Lennox FCM 85 Installation, Operating And Maintenance Manual page 47

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:
h
P = P x
meca fan meca Motor Transmission
h
P = P x
meca fan elec meca motor
= V x I x Ö3 x cosj x h
P
meca fan
This formula can be approximated in this way
P
= V x I x 1.73 x 0.78 x 0.87 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
G4
Filters
12000 1
85 15000 7
23000 28
14000 5
100 18500 15
23000 28
15000 7
120 20500 21
23000 28
18000 1
150
26000
12
35000 29
21000 5
170
30000 19
35000 29
24000 3
200 35000 18
43000 31
27000 7
39000 24
230
43000 31
FLEXYII_WSHP-IOM-1307-E
´
D /D
MOTOR M F
h
x
Transmission
x h
meca motor Transmission
UV Hot Hot
F7
LIGH Water Water
Filters
T coil S coil H
75 18 9 15
105 30 13 22
199 63 26 44
94 26 11 19
143 44 18 31
199 63 26 44
105 30 13 22
167 52 21 37
199 63 26 44
75 15 6 10
130 33 12 19
204 54 19 33
94 21 8 14
161 42 15 25
204 54 19 33
88 18 7 11
154 39 13 22
211 54 19 31
105 24 8 14
182 46 16 26
211 54 19 31
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.
D
P =
INT
Using the results from above, the external static pressure
(ESP) can then be estimated:
Table_ 2 Motor information
Motor Size Nom. Speed
0.75 kW
1.1kW
1.5kW
2.2kW
3.0kW
4kW
5.5kW
7.5kW
9.0kW
11.0kW
Electric Electric Electric Heating
Heater Heater Heater Gaz
S M H fired H
3 5 6 14
6 7 7 23
7 9 11 53
6 7 8 20
8 10 11 34
11 14 16 53
7 8 9 23
10 12 13 42
12 15 17 53
4 5 7 16
9 10 13 33
15 18 23 59
8 9 10 21
10 13 15 44
17 19 21 59
16 15 14 21
22 21 20 44
24 26 29 66
18 18 17 26
24 24 25 55
24 26 29 66
) and the corresponding dynamic
TOT
D D D
P + P + P
filter + coil Inlet
D
ESP = P - Pd - P
TOT INT
Cos j
1415 rpm 0,75
1435 rpm 0,78
1435 rpm 0,76
1450 rpm 0,78
1445 rpm 0,79
1445 rpm 0,75
1465 rpm 0,79
1460 rpm 0,79
1467 rpm 0,77
1460 rpm 0,79
Heat
Multidire
Adjustable Recovery
ctional
roofcurb Modul
Roofcurb
Fresh Air
17 22 164
27 33 204
63 73 313
23 30 191
41 51 252
63 78 313
27 35 204
50 62 279
63 78 313
30 35 170
62 72 245
112 131 329
40 49 198
82 95 282
112 131 329
53 67 173
112 133 252
169 195 310
67 84 195
139 163 281
169 195 310
Options
h
meca motor
79,9
83,7
84,2
87,1
85,7
86,7
89,0
89,1
90,9
90,4
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