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Rinnai Corporation Hydronic Furnace (37AHB) Manual 57
NOTES:
1. EWT - Entering Water Temperature (F).
2. CFM - Airflow in (Cubic Feet per Minute).
3. Legs - 3 inch diameter flexible ducts to diffusers.
4. 1 MBH = 1000 BTU/H.
5. Shaded box represents rating point; refer to wiring diagram for factory set speed taps.
6. Number of 3” diameter legs specified in table above is for rating point only (i.e. at External Static Pressure of 0.5
in. wc. and speed TAP3, TAP1, TAP2 , TAP2 for AHB45, AHB60, AHB75, AHB90 respectively). Final leg count is
to be determined by the installing contractor and is to be based on the following formula:
NUMBER OF LEGS = TOTAL AVAILABLE CFM
(AT THE SPECIFIC ESP)
/ DESIRED CFM per LEG
(40, 50, or 60 CFM)
Example: Given the design point for AHB045 of 0.8 ESP, Low fan speed (Tap5). From table 5.0, available CFM is
569 and the desired CFM per leg is 50 CFM. Therefore, Number of Legs = 569/50 = 11.38 rounded down to 11.
0 0.1 0.2 0.3 0.4 0.5 0.6 0.7 0.8 0.9 1.0
1700 1666 1635 1604 1576 1543 1518 1492 1465 1430 1402
120 50.1 49.1 48.1 47.2 46.4 45.4 44.7 43.9 43.1 42.1 41.3
130 59.7 58.5 57.4 56.3 55.3 54.2 53.3 52.4 51.4 50.2 49.2
140 68.8 67.4 66.2 64.9 63.8 62.5 61.4 60.4 59.3 57.9 56.8
150 79.9 78.3 76.9 75.4 74.1 72.5 71.4 70.1 68.9 67.2 65.9
160 89.5 87.7 86.1 84.5 83 81.2 79.9 78.6 77.1 75.3 73.8
1561 1524 1490 1456 1428 1396 1364 1330 1230 1265 1224
120
50.9 49.7 48.6 47.5 46.6 45.6 44.5 43.4 40.1 41.3 39.9
130
60.6 59.2 57.8 56.5 55.4 54.2 53.0 51.6 47.7 49.1 47.5
140
68.3 66.7 65.2 63.7 62.5 61.1 59.7 58.2 53.8 55.4 53.6
150
79.3 77.4 75.7 73.9 72.5 70.9 69.3 67.5 62.5 64.2 62.2
160
89.8 87.7 85.8 83.8 82.2 80.3 78.5 76.5 70.8 72.8 70.4
1391 1350 1320 1281 1245 1209 1170 1131 1090 1064 1031
120
51.5 50.0 48.9 47.4 46.1 44.7 43.3 41.9 40.3 39.4 38.2
130
60.6 58.8 57.5 55.8 54.2 52.6 50.9 49.2 47.5 46.3 44.9
140
71.7 69.6 68.0 66.0 64.1 62.3 60.3 58.3 56.2 54.8 53.1
150
81.0 78.6 76.9 74.6 72.5 70.4 68.1 65.9 63.5 61.9 60.0
160
91.2 88.5 86.6 84.0 81.6 79.3 76.7 74.2 71.5 69.8 67.6
1222 1174 1140 1100 1063 1014 979 937 887 829 777
120
47.3 45.4 44.1 42.5 41.1 39.2 37.9 36.2 34.3 32.1 30.0
130
53.2 51.1 49.6 47.8 46.2 44.1 42.6 40.8 38.6 36.1 33.8
140
64.3 61.7 60.0 57.8 55.9 53.3 51.5 49.3 46.6 43.6 40.9
150
73.4 70.5 68.5 66.1 63.8 60.9 58.8 56.3 53.3 49.8 46.7
160
81.8 78.6 76.3 73.6 71.1 67.9 65.5 62.7 59.4 55.5 52.0
37AHB07514KA5 + REU-VA3237FFU(W)-US/ASME
AHB75 + R98LSi(e)/ASME
TABLE 5.25: AIR DELIVERY AND PERFORMANCE DATA (BOTTOM OR SIDE RETURN w/ FACTORY SUPPLIED FILTER)
UNIT
SIZE
ECM
SPEED
TAP
SUPPORTS
COOLING CAP.
RANGE (TONS)
EWT (
O
F)
NOMINAL
HEATING
CAPACITY
External Static Pressure (ESP) in. W.C.
AIRFLOW (CFM)
TAP 1
(H)
4.0
NET
HEATING
CAPACITY
(MBH)
TBD
See Note 6.
AHB75 + R98LSi(e)/ASME
AIRFLOW (CFM)
TAP 2
(MH)
3.5
NET
HEATING
CAPACITY
(MBH)
27 32 40
Minimum Legs @
60 CFM/Leg
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
TBD
See Note 6.
TBD
See Note 6.
AHB75 + R98LSi(e)/ASME
AIRFLOW (CFM)
TAP 3
(ML)
3.0
NET
HEATING
CAPACITY
(MBH)
Minimum Legs @
60 CFM/Leg
TBD
See Note 6.
Minimum Legs @
60 CFM/Leg
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
Minimum Legs @
60 CFM/Leg
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
TBD
See Note 6.
TBD
See Note 6.
TBD
See Note 6.
NET
HEATING
CAPACITY
(MBH)
2.5
TAP 4
(L)
AIRFLOW (CFM)
AHB75 + R98LSi(e)/ASME
Number of 3" diameter branch legs applicable to High
Velocity Systems only. Uded only if methods other than
Table 3 is used to determine duct sizes.
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
TBD
See Note 6.
TBD
See Note 6.