Optional Piezometer Ring Airflow Measurement Device - Daikin Skyline IM 777-8 Installation And Maintenance Manual

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.
Below are the equations and factors required to calculate flow
using the piezometer ring:
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 2
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 1 below
Standard Density Method
The equation can be simplified by assuming standard
density and assuming funnel dimensions match the drawing
dimensions. Table 17 shows 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 2
ΔP = The differential in static pressure from the piezometer ring
and the front pressure tap (inches w.g.)
IM 777-8 • Skyline Air Handler
Table 16: DDPL Factors For Free and Ducted Inlet—
Non Standard Density Method
Product
DDPL Size 11-16
DDPL Size 18-44
Table 17: DDPL Factors For Free and Ducted Inlet—
Standard Density Method
DDPL Size Free Inlet F
11 and 12 944.92
15 1206.40
16 1518.58
18 1821.92
20 2185.80
22 2713.93
24 3285.02
27 3997.61
30 4945.21
33 5968.62
36 7290.21
40 8869.55
44 10827.92
Optional Transducer for Piezometer Rings
A transducer is available for Piezometer rings. Factory
mounting locations for the fan transducer is shown in
for direct-drive plenum fans.
for fan array. Wiring for the transducer is field-supplied and
installed.
28
o G
peraTIon uIdelInes
C1 Free Inlet C1 Ducted Inlet
753.06 794.06
692.03 740.14
Ducted Inlet F Area A
996.36 0.344
1272.08 0.439
1601.26 0.552
1948.58 0.721
2337.76 0.865
2902.60 1.074
3513.39 1.300
4275.53 1.582
5289.01 1.957
6383.56 2.362
7797.03 2.885
9486.16 3.510
11580.68 4.285
Figure 45
Figure 46 shows the installation
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