Answers to your Questions about Pressure Independent Valve Technology
Q: By definition, what exactly is Pressure Independent technology?
A:PI technology incorporated into Belimo’s Pressure Independent Characterized Control Valve (PICCV), combine the functions of automatic balancing valves and control valves into one self-contained unit. The PICCV is designed to maintain stable flow and temperature differential by means of a coil. This occurs despite pressure fluctuations commonly experienced in typical system with multiple control valves and interactive circuits.
Q: How does PI Technology save money?
A: PI Technology has been shown reduce both installation and operational costs by:
*Eliminating the need for a separate balancing valve
*Eliminating the labor (costs or actual labor) associated with installing a separate balancing valve.
*Eliminating the need for start-up and routine balancing required in systems with interactive circuits.
*Accurately minimizing flow during low load periods so less pump energy is required.
*Reducing the size of both pumping equipment and piping due to the fact that PI valves help minimize overall flow requirement through the system. Less flow means less friction loss through equipment!
*Helping owners realize the full benefit of variable flow pumping systems.
Q: Is it true that PI valves cost as much as five times more than a conventional valve?
A: No! Clearly a valve that incorporates self-balancing technology is going to initially be more expensive than a more antiquated version,however, such an extreme price difference is unlikely. As listed in the previous question, customers find that the longterm savings achieved by applying PI technology substantially surpasses the initial material cost.
Q: How do I know I will save using PI technology?
A: Similar to an Energy Star product, most of the savings associated with PI technology is realized in operational payback. However, both installation and operational savings are frequently achieved.The most compelling evidence originates from a study conducted on two high rise residential buildings in Florida. One building was installed with Belimo CCV valves and standard balancing valves, while the other was installed with PICCVs. The buildings were identical in terms of location, climate, size, mechanical design, occupancy, and load pattern. Identical test procedures were followed in both buildings, yielding the following results:
DATA COLLECTED FROM TEST SITES INDICATES THE FOLLOWING SAVINGS:
COST ESTIMATES COOLING HEATING TOTALS
2 POSITION VALVES
3-Way CCV $78,567 $77,272 $155,838
2-Way CCV $51,321 $50,568 $101,889
2-Way PICCV $41,871 $41,160 $83,031
MODULATING VALVES
3-Way CCV $78,567 $77,272 $155,838
2-Way CCV $56,669 $55,877 $112,545
2-Way PICCV $46,737 $45,864 $92,601
ENERGY SAVINGS PAYBACK
2 POSITION VALVES
PICCV over 3-Way $4,342 N/A
PICCV over 2-Way $1,882 N/A
MODULATING VALVES
PICVV over 3-Way $4,342 N/A
PICVV over 2-Way $998 N/A
Q: I am confused by what appear to be conflicting reports on the cost effectiveness of pressure independent technology. How do I separate the facts from the fiction?
A: Certainly different tests yield different results depending on the procedure. Consistent side-by-side comparisons are essential for accurate evaluation of the effectiveness of one methodology over another. When presented with comparative reports on PI versus non-PI technology, make sure:
*Testing involves interactive circuits which exhibit pressure fluctuations. After all, these are the systems for which PI Technology is developed. Tests only looking at valve performance in non-interactive environments do not confidently demonstrate the true performance value of PI technology; therefore, this data can sometimes be misleading.Tests incorporating the operations of multiple valves demonstrate the effect of simultaneously varying differential pressures across multiple coils. Producing results that are much more accurate to that of an actual system. PICCV technology can be used for both fixed or varied set point strategies and should be compared with systems that employ the same strategies, otherwise the test will not yield a true comparison.
Variables such as humidity, outdoor air requirements, and different loads should be accounted for within the testing procedure.
Q: What is the significance of Delta T when it comes to evaluating valve performance?
A: For optimum efficiency, control valves should maintain consistent Delta T across the coil closest to design, regardless of pressure fluctuations in the system. If the Delta T design is 12° but 6° of differential is being achieved, then energy and money are being wasted. PI technology consistnely maintains high Delta Ts despite varying conditions, thus saving money.
Q: Do all systems require some sort of balancing?
A: Virtually any system with multiple, interactive circuits requires start-up and routine balancing, even those that are considered to be “tightly” designed. There are two main reasons for this:
*First, mechanical systems are rarely designed to perfection. Most are designed (or updated) with one or
more of the following imperfections: inappropriately sized coils, oversized pumps, improper piping. All of these items lead to pressure fluctuations which impact overall performance and efficiency. Therefore balancing (and rebalancing) is necessary unless PI technology is used.
*Second, normal pressure fluctuations in a system WILL occur as a result of constant load changes due to outdoor air temperatures, humidity, building occupation, etc. While there has been some investigation into the viability of pressure dependent systems that do not employ balancing, we do not consider this realistic alternative for buildings with multiple, interactive circuits.
Q: Where can I find reliable, scientific data comparing PI with non-PI Technology?
A: Two excellent resources are available on the Belimo website:
*A technical paper summarizing the test results of a comparison study conducted by Integrated Energy Concepts Engineering. www.piccv.com
*An Analysis of the Iowa Energy Centers Independent Testing of the PICCV. www.piccv.com
Q:Other Questions?
Belimo is happy to answer any technical questions you may have regarding PI technology. As a manufacturer of BOTH PI and non-PI equipment, we realize that different products are suited for different applications. Our goal is not to persuade engineers to use one technology over another, but to help them select the control technology that provides the most cost-effective solution for their clients.
Stromquist & Company is a platinum distributor for Belimo products including the Belimo PICCV valves. So if you are Stromquist & Company customer or if you are located in Georgia or Florida please contact your friends at Stromquist & Company for all your Belimo and HVAC control needs, others can find great resources for Belimo USA products through one of our outstanding affiliates at Controls Group North America
*Information for this posting was obtained at: http://www.piccv.com/q-a.html
3 Responses
What is the difference between a PICCV and a PICV, if the PICV is not characterized what is the difference.
While I do not disagree with your contention of improved installation and maintenance costs, I do disagree with the operational savings.
Let’s say I have a commercial office building with 10 VAV AHUs, each with a 2-way modulating CCV. The control loop for each valve is accurately set and we maintain 55 deg discharge air temp from each coil, with small fluctuations throughout the day due to load changes. If I were to replace my CCV with PICCV, and each PICCV maintained 55 deg discharge air from each coil, how are these valves achieving the same outcome with less CHW flow? (Answer, they’re not) If I have a proper PID loop, I will be within +/- 1 degree of Discharge Air Setpoint all day long, so ‘fluctuations’ as you said are completely minimal.