Greenheck Fan Greenheck 240XP-CUb - Manual (Page 7)

Model RSF and BCF Selection
The RSF and BCF selection charts are different from all
other selection charts. For these models, the cfm
values are at the left side of the chart in a single column
and the rpms are in the performance boxes. It is just the
opposite for other models. The reason for this is that
the RSF and BCF models are forward curved, and the
fan industry historically catalogs forward curved fans in
this fashion.
Sample problem:
Choose the fan size and appropriate motor horsepower
to move 980 cfm against 0.625 in. Ps.
Solution: (Refer to table below)
The first row in the chart corresponds to 980 cfm.
Follow across to the right to the 0.625 in. Ps column.
The performance box reveals that size 90 will meet this
performance at 893 rpm and will require 0.20 Bhp.
Motor hp selection for forward curved fans is more
complicated. The Bhp is only 0.20, which suggests that
a 1/4 hp motor is adequate. However, forward curved
fans draw more horsepower at low Ps than at high Ps.
Assume this fan was running at about 893 rpm, but
instead of 0.625 in. Ps, it was operating at only 0.25 in.
Ps. The new performance box in the 0.25 in. Ps column
reveals 894 rpm at 0.45 Bhp. The airflow would then be
1860 cfm.
Notice that as the Ps was reduced from 0.625 in. to 0.25
in., the Bhp increased from 0.20 to 0.45. This would
burn out the 1/4 hp motor quickly. With this in mind, it is
good practice to size RSF and BCF motors at least one
size larger than necessary based on the Bhp value in
the performance box, especially if the estimated Ps is
questionable.
For this case, an RSF-90-3 (1/3 hp motor) would be a
good selection if we had confidence in the estimated
Ps. Otherwise, use an RSF-90-5 (1/2 hp motor).
RSF-90-4 (1/4 hp motor) is not recommended for this
job.
Matching a Specification
There will be times when a Greenheck model will have
to be matched to a competing manufacturer’s unit. To
aid in these circumstances, we have provided a cross
reference chart which includes our nine most common
competitors. If the manufacturer you need is not on this
chart, contact Greenheck for assistance.
To use the cross reference chart, on next page, start
with the manufacturer at the top. Then follow down
until the model in question is found. Follow across to
the left to determine which Greenheck model is
equivalent. Once this is determined, refer to the
Greenheck catalog to find the best size to meet the
specified performance.
Hint: Typically, when matching a Greenheck fan to a
competitive model, the size should also be matched. If
you are unsure of the size of the competitive unit,
compare fan rpm. Fans of equal size should move
approximately the same amount of air.
0.125 0.250 0.375 0.500 0.625 0.750 1.000 1.250 1.500 1.750
RSF-90
980 1065
1200 1304
1420 1543
1640 1783
1860 2022
2080 2261
1240 1097
1780 1575
2140 1894
STATIC PRESSURE / CAPACITY
MODEL
CFM OV
RSF-100
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
rpm
Bhp
521 630 725 812 893 967
0.08 0.11 0.13 0.16 0.20 0.23
593 685 771 849 925 994 1125
0.13 0.16 0.19 0.23 0.26 0.30 0.38
668 747 825 898 966 1031 1153 1267 1371
0.19 0.23 0.27 0.31 0.35 0.39 0.48 0.57 0.67
746 819 887 953 1016 1077 1191 1298
0.28 0.33 0.37 0.42 0.46 0.51 0.61 0.71
828 894 954 1014 1073 1128 1236
0.40 0.45 0.50 0.55 0.60 0.65 0.76
910 970 1027 1080 1134
0.54 0.60 0.66 0.71 0.77
476 572 656 733 807 876
0.10 0.13 0.16 0.19 0.23 0.27
605 679 748 813 873 931 1040 1143 1240
0.24 0.29 0.33 0.38 0.42 0.47 0.56 0.66 0.77
699 763 823 880 935 989 1086 1181 1269 1354
0.40 0.45 0.50 0.56 0.61 0.67 0.78 0.89 1.00 1.12
7