Shop Practice with Electrical
Code: Electrical System Design
(Residential)
Jayson Bryan E. Mutuc, REE, RME BSEE-PUP
TOPICS
• Service Entrance • Electric Meter
• Plans and Specification • Design Analysis
• Branch Circuit Load Calculation
SERVICE ENTRANCE
• It is described as the supply conductors which extends from the street main duct or transformer to the service or switchboard of the building supply.
• Most buildings service entrance are connected to the secondary line low voltage below 600 V.
• It can be 2, 3 or 4 wires including grounded neutral wire. • Size of wires varies depending on demand load
ELECTRIC METER
• It is a device that measures the amount of electrical energy supplied to or produced by a residence, business or machine.
1.3.2.1 Plan Requirements (p.28)
(a) Location and Site Plan (b) Legend or Symbol
(c) General Notes and/or Specification (d) Electrical Layout
(a) Plan for Power
(b) Plan for Lighting and Receptacle Outlets (e) Schedule of Loads
(f) Design Analysis (g) One Line Diagram
(1) Lighting and Receptacle Outlet Load (2) Motor Loads
(3) Feeders
(4) Load Center (h) Title Block
Plans and Specification
(c) General Notes and/or Specification. General Notes and Specifications, written on the plans or submitted on separate standard size sheets shall show:
(1) Nature of Electrical Service, including number of phases, number of wires, voltage and frequency;
(2) Type of Wiring;
a. Service entrance
b. Feeders, sub-feeder and branch circuit for lighting and/or power load
General Notes
1. All electrical works indicated herein shall be done in accordance with the latest edition of Philippine Electrical Code Part 1, the requirements of the local building official and the electric utility serving the area.
2. The electrical supply/service voltage is 230V, single phase, two wires, grounded, 60 Hz. 3. Contractor shall verify and orient the actual locations of concrete terminal.
4. All installation shall be concealed from view, wiring shall be incased in PVC pipe or flexible conduit except power service which shall be in RSC.
5. The minimum size of wire shall be 2-3.5mm2 and 15mmø conduit.
6. All materials shall be new and approved type. Appropriate for both location and intended use.
7. Electrical installation shall be under a direct supervision of duly licensed electrical engineer or registered master electrician.
8. No revision in the design shall be done without the prior knowledge and approval of the designer and the owner.
9. Ground resistance shall not exceed 25 ohms.
10. Mounting heights for switches and convenience outlet shall be in 1.37m and 0.30m respectively, unless otherwise indicated in architectural plans.
Plans and Specification
Legend
- Electrical Symbols
Schedule of Loads
- tabulated information of electrical loads, size of wire and conduit per circuit up to service.
Lighting System Layout
- shows the lighting fixture and switches location and its wiring system.
Power Layout
- shows the location of convenience outlets, special outlets (acu, range, water pump, water heater, etc.), panel board, meter, service head, and their wiring system
Design Analysis
Design Analysis shall be included on the drawings or shall be submitted on separate sheets of standard size, and shall show:
(1) Branch Circuit, sub-feeders, feeders, busways, and service entrance
(2) Types ratings, and trip settings of overload protective device
(3) Calculation of short circuit current for determining the interrupting capacity of overcurrent protection device for residential,
commercial, and industrial establishment (4) Calculation of voltage drops
Branch Circuit Load Calculation
• Lighting Branch Circuit
• Small Appliance Branch Circuit
• Laundry Branch Circuit
Article 2.10 (p.66) – Branch Circuits
2.10.1.3 Rating. Branch
Circuits recognized by this
article shall be rated in
accordance with the
maximum permitted
ampere rating or setting of
the overcurrent device.
Sizing of Conductors and Protective Devices
2.10.2. Branch Circuit Ratings (p.76)
2.10.2.1 (a)(1) Conductors – Minimum Ampacity and Size. General.
Branch Circuit conductors shall have an ampacity not less than the maximum load to be served.
Where a branch circuit supplies continuous loads or any combination of continuous and non continuous loads, the minimum branch circuit
conductor size, before the application of any adjustment or correction factors, shall have an ampacity not less than the non continuous load plus 125 percent of the non continuous load.
Note: same statement as in the Article 2.15 Section 1.2 p.91 For Feeders Minimum Rating and Size
Continuous Load (Art 1.1 p.9) – A load where the maximum current is expected to continue for 3 hours or
Sizing of Conductors and Protective Devices
2.10.2.2 Overcurrent Protection. Branch-circuit
conductors and equipment shall be protected by overcurrent
protective device that have a rating or setting
not greater than
the ampacity of the branch circuit conductors
2.10.2.2 (a) Continuous and Noncontinuous Loads.
Where a
branch circuit supplies continuous loads
or any
combination of continuous and non continuous loads, the
rating of the overcurrent device shall not be less than the
non
continuous load plus 125 percent of the non continuous
2.20.2 Branch Circuit Load Calculations
Lighting Branch Circuit2.10.2.5 (a)(p.81) A 15 or 20 – ampere branch circuits shall be
permitted to supply lighting units or other utilization equipment, or a combination of both.
2.20.2.3 Lighting Load for Specified Occupancies (p.99).
For dwelling units (Based on PEC 2009 Table 2.20.23 [p.100])
Total Lighting Load = Floor area (in sq.m) x 24 VA/sq.m
or sometimes you can use the actual wattage rating of the lighting equipment
The floor area for each floor shall be calculated from the outside dimensions of the building dwelling unit, or other area involved. For dwelling units, the calculated floor area shall not include open porches, garages or unused or unfinished spaces not adaptable for future use
Other Lighting Load Constants
Type of Occupancy Unit Load
Volt-Ampere per Square Meter
Armories, auditoriums, 8
Churches, and Assembly Halls
Banks, Office Buildings 28
Barber Shops, Beauty Parlors, 24
Type of Occupancy Unit Load
Volt-Ampere per Square Meter
Clubs, Court rooms, Hotels, Motel 16
Industrial Building, Hospitals, Restaurants
Garage – Commercial 4
Halls, corridors, closet, Stairways
2.10.1.11 (c)(1) Small-Appliance Branch
Circuit (p.75)
Also known as Convenience Outlet Branch
Circuit.
In addition to the number of branch circuits required,
two or more additional
20 - ampere
small appliance branch
circuits shall be provided for all receptacle outlets
2.20.2.5 (i) Receptacle Outlets (p.101)
receptacle outlets shall be calculated at not less than
180 volt-amperes
for each single or for each multiple
receptacle in one yoke. For four or more receptacle shall be
calculated not less than
90 volt-ampere
per receptacle.
2.10.1.11 (c)(2) Laundry Branch Circuit
(p.75)
In addition to the number of
branch circuits required by
other parts of this section, at
least
one or 20- ampere
branch circuit
shall be
provided to supply the
laundry receptacle outlet(s).
This circuit shall have no
other outlets.
Branch Circuit Rating:
1500
VA
4.30.2 Motor Circuit Conductors (p.684)
4.30.2.2 (a) Single Motor
(p.685). Conductors that
supply a single motor used in
a continuous duty application
shall have an ampacity of not
less than
125 percent of the
motors full load current
4.30.4 Motor Branch-Circuit Short-Circuit
and Ground Fault Protection (p.698)
4.30.4.2 Rating or Setting for Individual Motor Circuit.
(b) The motor branch-circuit short-circuit and
ground fault protective device shall be capable of carrying the starting current of the motor.
(c) In Accordance with Table 4.30.4.2 A protective
device that has a rating or setting not exceeding the value calculated according to the values given. In Table 4.30.4.2 shall be used
Table 4.30.4.2 Maximum Rating or Setting of Motor Branch-Circuit Short Branch-Circuit and Ground Fault Protective Device
Type of Motor
Percentage of Full Load Current Nontime Delay Fuse Dual Element (Time-Delay) Fuse Instanta neous Trip Breaker Inverse time Breaker Single-phase motors 300 175 800 250
2.20.3 Feeder and Service Load Calculations
(p.103)
2.30.3.1 General. The calculated
load of a feeder or service shall not be less than that the sum of the loads on the branch circuit supplied, after any applicable demand factors have been applied
2.20.3 Feeder and Service Load Calculations
2.20.3.3 General Lighting (p.103)
The demand factors specified in the Table 2.20.3.3 shall apply to that portion of the total branch circuit load calculated for general illumination. They shall not be applied in determining the number of branch circuit for general illumination
Table 2.20.3.3 Lighting Load Demand Factors (p.104)
Type of Occupancy
Portion of Lighting load Which Demand Factor Applies (Volt-Amperes) Demand Factor (Percent) Dwelling Units First 3000 or less at From 3001 to 120,000 at Remainder over 120,000 at 100 35 25
2.20.3 Feeder and Service Load Calculations
2.20.3.13 Small-Appliance and Laundry Loads – Dwelling
Unit (p.105)
(a) Small Appliance Circuit Load. In each dwelling unit, the
load shall be calculated at
1500 volt-amperes
for each
2-wire small appliance branch circuit required by 2.10.1.11
(c)(1)
(b) Laundry Circuit Load. A load not less than
1500
volt-amperes
shall be included for each 2-wire laundry branch
circuit installed as required by 2.10.1.11 (c)(2)
These loads shall be permitted to be included with the
general lighting load and subjected to the demand factors
provided in Table 2.20.3.3
2.20.3 Feeder and Service Load Calculations
2.30.3.11 Motors (p.105)
Motor loads shall be calculated in
accordance with 4.30.24
4.30.2.4 Several Motor or a Motor(s) and Other
Load(s)(p.687).
Conductors supplying several motors, or a motor(s) and other
load(s). Shall have an ampacity not less than
125 percent
of
the full-load current rating
of the highest motor plus
the sum
of the full load current ratings of all the other motors in the
group, plus the ampacity required for other loads.
Feeder Conductor Size = [125% FLA of Highest Motor load]+
[Sum of other connected loads]
2.20.3 Feeder and Service Load Calculations
4.30.5.3 Rating or Setting – Power and Lighting Loads (p.706)
Where a feeder supplies a motor load and in addition, a
lighting or a lighting and appliance load, the feeder protective
device shall have a rating sufficient to carry the
lighting or
lighting and appliance load plus the largest rating or setting
of the branch-circuit short-circuit and ground fault protective
device for any motor supplied by the feeder.
Overcurrent Protective Device Rating = [OCP rating of Highest
Motor load] + [Sum of the other connected loads]
Branch Circuit, Individual (Art 1.1) (p.7)
A Branch Circuit that supplies only one utilization equipment (ACU, Range, Water Heater, Water Pump, etc.)
Most Common Rating
Range: 8000 W
Water Heater: 5000 W
For Motors (see table 4.30.14.2 (p.732)) 1 Hp at 230 V = 8 A
1 ½ Hp at 230 V = 10 A 2 Hp at 230 V = 12 A
Range @ 8000 W computed @ 80% DF (see table 2.20.3.16(p.108)) ACU or motor load computed @ 100% DF
STANDARD RATING OF CIRCUIT BREAKERS
AT (AMPERE TRIP) AF (AMPERE FRAME)
15 50 20 50 30 50 40 50 50 50 60 100 70 100 80 100 90 100 100 100 110 225 125 225 150 225 175 225
Allowable Ampacities of Insulated Conductors Rated 0 Through
2000 Volts, 75°C Not More Than Three Current-Carrying
Conductors in Raceway, Cable, or Earth
Size (mm2) TYPE (THWN) Ampacity (A)
2.0 20 3.5 25 5.5 35 8.0 50 14 65 22 85 30 110 38 125 50 145 60 160 80 195
Some Conductor data's
Trade Name
Type Letter
Maximum
Operating
Temperature
Application
Provisions
Moisture – resistant ThermoplasticTW 60°C Dry and Wet
Location Moisture – and heat
resistant thermoplastic
THW or THWN 75°C Dry and Wet
Location Heat Resistant
thermoplastic
THHN 90°C Dry and Damp
Number of Conductors (THWN,THHN) in Rigid PVC Conduit Conductor Size (mm2) Trade Size (mm) 15 20 25 32 40 50 65 2.0 9 17 28 51 70 118 170 3.5 6 12 20 37 51 86 124 5.5 4 7 13 23 32 54 78 8.0 2 4 7 13 18 31 45 14 1 3 5 9 13 22 32 22 1 1 3 6 8 14 20 30 1 1 2 4 6 10 14 38 0 1 1 3 4 7 10 50 0 1 1 2 3 6 9 60 0 1 1 1 3 5 7 80 0 1 1 1 2 4 6
2.50.6.13 Size of Equipment Grounding
(Bonding) Conductor (p.240)
2.50.6.13 (f)(1) Based on Rating of Overcurrent Protective Device.
Each parallel equipment
grounding conductor shall be sized on the basis of the ampere rating of the overcurrent
protecting the circuit conductors in the raceway or cable in
Table 2.50.6.13 Minimum Size Equipment
Grounding Conductors for Grounding Raceway
and Equipment (p.241)
Minimum Size Equipment Grounding Conductors
Rating or Setting of Overcurrent Device in Circuit Conductor Size (mm2) 15 2.0 20 2.0 30 2.0 40 3.5 60 5.5 100 8.0 200 14
Sizing of Service Entrance Conductors
Size of Service Entrance Conductors
= sum of the computed load + 25% of the largest motor FLA
Size of Service Equipment
= largest motor protective device + sum of ampere rating of remaining branch circuit
Sample Computation
Ex. Single Family Dwelling Unit
The dwelling has a floor area of 145 m2. It has the typical household
appliances including one 8-kW electric range, two 1-Hp room air-conditioning unit, 1.5-Hp room air air-conditioning unit, and one 1-Hp water pump.
Total Load
a) General Lighting
145 m2 x 24 VA/ m2 = 3480 VA
The computed load is 3480 VA/230 V =15 A
One branch circuit of 20-ampere would be theoretically adequate, however for the flexibility and to allow future needs provide two 20 ampere branch circuits for lighting and convenience outlet.
b) Small Appliance Load
One 20-ampere @ 1500 VA = 1500 VA
Provide one 20-ampere small appliance circuit c) Laundry Circuit
One 20-ampere @ 1500 VA = 1500 VA
Provide one 20-ampere laundry circuit
Sub-Total = 6480 VA
Application of Demand Factors
First 3000 VA @ 100% DF = 3000 VA Remainder @ 35% DF
Other Loads:
One 8-kW electric range @ 80% = 6400 VA Provide one 40-ampere electric range circuit
Two 1-Hp room acu, 8A x 230V x 2
@ 100% DF = 3680 VA Provide two 30-ampere room acu circuits
One 1.5-Hp room acu, 10A x 230V
@ 100% DF = 2300 VA Provide one 30-ampere room acu circuit
One 1-Hp water pump, 8A x 230V
@ 100% DF = 1840 VA Provide one 30-ampere water pump circuit
Circuit Requirement:
Use two 20-ampere 2-wire branch circuits, two 20-ampere 3-wire branch circuits,
four 30-ampere 3-wire branch circuits, and one 40-ampere 3-wire branch circuit.
Service Entrance Conductors: Total Full Load Current:
[18438 + 25%(2300)] / 230V = 83 Amperes Use 2-38mm2 + 1-8.0mm2 THWN wire
Service Equipment:
Maximum Current Rating of Protective Device
Inverse Time Circuit Breaker:
[3000 VA + 1218 VA + 6400 VA + 3600 VA + 250%(2300 VA) + 1840 VA] / 230 V
= 95 Amperes
Service Equipment Rating: