Lennox FCM 85 Installation, Operating And Maintenance page 53

VENTILATION : AIRFLOW BALANCING
nd
2 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 formulae:
=
rpm rpm
FAN
Where: rpm :from the motor plate or table_2
MOTOR
D : from table_1
M
D : from machine
F
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:
η
P = P x
meca fan meca Motor Transmission
η
P = P x
meca fan elec meca motor
= V x I x √3 x cosϕ x η
P
meca fan
This formula can be approximated in this way
P
= V x I x 1.73 x 0.85 x 0.76 x 0.9
meca fan
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.
Table_3 Accessories pressure drops
Economiser
12000 12
85
15000 19
23000 45
14000 17
100
18500 29
23000 45
15000 19
120
20500 36
23000 45
18000 6
150
26000 12
35000 22
21000 8
170
30000 16
35000 22
24000 12
200 35000 26
43000 39
27000 15
39000 32
230
43000 39
FLEXYII_WSHP-IOM-0909-E
×
D /D
MOTOR M F
η
x
Transmission
x η
meca motor Transmission
UV Hot
G4 F7
LIGH Water
Filters Filters
T coil S
1 75 18 9
7 105 30 13
28 199 63 26
5 94 26 11
15 143 44 18
28 199 63 26
7 105 30 13
21 167 52 21
28 199 63 26
1 75 15 6
12 130 33 12
29 204 54 19
5 94 21 8
19 161 42 15
29 204 54 19
3 88 18 7
18 154 39 13
31 211 54 19
7 105 24 8
24 182 46 16
31 211 54 19
CHECKING AIRFLOW AND ESP
Using the fan curves on page 36 to 40, the airflow, the total
pressure available (P
pressure (Pd) can now be estimated, for a specific
operating point;
The next step consists in estimating the pressure losses
across the unit.
This can be achieved using the "dirty filter pressure sensor"
and the accessories pressure drop table: table_3
Also the pressure drop due to the duct inlet into the roof-top
unit can be taken as 20 to 30 Pa.
∆
P
INT
Using the results from above, the external static pressure
(ESP) can then be estimated:
Table_ 2 Motor information
Motor Size
0.75 kW
1.1kW
1.5kW
2.2kW
3.0kW
4kW
5.5kW
7.5kW
9.0kW
11.0kW
Hot Electric Electric Electric
Water Heater Heater Heater
coil H S M H
15 3 5 6
22 6 7 7
44 7 9 11
19 6 7 8
31 8 10 11
44 11 14 16
22 7 8 9
37 10 12 13
44 12 15 17
10 4 5 7
19 9 10 13
33 15 18 23
14 8 9 10
25 10 13 15
33 17 19 21
11 16 15 14
22 22 21 20
31 24 26 29
14 18 18 17
26 24 24 25
31 24 26 29
) and the corresponding dynamic
TOT
∆ ∆ ∆
= P + P + P
filter + coil Inlet
∆
ESP = P - Pd - P
TOT INT
Cos ϕ
Nom. Speed
1400 rpm 0.77
1429 rpm 0.84
1428 rpm 0.82
1436 rpm 0.81
1437 rpm 0.81
1438 rpm 0.83
1447 rpm 0.85
1451 rpm 0.82
1455 rpm 0.82
1451 rpm 0.85
Heating Multidire
Adjustable
Gaz ctional
roofcurb
fired H Roofcurb
14 17 22
23 27 33
53 63 73
20 23 30
34 41 51
53 63 78
23 27 35
42 50 62
53 63 78
16 30 35
33 62 72
59 112 131
21 40 49
44 82 95
59 112 131
21 53 67
44 112 133
66 169 195
26 67 84
55 139 163
66 169 195
Options
η
meca motor
0.70
0.77
0.79
0.81
0.83
0.84
0.86
0.87
0.88
0.88
Heat
Recovery
Modul
Fresh Air
164
204
313
191
252
313
204
279
313
170
245
329
198
282
329
173
252
310
195
281
310
Page 51