Balancing of a Water and Air System (PDF

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84 Strainers The purpose of strainers (Figure 11.14) is to catch sediment or other foreign material in the water. A strainer contains a mesh screen formed into a sleeve that fits inside the strainer body. This sleeve must be removed and cleaned. A strainer with a dirty sleeve or a sleeve with a screen that is too fine means that there will be excessive pressure drop across the strainer and lower water flow. Strainers placed in the suction side of the pump must be properly sized and kept clean to avoid cavitation. Strainers should have pressure taps installed at the inlet and outlet. Strainers should only be used where necessary to protect the components in the system. For example, in the case of cooling towers, strainers in the tower basin may provide adequate protection. Individual fine mesh strainers may need to be installed before automatic control valves or spray nozzles, which operate with small clearances and require protection from materials that might pass through the pump strainer. Valves Valves are used in hydronic systems to: • control water flow • isolate part, or all of the system for servicing 84
85 • allow draining of all or part of the system • restrict operation to specific subsystems • allow quick filling of the system by bypassing the pressure-reducing valve Manual Valves Manual valves fall into two major categories: manual service valves and check valves. Manual service valves regulate flow rate. These include gate, globe, plug, ball, and butterfly valves. Check valves limit the direction of flow. Another manual valve, the combination valve, both regulates flow and limits direction of flow. Gate Valves Gate valves (Figure 11.15) regulate flow only in that they are either fully open or fully closed. They should not be used for throttling purposes because they produce a highvelocity water stream when partly closed, resulting in erosion of the valve seat. This is called wiredrawing, and will result in leakage when the valve is fully closed. Gate valves should be used for tight shutoff, and for servicing equipment. Gate valves allow a straight-through flow pattern, resulting in low-pressure drop. Globe Valves Globe valves (Figure 11.16) can be used in partially open positions and therefore can be used for throttling fluid flow. However, globe valves have high-pressure drops, even when fully open. Therefore, globe valves can unnecessarily increase the required pump head, and should not be used for balancing. They can, however, be used in water make-up lines. Note: If globe valves are ever tampered with, or used to shut off a system, it is difficult to reset the system. 85
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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 and 80: 79 4. Read and record the actual pu
Page 81 and 82: 81 13. Record the coils design and
Page 83: 83 Air Control Air is always presen
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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