Page 54 - IOM / ROOFTOP BALTIC Series - 0704 - E
VENTILaTION : AIRFLOW BALANCING
2nd method when adjusting the pulley :
-Close the pulley fully and count the number of turns from
fully closed position. Using table 1 determine the motor
pulley actual diameter.
-Record the fix fan pulley diameter.(DF)
-Determine the fan speed using the following formula:
rpm
FAN
= rpm
MOTOR
x D
M
/ D
F
Where : rpm
MOTOR
:from the motor plate or table 2
D
M
: from table 1
D
F
: from machine
Once the pulleys are adjusted and the belt checked and
tensioned, start the fan motor and record the Amps and
Voltage between the phases :
Using the measured data and table 2
-Theoretical mechanical power at the fan shaft :
P
meca fan
= P
meca Motor
x η
Transmission
P
meca fan
= P
elec
x η
meca motor
x η
Transmission
P
meca fan
= V x I x √3 x cosϕ x η
meca motor
x η
Transmission
This formula can be approximated in this way
P
meca fan
= V x I x 1.73 x 0.85 x 0.76 x 0.9
With the fan "rpm" and the mechanical power at the fan
shaft an operating point and the supplied airflow can be
estimated using the fan curves.
CHECKING AIRFLOW AND ESP
Using the fan curves on page 25, 26, 27, the airflow, the
total pressure available (P
TOT
) and the corresponding
dynamic pressure (Pd) can now be estimated, for a
specific operating point;
The next step consist in estimating the pressure losses
across the unit.
This can be achieved using the "dirty filter pressure
sensor" and the accessories pressure drop table:
Also the pressure drop due to the duct inlet into the roof-
top unit can be taken as 20 to 30 Pa.
∆∆
∆∆
∆P
INT
=
∆∆
∆∆
∆P
filter
+ coil + P
Inlet
+
∆∆
∆∆
∆P
Options
using the results from above, the external static pressure
(ESP) can then be estimated:
ESP = P
TOT
- Pd -
∆∆
∆∆
∆P
INT
Table 2
MotorSize Nom. Speed Cosϕ η meca motor
0.75 kW 1400 rpm 0.77 0.70
1.1kW 1429 rpm 0.84 0.77
1.5kW 1428 rpm 0.82 0.79
2.2kW 1436 rpm 0.81 0.81
3.0kW 1437 rpm 0.81 0.83
4kW 1438 rpm 0.83 0.84
5.5kW 1447 rpm 0.83 0.86
7.5kW 1451 rpm 0.82 0.87
Table - 3 - Accessories pressure drops
EU4 F7 Hot Electric Multi- Heat Recovery
Economiser Filters Filters Water Coil heater (Pa) roofcurb directional module module
SIZE Airflow (Pa) (Pa) (Pa) (Pa) S M H (Pa) (Pa) fresh air (1)
2900 18 0 39 31 37 38 40 16 23 108 69
020 3600 28 6 66 46 55 57 59 24 35 161 105
4300 39 12 98 61 76 79 81 35 50 226 151
3600 28 6 66 46 55 57 59 24 35 161 105
025 4500 43 14 108 66 83 85 88 38 55 247 165
5400 62 25 160 89 117 120 123 55 79 352 238
4300 17 1 43 40 42 45 47 19 18 113 68
030 5400 26 8 74 59 63 66 69 29 28 172 123
6500 38 15 111 80 89 93 96 42 41 244 178
5000 22 5 62 51 55 58 61 25 24 149 105
035 6300 36 14 104 76 84 88 91 39 38 230 167
7600 52 24 155 105 119 123 127 58 56 331 243
5800 18 0 39 46 50 53 57 16 23 92 63
040 7200 28 6 66 67 74 78 82 25 35 136 98
8600 40 12 98 91 101 106 111 36 51 190 139
6500 23 3 52 56 61 65 69 20 29 113 80
045 8100 36 10 86 82 91 95 100 32 45 170 124
9700 51 18 127 113 126 131 137 46 64 239 177
7200 28 6 66 67 74 78 82 25 35 136 98
050 9000 44 14 108 99 110 115 120 39 55 207 153
10800 63 25 160 136 154 160 166 56 80 293 220
8600 16 3 50 58 42 47 52 19 12 129 91
060 10800 25 9 84 86 61 67 73 29 18 198 143
13000 37 18 125 119 82 89 97 43 26 282 207
9 950 22 7 70 75 54 59 65 25 16 171 123
070 12600 35 16 117 113 78 85 92 40 25 266 195
14000 56 31 194 172 116 125 134 65 40 326 240
(1) to be added to extraction fan ESP
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