Lennox ROOFTOP FLEXY FCA 100, Installation, Operation And Maintenance Manual

Page: 26 / 142

Page 24 - IOM / ROOF-TOP FLEXY™ Series
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 DM / DF
Where :
rpm MOTOR : ....... from the motor plate or table 2
DM : ...................... from table 1
DF: ........................ 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 cos
ϕ
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
Motor Size Nom, Speed Cos meca motor
0,75 kW 1400 rpm 0,77 0,70
1,1 kW 1425 rpm 0,82 0,77
1,5 kW 1430 rpm 0,81 0,75
2,2 kW 1430 rpm 0,81 0,76
3,0 kW 1425 rpm 0,78 0,77
4 kW 1425 rpm 0,79 0,80
5,5 kW 1430 rpm 0,82 0,82
Economiser EU7 Hot water coil Electric heater Roofcurb Horizontal Gaz
100% open Filter S H S H Base frame Roofcurb H
SIZE Air flow (m 3 /h) (Pa) (Pa) (Pa) (Pa) (Pa) (Pa) (Pa) (Pa) (Pa)
Min. 10 000 4 67 12 14 5 8 10 41 22
60
Nom. 12 000 6 93 16 19 8 8 11 59 26
Max. 15 000 9 135 24 28 8 10 13 92 31
Min. 12 000 6 56 6 12 5 5 13 59 29
70
Nom. 14 000 8 73 8 16 5 5 16 80 34
Max. 18 000 12 113 13 25 8 8 22 132 47
Min. 14 000 8 73 8 16 5 8 18 44 7
85
Nom. 16 000 10 113 13 25 8 8 26 57 10
Max. 22 000 16 159 18 36 8 10 32 109 12
Min. 16 000 10 93 10 20 8 10 26 57 10
100
Nom. 20 000 14 135 15 30 10 13 32 90 12
Max. 22 000 16 159 18 36 13 15 38 109 15
Min. 18 000 12 113 13 25 10 13 32 33 29
120
Nom. 22 000 16 159 18 36 13 15 38 49 35
Max. 24 000 18 184 21 41 15 18 44 58 40
Min. 20 000 14 135 15 30 10 15 35 40 31
140
Nom. 24 000 18 184 21 41 15 18 46 58 40
Max. 25 000 19 197 22 44 15 20 50 63 43
Min. 22 000 16 87 9 18 8 8 24 49 45
160
Nom. 28 000 22 132 13 27 8 10 30 79 56
Max. 32 000 26 165 17 34 13 13 34 103 64
Min. 24 000 18 101 10 20 10 10 34 58 64
190
Nom. 33 000 27 174 18 36 13 13 41 109 77
Max. 36 000 30 201 21 41 13 15 48 130 89
Table 5.52