5 Understating Coil Behavior Coil PerformanceResulting Coil OutputCoil Power / FlowΔTThis is how a new coil is controlled by a properly sized PI valveThe coil curve relates BTUh to flow (blue)Animation 1: The valve curve relates flow to control signal (orange)Animation 2: By combining these curves, we can relate BTUh to control signal, shown as he resulting coil output (black)The following 3 slides illustrate through the affect of degradation on the performance of the coil.Shown here is the coil as it was manufactured.Blue line = Coil OutputOrange line =Valve FlowGreen line = Delta TValve GPMBTUhFlow / Control Signal
8 Body Pressure Pressure Vessel Burst Rating Measured in psi Failure Threshold of the Vessel
9 Relationship between Pressure and Temperature Body PressureANSI Body RatingRelationship between Pressure and Temperature
10 Close-Off PressureP1The maximum pressure that a valve can withstand without leakage while in the fully closed position.
11 Close-Off Pressure Rule of Thumb 2-way Valve Close-off pressure should at least equal the maximum pressure produced by the circulating pump3-way ValveClose-off pressure should at least equal the system differential pressure
12 Close-Off Pressure Close-Off Leakage Bubble Tight is not an ANSI rating.Bubble Tight implies No water leakage.
13 Pressure DropP1P2The maximum allowable pressure differential that a fully open valve can withstand without damaging the internals of the valve.
14 Temperature Ratings Media Temperature (hydronic) Acceptable fluid temperature rangeMedia Temperature (steam)Commonly measured in lbs of steamAmbient TemperatureUsually an actuator rating
15 Characterization Curves Equal PercentageLinearQuick OpeningModified Equal Percentage?FlowVaries based on designButterfly Valves, others2 Position controlZone ValvesModulating Control of a CoilCCV, PI-Valves, Globe ValveModulating Control of Steam Coil or Bypass ApplicationsePIV, Globe ValvesValve Position
16 Rangeability & Turndown The ratio of maximum flow to minimum controllable flow of a valve body only under laboratory conditions with a constant differential pressure applied across the valve.Turndown Ratio:The ratio of maximum usable flow to minimum controllable flow of the valve assembly under installed conditions. It is always lower than the rangeability factor.
23 Hydronic Valve SizingChecking DPWhich should we select?And Why?
24 Valve Authority Coil Flow (%) Valve Opening (%) Balance Valve First animation: Discuss the formula form Valve Authority as it relates to the branch schematic. Walk through an example of a 20 psi drop on the branch, creating A=0.22nd animation: Show the distortions that result from A=0.2
26 Valve Authority Distortion 1009080Valve Opening (%)Flow (%)7060Flow / Coil Output (%)50400.2301201st animation: Explain how EQ% valve curve acts opposite the coil curve and creates a linear 1:1 heat output (in other words, 20% control signal should result in 20% heat output)2nd animation: When A=0.2, this starts to fall a part3rd animation: The nice EQ% curve and the linear output are no longer valid (the equal percent curve will fade to make the graph easier to read, the output line will remain dotted, for comparison.)4th animation: When we combine the new valve curve with the existing coil curve, we get a new out put that is quite fast acting at low flows.Note that at 10% valve opening the original output curve puts out 10%, but the new one puts out 20%.Note that at 20% valve opening the original output curve puts out 20%, but the new one puts out 40%.At low flows, the space is seeing twice the heat output that the is anticipated by the controller.5th animation: discuss the over flow and underflow caused by riding up and down the much steeper output curve.10102030405060708090100Valve Opening (%)
27 Should be greater than coil DP Valve Authority > 0.4 Hydronic Valve SizingRules of ThumbDifferential Pressure Across the ValveShould be greater than coil DPValve Authority > 0.4Typically between 3psi - 5psi for modulatingTypically about 1 psi for on/off
28 Pipe Reduction Factor ½" valve in a ½" pipe with a Cv tested at 10 Same ½" valve in a 1" pipe will test at Cv = 6.3
30 Pipe Reduction FactorOnly for Valves with High Cv relative to line size
31 The control valve shall be no less than ½ the pipe size… Pipe Reduction FactorRules of ThumbChoosing Valves Smaller than Line sizeThe control valve shall be no less than ½ the pipe size…However, it’s best to keep the valve size reduction no greater than 2 pipe sizes.Large pipe reductions can increase the effects of cavitation
32 Piping Considerations Which is Correct?AndWhy is it Correct?Templateday month year
46 CCV Pros Cons Applications Valve Summary Inexpensive Equal Percentage CharacteristicHigh Close OffLarge Range of CvConsHot and Chilled Water with Glycol OnlyApplicationsHot & chilled water coils (for air handling units)Unit ventilatorsFan coilsVAV units
53 Globe Valves Pros Cons Applications Valve Summary Equal Percentage or Linear CharacteristicSS Trim works for SteamConsExpensiveLarge2 Versions of 3-wayClose off depends on ActuatorApplicationsHot & chilled water coils (for air handling units)Chillers
54 Holes in Plate Balance the Pressure Globe ValvesWhat is a Pressure Compensated Globe Valve?PuPdHoles in Plate Balance the Pressure
58 Butterfly Valves 3-Way Butterfly Valves 2 Valves linked on a Tee Mixing or Diverting1 or 2 Actuators
59 Butterfly Valves 3-Way Butterfly Valves 2 Valves linked on a Tee Mixing or Diverting1 or 2 Actuators
60 Butterfly Valves Sizing a BFV: Velocity 12 ft/sec in Standard BFV 32 ft/sec in High Performance BFV
61 Butterfly Valves Pros Cons Applications Valve Summary Up to 30” InexpensiveHigh Close-OffSS and HP AvailableConsModified Eq %High Cv Relative to SizeVelocity LimitationsApplicationsChiller and Cooling Tower IsolationChange Over SystemsLarge Air HandlersBypass Controls
68 Pressure Independent Valves Pressure Independent Control Valves2-way valve that supplies a specific flow for each value of the control signal –– Regardless of pressure variations in the systemPI ValvePressureFlow
69 Pressure Independent Technologies Mechanical Regulator Electronic Flow Meter
70 Pressure Independent Valves Valve SummaryProsAccurate Flow Regardless of Pressure ConditionsIncreased Water-side DTReduced Pump Energy UsageValve Authority = 1.0Eliminates need of Automatic Balancing ValvesConsHigher Initial CostApplicationsHot & chilled water coils (for air handling units)Unit ventilatorsFan coilsVAV units
71 Control Valves: Specifications, Sizing & Technologies Questions?