Residential Electrical

2. Chapter 28 Residential Electrical

3. Objectives • Explain the characteristics of electricity in terms of amperes, volts, resistance, and watts. • Describe how electricity is delivered to and distributed through residential structures. • Identify the three types of branch circuits used in a residential structure. • Calculate circuit requirements for a residence.

4. Objectives • Describe the types of outlets and switches. used in a residence and their typical locations. • Explain the advantages of low-voltage exterior lighting.

5. Introduction • Planning for electrical needs of home requires basic understanding of: • Related terms • Electrical requirements • Code restrictions • Safety considerations

6. Electrical Terms • Ampere (amp) • Ohms • Voltage • Volt • Watts • Amp  Volts = Watts

7. Service Entrance andDistribution Panel • Service entrance • Fittings and conductors that bring electricity into building • Distribution panel • Receives electricity and distributes it to various points in house through individual circuits

8. Service Entrance andDistribution Panel • Circuits consist of conductors that permit flow of electricity • Distribution panel also contains main disconnect switch fuse or breaker

9. Service Entrance Equipment • Residence may have 120- or 240-volt service • Two conductors required for 120-volt service • Three conductors required for 240-volt service • 240-volt service is recommended

10. Service Entrance Equipment • Incoming electrical service usually enters house through meter • Service may be overhead or underground • Conductors are generally run from service drop or from underground cable through run of heavy conduit

11. Underground Service Layout

12. Overhead Service Layout

13. Service Entrance Designs • Service head is used if service entrance is located along eaves line of single-story home • Service drop must be: • At least 10 above grade at service entrance • 12 above residential property and driveways • Conductors must be at least 3 away from structures where they may be touched

14. Conductor Sizing • Conductors bring current from service head or underground cable to meter and then to distribution panel • Conductor diameter increases as designation number decreases

15. Conductor Sizing • Smallest circuit conductor permitted by NEC is 14 AWG • 12 AWG is recommended for branch lighting circuits • If wire is too small for current, fire may result

16. Distribution Panel • Conductors from meter run to distribution panel • Electricity is distributed to various points in house through branch circuits • Distribution conductors are color-coded • NEC recommends minimum of 100-amp service

17. Typical Distribution Panel

18. Circuit breaker Found in most new homes Can be reset Overcurrent Protection • Fuse • Fusible link • Cannot be reused

19. Branch Circuits • Branch circuits • Lighting circuit • Small-appliance circuit • Individual circuit

20. Lighting Circuits • Serve permanently installed lighting fixtures and outlets for amps, radios, TVs, etc. • Frequently 12 AWG copper wire conductor with 20-amp overcurrent protection • Three watts of lighting power per sq. ft. of floor space is required • One lighting circuit for each 400 sq. ft. is good rule of thumb

21. Small-Appliance Circuits • Located in the kitchen, garage, or shop • Usually above a countertop or workbench • Designed for tools and appliances that require large amounts of current • Electric fry pans, blenders, electric drills, power hand saws

22. Small-Appliance Circuits • 12 AWG copper wire with 20-amp overcurrent protection • Lighting outlets should not be operated from these circuits • NEC requires at least two small-appliance circuits in kitchen

23. Examples: Air conditioner Clothes washer Dishwasher Furnace Range Table saw Water heater Individual Circuits • Serve single, permanently installed appliances or equipment • Each appliance has its own circuit

24. Individual Circuits • Any 120-volt, permanently connected appliance that is rated over 1400 watts or starts automatically must also have its own circuit • Individual circuits may be 120 or 240 volts

25. Circuit Requirement Calculations • Several factors affect size of service entrance and number of branch circuits • Size of house • Size and number of appliances • Lighting to be installed • Planned future expansions

26. Circuit Requirement Calculations Example • Size of residence = 1500 square feet • Lighting circuits: (3 × 1500 = 4500 watts) • Small-appliance circuits: 2 for kitchen (120 volts x 20 amp × 2 = 4800 watts) • Individual circuits: 7 circuits (totaling 22,000 watts) • Total = 31,300 watts/240 volts = 130.4 amps • House will require 150 amp service

27. Employability • Professional language • No slang or profanity • Workplace communications should be polite, grammatically correct, and respectful • Professional language is essential to employability and workplace success

28. Outlets and Switches • Outlets, switches, and joints where conductors are spliced must be housed in electrical box • Lighting fixtures must be mounted on box

29. Outlets • Lighting outlet • Receptacle outlet • Also called receptacle or convenience outlet • General-purpose • Special-purpose outlet • Examples: Telephone jacks, TV outlets, burglar alarm systems

30. GFCI • Ground-fault circuit interrupter (GFCI) • Safety device that continually monitors flow of current in circuit • GFCI responds in 1/30th of a second • GFCIs can be placed as any receptacle • NEC defines when and where GFCIs are used

31. Outdoors All receptacles that are readily accessible Unfinished basements and crawl spaces All receptacles except for receptacle supplying permanently installed alarm system GFCI Locations • Kitchen • All receptacles serving countertop surfaces • Bathroom • All receptacles • Garage • All receptacles

32. Switches • Single-pole switch • Three-way switch • Allows fixture to be switched from two locations • Dimmer switch

33. Locating Outlets and Switches • Placement is affected by codes, furniture arrangements, and personal preference • NEC requires that no point along a wall should be more than 6′ away from a receptacle outlet • 8′ is recommended

34. Locating Outlets and Switches • Receptacle outlets: • 12" or 18" above floor, except for kitchen • Switches • 48" above floor, in a logical place • 30" to 40" is preferred for wheelchair users • Do not mount in inaccessible locations • Do not locate bathroom switches within reach of bathtub or shower

35. Low-Voltage Exterior Lighting • Good outdoor lighting is both functional and aesthetic • Low voltage lighting system consists of lights, wire, one or more controllers, and transformers • More expensive than 120-volt lighting, but safer and easier to install

36. Planning Low-VoltageExterior Lighting • Decide where light is needed for safety, security, and activities • Then plan for decorative lighting • Try to avoid glare • Outdoor light fixtures are either decorative or hidden

37. Planning Low-VoltageExterior Lighting • Use shielded fixtures to hide light source • Hide fixtures where they cannot be seen • Use more, smaller lights • Remember safety when planning lighting • Use light to shape an outdoor space

38. Low-Voltage Wiring Considerations • Lights farther away from transformer produce less light due to voltage drop • Put no more than 100 watts of lighting on one leg of tee

39. Low-Voltage Wiring Considerations • Choose proper size transformer • Use GFCI receptacle as power source • Consider indoor switch and timer combination • Try to prevent corrosion before it starts • Call utility company before digging

40. Low-Voltage Wiring Considerations • Leave a little extra wire in layout • After checking entire setup, bury wires at least 6" deep

41. Architecture Green • Passive energy sources • Solar, wind, or geothermal • Research what systems are available • Check code restrictions • May cost more but can be much more sustainable