Balancing of a Water and Air System (PDF

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80 The entire water system must be operational: all inspections performed, final strainers installed and clean, all controls operational with all valves fully open. Set the system for balancing in the following manner: 1. Determine the total coil flow and determine: 2. Diversity-is there enough pumping capacity to provide 100% design water flow to each coil? If there is not enough pumping capacity to provide 100% design water flow to each coil, close the valves to the coils closest to the pump until the pump can provide 100% flow to the open coils. If there are three-way valves or a bypass valve in the system, observe that it is closed prior to balancing. 3. Record the pump (s) model and serial number, the motor nameplate, the design gpm flow, and the design head. Record the variable frequency drive (VFD) data if installed. 4. If a VFD is installed, set the VFD bypass for 100%. Verify the impeller size on each pump. 5. Read and record the actual pump head and flow with actual motor amperage and voltage. Record starter data and motor over-load protection devices size and rating. 6. Set each pump to provide approximately 10% more water flow than designed. 7. Record all flow meter nameplate data. Read all flow meter flows and pressure drops throughout the entire system, (ie. chillers, converters, coils, etc.), and establish flow using Equation 11.4. 8. Starting with the coil having the greatest flow, adjust the coil to the design flow. 9. Continue to proportion the water to each coil until all coils are balanced within ± 10% of design flow with the balancing valve of at least one coil remaining 100% open. If the system has diversity, close an equal amount of valves nearest to the pump and open the initially closed valves. Continue to proportion the water to each coil (starting with the coil closest to the pump) until all the coils are balanced within ± 10% of the design flow. 10. Re-verify and record the final pump gpm and head, amperage and voltage of each pump (discharge valve position if the system does not have a variable frequency drive). When the system has a VFD and the VFD is at 100% with the discharge valve throttled to obtain design flow, it is recommended that the impeller be trimmed or the VFD limited with the discharge valve fully open. 11. Record the system’s pressure differential at the pressure transmitter with the system at full flow. Adjust the coil closest to the pump closed and verify the pressure transmitter setting. Continue with the next coil until enough coils are closed to equal the minimum speed of the pump or the minimum flow through the primary heat exchangers. Verify that the closed valves closest to the pump remain closed and are not lifting off their seats. Note that most bypasses in two-way valve systems act as a relief valve and the pump will ride its pressure curve until bypass opens. Record the minimum flow across the heat exchanger. 12. Verify the coil or heat exchangers controller calibration, and record the entering and leaving water temperatures. 80
81 13. Record the coils design and actual flow (coils open for diversity) on a coil summary sheet and verify total coil flow equals within 10% of total pump flow, total primary heat exchanger flow, and total flow meter flow. 14. Show the actual gpm and head on the pump curve and establish and record the brake horsepower. (Note: with VFD, discharge valve and VFD must be at l00%.) Expansion or Compression Tanks Water expands, when heated, in direct proportion to its temperature. In hydronic systems, an allowance must be made for this expansion, otherwise a pipe or piece of equipment could burst. Open systems have expansion tanks to safely accommodate the increased volume of heated water. These tanks, open to the atmosphere, are installed about 3 feet above the highest point in the system. As the water volume increases, the water level rises in the tank (Figure 11.10). A better solution is to use a closed expansion or compression tank containing a gas, such as air. When water expands into such closed tanks, it compresses the gas (Figure 11.11). Once the system is filled with water (up to about two-thirds of the tank’s diameter) and the water is heated or cooled to operating temperature, the expansion tank will accommodate the fluctuations in water volume and will control the pressure change in the system. 81
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Balancing of a water and air system
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3 8 TBA (Testing, Balancing and Adj
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5 Air Balancing Multiple Hood syste
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7 87 Series Loop 88 One pipe main 9
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9 Testing and Balancing HVAC A syst
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11 13. Filter frame properly instal
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13 13. Measure and record all requi
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15 15 Example 3: Find the nearest s
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17 For traverses taken in round duc
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19 Flat Oval Duct Traverses For fie
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21 Balancing Devices Volume Dampers
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23 Turning Vanes Turning vanes (Fig
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25 Balancing the VAV System The gen
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27 maximum out-side air damper for
Page 29 and 30: 29 determines how much energy is in
Page 31 and 32: 31 the water removing capacity of a
Page 33 and 34: 33 Table 8A Dry Bulb on left, Wet B
Page 35 and 36: 35 60 58 56 54 52 50 48 46 44 42 40
Page 37 and 38: 37 Foot³ per 1lb Altitude 0 Feet A
Page 39 and 40: 39 Table 9 C Air Density at 29.29
Page 41 and 42: 41 41 Wet-Bulb (F) .0 .1 .2 .3 .4 .
Page 43 and 44: 43 Table 11A Enthalpy at saturation
Page 45 and 46: 45 Table 11 C Enthalpy at saturatio
Page 47 and 48: 47 Wet bulb temperature____________
Page 49 and 50: 49 and replacement should be shut o
Page 51 and 52: 51 duct may be great; the balancing
Page 53 and 54: 53 Design below the 250°F limit (A
Page 55 and 56: 55 Differential Pressure Gauges The
Page 57 and 58: 57 Venturi The venturi is a device
Page 59 and 60: 59 Pressure Total pressure Velocity
Page 61 and 62: 61 Table 1 shows that if the coil i
Page 63 and 64: 63 adjustment of these devices is n
Page 65 and 66: 65 Grouting Motor and lubrication N
Page 67 and 68: 67 For every outside temperature ot
Page 69 and 70: 69 4. Identify the riser with the h
Page 71 and 72: 71 2. Turn the pump off 3. Close th
Page 73 and 74: 73 Net positive suction head availa
Page 75 and 76: 75 All automatic control valves mus
Page 77 and 78: 77 77
Page 79: 79 4. Read and record the actual pu
Page 83 and 84: 83 Air Control Air is always presen
Page 85 and 86: 85 • allow draining of all or par
Page 87 and 88: 87 Valves have linear throttling ch
Page 89 and 90: 89 to all the terminals down the li
Page 91 and 92: 91 Pump Circuits Primary-Secondary
Page 93 and 94: 93 • Evaporator: • the design a
Page 95 and 96: 95 95
Page 97 and 98: 97 Condenser • the design and act
Page 99 and 100: 99 • Each reading of liquid tempe
Page 101 and 102: 101 • Design and actual entering
Page 103 and 104: 103 differs from the average by mor
Page 105 and 106: 105 • Orifice plate • Turbine m
Page 107 and 108: 107 BTUH = GPM X 60 X 8.337 X ∆T
Page 109 and 110: 109 Lam = lbs. of air per minute th
Page 111 and 112: 111 When dry bulb temperature measu
Page 113 and 114: 113 GPM = FPM X Gallons per foot FP
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