ATU Considerations

1

• ATU Considerations
• Jim Meats VP of Engineering, Metal Industries,
  Inc.
• ASHRAE Luncheon Presentation August 19, 2009

2
Topics for Discussion

• Parallel vs. Series Fan Powered ATUs
• ECM vs. PSC
• AHRI (ARI) Data
• ARI 880
• ARI 885
• Things Coming

3
Series ATU (CV)

• Operating Characteristics
• Constant Volume
• Fan is ALWAYS ON
• Temperature is varied

4
Parallel ATU (VAV)

• Operating Characteristics
• Variable Volume
• Fan is OFF in COOLING
• Fan is ON in HEATING

5
Which is Cheaper to Operate?

• Traditionally Parallel Boxes
• Turn Fan on and off for Reheat/Heating
• Variable noise can be issue
• ASHRAE Research
• Revealed leakage of Parallel ATUs up to 30!

Holy Cow!
6
ASHRAE Research (RP 1292)

• No Leakage Model (12 hour schedule)
• Series uses 17 more energy
• With Leakage
• 10 - Series uses 4 more energy
• 20 - Series uses 6 less energy
• Reality
• Parallel Series

7
What to Do?

• Leakage Specifications
• BE CAREFUL!
• Look for Other Options

8
ECM vs. PSC

• PSC Permanent Split Capacitor

6-pole 1075 rpm max
AC power in
550 min rpm (vertical) 400 min rpm (horizontal)
Sleeve bearing
9
How Do You Control It?

• SCR
• Chops the voltage
• Increases slip/inefficiency
• Reduces electric quality
• Doesnt control torque
• Susceptible to reverse free wheeling with FC
• Can increase tonal quality of motor at low RPM
• Generally recommend no less than 60 turndown

10
Part Load Efficiencies
11
ECM vs. PSC

• ECM Electrically Commutated Motor

Ball bearings
AC power in
Inverter and electronics
Brushless DC motor
200 min rpm or less
12
How Do You Control It?

• Programming
• Laboratory Testing
• ECM is taught relationship between speed,
  torque, airflow and external static pressure.
• ECM is ATU specific

13
Energy Consumption
Measure Watts vs. CFM for Air Terminal Unit
14
ECM vs. PSC
1/2hp ECM 200 to 1200 cfm
15
ECM in Parallel Boxes

• Consortium working with AM
• Advantages of ECM in parallel boxes
• Conclusions
• Ramifications
• LEED Points

16
ARI/AHRI Certified

• ARI and GAMA Merger gtAHRI
• ARI 880
• ARI 885

17
AHRI 880 (ARI 880)

• Participants must certify all products
• Performance verified by 3rd party annually
• Rated points are certified
• Other points are application data
• If NC ratings published, must conform to ARI
  885
• Tolerance between mfrs
• Electronic selection tools

18
AHRI 885 (ARI 885)

• Transfer function from sound power data to
  estimated room sound levels
• Appendix E applies to VAV data when NC data are
  published
• Standard deducts applied to radiated and
  discharge sound power
• Provides apples to apples comparison and
  estimated performance in generic space
• Spec latest standard version

19
Things To Look For

• AHRI
• You will see a change in the formatting of data
  presentation
• Used to be a separate table
• Will be integrated and highlighted
• Compliance Committee
• Computer selection program data to be addressed

20
Where Do We Go From Here?

• Research, Legislation and Bldg Users will drive
  specification changes
• Additional industry research will drive
  innovation and clear up misconceptions
• Beware of non-certified product
• Understand NC ratings and application data
• Series vs. parallel
• ECM motors for series boxes

21
Questions?