Water Flow Rates And Pressures - Rinnai REU-V1620WG Service Manual

3. Water Flow Rates and Pressures

Water Flows
Table 1 shows unmixed and mixed water flow rates and approximate gas consumptions for various
temperature rises. The unmixed flow rates are the flow rates available at the given temperature rise directly
at the outlet of the water heater. The mixed water flow rates are available at the given temperature rise by
mixing hot water from the outlet of the water heater with cold water from the mains supply.
Water Flows can also be calculated by the following formula :
Q = Heat energy available in kW = 28 kW for the REU-V1616W / REU-V1620W
C = Specific heat of water = 4.2KJ/Kg °C. C does not change for the purpose of this calculation.
∆
T = Temperature rise required (°C)
Example:
What is the flow rate available with an incoming water temperature of 10°C and a required temperature of
20°C?
∆
T = 20 - 10 = 10°C
Q = 28
C = 4.2
M = 60 x ( 28 / (4.2 x 10) ) = 40 l/min. Since 40 is greater than 16 this flow rate is mixed. This result
corresponds with the value in Table 1.
REU-V2018W and REU-V2020W
Q = Heat energy available in kW = 36 kW for the REU-V2018W / REU-V2020W
C = Specific heat of water = 4.2 KJ/Kg °C. C does not change for the purpose of this calculation.
∆
T = Temperature rise required (°C)
Example:
What is the flow rate available with an incoming water temperature of 10°C and a required temperature of
20°C?
∆
T = 20 - 10 = 10°C
Q = 28
C = 4.2
M = 60 x ( 28 / (4.2 x 10) ) = 40 l/min. Since 40 is greater than 20 (18) this flow rate is mixed. This result
corresponds with the value in Table 1.
Infinity REU-V1616W / REU-V1620W / REU-V2018W / REU-V2020W- 5 -
Issue 2 - 21/03/06 ©Rinnai