This document provides guidelines for circuit wiring in residential buildings according to the National Electrical Code (NEC). It discusses requirements for branch circuit ampacity and sizing, circuit breaker sizing, wire sizing, circuit load limits, minimum circuiting requirements, and guidelines for specific circuits and areas like kitchens, laundries, and bathrooms. Safety features like ground-fault circuit interrupters (GFCIs) and arc-fault circuit interrupters (AFCIs) that must be installed on certain circuits are also covered.

1. BRANCH
CIRCUIT

2. WIRE AMPACITY AND SIZE
• Maximum loading for any branch
circuit is 80% of rating of circuit for
ampacity of wire for any load
• If circuit is loaded up to ampacity
and distance to load is around 100
feet, then voltage drop will govern
and will require larger wire size.

3. WIRE AMPACITY AND
SIZE

4. CIRCUIT BREAKER SIZE
• Maximum loading of any circuit breaker is
80% of rating for non-motor loads with
exceptions as noted below. Breaker cannot
be larger than ampacity of wire, except for
motors and a few other loads.

5. CIRCUIT BREAKER SIZE

6. WIRE SIZE

9. CIRCUITING
GUIDELINES (NEC)
• Sufficient circuitry to supply
residential load of 30 watts per
square meter in buildings excluding
porches, garages and basements
• The requirement of 30 watts per
square meter is up to 80 sq.m. for a
20 amperes circuit (2,400 watts) or
60 sq.m. for 15 amperes circuit
(1,800 watts)

10. • The load should ne exceed 1,600 watts
for 20 amperes circuit and 1,200 watts for
a 15 amperes circuit.
• Observe a minimum load of 1,200 watts on
a 15 ampere circuit with a maximum area of
40 square meters.
• A maximum load of 1,600 watts on a 20
amperes circuit with a maximum area of 53
square meters
CIRCUITING
GUIDELINES (NEC)

11. • A minimum of 20 amperes appliance
branch circuit to feed all small
appliance outlets in the kitchen,
pantry, dining and family room
• The general purpose branch circuit
shall be rated at 20 amperes circuit,
wired with no. 12 AWG as minimum
size of conductors required for all
convenience outlet
CIRCUITING
GUIDELINES (NEC)

12. • Circuit load on a 15 ampere circuit shall
be limited to values given below
Branch Circuit Capacity – Electric Heater
CIRCUITING
GUIDELINES (NEC)
Circuit Breaker
size
Maximum Wattage
120 Volts Supply 240 volts
Supply
15 amps 1440 2880
20 amps 1920 3840
30 amps 2880 5760

13. BRANCH CIRCUIT
REQUIREMENTS
15 amps 20 amps 30
amps
40 amps 50 amps
Maximum size of
conductors
# 14 # 12 # 10 # 8 # 6
Maximum size taps 14 14 14 12 12
Over current device
rating
15 amps 20 amps 30
amps
40 amps 50 amps
Lamp Holders
permitted
Any
type
Any type H-Duty H-Duty H-duty
Receptacle rating
permitted
15 amps 15-20
amps
30
amps
40-50
amps
50 amps
Maximum Load 15 amps 20 amps 30
amps
40 amps 50 amps

14. • Plug outlets or convenience outlet shall be
counted in computing the load if it is not
included in the load for general lighting circuit.
• For 15 amps circuit = 9/1.5 = 6 outlets
• For 20 amps circuit = 12/1.5 = 8 outlets
• Convenience receptacles should be planned
properly so that in case of failure by any one of
the circuitry, the entire area will not be deprive
of power supply. Each area should be provided
alternately with different circuits.
CIRCUITING
GUIDELINES (NEC)

15. • All kitchen outlets should be fed
from at least two of convenience
receptacles.
• Certain outlets in the room should
be designed as appliance outlet like;
•All kitchen receptacles
•Dining room receptacles
•One in the living room
CIRCUITING
GUIDELINES (NEC)

16. • At least one 20 amps circuit supplies
the laundry outlets
• Provide a separate circuit for an air
conditioning unit
• Lighting and receptacles should not be
combined in a single circuit
• Avoid connecting all building lights on
a single circuit
CIRCUITING
GUIDELINES (NEC)

17. • Lighting and receptacles should be
supplied with current from at least two
circuits so that, if a single line is out, the
entire area in not deprived of power
• Do not allow combination switch and
receptacle outlets
• Provide at least 1 receptacle in the
bathroom, and outside the house with
GFCI type.
CIRCUITING
GUIDELINES (NEC)

18. • Provide switch control for closet lights.
• Convenience outlet must be limited to 6 C.O
on a 15 ampere circuit and 8 C.O on a 20
amperes circuit
• At least one 20 Amperes circuit supply shall
be installed to the laundry outlets
• C.O shall be laid out in such a manner that
no point on a wall is more than 2 meters from
an outlet with GFCI type used.
CIRCUITING
GUIDELINES (NEC)

19. OTHER
GUIDELINES

20. SPACES ABOUT ELECTRICAL EQUIPMENT –
ENTRANCE TO AND EGRESS FROM
WORKING SPACE – PERSONNELDOORS
Dedicated equipment space shall be provided for
switchboards, switchgear, panel boards, and
motor control centers installed in outdoor
locations.
The space shall be equal to the width and depth
of the equipment and extend from grade to a
height of 6 ft above the equipment.

21. WHAT ARE THE WORKING SPACE AND
DEDICATED EQUIPMENT SPACE
REQUIREMENTS FOR OUTDOOR
ELECTRICAL EQUIPMENT?
3-4 ft deep,
depending on the
voltage and other
conditions; the
greater of 30 in. or
the width of the
equipment; and the
greater of 6½ ft or the
height of the

22. NEUTRAL CONDUCTORS
– MULTIPLE CIRCUITS
Significance
Neutral conductors are generally not
protected by overcurrent devices. It is
necessary to be able to correctly identify
circuit conductor pairs (grounded and
ungrounded conductors of the same circuit)
when splicing and terminating conductors
to prevent overloading and mis-wiring.

23. IS THERE A NEUTRAL CONDUCTOR IN A 2-WIRE DC
CIRCUIT (POSITIVE AND NEGATIVE POLARITY) THAT
IS NOT “EARTHED” AT ANY POINT
No, regardless of whether the circuit
has either polarity connected to earth.
A conductor connected to earth is a
grounded conductor. A 3-wire, DC
system contains a neutral point (at its
mid-point).

24. GROUND-FAULT CIRCUIT-
INTERRUPTER PROTECTION FOR
PERSONNEL – DWELLING UNITS –
BATHTUBS OR SHOWER STALLS
In dwelling units, all 125-220 volt, single-
phase, 15- and 20-ampere receptacle
outlets installed within 6ft of the outside
edge of a bathtub or shower stall shall be
GFCI protected.

25. GROUND-FAULT CIRCUIT-
INTERRUPTER PROTECTION FOR
PERSONNEL – DWELLING UNITS –
LAUNDRY AREAS
All 125-240 volt, single-phase,
15- and 20-ampere receptacle
outlets installed in dwelling unit
laundry rooms or areas shall be
GFCI protected.

26. GROUND-FAULT CIRCUIT-
INTERRUPTER PROTECTION
FOR PERSONNEL – OTHER THAN
DWELLING UNITS
All 125-250 volt, single-phase, 15-
and 20-ampere receptacles installed
in nondwelling garages, service
bays, and similar areas shall have
GFCI protection for personnel.
Vehicle showrooms and exhibition
halls are exempt from the GFCI
requirement.

27. GROUND-FAULT CIRCUIT-
INTERRUPTER PROTECTION FOR
PERSONNEL – KITCHEN
DISHWASHER BRANCH CIRCUIT
Dishwashers in dwelling
units shall be GFCI
protected.

28. The requirement for AFCI protection for 120-
250 volt, single phase, 15- and 20-ampere
branch circuits in dwelling units has been
expanded to include all such circuits in
kitchens and laundry areas.
The only branch circuits that are exempt
from AFCI protection: bathrooms, garages,
outdoors, and basements
Arc Fault Circuit-Interrupter
(AFCI) Protection – Dwelling
Units

29. ARC-FAULT CIRCUIT-INTERRUPTER
PROTECTION – BRANCH CIRCUIT
EXTENSIONS OR MODIFICATIONS —
DWELLING UNITS
AFCI requirements are not applicable to
dwelling unit branch circuit extensions,
where the circuit extension is not more than
6′ in length and no additional outlets or
devices are added to the existing branch
circuit.

30. ARC FAULT CIRCUIT-
INTERRUPTER (AFCI)
PROTECTION – DWELLING
UNITS

31. ARC FAULT CIRCUIT-
INTERRUPTER (AFCI)
PROTECTION – DWELLING
UNITS