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7/31/2019 Shop Practice

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NATIONAL ELECTRICAL CODE (NEC) AND PHILIPPINES ELECTRICAL CODE (PEC)

RULES AND REGULATIONS ON DIFFERENT WIRING METHODS

I. NON METALLIC RACEWAY OR WOODEN MOLD WIRING

A. Definition

Non metallic raceway or wooden mold wiring is a

wiring method where conductors are installed in a surface

container which lay out along the surface of ceiling and

walls and not concealed (or not hidden).

B. Use

The use of this wiring shall be permitted only in dry

locations (places not affected by rain or moisture). It

shall not be used, however:

1. When or where concealed.

2. Where subject to severe physical damage unless approved

for the purpose.

3. When voltage is more than 300V between conductors.

4. In hoist ways.

5. In hazardous location.

6. Where subject to ambient temperature exceeding 50C.

C. Size of Conductors

No conductor larger than that for which the raceway is

design shall be installed in non metallic surface raceway.

D. Number of Conductors in Raceway


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The number of conductors installed in any raceway

shall be no greater than the number for which the raceway

is designed.

E. Fittings for Taps and Joints

Any junction point requiring joints and taps shall use

porcelain tee or porcelain cross with base. When junction

points come from one direction from top or from below, the

run wire porcelain tee is used. Where taps come from both

direction, porcelain cross is used.


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F. Need for Porcelain Tube or Flexible Circular Loom

Where conductors are entering switches, convenience

outlet, lamp socket, cutout box, and safety switch shall be

protected by circular loom.

If the wire or wires passing through walls porcelain

tube or circular loom may be used. Where circular loom or

mica tube is used at the end of the wooden mold or raceway

a V cut or M cut must be made the molding end.

G. Wall Switch, Convenience Outlet and Lamp Holder

Wall switch and convenience outlet used must be of the

surface type. In case of the wall switch is must be mounted

on a switch base when installed. The lamp holder used must

be of the cleat type.


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II. OPEN WIRING OR INSULATOR OR EXPOSED KNOB AND TUBE WIRING

A. Definition

Open wiring or insulators is a wiring method usingknob tubes, cleats and flexible tubing for the protection

and support of insulated conductors run is and on building

and not concealed by the building structure.

B. Use

1. The wiring method may be used for or outside the

building.

a. Exposed work, either inside or outside the building.

b. In wet or dry location

c. When subject to corrosive

2. This wiring method, however shall not be used

a. Commercial garage

b. In theater or movie houses

c. In motion picture studios

d. In hazardous location

C. Conductors

Any conductors shall be insulated. Only single

conductor may be used on a knob (split or solid) or tubing

hence conductor such as TW, THW, RW, RHW, etc. are

permitted.

In figuring the ampacities (meaning current carrying

capacity of wire) allowed, the table for copper or aluminum

conductor must be consulted.

D. Supports


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1. Conductor must be separated or must not take contact with

any object over than its insulating supports. The

supports shall be non combustible and non absorptive.

a. Under ordinary conditions and conductor support shall

not be more than 4 feet apart or closer as the

condition warrants.

b. Conductors of number 8 or larger that are installed

across open space where they are not liable to be

disturbed may have the support spaced is feet apart.

However, non combustible, non absorptive support

shall be speed at interval not to exceed 4 feet apart

and a minimum spacing of 2 inch between conductors.

c. In buildings of mill constructions where feeders of

number 8 or longer are used and a minimum spacing 6

between conductors maintained the conductors may be

supported at the timbers only.

2. Exceptions:

a. Approved flexible non metallic tubing may be used to

cover the conductor in a continuous length not to

exceed is 15feet when not exposed to physical damaged

and in a dry location and shall be secured by straps

not more than 4 feet apart.

b. Conductors of number 8 or larger that are installedacross open spaced wire. They are not liable to be

disturbed may have the support spaced is feet apart.

However, non combustible, non absorptive support

shall be speed at interval not to exceed 4 feet apart

and a minimum spacing of 2 inch between conductors.

c. In buildings of mill constructions where feeders of

number 8 or larger are used and a minimum spacing of

6 between conductors maintained the conductors may be

supported at the timbers only.

E. Conductor Separation

1. For voltage not exceeding 300V between conductors

a. A minimum of 2 inches separation between conductors.


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J. Protection from Physical Damage

Open conductors exposed to physical damage they shall

be separated by any of the following:

a. By guard strip not less than inch in thickness and as

high as the insulating support place on each side.

b. By substantial running board at least inch thick or by

wooden molds.

c. By metal strips or metal mold.

d. By conduit pipe in continuous length.

K. Entering Spaces Subject to Dampness

All conductor of open wiring that enter or leave a

damp wet or corrosive space shall have drip loops and the

tube entering the walls shall be non combustible and non

absorptive mounted on a slope so that the moisture will

not enter other parts of the building.


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III. CONCEALED KNOB AND TUBE WIRING

A. Definition

Concealed knob and tube wiring is a wiring methodusing knobs, tube and flexible non metallic tubing for

the protection and support of insulated conductor concealed

or hidden in hallow spaces of walls and ceilings of

buildings.

B. Use

This type of wiring shall be use in hallow spaces of

walls and ceilings it shall not be use in:

1. The commercial garage

2. Theaters

3. Motion picture studios

4. Hazardous location

C. Conductors

The same provision as that in open wiring or

insulator.

D. Supports


insulator.

E. Conductive Separation

a. Conductor shall be separated at least 3 and maintained

at least 1 from the surface wired over.

b. At distributing center outlets, switches or other places

where spaces are limited each conductor shall be encased

in a continuous length of flexible tubing.


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F. Separation from Other Objects and Protections


insulator.

G. Boxes of Insulating Materials

The use of non metallic boxes is permitted. Provided

that the conductors are supplied with in 8 inches of the

box.

H. Switches


insulator.


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IV. METAL MOLD OR SURFACE METAL RACEWAYS

A. Definition

Surface metal raceways provide in wiring method thathas many advantages. This wiring method not intended for

new construction, but is quite valuable in additions to

existing wiring systems that must be expanded without

cutting into the existing building to add conduit and other

component surface metal raceway have been use for many

years and have been found quite satisfactory for the

purpose for which they are intended.

B. Use

Surface metal raceways may be installed in dry

location in most any case except the following:

1. Where concealed except that it may be used for under

paster extensions when approved for that purpose.

2. Where exposed to severe physical damage unless approved

for that purpose.

3. Where the voltage between conductors exceed 300V.

4. Where subject to corrosive vapors.

5. In hoist ways.

6. In hazardous areas.

C. Grounding Metal Enclosures

Metal raceways, boxes, cabinets and fittings shall be

grounded.

D. Electrical Continuity of Metal Raceways Enclosures

Metal raceways or metal enclosures for conductors

shall be metallically joined together into a continuous

electrical conductor.


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E. Secured Place

All raceways, boxes, cabinets and fittings shall be

securely fastened in place with approved screws.

F. Mechanical Continuity of Raceways and Conductors

Raceways and other assemblies shall be continuous from

outlet to outlet and from fitting conductors shall be

continuous between outlet and devices. No splices shall be

permitted in raceways.


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V. ARMORED CABLE OR BX WIRING

A. Definition

Armored cable wiring is a wiring method using afabricated assembly of insulated conductors in a flexible

metallic enclosure.

B. Use

Armored cable wiring may be use in the following:

1. For dry location

2. Under plastic extensions

3. Embedded in plaster finish

4. Embedded in brief or other masonry except in wet or damp

location.

5. May be run or fish in air void, of masonry block of the

walls that are not exposed to moisture or dampness are

below grade lines.

6. In damp places and where exposed to oil or other

conditions that might deteriorate the insulation if thearmored cable is of the ACL type (lead - covered)

Armored Cable may not be use in:

1. Theaters

2. Motion pictures studios

3. Any hazardous locations

4. Crane or hoists

5. Storage battery rooms

6. Where exposed to corrosive vapors

7. To hoist ways of elevators

8. Commercial garage


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C. Types

There are numbers of types of armored cable such as

type AC, type ACL, type ACI, etc.

Armored cables are for branch circuits. This cable are

made of flexible metal type but an internal strips of

bonding composed of copper or aluminum shall be continue

throughout the length and


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D. Conductors

The insulated conductors shall be of the following

types:

1. Rubber

2. Thermoplastic

3. Varnished cloth

4. Asbestos varnished cloth

5. Special type approved for the purpose

E. Supports

All supports for armored cable must be of the approved

type and must be installed so as not to damage the cable.

Armored cable shall be secured at interval not to

exceed 4 feet and within 12 may be extended to not over

24 at terminal where there is a necessity for flexibility.

F. Bends

All bends are to be made so as not to damage the

cable.

The bend radius shall not be less than 5 times the

diameter of the cable.

G. Electrical Continuity of Armored Cable and Enclosures

The armor of armored cable shall be metallically

joined together into a continuous electrical conductor. The

armor covering shall be securely and effectively connected

to boxes fittings and cabinets locknuts and connectors

supply this continuity.

H. Mechanically Continuity of Armored Cable


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D. Wet Locations

All supports volts straps concrete shall be of

corrosion resistant materials or protected against

corrosion by approve corrosion resistant materials. In

exposed work under wet or damp location it is required that

a air space between the conduit system (including boxes

and fittings and the surface wired over).

E. Minimum Sizes

For practical purposes inch trade size rigid conduit

is the smallest allowable however for under plaster

extensions conduit with a minimum inside diameter of 5/16

is permitted in some cases.

F. Number of Conductors in Conduit

A table for a minimum number of conductors in table

sizes of conduit shall be consulted. Example is given below:

Wire

Type

Conductors

Size

1/2 3/4 1 1/4 2 2

TW,

THW

14 9 15 25 44 99 142

RW,

RHW

10

12

8

7

5

2

12

9

4

19

15

7

35

26

12

78

60

28

111

85

40


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VII. Non Metallic Sheated or Loomex Cable Wiring

A. Definition

Non metallic sheated, which is commonly termed asloomex cable is a factory assembly of two or more insulated

conductors having an outer sheat or moisture resistance,

flame retardant or sometimes corrosion resistant, non

metallic material.

B. Use

This type of wiring either for exposed or concealed

wiring it maybe regarded as a substitute for open wiring on

insulator or exposed knob and tube work, and has the

advantages that continuous protection is provided over the

entire length of the conductor. In addition to the

insulation supplied to ordinary thermoplastic were in the

case of armored cable no insulating supports are required

and only one hole need be bared when the cable passes

through a timber.

Insulating bushing or grommets shall be used where the

cable passes through holes in metal part or similar members.

C. Types

Non metallic sheated cable are manufacture in the

following types, type NM which has an overall covering of

the flame retardant materials and the type NMC which has an

overall covering of flame retardant, moisture resistance,

fungus resistant and corrosion resistant materials.

Both types are emitted to be used in one and two

familiar dwelling and other structure exceeding three

floors.

Type NM, non metallic sheated cables are permitted

to be installed for exposed and concealed work in normally

dry location. It is also permissible to be ferned in air

voids, in masonry blocks on tiles, walls where such walls

are not expose on suggested to excessive moisture or

dampness. This cable (type NM) shall not be installed in


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Both types however shall not be use at

1. Service entrance cable

2. In commercial garage

3. In theaters

4. Motion picture studios

5. Hoist ways

6. Hazardous location

7. Embedded in poured cement or concrete

D. Supports

Non metallic sheated cable shall be seaved by wire

staple strap or similar fittings so designed and installed

as not to injured, the cable shall be secured in place at

interval not exceeding 4ft. and within 12 from every

cabinet, box or fittings.

E. Bends

Bends in cable shall be made so that the protective

covering of the loomex not allowed the cable must be

injured. No bends shall have the radius less than five

times the diameter of the cable.


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RULES AND REGULATION ON SERVICE ENTRANCE INSTALLATION

1. Service conditions supplying a building or other structureshall not pass through the other interior or another

building.

2. Service conductors shall normally with stand exposure to

atmospheric and other condition of use without deter mental

lockage of current.

3. Ungrounded conductors of service entrance for limited loads

of a single branch ckt. shall be number 12 or number 1 but

it is no case smaller than the branch ckt. conductors.

4. Service entrance conductor shall not have be splice.

5. Service raceways or tubing shall be equipped with a rain

tight or weather head.

6. Drip loops shall be formed on end service entrance

conductor to prevent entrance of water and moisture.

7. Any service entrance raceway tubing or cable shall

terminate at the


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RULES AND REGULATION ON SERVICE, SWITCH FEEDER AND DISTRIBUTION

BOARD INSTALATION

1. Conductors and bus bars on a distribution board shall be located

as to be free from physical damage and shall be held firmly in

place.

2.The arrangement of bus bars and conductors shall be such as to

avoid over heating due to inductive effect.

3.Feeder conductor shall have an ampacity not lower than required

to apply the load.

4.Feeder conductor shall not be smaller than number 10 where the

load supplies consist of the following number and types of

circuit

a. Two or more two wire branch circuit supplied by a two wire

feeder.

b. More than two wire branch ckt. supplied by three wire feeder.

c. Two or more three wire branch ckt. supplied by three wire

feeders.

5. Feeder conductors ampacity shall not be lower than that of

the service entrance conductor.

6. Service switch, containing the main protective devices such

as fuse or circuit breaker must be installed as near as

possible to the point of entrance.


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