossarms.

(3)    Attached To Poles: On poles which carry no supply conductors and no crossarms, communication cables or messengers attached to the sides of poles may be placed in any position within 3 feet of the top of the pole pro- vided metal-sheathed cables or messengers are separated from open wire conductors in this section of the pole by a vertical distance of not less than 12 inches.

On poles which carry no supply conductors (except supply service drop clearance attachments) and which support communication conductors on crossarms, messengers and cables may be attached to surface of pole between crossarms or less than 2 feet below the conductors on the lowest crossarms, provided such messengers or cables are placed on one side of pole only and any conductor on the opposite side of the pole, less than 36 inches vertically from such messenger and cable, shall be not less than 24 inches (if an exchange conductor) or not less than 18 inches (if a toll conductor) horizontally from such messenger or cable (see .App. G, Fig. 84).

On poles which carry no supply conductors (except supply service drop clearance attachments) and which support communication conductors on crossarms, messengers and cables may be attached directly to opposite sides of pole provided such attachments are not less than 2 feet below the lowest level of communication conductors supported on a crossarm and provided that the vertical separation between such messengers or cables and open wire conductors in the same configuration shall be not less than 12 inches.

Cables or messengers where attached to the surface of poles which support supply conductors, shall be not less than 6 feet vertically below the level of supply conductors, except that this minimum clearance of 6 feet may be reduced to not less than 4 feet below supply conductors of 0-750 volts provided a guard arm is placed above the messenger and cable (or self-supporting cable) in accordance with the provision of Rule 87.7-B (see Rule 20.9-D for guard arm definition). No cable or messenger, where attached to surface of such a pole, shall be less than 2 feet below the lowest level of communication conductors on crossarms unless a horizontal separation of not less than 30 inches is maintained between the messenger or cable and the communication conductors on the opposite side of pole.

D.    From Poles

(1)    Cables Or Messengers Supported On Crossarms: Cables or messengers supported on crossarms shall have a clearance of not less than 15 inches from the center line of poles which support supply conductors.

Cables or messengers supported on crossarms shall have a clearance of not less than 9 inches from the center line of poles which support only communication conductors.

(2)    Cables Or Messengers Not Supported On Crossarms:  Cables or messengers may be attached directly to the surface of poles and the clearance specified in Table 1, Cases 8 and 9, shall not be held to apply provided all vertical clearances between conductors are maintained as specified throughout these rules.

(3)    Colinear Lines: See Rule 84.4-D3.

(4)    Cables Or Messengers Passing Supply Poles And Unattached Thereto: See Rule 84.4-D4.

E.    Above Or Beside Buildings, Bridges And Other Structures: See Rule 84.4-E.

F.    Between Cables And Messengers

Cables supported by messengers are not required to be any specified distance from their supporting messengers.

G.    Between Messengers

No clearance between messengers is required where messengers of the same system branch or cross and the clearance specified in Table 2, Case 1, Column A, does not apply in such instances.