15
RP-HRPD-IOM (07-22) 132210-B
Duct Furnace Airflow
•
The duct furnace must be installed on the positive pressure side of the field-supplied blower .
•
The air distribution must be even over the entire heat exchanger . Turning vanes should be employed in elbows
or turns in the air inlet to ensure proper air distribution (refer to
Duct Furnace Blower Connections
section) .
•
The air throughput must be within the CFM range stated on the heater rating plate .
•
If it is determined that the blower CFM is greater than allowed or desirable, refer to the
section for instructions on determining the correct size of bypass duct required or refer to the
section for instructions on converting the furnace for a higher CFM application .
•
To determine temperature rise, the inlet and outlet air temperatures should be measured at points not affected by
heat radiating from the heat exchanger .
list the approved temperature rise range with the
required CFM and the internal pressure drop for each size of unit .
Table 9. Model RP Pressure Drop and Temperature Rise
Unit Size
Temperature Rise*
50°F
60°F
70°F
80°F
90°F
CFM/Pressure Drop
125
1840/0 .50
1535/0 .33
1315/0 .25
1150/0 .21
1020/0 .18
150
2210/0 .38
1840/0 .26
1580/0 .19
1380/0 .15
1225/0 .12
175
2580/0 .52
2150/0 .35
1840/0 .26
1610/0 .19
1430/0 .16
200
2945/0 .42
2455/0 .28
2105/0 .22
1840/0 .17
1635/0 .14
225
3315/0 .53
2765/0 .36
2370/0 .27
2070/0 .22
1840/0 .17
250
3685/0 .40
3070/0 .28
2630/0 .23
2300/0 .22
2045/0 .21
300
4420/0 .58
3685/0 .39
3160/0 .29
2765/0 .25
2455/0 .22
350
5160/0 .65
4300/0 .44
3685/0 .31
3225/0 .25
2865/0 .23
400
5895/0 .70
4915/0 .50
4210/0 .30
3685/0 .30
3275/0 .20
*
80% thermal efficient .
Table 10. Model HRPD Pressure Drop and Temperature Rise
Unit
Size
Temperature Rise
40°F
50°F
60°F
70°F
80°F
90°F
100°F
CFM/Pressure Drop
250
4630/1 .97
3704/1 .26
3086/0 .88
2646/0 .64
2315/0 .49
2058/0 .39
1852/0 .32
300
5556/1 .45
4444/0 .92
3704/0 .64
3175/0 .47
2778/0 .36
2469/0 .29
2222/0 .23
350
6481/2 .02
5185/1 .29
4321/0 .90
3704/0 .66
3241/0 .51
2881/0 .40
2593/0 .32
400
7407/1 .70
5926/1 .09
4938/0 .76
4233/0 .56
3704/0 .43
3292/0 .34
2963/0 .27
500
9259/1 .53
7407/0 .98
6173/0 .68
5291/0 .50
4630/0 .38
4115/0 .30
3704/0 .24
600
11,111/2 .14
8889/1 .37
7407/0 .95
6349/0 .70
5556/0 .54
4938/0 .42
4444/0 .34
700
12,963/2 .09
10,370/1 .34
8642/0 .93
7407/0 .68
6481/0 .52
5761/0 .41
5185/0 .33
800
14,815/2 .09
11,852/1 .34
9877/0 .93
8466/0 .68
7407/0 .52
6584/0 .41
5926/0 .33
Duct Furnace Blower Connections
⚠ WARNING ⚠
The furnace must be installed on the positive pressure side of the air-circulating blower.
•
Blowers should be bottom horizontal discharge when coupled to the duct furnace .
•
When a top horizontal discharge blower is connected to the duct furnace, ensure that sufficient length of duct is
provided to permit even flow of air at the end of the duct . Or, baffles may be inserted between the blower and the
heater to ensure an even flow of air across the heat exchanger .
•
Proper arrangements of blower and duct furnace with respect to angle of approach of the duct connection and the
arrangement of the discharge opening of the blower are shown in
.
