Rinnai 37AHA04508KA5 Installation, Operation And Maintenance Manual page 28

Selection Guide
SELECTION PROCEDURE (WITH EXAMPLE)
I. Define hot water load for the total required
domestic hot water usage.
To help with the sizing and selection of your new
Rinnai Tankless Water Heater (TWH), refer to our
website at: http://www.foreverhotwater.com/
contact Rinnai's Application Engineering Department
at: 1-800-621-9419
As an example let's assume that the selected Rinnai
Tankless Water Heater for your whole house solution
is the REU-V2020WC (C53) and your calculated heat
gain and heat loss values are as stated in section II.
II. Determine cooling and heating requirements at
design conditions:
The ACCA's Manual J Residential Load Calculation
method is the established trade standard, approved by
ANSI, for the correct sizing and selection of Heating,
Ventilation, Air-Conditioning and Refrigeration
(HVACR) equipment in residential homes. The most
recent revision is the eighth edition, an all-inclusive
new approach to ensuring that Indoor Air Quality (IAQ)
systems are as efficient, safe, and healthy as possible.
Refer to the Air Conditioning Contractors of America
website at: http://www.acca.org/tech/manualj/
qualified HVACR contractor for further assistance.
Assumptions:
Required Cooling Capacity ...................34,500 Btuh
(Total Capacity)
Required Heating Capacity....................60,000 Btuh
Evaporator Air Quantity........................1200 CFM
External Static Pressure .......................0.2 in. WC
Electrical Characteristics......................115-1-60
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III. Determine total external static pressure (ESP)
Before using the Dry Coil Air Delivery Table 4,
calculate the total static pressure required. From the
given example, note the Wet Coil Pressure Drop
(selected from the field supplied Evaporative Cased
or
Coil Installation Instructions), and the Filter Pressure
Drop (for the Rinnai factory supplied filter this number
is 0.08 WC – if other than the Rinnai factory supplied
filter is employed refer to filter manufacturer's
installation Instructions). Determine both static
pressures at 1200 CFM:
Wet Coil Pressure Drop......0.21 in. WC
Manufacturer's Installation Instructions).
External Static Pressure......0.2 in. WC
Filter Pressure Drop...........0.08 in. WC
(
the filter manufacturer's installation instructions).
Total Static Pressure.......... 0.49 in. WC
IV. Select unit based on required cooling capacity
For an initial selection, choose a unit size that will
provide the required airflow. Refer to Table 4 Dry Coil
or a
Air Delivery. Note that at 0.5 ESP (external static
pressure) the 37AHA06012KA5 unit will deliver 1240
cfm when configured for HIGH Speed.
V. Select heating capacity of unit to provide the
From the Hydronic Air Handler Output table for the
37HAH045 & 060 units (Table 5), note that the unit
37AHA06012KA5 (as selected above) when matched
with the REU-V2020WC (C53) TWH will provide 61.1
MBH (61,100 Btuh) at an input water temperature (to
Air Handler) of 150
VI. Select unit that corresponds to power source
Refer to Model Number Nomenclature; note the
eleventh digit denotes the voltage code; therefore the
"K" model (37AHA06012KA5) unit is the unit that
should be selected for the above stated hypothetical
conditions. This unit is designed to operate at
115/120-1-60.
Rinnai Corporation Hydronic Air Handler Manual
at design conditions:
0.08 inches if the included Rinnai filter is used; otherwise refer to
airflow:
requisite design condition.
O
F.
available:
(From Coil
(Ductwork etc.)