Infinity REU-V3232W / HD250E REU-V3232WC - 4 - Issue 1 - 8/09/03 ©Rinnai
3. Water Flow Rates and Pressures
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:
M = 60 x ( Q / C x T )
Where M = Water flow rate in litres/minute. If M is ≤ to 32, the water is unmixed, the entire flow goes
through the water heater. If M > 32 the hot water from the unit is mixed with cold water.
Q = Heat energy available in kW = 56kW for the Infinity 32e and 70e
C = Specific heat of water = 4.2KJ/Kg C. This 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 = 56
C = 4.2
M = 60 x ( 56 / (4.2 x 10) ) = 80 l/min. Since 80 is greater than 32, this flow rate is mixed. This result
corresponds with the value in Table 1.
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