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Rinnai Corporation Hydronic Furnace (37AHB) Manual 51
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
948 921 891 868 841 819 795 772 701 596 567
120 34.4 33.5 32.4 31.5 30.6 29.8 28.9 28.0 25.5 21.7 20.6
130 40.1 38.9 37.7 36.7 35.5 34.6 33.6 32.6 29.6 25.2 24.0
140 46.6 45.2 43.8 42.6 41.3 40.2 39.1 37.9 34.4 29.3 27.9
150 54.5 53 51.3 49.9 48.4 47.1 45.7 44.4 40.3 34.3 32.6
160 59.6 57.9 56 54.6 52.9 51.5 50.0 48.5 44.1 37.5 35.6
921 891 864 836 812 788 768 742 699 594 559
120 33.7 32.6 31.6 30.6 29.7 28.8 28.1 27.1 25.6 21.7 20.4
130 40.2 38.9 37.8 36.5 35.5 34.4 33.6 32.4 30.5 26.0 24.4
140 46.6 45.1 43.7 42.3 41.1 39.9 38.8 37.5 35.4 30.0 28.3
150 54.2 52.4 50.8 49.2 47.8 46.4 45.2 43.7 41.1 34.9 32.9
160 60.2 58.2 56.4 54.6 53.0 51.5 50.2 48.5 45.7 38.8 36.5
803 768 740 712 682 652 628 596 569 541 510
120 32.2 30.8 29.7 28.5 27.3 26.1 25.2 23.9 22.8 21.7 20.4
130 38.2 36.5 35.2 33.8 32.4 31.0 29.8 28.3 27.0 25.7 24.2
140 44.9 42.9 41.4 39.8 38.1 36.5 35.1 33.3 31.8 30.2 28.5
150 51.4 49.2 47.4 45.6 43.7 41.7 40.2 38.2 36.4 34.6 32.6
160 57.4 54.9 52.9 50.9 48.8 46.6 44.9 42.6 40.7 38.7 36.5
EWT (
O
F)
NOMINAL
HEATING
CAPACITY
External Static Pressure (ESP) in. W.C.
SUPPORTS
COOLING CAP.
RANGE (TONS)
TBD
See Note 6.
TBD
See Note 6.
Maximum Legs @
40 CFM/Leg
37AHB04508KA5 + REU-VA2024WD(A)-UC
AHB45 + R63LSe2
AIRFLOW (CFM)
TAP 3
(H)
2.0
NET
HEATING
CAPACITY
(MBH)
13
AHB45 + R63LSe2
AIRFLOW (CFM)
TAP 4
(M)
2.0
NET
HEATING
CAPACITY
(MBH)
TBD
See Note 6.
Minimum Legs @
60 CFM/Leg
AHB45 + R63LSe2
AIRFLOW (CFM)
TAP 5
(L)
1.5
NET
HEATING
CAPACITY
(MBH)
TBD
See Note 6.
Minimum Legs @
60 CFM/Leg
Optimal Legs @
50 CFM/Leg
16 20
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.
Minimum Legs @
60 CFM/Leg
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
TABLE 5.19: AIR DELIVERY AND PERFORMANCE DATA (BOTTOM OR SIDE RETURN w/ FACTORY SUPPLIED FILTER)
UNIT
SIZE
ECM
SPEED
TAP
Optimal Legs @
50 CFM/Leg
Maximum Legs @
40 CFM/Leg
TBD
See Note 6.
TBD
See Note 6.