Upload
dinthorpe3248
View
20
Download
0
Tags:
Embed Size (px)
Citation preview
Goals Today
• ATU Terminology • ATU Types • ATU Motors • ATU w/ECM Selection Sweet Spot • ATU Box Leakage – Casing/Valve • ASHRAE 90.1 Requirements • AHRI Response
ATU Terminology
• ATU = air terminal unit • VAV Box = ATU • ATU inlet valve = damper • Primary air = air from AHU that enters through inlet valve • Plenum air = air from ceiling space that enters ATU through
induction port (fan powered boxes) • Inlet flow sensor + pressure transducer + controller =
knowing flow rate through primary
ATU Terminology
• ATU inlet valve = damper • Primary air = air from AHU that enters through inlet valve
Inlet valve
Primary Air
ATU Box Types
Non Fan Powered • Single-duct (controls cfm) • Dual-duct (controls cfm and temperature)
Fan powered • Series boxes (on all the time) • Parallel boxes (fan on during heating demand)
Single-Duct
AHU air
Energy Savings: 1) Reduce ATU motor electrical requirements 2) Reduce amount of AHU air leakage
Dual-Duct
ATU Box Types
Cold deck
Hot deck
Mixing Downstream
Cool Primary Air Warm Plenum Air
Series Plenum air
AHU air
Parallel
Fan ON all the time Fan ON in heating
ATU Motor Types - PSC
AC power in
550 min rpm (vertical)
400 min rpm (horizontal) Sleeve bearing
6-pole = 1075 rpm max
ATU Motor Types - ECM
AC power in
Inverter and electronics
Brushless DC motor
Ball bearings
200 min rpm
ECMs are programmed
1400+ max rpm
Programming ECMs
Laboratory testing. ECM is “taught” relationship between rpm, torque, airflow and external static pressure. ECM is programmed. ECM is specific to the ATU.
43 AA21 CFMRPMARPMAT
ECM Factory Set Airflow
000 %PWM Flow Rate
(cfm)
0 650
10 825
20 1000
30 1175
40 1350
50 1525
60 1700
70 1875
80 2050
90 2225
100 2400 100
Outlet Ps
Average Watts/CFM PSC ECM
0.1 0.44 0.09 0.2 0.44 0.17 0.3 0.45 0.20 0.4 0.43 0.22 0.5 0.44 0.25 0.6 0.43 0.27
Average: 0.44 0.20
Test VAV Energy Usage (PSC vs ECM)
Watts/cfm vs. Outlet Ps
ATUs with ECM – Bottom Line
•Series boxes best application (Fan ON all the time) •Select ATU where
cfmdesign < 75% of ATU cfmmax
Leakage of Parallel ATUs was
Significant
Up to 30%!
ATUs – ASHRAE Research
Forced Manufacturers to Design Better Box
2010 Addendum cq •Ductwork and plenums = Seal Class A •Round and rectangular duct: Leakage Class 4 •Test 25% of all duct over 3 in.wg. •Test 25% of outdoor duct
ASHRAE 90.1 – Now
•Single and Dual-duct VAV box leakage requirements •Efficiency requirements for fractional hp motors
ASHRAE 90.1 - Future
AHRI Certification – ATU Leakage
AHRI requires certified leakage ratings
•Casing leakage for single-duct ATUs at 0.5 in.wg.
•Damper leakage for single-duct ATUs at 1 in.wg.
•Casing leakage for dual-duct ATUs at 1 in.wg.
•Damper leakage for dual-duct ATUs at 6 in.wg.
Summary
• ATU w/ECM efficiency far exceeds standard ATU boxes • Series ATU best suited for ECM option • Select ATU w/ECM at up to 75% box capacity • Pre-2010 Parallel box backdraft damper leakage is significant! • ASHRAE 90.1
• Does not cover fractional hp motors • Will have single and dual-duct casing and inlet valve leakage limits
• AHRI • Added casing and valve leakage to the VAV Certification program