Change List for this Rule

 

General Order 95

 

Section VIII

 

Detailed Construction Requirements for Communication Lines
(Class C Circuits)

 

84.4    Clearances

 

Allowable variations in clearances due to temperature, loading, dead ending, etc., are given in Rules 37 and 38 .

 

A.    Above Ground

The minimum vertical clearances shall be those specified in
Rule 37 , Table 1 , with the following modifications:

 

(1)    Across Arid or Mountainous Areas: The clearance of 15 feet specified in Table 1, Case 4, Column B may be reduced to not less than 13 feet over arid or mountainous areas which are not under cultivation and over which there is no likelihood of vehicular travel.

 

(2)    In Rural Districts: The clearance of Table 1, Case 4, Column B may be reduced to not less than 13 feet above ground along thoroughfares in rural districts where no part of the line overhangs any part of the thoroughfare which is ordinarily traveled and where it is unlikely that vehicles will be required to cross under the communication conductors.

 

(3)    Accessible to Pedestrians Only: Communication conductors of not more than 160 volts which transmit not more than 50 watts and communication cables having grounded metal sheaths may have a clearance above ground accessible to pedestrians only less than as specified in Table 1, Case 5, Column B , (10 feet) but not less than 8 feet.

 

(4)    Fenced Railway Rights–of–Way: Railway signal cables between line poles and signaling devices, which are entirely on fenced railway rights–of–way, and which are exposed to vehicular traffic but do not cross thoroughfares, may have clearances above ground less than as specified in Table 1, Column B, Case 4 (15 feet) but not less than 10 feet. Such cables which are entirely on fenced railway rights–of–way and which are in areas accessible to pedestrians only may have clearances above ground less than as specified in Table 1, Column B, Case 5 (10 feet) but not less than 7 feet.

 

(5)    Over Swimming Pools (See Figure 84–1 ):

 

a)    Line Conductors, Cables, Messengers and Span Wires: Crossings of communication line conductors over swimming pools shall be avoided where practicable. Line conductors shall have radial clearances from the top edge of the pool wall and vertical clearances above the highest water level of the pool of not less than 18 feet.Grounded metallic sheathed cables, plastic–jacketed cables with an inner grounded metallic sheath, and grounded messengers and grounded span wires which support cable may have minimum radial and vertical clearances as hereinabove stated of not less than 16 feet. Service drops installed over swimming pools and used in line cable construction may have minimum radial and vertical clearance as hereinabove stated of not less than 14 feet.

 

b)    Service Drops: Installation over swimming pools shall be avoided where practicable. Service drops above swimming pools shall have vertical clearances over the pool and radial clearances from the edge of the pool wall of not less than 14 feet for public and commercially operated pools and not less than 10 feet for residential pools.

No service drop may be installed less than 14 feet vertically over the horizontal plane through a diving board or platform, the area of such plane being within 8 feet radially of the diving board or platform and over the water surface of the pool.

No service drop may be installed less than 10 feet vertically over the horizontal plane through a diving board or platform, the area of such plane being the area within 3 feet radially of the diving board or platform and not over the water surface of the pool.

 

c)    Communication Guys: Guys shall have vertical clearances above the highest water level of the pool of not less than 16 feet.

No communications guy may be installed less than 16 feet vertically over the horizontal plane through a diving board or platform, the area of such plane being within 8 feet radially of the diving board or platform and not over the water surface of the pool.

No communications guy may be installed less than 8 feet vertically over the horizontal plane through a diving board or platform, the area of such plane being the area within 3 feet radially of the diving board or platform and not over the water surface of the pool.

 

Note:    Added January 2, 1962 by Resolution No. E–1109 and Revised November 21, 1990 by Resolution SU–6.

 

(6)    Across or along Public Thoroughfares: Communication conductors over or across public thoroughfares shall have a clearance of 18 feet above ground (Table 1, Case 3, Column B ). A reduced clearance to 16 feet is permitted for the portions of communication conductors where no part of the line overhangs any part of the thoroughfare which is ordinarily traveled, or where the line is behind an established curb, ditch or berm that serves to protect such communication conductors from encroachment by vehicular traffic.

 

Note:    This 16 foot clearance shall not be reduced because of temperature or wind loading as specified in Rule 43 .

Note:    Added November 21, 1990 by Resolution SU–6.

 

B.    Above Railways and Trolley Lines

 

(1)    Which Transport Freight Cars: The clearance specified in Table 1, Case 1, Column B (25 feet) is based upon the maximum height of standard freight cars, 15 feet 6 inches between top of rail and top of running board. This clearance shall in no case be reduced more than 5% because of temperature and loading as specified in Rule 43 .

 

(2)    Operated by Overhead Trolleys: The clearance specified in Table 1, Case 2, Column B (26 feet) is based upon a trolley pole throw of 26 feet, the usual maximum height of a free trolley pole above the rails or other traveled surfaces used by trolley cars or coaches. Where trolley lines have a maximum trolley throw at variance with 26 feet the specified clearance shall be increased or may be reduced accordingly except that in no case shall the clearance be less than 25 feet. See Rule 87.4–B2 for the clearance of grounded cables and messengers.

Where railways operated by overhead trolleys transport freight cars, the clearance requirements of
Rule 84.4–B1 also apply.

 

C.    Between Conductors

The minimum clearances shall be those specified in
Rule 38 , Table 2 (see also Rule 32.2–D ) with the following modifications:

 

(1)    Open Wire

 

a)    On Related Line and Buck Arms: The clearance of 6 inches specified in Table 2, Case 14, Column C is not required between conductors on line arm and related buck arm where the conductors supported by such arms do not cross.

 

b)    On Brackets Attached to Crossarms: The radial clearance for communication line conductors supported on brackets or extensions attached to crossarms at, or outside of, the outer pin or dead–end positions shall not be less than 3 inches from any other communication line conductor supported by the same crossarm as specified in Table 2, Case 15, Column C . Not more than two conductors on the same side of the pole on any crossarm may be supported on brackets within the outer pin position and below conductors normally supported on pins.

There shall not be less than a 12 inches vertical separation between communication conductors supported on brackets within the outer pin positions on one crossarm and the communication conductors on another crossarm. The vertical clearances specified in
Table 2, Cases 1 to 14, Column C shall be provided between the conductor on a bracket and the conductor level of any other conductors not supported on the crossarm to which the bracket is attached.

 

EXCEPTION:    This rule shall not apply to clearances between conductors of the same or similar circuits at points of transposition.

 

Note:    Revised November 21, 1990 by Resolution SU–6.

 

c)    Attached Directly to Poles: On poles which carry no crossarms, open wire conductors which are attached to the sides of poles by means of hooks, knobs or brackets may be placed in any position within the 3 feet next below the topmost conductor on the pole.The vertical separation between conductor supports on the same side of pole in this space of 3 feet shall be not less than 6 inches. Below this point (3 feet below the topmost conductor) conductors shall be attached to one side of pole only, not more than 6 conductors shall be so attached, and the vertical separation between these conductors shall be not less than 12 inches.

On poles which carry communication crossarms only, one pair of open wire conductors may be attached to opposite sides of the pole by means of hooks, knobs, or brackets, at a point not less than 2 feet below the lowest level of conductors supported on crossarms. Below this point (2 feet below conductors on crossarm) other conductors which are attached to surface of pole shall be attached to one side of pole only, not more than six conductors shall be so attached, and their vertical separation shall be not less than 12 inches.

Branch or tap lines and service drops from conductors attached to poles may be similarly attached to the face or back of a pole, but not both.

 

(2)    Duplex, Triplex and Cables: Insulated single conductors (rubber insulated), duplex, triplex and paired conductors are considered as cables (see definition, Rule 20.3 ) and the clearances for such conductors are specified in Rule 87.4 .

 

D.    From Poles and Crossarms

Table 1, Case 8, Column B specifies a minimum clearance of 15 inches from center line of pole which is applicable to communication conductors including cables and service drops. Modifications of this basic 15 inches clearance are specified in Rule 37 and by the following provisions where conductors are not on poles jointly used for supporting supply conductors excepting supply service drop clearance attachments (see Rules 54.8–C2 and 54.8–C3 ).

The clearance of 3 inches specified in
Table 1, Case 9, Column B is not intended to apply to communication conductors.

 

(1)    Conductors Supported on Crossarms: The 15 inches minimum clearance from the center line of the pole specified for communication conductors supported on crossarms may be reduced under the following condition:

For communication conductors the clearance from center line of pole shall not be less than 9 inches. This clearance shall apply only to communication conductors under the following conditions:

 

a)    When supported on a crossarm in the pole top position, and

 

b)    When no conductors are supported below such crossarms except supply service drops on clearance crossarms. This provision is intended to permit the use of a related buck arm, in which the climbing space shall conform to the requirements of Rule 84.7–B .

To maintain climbing space, cables or messengers may have clearances less than 15 inches from center line of pole under the following conditions:

 

1)    When placed between crossarms, or

 

2)    When placed less than 2 feet below the level of the lowest communication conductor supported on crossarms.

These cables or messengers are to be placed on one side of the pole only. Any conductor on a crossarm on the opposite side of the pole that is within 36 inches vertically of the cable or messenger shall be at least 18 inches horizontally from the vertical plane of such cable or messenger (see
Figure 84–2 ).

 

Note:    Revised November 21, 1990 by Resolution SU–6.

 

(2)    Conductors Not Supported on Crossarms: Communication conductors which are not supported on crossarms may be attached to poles by means of hooks, knobs, or brackets and thus are not required to be any specified distance from center line of poles provided the clearance between conductors complies with the requirements of Rule 84.4–C1c .The minimum clearance of such conductors from the surface of poles shall be such that suitable insulation is maintained.

 

(3)    Colinear, Conflicting or Crossing Lines (See Rule 32.3 ):Where two communication lines are colinear or otherwise in conflict or where a pole of one line is interset in another line at crossings, the clearances of Rule 32.3 and Rule 37 , Table 1, Case 8, Column B may be modified as follows:

In applying any of the provisions of
Rule 84.4–D3 an unobstructed climbing space on each pole concerned shall be maintained with horizontal dimensions of not less than 18 inches wide and 30 inches deep for communication conductors.

 

a)    Where Clearance Arms Are Used: Where clearance arms are used to support the conductors of a colinear or conflicting communication line on poles which support only communication conductors, the clearance of such conductors from the center line of pole shall not be less than 15 inches.

 

Note:    Revised November 21, 1990 by Resolution SU–6.

 

b)    Where Clearance Arms Are Not Used: Communication conductors which in passing another communication pole unattached would be less than 15 inches from the center line of pole or less than 5 inches from the surface of pole shall be attached to the pole in accordance with the provisions of Rules 84.4–C1c and 84.4–D2 .

 

(4)    Conductors Passing Supply Poles and Unattached Thereto: The center line clearance between poles supporting supply conductors and any communication conductors which pass such poles unattached shall be not less than 22 1/2 inches (1 1/2 times the clearance specified in Table 1, Case 8 ), except where the supply pole is within 10 feet of the pole on which the communication conductors are supported.Where poles of the two lines are less than 10 feet apart, clearances not less than as specified in Table 1, Case 8 , shall be maintained.

 

Note:    Resolution E–999 effective October 7, 1958, is rescinded and replaced by new Rule 84.4–D(4)(a); deleted and revised January 8, 1980 by Decision No. 91186.

 

a)    From Nonclimbable Street Lighting or Traffic Signal Poles or Standards (including mastarms, brackets and lighting fixtures): When passing street lighting, traffic signal poles or standards (including mastarms, brackets and lighting fixtures) a clearance of 12 inches, as specified in Table 1, Case 10, Column B , may be reduced when suitable insulation for the highest voltage of open wire involved and mechanical protection from abrasion is provided where necessary.Such mechanical protection shall extend not less than 15 inches in each direction from centerline of pole, standard, attaching mastarm or fixture, whether passing above, below or alongside.There shall be no interference with light distribution from lighting fixtures and workers shall not be hampered or endangered in the performance of their duties.

 

Note:    Added January 8, 1980 by Decision No. 91186; Revised March 9, 1988 by Resolution E–3076 and November 6, 1992 by Resolution SU–15.

 

(5)    Center Line Clearance at Angles in Lines and at Transpositions: The clearance of 15 inches from center line of pole specified in Table 1, Case 8, Column B (and the reduced clearance of 9 inches permitted by Rules 84.4–D1 and 84.4–D3a ) may be reduced at angles in lines and at transposition supports provided that at angles in lines the reductions of the 30 inches and 18 inches widths of climbing spaces shall not exceed the reduction specified in Rule 84.7–A1 , and further provided that the 30 and 18 inches widths of climbing space shall not be reduced at transposition supports (see Figure 84–3 ).

 

E.    Above alongside or in Immediate Proximity to Buildings, Bridges and Other Structures

Conductors should be arranged so as not to hamper or endanger firefighters and workers in performing their duties.The basic clearances of communication conductors from buildings are specified in
Table 1, Cases 6 and 7, Column B . The horizontal clearance ( Table 1, Case 7 ) shall be maintained until the vertical clearance ( Table 1, Case 6 ) is attained (see Figure 84–4 ). The requirements of Table 1, Case 7 , Column B also apply at fire escapes, windows, doors, and other points at which entrance or exit might be reasonably expected.

Communication cables are not required to be any specified distance from the sides of buildings, bridges and other structures, but they shall be installed so that they do not interfere with the free use of fire escapes, windows, doors and other points at which entrance or exit might be reasonably expected.

The vertical clearance of communication conductors (including cables) above buildings specified in
Table 1, Case 6, Column B may be reduced to not less than 2 feet under either of the following conditions:

 

(1)    Over roofs whose slope exceeds 9 inches of rise per 12 inches of run (see Sketch), or

 

 sketch

 

(2)    Over roofs where the conductor does not overhang the building by more than 6 feet.

See Rule 84.8–C4 for service drop clearance requirements.

 

Note:    Revised November 21, 1990 by Resolution SU–6; November 6, 1992 by Resolution No. SU–15 and October 9, 1996 by Resolution SU–40.

 

F.    Below, alongside, through or in Immediate Proximity to Bridges, Viaducts or Similar Structures

Open wire communication conductors which cross below, through or in immediate proximity to bridges, viaducts, or similar structures shall be maintained at clearances above ground and walkways as specified in
Table 1, Cases 1 to 6 ; at a radial clearance from unprotected conductors of other classifications of not less than as specified in Table 2, Case 3 ; at clearances from walls and the underside of such structures as specified in Table 1, Case 7 . The horizontal clearance ( Table 1, Case 7 ) shall be maintained until the vertical clearance ( Table 1, Case 6 ) is attained (see Figure 84–4 ). Where it is not practicable to obtain the 3 foot clearance this clearance may be reduced to not less than 6 inches where the voltage does not exceed 160 volts; or where supported on the walls or underside of such structures at clearances as specified in Table 1, Case 9 with supports at least every 50 feet.

In lieu of the above requirements, conductors which cross below or through bridges, viaducts, or similar structures shall be enclosed in metal sheaths, run in metal conduits, or be placed in ring construction on a messenger.

 

Note:    Revised November 6, 1992 by Resolution No. SU–15.

 

G.    From Guys and Messengers (See Table 2, Cases 18 and 19, Column C ; also Rules 86.4–C and 87.4 )