1. 1) What is the NEC? A.National Electrical Code B.National Electrical Corporation C.A kind of cookie D.National Energy Code

2. Objectives Use CPS website - Copernicus Submit ASHRAE form and get textbook Understand grade on homework 0 and quiz 1 Complete homework 1 Size residential electrical system (NEC 220- 30) List differences between residential and commercial systems

3. Copernicus http://utwired.engr.utexas.edu/cps/ Questions and answers Absences and lates

4. ASHRAE Can still bring it to me if you want a copy You are responsible for sending it in and following up with ASHRAE Chapter is Austin Don’t worry about UT address (zip = 78712) 3 options for handbook (IP, SI, CD) Money that you send ASHRAE needs to include $16 dues

5. Quiz 1 and HW 0 Both graded Solutions to Quiz 1 on class website Grader very generous and I upped grade in a few cases (avg. ?, st. dev. ?) Will give back at end of class Can drop lowest grade HW 0 (avg. ?, st. dev. ?) Come see me to see your score (I will not hand back until end of semester) Extremely generously graded

6. Residential Systems Very little variation Many similarities to commercial buildings Particularly as you get close to end uses Need to be watchful for unusual circumstances

7. Procedure 1.Analyze building needs 2.Determine electrical loads 3.Select electrical systems 4.Coordinate with other design decisions 5.Prepare plans and specifications

8. List of needs Appliances (incl. HVAC) Receptacles Ground fault protected (GFI/GFCI) Switched Lighting Switches Ceiling Fans

9. Example House Master Bedroom Bathrooms Entry and Outdoor (AC compressor) Bedrooms Dining and Mechanical Closet (resistance heat) Kitchen (appliance circuits, range, oven) Family Garage/Laundry/Closet (resistance water heater, dryer)

11. 2) Where are receptacles grounded? A.Kitchen near sink only B.Kitchen, bathroom only C.Kitchen, bathroom, outside only D.Bedrooms

12. Ref: Tao and Janis (2001)

15. 3)Why do we include 65% of the heating electrical load and 100% of the air conditioning load ? A.Air conditioning happens during periods of peak electrical demand. B.Other electrical uses contribute to heating and not to air conditioning. C.Furnaces are often more closely sized to match the heat loss of a house. D.The NEC was designed for homes in Southern climates.

16. 4)A residential electrical system is sized to meet: A.40% of the maximum load B.50% of the maximum load C.More than 50% of the maximum load D.It depends.

17. Summary Include enough capacity for heating and cooling Work through kitchen and then other rooms Include any items that are unusual Take first 10 kVA and then 40% of remaining load

18. Commercial buildings-Differences 5)Why do you specify conduit for all conductor in commercial buildings A.Three phase power requires conduit B.Higher voltage requires conduit C.Conduit looks pretty D.No NMC wiring allowed

19. Other differences? Three phase Multiple panels More attention to expansion possibilities More voltage levels available

20. Typical Building Electrical Services Voltage/Phase [V] Current [A] Building Type 120/240 1  120/208 1  <200Residential 120/240 3  120/208 3  200-800Small Commercial 240/480 3  277/480 3  347/600 3  400-2000Large Commercial 5-15 kVVery lowVery Large Commercial

21. Building Needs: Lighting and Duplexes Lighting Typically use lighting power densities for building type Sometimes actual lighting load Requires neutral Duplexes NEC/local electrical code specifies number that are required for different applications Requires a transformer Requires neutral wire

22. Building Needs: HVAC/Other/Auxiliary HVAC from system sizing Don’t forget fans, reheat coils, etc. Building equipment Transportation (elevators etc.) Food service Specialty uses No neutral conductor on power panel typically Auxiliary Energy management, security and safety, data transfer, telecommunications

23. Selecting Electrical Systems MLO/MCB Aluminum wiring

24. Duplexes (receptacles) Main Lugs Only (remote protection) Phase total 60 kVA, 14kVA (neutral) 30 poles Panel D

25. 6) How do you calculate current flow through a neutral conductor in a 3  system? A.I =√3 E P B.I =P/ (√3 E ) C.I =P/ E D.I= E P

26. Duplexes (receptacles) Main lugs only (remote protection) 3 Phase total 60 kVA, 14kVA (neutral) 30 poles 60 kVA / (208V √3 ) = 167A 200A panel Neutral 14000/120 = 117A Table 11-2 Hot wires should be 250 MCM, Neutral #2/0 aluminum 2½ inch conduit Panel D

27. Transformer capacity 200∙208∙√3 = 72 kVA ~ 75 kVA 200∙208 / 480 = 86 A 100 A switch Neutral 117*208/480 = 50 A Three #1 and one #6 aluminum (could use #4) 100A fuse - could use 90, but likely same price

28. Ref: Tao and Janis (2001)

30. Summary Size residential systems List differences between commercial and residential systems Differentiate and size commercial panels