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General Order 64-A

 

Section VIII

 

Detailed Construction Requirements For Communication Lines

(Class C Circuits)

 

84.4    Clearances.

 

A.    Above Ground.

 

(1)    Normal:  The normal minimum vertical clearances shall be those specified in Rule 35, Table 1.  Notes following this table are references to rules which modify the normal minimum clearances.

 

(2)    Reduced Ground Clearances:  Communicate conductors transmitting not more than 50 watts and limited to 160 volts may be permitted a clearance to 160 volts may be permitted a clearance of 8 feet above the ground where accessible to pedestrians only.

 

(3)    Along Thoroughfares:  The clearances of Table 1, Case 4, Column B, for communication conductors above ground in rural districts may be reduced to 13 feet along thoroughfares where no part of the line overhangs any part of the highway which is ordinarily traveled and where it is likely that vehicles will be required to cross under same.  The reduced clearance may also apply over arid or mountainous areas which are not under cultivation and over which there is no likelihood of vehicular traffic.

 

(4)    Fenced Right of Way:  Railway Signal Cable (between the line pole and the signaling device) which are entirely on fenced right of way shall have a vertical clearance above the ground of not be less than 10 feet where the conductor involved is exposed to vehicular traffic other than crossings.

 

B.    Above Railways.

 

(1)    Tracks:

 

a)    Trolley Throw:  For railways having a trolley throw at variance to 26 feet, the clearances specified in Table 1, Case 2, Columns A. B and C may be reduced and shall be increased accordingly, except that in no case other than provided in these columns shall it be less than 25 feet.  This clearance shall not be reduced for railways which transport or propose to transport standard freight cars.

 

b)    Freight Cars:  Freight Cars measuring 15 feet from the top of the rail to the running board are the basis for the clearances of Table 1, Case 1.  These clearances may be reduced a maximum of 2 feet for cars of a lesser height to afford the same clearance above such cars.

Where freight cars exceed 15-foot dimension above, the vertical ground clearances shall be increased accordingly to provide the same clearances between conductors and top of car.

 

(2)    Trolley Cables:  Cables and messengers which are suitably protected may have a clearance of not less than 4 feet above the trolley contact conductors, providing the clearance above the top of rails is in no case less than 23 feet.  This clearance is dependent upon the ultimate location of the trolley contact conductor.

 

C.    Between Conductors.

 

(1)     Normal:  The normal minimum horizontal and vertical clearances shall be those specified in Rule 36, Table 2.  Notes following this table are references to the rules which modify the normal minimum clearances.

 

(2)    Attached Directly to Poles.

 

a)    Open Wire:  Open wire conductors attached directly to poles (which carry no cross arms) by means of knobs or brackets are not restricted in the use of the 3 feet of the pole next below the topmost conductor.  Below this point (3 feet below the topmost conductor) 6 additional attachments may be made on one side of the pole at intervals not less than 12 inch conductor separation.

One pair of open wire conductors may be attached to opposite sides of the pole below cross arms carrying circuits by means of knobs or brackets at a distance sufficient to provide a vertical clearance of not less than 2 feet between such conductors may be attached to one side of poles by means of knobs or brackets at not less than 12 inch intervals in the space between 2 feet and 8 feet below the conductors supported on the lowest crossarm provided all other clearances are maintained.

Branch lines and service drops from conductors supported by knobs or brackets, as above, may be attached by means of knobs or brackets to the face or back of the pole, but not both.

 

b)    Cables.  (See Rule 87.4-B2.)

 

(3)    Duplex or Triplex.  (See Rule 87.4-B1.)

 

D.    From Poles.

 

(1)    Center Line:  (See Table 1, Case 7.)

 

a)    Exchange:  Exchange Conductors supported by line cross arms shall clear the center line of the pole 15 inches except toll arms used as exchange in the original location and where no buck arm construction is involved.

 

b)    Toll:  Open wire toll, trunk and other line conductors not used for exchange or distribution purposes supported by cross arms shall clear the center line of poles by a horizontal distance of not less than 9 inches.  For exception see Rule 36.

 

c)    Cables:  (See Rule 87.4-D1.)

 

(2)    Surface:  (See Table 1, Case 9.)

 

a)    Open Wire:  The minimum separation of wires from the surface of poles shall be such that suitable insulation is maintained.

 

b)    Cables:  (See Rule 87.4-D2.)

 

E.    From Buildings, Bridges and Other Structures.

The normal minimum clearance of wires from surface of buildings, etc., is given in Table 1, Case 8.

Communication cables ore not required to clear sides of buildings or other structures any specified distance, but they shall be installed so that they do not interfere with the free use of fire-escapes, exits, etc.
  Nothing herein shall prohibit the attachment of such cables to buildings provided they are installed in accordance with the safety orders of the Industrial Accident Commission.

The vertical clearance of 8 feet between communication conductors and buildings (Table 1, Case 6, Column B) may be reduced to 2 feet under the following conditions:

 

Over roofs ¼ pitch (26° from the horizontal or greater,

 

Over buildings where the horizontal overhang does not exceed 6 feet.

 

The 8 foot vertical clearance between communication service drops and buildings (Table 1, Case 6, Column B) need not apply on the premises served.

 

F.    From Guys and Messengers.  (See Rule 86.4-A; also Table 2, Case 16.)

 

G.    From Cross Arms.

The minimum clearance of wires from surface of cross arms is given in Table 1, Case 9.