ASHRAE Journal - November 2009 - 21

400 350 300 High Efficiency 85°F VSD 85°F High Efficiency 75°F VSD 75°F High Efficiency 65°F VSD 65°F) Figure 2: VSD chiller versus same price high-efficiency chiller. 250 kW 200 150 100 50 0 0% 20% 40% % Load 60% 80% 100% Figure 2 presents the results of selecting a smaller chiller (assuming cooling load has been reduced due to lighting retrofits) and compares the performance of a 600 ton high-efficiency chiller with an equally priced VSD chiller that meets Standard 90.1-2007 requirements at ARI 550/590 standard rating conditions. Note that Standard 90.1 requires both full and part load requirements to be met, and drive losses are included in the rating. Present Standard 90.1 requirements: • 0.576 kW/ton full load and 0.549 integrated part load value (IPLV). Standard 90.1 requirements as of Jan. 1, 2010 (from Standard 90.1-2007 Addendum m): • Either 0.570 kW/ton full load and 0.539 IPLV; or • 0.590 kW/ton full load and 0.400 IPLV. An example of same price chillers at ARI 550/590 standard rating conditions gives the following performance: • VSD: 0.572 kW/ton full load and 0.357 IPLV; and • High Efficiency: 0.501 kW/ton full load and 0.430 IPLV. Once again it is obvious that energy savings are accrued by using a VSD on a chiller when cooler tower-water temperature is available, that is, the refrigerant pressure differential or “lift” is reduced. This makes sense since the drive speed cannot reduce without causing the chiller to surge, unless the required compressor lift is reduced. Given the previous information, a comprehensive analysis may show that November 2009 one high-efficiency and one VSD chiller provide the best payback. In a humid environment where there are fewer hours with low tower-water temperature (such as San Juan, Puerto Rico, or Houston) two high-efficiency chillers may offer the best payback. This is true particularly when the maintenance and life-cycle replacement cost of the VSD is factored into the analysis. This again underscores the importance of performing a comprehensive analysis. Design Parameters When asked to retrofit a chilled-watersystem, project teams often use the same design chilled-water and condenser-water flow rates and temperature differences. This is not likely to produce optimal results. Instead, judicious use of existing infrastructure—and using different flow rates and temperature differences—offers significant benefits to the building owner. The chilled-water options apply to aircooled and water-cooled chillers. Reducing Chilled-Water Flow Rate, Expanding DT The ASHRAE GreenGuide4 references the CoolTools Chilled Water Plant Design and Specification Guide5 and recommends “starting with a chilled-water temperature difference of 12°F to 20°F (7°C to 11°C).” While primarily intended for new systems, this guidance can be used for many existing systems. Reducing Pumping Energy. Significant pump savings can be realized by reducing flow rates, especially in constant-flow chilled-water systems. This may be achieved by making those flow www.info.hotims.com/25210-14 ASHRAE Journal

ASHRAE Journal - November 2009

Table of Contents for the Digital Edition of ASHRAE Journal - November 2009

ASHRAE Journal - November 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
Feature Articles
Upgrading Chilled-Water Systems
50th Anniversary Feature: Energy Savings from Pump Impeller Trimming
Building Sciences
InfoCenter
Special Supplement: BACnet® Today
BACnet Table of Contents
BACnet and the Smart Grid
An Untangled Web: How BACnet is Connecting at ASHRAE’s Headquarters
Visualizing BACnet
BACnet & Trigeneration
BACnet Gets Smaller
Technical Topics
Washington Report
Special Products
Emerging Technologies
People
Research Topics
Products
Classified Advertising
Advertisers Index
ASHRAE Journal - November 2009 - ASHRAE Journal - November 2009
ASHRAE Journal - November 2009 - Cover2
ASHRAE Journal - November 2009 - 1
ASHRAE Journal - November 2009 - 2
ASHRAE Journal - November 2009 - Contents
ASHRAE Journal - November 2009 - 4
ASHRAE Journal - November 2009 - Commentary
ASHRAE Journal - November 2009 - Industry News
ASHRAE Journal - November 2009 - 7
ASHRAE Journal - November 2009 - Letters
ASHRAE Journal - November 2009 - 9
ASHRAE Journal - November 2009 - 10
ASHRAE Journal - November 2009 - 11
ASHRAE Journal - November 2009 - 12
ASHRAE Journal - November 2009 - 13
ASHRAE Journal - November 2009 - Meetings and Shows
ASHRAE Journal - November 2009 - 15
ASHRAE Journal - November 2009 - Upgrading Chilled-Water Systems
ASHRAE Journal - November 2009 - 17
ASHRAE Journal - November 2009 - 18
ASHRAE Journal - November 2009 - 19
ASHRAE Journal - November 2009 - 20
ASHRAE Journal - November 2009 - 21
ASHRAE Journal - November 2009 - 22
ASHRAE Journal - November 2009 - 23
ASHRAE Journal - November 2009 - 24
ASHRAE Journal - November 2009 - 25
ASHRAE Journal - November 2009 - 26
ASHRAE Journal - November 2009 - 27
ASHRAE Journal - November 2009 - 28
ASHRAE Journal - November 2009 - 29
ASHRAE Journal - November 2009 - 30
ASHRAE Journal - November 2009 - 31
ASHRAE Journal - November 2009 - 32
ASHRAE Journal - November 2009 - 33
ASHRAE Journal - November 2009 - 33A
ASHRAE Journal - November 2009 - 33B
ASHRAE Journal - November 2009 - 50th Anniversary Feature: Energy Savings from Pump Impeller Trimming
ASHRAE Journal - November 2009 - 35
ASHRAE Journal - November 2009 - 36
ASHRAE Journal - November 2009 - 37
ASHRAE Journal - November 2009 - 38
ASHRAE Journal - November 2009 - 39
ASHRAE Journal - November 2009 - 40
ASHRAE Journal - November 2009 - 41
ASHRAE Journal - November 2009 - 42
ASHRAE Journal - November 2009 - 43
ASHRAE Journal - November 2009 - 44
ASHRAE Journal - November 2009 - 45
ASHRAE Journal - November 2009 - Building Sciences
ASHRAE Journal - November 2009 - 47
ASHRAE Journal - November 2009 - 48
ASHRAE Journal - November 2009 - 49
ASHRAE Journal - November 2009 - 50
ASHRAE Journal - November 2009 - 51
ASHRAE Journal - November 2009 - 52
ASHRAE Journal - November 2009 - 53
ASHRAE Journal - November 2009 - InfoCenter
ASHRAE Journal - November 2009 - 55
ASHRAE Journal - November 2009 - 56
ASHRAE Journal - November 2009 - 57
ASHRAE Journal - November 2009 - 58
ASHRAE Journal - November 2009 - 59
ASHRAE Journal - November 2009 - 60
ASHRAE Journal - November 2009 - 61
ASHRAE Journal - November 2009 - 62
ASHRAE Journal - November 2009 - 63
ASHRAE Journal - November 2009 - 64
ASHRAE Journal - November 2009 - Special Supplement: BACnet® Today
ASHRAE Journal - November 2009 - B2
ASHRAE Journal - November 2009 - B3
ASHRAE Journal - November 2009 - BACnet Table of Contents
ASHRAE Journal - November 2009 - B5
ASHRAE Journal - November 2009 - B6
ASHRAE Journal - November 2009 - B7
ASHRAE Journal - November 2009 - BACnet and the Smart Grid
ASHRAE Journal - November 2009 - B9
ASHRAE Journal - November 2009 - B10
ASHRAE Journal - November 2009 - B11
ASHRAE Journal - November 2009 - B12
ASHRAE Journal - November 2009 - B13
ASHRAE Journal - November 2009 - An Untangled Web: How BACnet is Connecting at ASHRAE’s Headquarters
ASHRAE Journal - November 2009 - B15
ASHRAE Journal - November 2009 - B16
ASHRAE Journal - November 2009 - B17
ASHRAE Journal - November 2009 - B18
ASHRAE Journal - November 2009 - Visualizing BACnet
ASHRAE Journal - November 2009 - B20
ASHRAE Journal - November 2009 - B21
ASHRAE Journal - November 2009 - B22
ASHRAE Journal - November 2009 - B23
ASHRAE Journal - November 2009 - BACnet & Trigeneration
ASHRAE Journal - November 2009 - B25
ASHRAE Journal - November 2009 - B26
ASHRAE Journal - November 2009 - B27
ASHRAE Journal - November 2009 - BACnet Gets Smaller
ASHRAE Journal - November 2009 - B29
ASHRAE Journal - November 2009 - B30
ASHRAE Journal - November 2009 - B31
ASHRAE Journal - November 2009 - B32
ASHRAE Journal - November 2009 - Technical Topics
ASHRAE Journal - November 2009 - Washington Report
ASHRAE Journal - November 2009 - 67
ASHRAE Journal - November 2009 - Special Products
ASHRAE Journal - November 2009 - 69
ASHRAE Journal - November 2009 - Emerging Technologies
ASHRAE Journal - November 2009 - 71
ASHRAE Journal - November 2009 - People
ASHRAE Journal - November 2009 - 73
ASHRAE Journal - November 2009 - Research Topics
ASHRAE Journal - November 2009 - Products
ASHRAE Journal - November 2009 - Classified Advertising
ASHRAE Journal - November 2009 - 77
ASHRAE Journal - November 2009 - 78
ASHRAE Journal - November 2009 - 79
ASHRAE Journal - November 2009 - Advertisers Index
ASHRAE Journal - November 2009 - Cover3
ASHRAE Journal - November 2009 - Cover4
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