Magic Aire HHA Series, Installation, Operation And Maintenance Manual

Page: 51 / 66

035-000029-001 Page 51 HHA IOM 1.4 10/11/2021
Table 5a—5c
Constant CFM Differential Pressure (DP) Set Points
SERVICE-VFD Parameters—Cont’d
DP SET POINT
(inches w.g.)
Parameter 4011
CFM
0.5 353
1.0 433
1.5 521
2.0 560
2.5 614
3.0 694
3.5 752
4.0 793
4.5 832
5.0 869
5.5 916
6.0 950
6.5 983
7.0 1015
7.5 1045
8.0 1075
8.5 1104
9.0 1132
9.5 1169
10.0 1205
10.5 1239
11.0 1264
11.5 1305
DP SET POINT
(inches w.g.)
Parameter 4011
CFM
2.0 1095
2.5 1222
3.0 1372
3.5 1475
4.0 1561
4.5 1662
5.0 1775
5.5 1838
6.0 1916
6.5 1975
7.0 2040
7.5 2223
8.0 2288
8.5 2352
9.0 2406
9.5 2567
10.0 2641
10.5 2701
11.0 2748
11.5 2805
Table 5a
HHA04 through HHA12
Table 5b
HHA16 through HHA25
Constant CFM Control Option
With the constant CFM option the pressure transducer measures differential pressure (DP, units of in
w.g.) across the fan inlet “nozzle”. The DP signal goes to the VFD which has the control logic, and the
controls change fan RPM to try to maintain the DP setpoint. As the filters load up, the airflow drops
and the control loop speeds up the fan to compensate, keeping the DP (and therefore CFM) the
same. Below is the procedure for changing the DP setpoint. Tables 5a and 5b show airflow and cor-
responding DP settings to choose from. Note that the VFD will limit the max RPM and motor current to
protect the motor and drive, so some of these settings won’t be possible with all static pressures.
To change constant CFM setpoint: change VFD parameter 4011 to the value in the table that corre-
sponds to the desired CFM.
For example: HHA20 needs to operate at 2040cfm. Go to the HHA16-25 table, locate 2040cfm, read
DP Set Point of 7.0 inches w.g. (first column), so 7.0 will be the setting for parameter 4011.
Table 5c
HHA30 through HHA40
DP SET POINT
(inches w.g.)
Parameter 4011
CFM
0.5 1785
0.8 2075
1 2243
1.3 2467
1.5 2600
1.8 2784
2 2898
2.3 3059
2.5 3162
2.8 3310
3 3406
3.3 3544
3.5 3634
3.8 3763
4 3846
4.3 3965
4.5 4041
4.8 4151
5 4222