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HYDRONICS e Continued from p 50


Every designer should plan for energy efficiency by accurately controlling flow. Installing PICVs at terminal units in order to correct flow issues is a simple solution.


Features of the PICV Features vary with manufactured


52


PICV models. A benefit of all models is that they are compact; one valve takes the place of two. Common to all PICVs is a pressure regulator, consisting of a spring and diaphragm cartridge assembly. Differences are in the flow control mechanism. Some models have a control disc to fine tune flow; others use the turn of a


It is important in low energy buildings, to have design flow at the control of a fan coil, air handler, chilled beams, radiant heat appliance or convector.


ball-style valve. Multiple flow rates may be available in one valve. Some of these models incorporate a field-adjustable dial for setting the top end flow rate. These dials are lockable. Getting to them may require removing the actuator or opening a side hatch; in others, the dials on the valve can be turned and are readable in any position. Some dials are in percentage


values, while others are marked in gpm. Pressure test points are available on most models. In addition to being easy to design with, PICVs offer a simplified balancing procedure. Some valves are not adjustable and are set at the factory; others are set in the field. Both types only require the differential pressure across the valve to be verified to ensure proper flow. PICVs are designed to


operate within the specifications that most HVAC systems will require. Flow control starts at 0.5 gpm with a ½-inch valve and covers the range of flow to over 700 gpm with a 6-inch valve. PICVs operate over a wide range of differential pressures. Minimum differential pressure, which can be as low as 3, is typically at 5 psi. Maximum differential pressure is up to 50 or 60 psi. Some models can operate with differential pressure as high as 90 psi. Flow accuracy per model varies from +/-3% to +/-10%. Depending on the model, working temperatures may range from 0 F to 250 F. Maximum working pressure for a PICV may be as high as 300 psi. Please consult manufactured models for product specification.


PICVs with variable flow systems There is no doubt why


PICVs have gained wide acceptance in today’s energy efficient market. Using variable frequency drive (VFD) for pump control enables the pump to change speed based on a control


e Circle 35 on reader reply form on page 84 e Continued on p 81


phc october 2011 www.phcnews.com


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