Lennox Baltic BCK 020 Installation, Operating And Maintenance page 56

VENTILaTION : AIRFLOW BALANCING
EXAMPLE
The unit used for this example is a BGK035ND1M with Economiser and Electric Heater type H
It is fitted with a fan which curve is shown on page 57 and a 2.2kW motor.
- Motor rpm: 1430 rpm
- cos ϕ = 0.81
- Voltage = 400V
- Current = 3.77A (measured)
The unit is also fitted with a transmission kit 7
- Fixed Fan pulley : 160mm
- Motor adjustable pulley type "8450" opened 4 turns from fully closed or measured distance between pulley end plates is
26.4mm: from table 1 it can be determined that the motor pulley has a diameter of 99.2mm
Using the fan curve below the operating point can be located.
It can be determined that the fan is providing approximately 6300 m3/h with a total pressure P
530
Hd (mmH2O)
= V x I x √ √ √ √ √ 3 x cosϕ ϕ ϕ ϕ ϕ x η η η η η
P
mech fan
= 400 x 3.77 x 3 x 0.81 x 0.76 x 0.9 = 1.45kW
rpm = rpm x D / D
FAN MOTOR M
1,45
63
x η η η η η
mech motor Transmission
= 1430 x 99.2 / 160 = 886 rpm
F
Fig. 36
The pressure losses in the unit are
the sum of all pressure drops across
the different parts of a unit :
- Coil and filter (measured) = 104 Pa
886
- Inlet into the unit = 30 Pa
- Options = 23 Pa for economiser and
91 Pa for electric heater H
The dynamic pressure at 6300m3/h is
given at the bottom of the fan curve P 57
The external static pressure available
is therefore
ESP
IOM / ROOFTOP BALTIC Series - 0704-E Page 55
= 530 Pa
TOT
∆P = 104 + 30 + 23 + 91 = 248 Pa
Pd = 81Pa
- Pd - ∆PI
= P
TOT NT
= 530 - 81 - 248 = 201 Pa