1. Objective Summarize house ventilation/infiltration and duct leakage Power measurement – Review/learn Electric power Electric power measurements Instrumentation

2. Summary of last week lab measurements Not quite successful filed work – …… – ….. – … Data are posted on the course website

3. 3 Air Handler Flow Measurement Often need to know flow through air handler – Historically many methods, all problematic: Non-uniformity of flow (i.e., very turbulent) True Flow Plate – Specialized type of orifice – Replaces filter – Gives air handler flow Pressure correction 3

4. Duct pressurization

5. Duct and house pressurization

6. Nulling test Use a Duct Blaster as envelope fan to “null out” change in envelope pressure caused by unbalanced duct leakage First with normal operation –unbalanced leakage Second with return isolated and a Duct Blaster assisting the AH fan so there is no return leakage –supply leakage Difference is return leakage Measures leakage directly – Thought to be accurate Very sensitive to wind

7. General Comments about Fan Tests Buildings are complicated, go slowly and methodically – Practice/experience are key – Practical matters (HVAC turned on, someone stepped on a tube, wind, etc.) untapped register, etc. are very important Cardboard and tape are useful research tools/skills

8. 8 Why to know about power measuring techniques Used fro any kind of energy consumption monitoring of building and/or building systems Electric power is used in various indoor environment experiments to generate heat source

9. 9 Some examples of power measurements Fan power for air movementHeat generated by thermal manikin

10. 10 AC or DC current source Voltage and Current V [V]R [Ω] I [A]

11. 11 Power measurement V = IR P = VI = I 2 R Are these for : A) AC or B) DC or C) both? V [V] R [Ω] I [A]

12. 12 Single-Phase vs. Three-Phase Ref: Tao and Janis (2001) Single phase 3 wire system Common for US residential buildings For three phase: P = √3 E I V-V Or P = 3 E I V-N

13. 13 Voltage measurement R [Ω] I [A] voltmeter V Current measurement I=V/R shunt

14. 14 Other methods for current measurement Measure Induction

15. 15 Electric energy vs. Electric power Electromechanical induction watt-hour meter Counts the revolutions of an metal disc which rotates at a speed proportional to the power. Use magnetic flux

16. AC circuits Reminder - Quick Reference http://hyperphysics.phy-astr.gsu.edu/hbase/electric/accircon.html#c1 Check for this class Check for your general education

17. 17 Power factor Voltage current phase Power: P(  )=V(  )·I(  ) P(  )

18. 18 Power factor Voltage current phase shift Devices in electric motors

19. Voltage current phase-shift Power factor P(  ) P=I·V·cos Φ Power factor = cos Φ

20. 20 Some facts about Power factor Low power factor is expensive and inefficient Utility companies charge large commercial and industrial customers an additional fee when power factor is less than about 0.95. Low power factor reduces an electrical system’s distribution capacity by increasing current flow and causing voltage drops. Increasing power factor you can reduce electric bills and enhance your electrical system’s capacity.

21. 21 Portable power meter and data logger

22. 22 Single phase two wire

23. 23 Single phase three wire

24. 24 Three phase four wire

25. 25 Electric power meters Power meter with power supply Inexpensive power meter Large variety: power meter with data logger +

26. 26 Power control Lab exercise Measure the power consumption of variable power transformer (Variac)