Daikin Skyline OAH003GDAC, Руководство по установке и обслуживанию

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IM 777-18 • SKYLINE OUTDOOR AIR HANDLER 36 www.DaikinApplied.com
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Optional Piezometer Ring Airflow Measurement Device
Piezometer rings are available as an option on direct drive
plenum fans to measure airflow though the fan. The device
consists of a piezometer ring mounted in the throat of the
funnel and a static pressure tap mounted near the inlet of the
funnel. The pressure drop is measured from the tap located
near the inlet of the funnel to the piezometer ring in the throat.
The inlet tap is connected to the high-pressure side of the
transducer and the piezometer ring is connected to the low-
pressure side.
See the equations and factors required to calculate flow using
the piezometer ring.
NOTE: There are two manufacturer options for the piezometer
ring. Care should be taken to ensure that the
appropriate coefficients are used, otherwise airflow
measurement may be incorrect. Reference Figure 64
to determine which piezometer ring you have.
Figure 65: Determining the Manufacturer
Non-Standard Density Method
The following equation is used to measure the flow for non-
standard density:
ACFM = C1 × A × √(ΔP/ρ)
where: A = Inlet funnel throat area (square feet) - from Table 17
and Table 19
ΔP = The differential in static pressure from the piezometer ring
and the inlet pressure tap (inches w.g.)
ρ = Air density (pounds mass/cubic foot)
C1 = Value from Table 16 and Table 18
Standard Density Method
The equation can be simplified by assuming standard
density and assuming funnel dimensions match the drawing
dimensions. Table 17 and Table 19 show the factor (F) for each
fan size and type. The equation then becomes the following:
For standard air (ρ = 0.075 lb/ft3):
ACFM = F × √ (ΔP)
where: F = factor from Table 17 and Table 19
ΔP = The differential in static pressure from the piezometer ring
and the front pressure tap (inches w.g.)
Table 16: DDPL Factors For Free and Ducted Inlet —
Non Standard Density Method, TCF Piezo Ring
Product C1 Free Inlet C1 Ducted Inlet
DDPL Size 11-16 753.06 794.06
DDPL Size 18-44 692.03 740.14
Table 17: DDPL Factors For Free and Ducted Inlet —
Standard Density Method, TCF Piezo Ring
DDPL Size Free Inlet F Ducted Inlet F Area A
11 and 12 944.92 996.36 0.344
15 1206.40 1272.08 0.439
16 1518.58 1601.26 0.552
18 1821.92 1948.58 0.721
20 2185.80 2337.76 0.865
22 2713.93 2902.60 1.074
24 3285.02 3513.39 1.300
27 3997.61 4275.53 1.582
30 4945.21 5289.01 1.957
33 5968.62 6383.56 2.362
36 7290.21 7797.03 2.885
40 8869.55 9486.16 3.510
44 10827.92 11580.68 4.285