David Marne

1Copyright © 2007 Marne and Associates, Inc. (with Permission from the McGraw-Hill Companies, Inc.)

All Rights Reserved – Do Not Duplicate.

National Electrical Safety Code® (NESC®) Rules for

Joint Use Construction

Marne and Associates, Inc.

Experts in Electrical Code

619 S.W. Higgins, Suite C

Missoula, MT 59803

(406) 544-8997

www.marneassociates.com

David J. Marne, P.E. Grant D. Glaus, P.E.



Section 01. Introduction

• Rule 011. Scope

• Used by engineers and linemen

• Administrative authority is

typically the state public service or

utility commission.

• Used by engineers and electricians

• Administrative authority is typically a

state, city, or local electrical

inspector.



NESC® Rules for Joint Use Construction

• Joint Use

– NESC defines joint use as simultaneous use by two

or more kinds of utilities.

– Power and

communications.



Part 2. Overhead Lines

WORK RULES

UNDERGROUND LINES

PART 4

OVERHEAD LINES

PART 3

ELECTRIC SUPPLY STATIONS

PART 2

PART 1

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INFO General

SAG chart needed to check clearance?

YES NO

Clearances of supporting structures from other objects

NOYES

Vertical clearances of wires, conductors, cables, and equipment above ground, roadway, rail, or water surfaces

RULE 232YES NO

RULE 230

RULE 231

Clearances between wires, conductors, and cables carried on different supporting structures

RULE 233YES NO

Clearances of wires, conductors, cables, and equipment from buildings, bridges, rail cars, swimming pools, and other installations

RULE 234YES NO

Section 23. Clearances




Clearance for wires, conductors, or cables carried on the same supporting structure

RULE 235YES NO

Climbing spaceRULE 236YES NO

Working spaceRULE 237YES NO

Vertical clearance between certain communications and supply facilities

RULE 238YES NO

Clearance of vertical and lateral facilities from other facilities and surfaces on the same supporting structure

RULE 239YES NO



• Clearances are based on:

– Reference component.

– Mechanical and electrical component.





• 235C4. Communication

Worker Safety Zone

– Rules 235C and 238 create a communication worker safety

zone.

– No supply or communication facility may be located in the

communication worker safety

zone except as allowed by Rules 238C (light fixtures and traffic

signals), 238D (light fixture and

traffic signal drip loops), and 239 (vertical risers).




• Clearance from supply conductors

– NESC Table 235-5

• 40 in

– Rule 235C2b(1)(a)

• 75% of that required at

the pole

– Rule 238

• No hardware in

communication work safety zone

30"

40"

12.47/7.2 KV, 3Ø, 4Wdistribution line

Comm

unica

tion

Comm

unica

tion

Cable

TV

Telep

hone



Comm

unica

tion

Comm

unica

tion

Cable

TV

Telep

hone

distribution line24.94/14.4 KV, 3Ø, 4W

43"

33" • Clearance from supply conductors


• 40 in plus 0.4 in per kV

over 8.7kV

– Rule 235C2b(1)(a)

• 75% of that required at the pole

– Rule 238

• No hardware in communication work

safety zone





• Clearance from a neutral

in the supply space


• 30 in at the pole

– Rule 235C2b(1)(a)

• 12 in in span (by

exception)

– Rule 238

• No hardware in communication work

safety zone

12"

30"

Effective

ly grou

nded

neutral (

230E1)

Commu

nicatio

n Com

munica

tion

Cable T

V

Teleph

one




30"

40"Effectively grounded

neutral (23

0E1)

12.47/7.2 kV, 3Ø, 4W distribution line

Comm

unica

tions

(Tele

phone)

Comm

unications

(Cable TV)

120/2

40V, 1Ø

, 3W

secondary

triple

x (230C3)

• Clearance from secondary


• Clearance at the pole

– Rule 235C2b(1)(a)

• 75% of that required

at the pole

– Rule 238

• No hardware in

communication work safety zone



• Rule 235H. Clearance and spacing between

communication conductors, cables, and equipment

– The spacing between

communication messengers

should not be less than 12 inches.

– The clearance between the

conductors, cables, and

equipment of one communication utility to those of

another shall not be less than 4

inches anywhere in the span.

– Both requirements may be reduced by agreement of the

parties involved.

Communications

(Cable TV)

Communications

(Telephone)





• Rule 235I. Clearances in any

direction from supply line conductors to communication

antennas in the supply space attached to the same

supporting structure

– Antennas should be installed and maintained only by

personnel authorized and

qualified to work in the supply space

– The clearance between a

communication antenna

operated at a radio frequency of 3 kHz to 300 GHz and a supply

line shall be not less than

specified in Table 235-6, row 1b.

– See Rule 420Q




• Rule 235I. Clearances in any

direction from supply line conductors to communication

antennas in the supply space attached to the same

supporting structure




• 238E. Communication

Worker Safety Zone

– Rules 235C and 238 create a communication worker safety

zone.

– No supply or communication facility may be located in the

communication worker safety

zone except as allowed by Rules 238C (light fixtures and traffic

signals), 238D (light fixture and

traffic signal drip loops), and 239 (vertical risers).




• Table 238-1

– Row 2

Telephone

CATV

40"

Highest communications equipment


Lowest supply equipment



• Table 238-1

– Row 3


Telephone

CATV


43"






Telephone

CATV

30"


Effectively grounded neutral (230E1) • Table 238-1

– Row 1





Highest communicationsequipment


CATV

Telephone

40"

• Table 238-1

– Row 2




• Table 238-1

– Row 2



• Rule 239G. Requirements for vertical

supply conductors and cables passing through the communication space on

jointly used line structures

– Conduit must guard the supply cable:

• 40” above the highest communication

attachment.

• 6’ below the lowest communication attachment.

– Rule 239D requires guarding within 8’ of the

ground.

40"

6’

8’





• Rule 239G. Requirements for vertical supply …



• Rule 239G. Requirements for

vertical supply …

– 40” clearance required from highest communication

equipment to top of secondary

riser.

40" min.





• Rule 239G. Requirements for

vertical supply …

– 40” clearance required from highest communication

equipment to top of secondary riser.



Strength and Loading

• Section 24 – Grades of construction

• Section 25 – Loadings for Grades B and C

• Section 26 – Strength requirements

• Section 27 – Line insulation



Part 3. Underground Lines

WORK RULES

UNDERGROUND LINES

PART 4

OVERHEAD LINES

PART 3


PART 2

PART 1

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Section 32. Underground conduit systems

• Rule 320B2. Separation

between supply and communication conduit

systems

– Conduit systems to be occupied by communication lines shall be

separated from conduit systems

to be used for supply systems by not less than

• 3 in of concrete

• 4 in of masonry

• 12 in of well-tamped earth

3"

12"

4"



• Table 353-1

– No burial depths are specified for communication cables, however, the burial depth must be “sufficient to protect the cable from damage” per Rule

352D1.

– NESC® Table 353-1 applies to direct-buried supply cables only

Supply cable601V − 50KV

Over 50KVSupply cable

0−600VSupply cable

24"30"

42"

Any surface

CommunicationCable

Rule 352D1

Section 35. Direct buried cable



Part 4. Work Rules

WORK RULES

UNDERGROUND LINES

PART 4

OVERHEAD LINES

PART 3


PART 2

PART 1

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Supply

AND

Communications

General Rules for Employees

Employee Employee

ELECTRIC COMPANY

Supply and Communications SystemsRules for Employers

AND

COMMUNICATIONSCOMPANY

Additional Rules for Communications Employees

Communications Employees Only!

Additional Rules for Supply Employees

Supply Employees Only!

Section 41 Section 42

Section 44Section 43

Part 4. Rules for the Operation of Electric Supply and Communications

Lines and Equipment



Section 43. Additional rules for communication employees

• Rule 431. Approach to

energized parts

– No employee shall approach, or

bring any conductive object, closer to exposed energized

parts than the distances shown

in Table 431-1

– Treat all supply lines and equipment as energized unless

they are deenergized and grounded following the rules in

Section 44



Section 43. Additional rules for communication employees



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