User manual

REU-V1616W/REU-V2018W/REU-V2020W - 5 - Issue 1 - 10/10/03 ©Rinnai

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 16e

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.

20e

Q = Heat energy available in kW = 36 kW for the 20e

C = Specific heat of water = 4.2 KJ/Kg C. C does not change for the purpose of this calculation.