ASHRAE Journal - December 2009 - 11

Explore How to Use What’s New Technology Transitory Re: Balancing Valves I think it is time our profession matures to the point where we look excitedly at new technology rather than continue to hash and rehash the merits of applying old technology to today’s systems. Our chilled water and heating water systems are hopefully being designed applying best available technology, hardware and software. Our professional discussions should include a focus on exploring how to properly apply these new technologies to new system design, as well as upgrading existing systems (systems optimization). More specifically, the control valve industry has progressed from three-way control valves (constant-flow devices) to two-way control valves (variable-flow devices) to pressure independent twoway control valves (pressure independent variable-flow devices). Modulating actuators have progressed from step control to full modulation with actuator sensitivity increasing from 50:1 or less to 200:1 and higher. Controller input/output has changed from pneumatic to electric using DDC communication protocols. The high rangeability, pressure independent control valve (PICV) technology came across my desk when I was a practicing consulting engineer about 16 years ago. It was immediately apparent that this technology would provide chilled water and heating water system designers the ability to serve cooling/heating loads with less water by increasing system part load DT performance at the cooling coil/ control valve interface. Once system flow rates were lowered, pumping and piping systems also could be optimized. Central plants also could be optimized, accessing all installed cooling capacity and eliminating the existing flow limited condition, wherein chillers were staged on flow and not load. This was a new technology and had to experience the growing pains of maturity. Today, the PICV technology is a proven and tested system component December 2009 Author Responds This indeed is a thoughtful letter. It is based upon the belief that all science is transitory. Yesterday’s cutting-edge is today’s obsolescence. When we developed variable flow 30 years ago, we would hold constant differential pressures as high as 35 ft, often just to serve a large air handler. Today, we have variable differential pressures that range from 35 ft of water down to as low as 4 ft of water at night when the cooling loads are at a minimum. We have one system of mostly small air handlers that reaches 2 ft of water at night. We have a number of systems that use PICV technology and function very satisfactorily, but we are concerned that most PICV require 5 psi or around 11 ft minimum differential pressure all of the time. Also, their capacity is quite low when compared to other valves such as the segmented ball valve. Rather than concentrate on valve type, we have been recommending valves with a shutoff pressure of 200 psid and a rangeability of 300:1. With digital control, we have had no problems with them on systems as large as 15,000 tons with terminal units of all sizes. Thanks again to Mr. Rogers. James B. (Burt) Rishel, P.E., Life Member ASHRAE, Cincinnati Automatic maximum flow limiting devices are not required, as maximum hydronic flow can be limited by software within the controller as well as by setting physical valve stroke limits. The PICV technology, when applied on new and existing systems, must be properly commissioned to ensure all system components are operating as specified. In conclusion, I would hope that we adopt an industry standard to read: “Today’s engineering practices rely on the use of best available technology products and methods to design and optimize new or existing hydronic systems.” David A. Rogers, P.E., Life Member ASHRAE, Sacramento ASHRAE Journal 11 application that provides precise metered flow to the coil based on controller output signals to the PICV actuator. Hydronic flow change via the PICV and associated actuator is in direct response to the controller output signal and does not change because of dynamic system differential pressure variations that exist across all components within an operational hydronic system. Variable-flow pumping does not in and of itself balance system flow rates. However, variable-flow pumping will maintain proper differential system pressure when properly controlled via the hydraulically most remote point(s) (chilled water control valve[s] for chilled water systems). The hydraulically most remote point(s) in a system are identified through computer modeling of the system. A variable-flow pumping system, when controlled in this manner, will develop only that amount of head required to satisfy the differential pressure setpoint at these locations. System PICVs will then maintain dynamic system balance by providing only the amount of flow required to satisfy the controller output demands within the associated hydraulic profile. Balancing valves do not provide dynamically balanced flows for all load conditions in a system. Therefore, they are not appropriate for variable-flow systems applications when using PICV technology.

ASHRAE Journal - December 2009

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

ASHRAE Journal - December 2009
Contents
Commentary
Industry News
Letters
Meetings and Shows
ASHRAE Building EQ Program
Feature Articles
A Closer Look at Chiller Ratings
Cooling With Less Air: Using Underfloor Air Distribution and Chilled Beams
Cooling Concrete: Containerized Water Chilling Plant
Geothermal for Community Center
Anniversary Feature: Air-Recovery System Versus Conventional Air Conditioning
Technical Topics
New Product Preview
Products
Emerging Technologies
Washington Report
People
Special Products
2009 Feature Articles Indices
Classified Advertising
Advertisers Index
ASHRAE Journal - December 2009 - ASHRAE Journal - December 2009
ASHRAE Journal - December 2009 - Cover2
ASHRAE Journal - December 2009 - 1
ASHRAE Journal - December 2009 - 2
ASHRAE Journal - December 2009 - Contents
ASHRAE Journal - December 2009 - 4
ASHRAE Journal - December 2009 - Commentary
ASHRAE Journal - December 2009 - Industry News
ASHRAE Journal - December 2009 - 7
ASHRAE Journal - December 2009 - 8
ASHRAE Journal - December 2009 - 9
ASHRAE Journal - December 2009 - 10
ASHRAE Journal - December 2009 - Letters
ASHRAE Journal - December 2009 - 12
ASHRAE Journal - December 2009 - 13
ASHRAE Journal - December 2009 - 14
ASHRAE Journal - December 2009 - 15
ASHRAE Journal - December 2009 - Meetings and Shows
ASHRAE Journal - December 2009 - 17
ASHRAE Journal - December 2009 - Feature Articles
ASHRAE Journal - December 2009 - 19
ASHRAE Journal - December 2009 - 20
ASHRAE Journal - December 2009 - 21
ASHRAE Journal - December 2009 - A Closer Look at Chiller Ratings
ASHRAE Journal - December 2009 - 23
ASHRAE Journal - December 2009 - 24
ASHRAE Journal - December 2009 - 25
ASHRAE Journal - December 2009 - 26
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ASHRAE Journal - December 2009 - 29
ASHRAE Journal - December 2009 - 30
ASHRAE Journal - December 2009 - 31
ASHRAE Journal - December 2009 - 32
ASHRAE Journal - December 2009 - 33
ASHRAE Journal - December 2009 - Cooling With Less Air: Using Underfloor Air Distribution and Chilled Beams
ASHRAE Journal - December 2009 - 35
ASHRAE Journal - December 2009 - 36
ASHRAE Journal - December 2009 - 37
ASHRAE Journal - December 2009 - 38
ASHRAE Journal - December 2009 - 39
ASHRAE Journal - December 2009 - 40
ASHRAE Journal - December 2009 - 41
ASHRAE Journal - December 2009 - Cooling Concrete: Containerized Water Chilling Plant
ASHRAE Journal - December 2009 - 43
ASHRAE Journal - December 2009 - 44
ASHRAE Journal - December 2009 - 45
ASHRAE Journal - December 2009 - 46
ASHRAE Journal - December 2009 - 47
ASHRAE Journal - December 2009 - Geothermal for Community Center
ASHRAE Journal - December 2009 - 49
ASHRAE Journal - December 2009 - 50
ASHRAE Journal - December 2009 - 51
ASHRAE Journal - December 2009 - Anniversary Feature: Air-Recovery System Versus Conventional Air Conditioning
ASHRAE Journal - December 2009 - 53
ASHRAE Journal - December 2009 - 54
ASHRAE Journal - December 2009 - 55
ASHRAE Journal - December 2009 - 56
ASHRAE Journal - December 2009 - 57
ASHRAE Journal - December 2009 - 58
ASHRAE Journal - December 2009 - 59
ASHRAE Journal - December 2009 - 60
ASHRAE Journal - December 2009 - 61
ASHRAE Journal - December 2009 - Technical Topics
ASHRAE Journal - December 2009 - 63
ASHRAE Journal - December 2009 - 64
ASHRAE Journal - December 2009 - New Product Preview
ASHRAE Journal - December 2009 - 66
ASHRAE Journal - December 2009 - 67
ASHRAE Journal - December 2009 - 68
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ASHRAE Journal - December 2009 - 112
ASHRAE Journal - December 2009 - 113
ASHRAE Journal - December 2009 - Products
ASHRAE Journal - December 2009 - 115
ASHRAE Journal - December 2009 - 116
ASHRAE Journal - December 2009 - Emerging Technologies
ASHRAE Journal - December 2009 - Washington Report
ASHRAE Journal - December 2009 - 119
ASHRAE Journal - December 2009 - People
ASHRAE Journal - December 2009 - Special Products
ASHRAE Journal - December 2009 - 2009 Feature Articles Indices
ASHRAE Journal - December 2009 - 123
ASHRAE Journal - December 2009 - 124
ASHRAE Journal - December 2009 - 125
ASHRAE Journal - December 2009 - Classified Advertising
ASHRAE Journal - December 2009 - 127
ASHRAE Journal - December 2009 - Advertisers Index
ASHRAE Journal - December 2009 - Cover3
ASHRAE Journal - December 2009 - Cover4
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