Part 2: Why Automatic Flow Control Valves should be preferred over Manual Flow Control Valves?

In Part 1 we discussed the basics of flow control valves. Selection of the two control valves will change for every application, but below are some key benefits of Automatic Control Valves (ACV’s) operation over Manual valves operation:

Pictured: Model 2519 Mesurflo

  • Better Control: Automatic Valves maintain constant flow irrespective of the system pressure variations, thereby eliminating any balancing issues. Whereas in case of Manual Valves, the flow rate varies with any change in system pressure, thereby losing balancing control capability. Hence the system will need to be monitored and re-balanced again.
  • Cost Effective: Automatic Valves are more expensive than Manual Valves, but with an automatic balancing option the valves only need to be installed at the terminals as oppose to all the distribution lines, branches and risers. Saves money for installation cost.
  • Less Maintenance: ACV’s regulate the flow at constant rates according to their pre-set values. Once they are installed in the system, they do not require any balancing labor cost or any repetitive maintenance for monitoring.
  • Easy to install/accessible: ACV’s are easy to install. Moreover, they are easy to calibrate and the flow cartridge can be easily replaced or changed in the same valve rather than replacing the whole valve body.
  • Better Stability: Poor valve sizing can cause major balancing issues throughout the system whereas Automatic Valves are typically sized by designed flow rates only.
  • Energy Efficient: ACV’s are always endorsed for saving pump energy cost with added benefits of better chiller and cooling tower performance.
  • Ease to future extension: ACV’s eliminate the need for balancing labor and allows coils to be added or removed from the existing system without needing to re-balance the entire HVAC system. In the case of manual valves, the balancing is lost even if the load demand fluctuates in any of the existing branches. Moreover, complete re-balance may be required in cases of any addition or removal of coils.Pictured:

ACV’s provide much better system balance and control. The system will run more efficiently at all the load conditions. Ultimately, this will help to save the associated pump energy cost and make the whole system perform energy efficiently while achieving proper thermal comfort.

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Why Automatic Flow Control Valves should be preferred over Manual Flow Control Valves? Part 1

There have always been a lot of discussions regarding the balancing issues in HVAC systems. Fixing hydronic balancing problems in any HVAC system adds energy-efficiency and comfort. Most experts foresee a high potential to reduce pumping-energy-consumption cost by inculcating proper designing, selecting proper pumping system and using the correct control valves.

Selecting the proper control valve for the system ensures optimum heating and cooling performance and plays vital role in balancing the system. Technically, there are many ways to control the flow in a system but the topic focuses on two of the most common ways; Manual and Automatic valve operation. Manual is the traditional way of balancing system, whereas Automatic is a technology advancement.

Working Principle

Manual Valve Operation: Requires throttling valves and provides the means to measure flow at each branch. Flow is measured and valve openings are adjusted by the test and balance contractor to achieve design flow rates. The manual operation can keep the system balanced at full-load conditions (designed load) where it tends to operate for less than 2-3% of the year. As soon the system dynamics differ slightly, the system tends to remain unbalanced throughout the operation. Constant “Cv” operation. 

Automatic Valve Operation: Maintains the designed flow rate within the psid range, specified by the manufacturer’s, even as the system pressure varies. Provides system stability as it reacts to maintain overall system balance even when other branches modulate. Full authority temperature control can be thereby achieved. Acts as a pressure differential regulator at all varying load conditions by absorbing additional system pressure changes within the valve itself. Constant “Flow rate” operation. mesurlfo

Even though Automatic and Manual balancing have been debated for over a decade it is still hard to justify the clear winner. Manual flow control valves do serve a purpose and might be cost effective considering the initial investment cost, however Automatic valves (including PICV’s) have more benefits compared to manual valves over the years of operation. Several case studies have shown Automatic balancing valves to be very worthwhile. In Part 2 we will compare the benefits of Automatic valves over manual valves.

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Hydronic System Balancing with ASHRAE 90.1-2013

Unbalanced hydronic systems are typically easy to spot. Issues range from loud noises to large spikes in energy use. Typical hydronic systems are balanced during initial installation at full load design conditions where the system normally operates for only less than 2-3% of the time annually. Moreover they rarely stay proportionally balanced at varying loads in the years to follow. Systems will start to unbalance when occupants adjust the individual room controls which can lead to wide temperature spreads throughout the building, excessive energy use and higher pumping cost. ASHRAE now requires that all commercial building codes meet or go beyond the new energy efficiency standard 90.1-2013.[1]

untitledASHRAE 90.1-2013 is a US standard that provides the minimum energy efficient requirements for building designs.[2] To comply with ASHRAE 90.1-2013 building designers have two different paths to follow. The Prescriptive path makes sure all components of a building meet the minimum ASHRAE standards, while the Performance path uses a scale simulation to demonstrate that the proposed energy cost budget must be less than or equal to the baseline energy cost in order to comply with the standard from ASHRAE 90.1-2013:

Section 6.5.2.2.3 a. Controls that are capable of providing a heat pump water supply temperature dead band of at least 20° F between initiation of heat rejection and heat addition by the central devices (e.g., tower and boiler).

Section 6.7.2.3.3 Hydronic systems shall be proportionately balanced in a manner to first minimize throttling losses; then pump impeller shall be trimmed or pump speed shall be adjusted to meet design flow conditions.

Two important conditions are:

  1. The design flow must be available at all terminals – to deliver specified comfort level.
  2. The differential pressures across the control valves must not vary too much – to ensure that the first condition is met using minimum energy usage.

Our pressure drop and velocity calculator are great tools to determine the proper pump size and flow rate. Correct flow and pressure balances the system by optimizing the distribution of water in a building’s heating and cooling system. If balanced correctly the system will not only comply with ASHRAE 90.1-2013 minimum, it will reduce energy and operating costs while increasing thermal comfort. A properly balanced hydronic HVAC system results in an energy efficient building.

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Good Customer Service

For any business to have good customer service externally there must be good customer service internally. So what is the definition of customer service? There is no exact definition of what customer service is, but here are a few guidelines that professionals can follow:

  • Always be clear, pleasant, courteous, and helpful
  • Be a good listener
  • Pay attention to the details
  • Ask the right questions
  • Be flexible and have the power to adapt
  • Communication, Communication, Communication
  • Only commit to things you can deliver
  • Have a strategy when handling complaints
  • Go the extra mile
  • Have a well-trained staff
  • Follow-through, with respect and sincerity, quickly

Even after following these tips, only the customer’s definition of customer service counts. The definition of customer service will change for each individual, but the goal should always be to exceed the customer expectations. If you’ve done your job well the customer will be happy enough to pass positive feedback about your business to others.

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Water Hammer – The Causes and Effects

Water hammer occurs in installations where sudden closure of a valve causes water to surge back and forth at supersonic speeds. Due to this phenomenon, the reservoir end of the pipe reflects negatively whereas the valve end reflects positively causing pressure to fluctuate rapidly. Immediately after valve closure, a steam column is generated and an air pocket forms behind the moving water. As the water hits the closed valve, the water reverses its direction and quickly fills the void where the air pocket had formed. The waters change in direction causes massive forces back through the pipe.WH

The quicker the valve closes the more the pipe deflects. A strong enough force can dislodge diaphragms and rupture valve seals. The amplitude of the transient pressures and time duration of the transient position depends on various factors in a system such as flow velocity, pipeline material and system boundary conditions. The magnitude of a pressure change under a transient condition is expressed by Joukowsky’s law for instantaneous valve closure (ASHRAE Standards)

Equation

                     where:

defenition

The Cs for water is 4720 fps, although the elasticity of the pipe reduces the effective value. The above equation is valid for a pulse propagating in downstream direction. Conversely, the pressure change will be negative for a wave propagating in upstream direction

Water-hammer proof features are critical to design because they decrease the pressure spikes caused by a quickly closed valve. Decreasing the water pressure will reduce the pipes deflection and secure the diaphragms and valve seals.

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Why Pipe Flow Velocity is Important in HVAC Applications

Flow is primarily driven by pressure difference. Back pressure is exponentially dependent on the velocity. Higher flow will cause the back pressure to spike. The difference inVel pressure, along with surface roughness, velocity, temperature and geometry, determines whether the fluid is considered to be laminar or turbulent. Laminar flow occurs where systematic motion appears, whereas turbulent flow occurs where there is rapid velocity fluctuations.

Turbulent flow is encountered in practice when dealing with the majority of HVAC applications. The correct pipe size can minimize turbulence (vortex formations) in the flow, thereby reducing the system pressure drop resulting in increased overall system efficiency and lower pump operating costs. In HVAC design, flow velocity is a very useful value to calculate because a lower flow velocity rate will lower noise and friction in the pipes.

Our new calculator program determines the fluid velocity based off of pipe diameter and flow rate. The calculator also has helpful tools to recommend pipe sizes based off desired flow rates. When designing an overall system we recommend a maximum velocity of 7 ft/sec for most of the HVAC applications. The velocity limits are based on several factors which can cause erosion, noise, turbulence, cavitation, entrained air, and/or water hammer in the piping systems. However the limits do differ based on system applications.

 

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Automatic Balancing Valves for Supermarket Secondary Glycol Systems

2510-LT-ExtensionsInstallers can spend weeks adjusting and re-adjusting traditional manual valves on individual display cases and walk-in coolers attempting to achieve desired temperature and system balance only to have a change in pressure upset the entire system.

Mesurflo® automatic balancing valves, by Hays Fluid Controls, are specifically designed for medium temperature glycol systems.  The valve accurately controls the flow rate of 35% glycol @ 20° F.  The Mesurflo® valve responds to pressure fluctuations by automatically adjusting the orifice area resulting in constant flow.  There is no adjustment required.

Mesurflo® ensures each heat exchanger receives the design glycol flow resulting in a stable coolant temperature that ensures the highest food quality and integrity.

Another significant benefit provided by the Mesurflo® valve is energy savings.  Mesurflo® valves have been described as the silent hero in reducing energy consumption.  Since water flow in a hydronic system is difficult and expensive to physically observe on a constant basis, it is often taken for granted that the system is properly balanced when in reality it is using significant amounts of excess energy.  Overflows are eliminated by the Mesurflo® valve resulting in less energy consumption by the pump.

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Hays Fluid Controls’ Pressure Independent Characterized Valve

Hays Fluid Controls’ Pressure Independent Characterized Valve, often referred to as a PICV, combines a modulating temperature control actuated valve with a flow control valve that utilizes a characterized disk to convert the valve and heat exchanger characteristics to a linear output. The Mesurflo® selection of PICV valves offer a tremendous value to building owners, providing an economical, reliable solution to optimum flow control at a fraction of the cost of competitive PICV valves.

The Mesurflo® PICV prevents the operating system from experiencing excessive flow. In conditions of higher than normal pressure, Mesurflo® PICV lowers total system flow. This saves energy and further reduces costs. Mesurflo® PICV also protects equipment from the detrimental effects of flow-induced erosion.

As the control signal from the thermostat demands less than rated flow, the characterized control valve portion gains authority to control the flow. Even as the pressure changes, this characterized control valve combines with the specially designed actuator to control the flow. The control valve’s equal percentage characteristic guarantees a linear output. With Mesurflo® PICV, all movement is external to the valve in modulating conditions. The uniquely designed ball valve and characterized disc combination combine to produce the required flow rate. The flow then is maintained solely by the movement of one element – the ball valve. The actuator utilizes sophisticated algorithms to precisely position the valve. This eliminates over-reaction and sluggishness. At flow rates below the design point, no interaction for authority occurs between the Mesurflo® and the control valve, as the Mesurflo® acts like a fixed orifice. During this condition, unlike spring-type valves, the Mesurflo® still functions to damp out any pressure spikes to maintain constant set flow and eliminate any branch-to-branch interaction in the system. The impact on the control system of limiting flow to the design flow rate is minimal, due to the diminishing returns of heat exchangers.

Modulating valves controlled by a temperature feedback system benefit from the robust design of the Mesurflo® PICV. Mesurflo® PICV provides the same benefit as expensive, complex competitive pressure independent control valves constructed with tiny springs and thin diaphragms.

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AHR EXPO Recap: Another Great Year!

Last month we shared with our readers our excitement over the upcoming 2015 AHR Expo; now, with the event come and gone, we can officially say it was a great success.
Having attended the Expo for over fifteen years, we knew to expect good things—and our expectations certainly were met! This year’s event saw 62,000 attendees, an incredible 11 acres of exhibition space, HVAC pros and enthusiasts from over 140 countries, and countless opportunities. In fact, the record-high attendance was just one of the many highlights.

At our booth—featuring an exciting new design—we debuted two products of which we are extremely proud: Our patented Mesurflo® for supermarket medium temperature glycol systems and a flow-limiting seawater valve for the marine industry.

We were eager to introduce these new, innovative products to the public, and weren’t surprised when they were well received.

Of course, our favorite part of any trade show is interacting and having a chance to connect face-to-face with our customers and industry friends. This year, we met 60 potential new customers, and now that the show is behind us, we’re excited to reach back out to them and build a new relationship.

We were also very happy to have the chance to reconnect with existing friends, such as those from ACE Mechanical, Hoffman and Hoffman, Trane, TriState Hvac and more. It’s wonderful when we can reconnect with them.

 

 

There’s much to look forward to in the months and year ahead, including another great trade show. Next month we’ll be attending NFMT 2015, March 10-12 in Baltimore. We can’t wait to demonstrate the features and benefits of our patented Mesurflor® to facilities management professionals.

Meanwhile, we’d like to thank everyone who helped make this year’s AHR Expo such a great success—and we look forward to what the future holds!

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Don’t Miss Us At The AHR EXPO: Booth #2451!

HAYS Fluid Controls is proud to announce the details of our attendance at the 2015 AHR Expo. For this year’s event we’ve pulled out all the stops, including a new booth design which makes a great pedestal to debut two of our new exciting product line additions! These two new additions include expanding our patented Mesurflo® balancing valve into low temperature applications and into the commercial marine industry.

We have been going to AHR Expo for over 10 years and every year we look forward to all it has to offer. Of course we’re not the only ones gearing up, considering AHR Expo has just announced that this year’s exhibit has already accounted for over 2,000 exhibitors (from over 30 countries) and over 40,000 visitors. With those kinds of numbers we are sure to see some great presentations, innovations, and technologies within our industry.

There is no exception to how influential this expo is within the HVAC industry. In fact, the mayor of Chicago, Mayor Rahm has gone as far as to declare January 26-28 “Air Conditioning, Heating and Refrigerating Week in Chicago”. The proclamation cites AHR Expo’s contribution to educating the industry, “improving our greater society” and making donations to local charitable organizations.

Ultimately, the most exciting part for Hays Fluid Control is the chance to connect face-to-face with new and existing customers. We can’t wait to shake hands and engage with the visitors about all that Hays Fluid Controls has to offer. We look forward to showing our latest equipment, connecting with all prospective customers, and educating the public about how Hays Fluid Control provides superior fluid control solutions.

Don’t miss out on our demonstration of our new and outstandingly timeless solutions.  Come see us at booth # 2451 located in the north hall.  We can’t wait to meet you!

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