Balancing of a Water and Air System (PDF

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22 and grilles should not be used for balancing because when throttled they create noise, change the flow factor, can be easily tampered with and are an unnecessary expense. Proper installation and location of balancing dampers in the takeoffs eliminates the need for volume controls at grilles and diffusers. Each damper should be adjustable with a locking quadrant handle or regulator and end bearings that have sufficient strength and rigidity for the pressures being controlled. The locking quadrant must be located outside the vapor seal of the insulation. Generally, parallel-blade dampers are used in mixing plenum applications, and opposed-blade dampers are used in a volume-control application. It should be noted that only a slight opening of an opposed blade volume damper might generate a relatively high noise level as the air passes through. To minimize generated duct noise at volume dampers, dampers should be located at least two duct diameters from a fitting and as far as possible from an outlet/inlet. A spin-in collar with a volume damper is used to make a run out to a grille or diffuser. They can be conical, bell mouth, flanged or notched. They should be used for ducts with velocities below 1000 fpm (5.1 m/s) and under 0.50” static pressure. The round damper must have a square rod with end bearings and standoff for externally insulated ducts and locking quadrants. The square rod must be continuous for all dampers 12” (300 mm) and above. The damper should also be stiffened to prevent movement in the airstreams. Splitter devices offer little or no control of air volume in ducts. They should be regarded as air diverters only with maximum effectiveness when present in duct systems exhibiting low resistance to airflow. When used as a diverter, splitter devices must have at least one push rod with a locking device. The push rod must be connected to the leading edge of the splitter at 90 degrees to the blade, not controlled by the quadrant handle on the pivot shaft. Splitter devices should be long enough to divert the airflow in the duct. As a minimum, the length should be twice the size of the smallest throat of the nested connection. The use of adjustable extractors (Figure 6.2) is not generally recommended because they can cause turbulence in the main trunk line, thereby increasing the system total pressure and affecting the performance of other branch outlets downstream. Extractors are not balancing devices and should not be used at branch or main duct takeoffs to provide volume control. Extractors are principally used to divert air to branch ducts when they are the full height of the duct. 22
23 Turning Vanes Turning vanes (Figure 6.3) reduce the pressure loss and provide a uniform velocity distribution downstream from mitered rectangular elbows when smooth radius rectangular elbows are not used. Turning vanes should be installed so that the air entering and leaving the vanes is parallel to the duct walls. Double thickness or single thickness with a trailing (extended) edge turning vanes should be used in all rectangular elbows. Air Balancing Tolerances All air quantities shall be measured according to National Standards. All air balancing tolerances shall be superseded by the specification if different. Total air quantity to each space shall be within ± 10% of design. Terminals shall be adjusted to design quantities in accordance with Figure 6.5. 23
Page 1 and 2: Balancing of a water and air system
Page 3 and 4: 3 8 TBA (Testing, Balancing and Adj
Page 5 and 6: 5 Air Balancing Multiple Hood syste
Page 7 and 8: 7 87 Series Loop 88 One pipe main 9
Page 9 and 10: 9 Testing and Balancing HVAC A syst
Page 11 and 12: 11 13. Filter frame properly instal
Page 13 and 14: 13 13. Measure and record all requi
Page 15 and 16: 15 15 Example 3: Find the nearest s
Page 17 and 18: 17 For traverses taken in round duc
Page 19 and 20: 19 Flat Oval Duct Traverses For fie
Page 21: 21 Balancing Devices Volume Dampers
Page 25 and 26: 25 Balancing the VAV System The gen
Page 27 and 28: 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
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79 4. Read and record the actual pu
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81 13. Record the coils design and
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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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