Water Flows - Rinnai REU-2018W Service Manual

11. Water Flows

A simple calculation of the water flow rate, in litres per minute, can be made using the charts on
the next page, or simply using the formula provided below. The charts on the following pages
indicate the water flow from the Infinity at various combinations of incoming water temperatures,
and the selected temperature at the remote control.
How to read the charts:
The vertical plane indicates the selected temperature at the remote, and the horizontal plane
indicates the flow of water in litres per minute. Remote control range is between 50°C, therefore
the water flow charts only show the temperatures in that range. The temperature rise is the
difference between the temperature of the incoming water and the selected temperature at the
remote controls.
Select the appropriate chart depending on the incoming water temperature. Draw a horizontal line
across the graph from the selected temperature at the remote until it intersects the curve. At this
point draw the line in the vertical direction. The water flow is indicated where the line intersects
the bottom of the chart.
How to calculate water flows:
The following information is an outline of the formula required to measure accurately the flow rate
in litres per minute, as well as being the base for the charts on the next page. The most useful
way in which this formula can be utilised, is to calculate the water flow rate where there is
maximum gas input of 188MJ/h.
Where: T
IN
T
OUT
IN
TE
Q
# This is the maximum gas input converted from MJ/h into kilocalories. As 1 kilocalorie raises
the temperature of 1 litre of water by 1 degree centigrade, the method of calculation is to
multiply the input in MJ/h by 239.
* Thermal efficiency may be in the range of 78% to 90%, depending on the
temperature rise and water flow. For the purpose of the following calculation we
have assumed an efficiency of 80%.
Example Data
TIN =15°C
TOUT = 60°C
IN = 45000kcal/h
TE = 80%
Q = Water flow in Litres per minute
Infinity REU-2425W
T
Formula: IN x TE = (
= Incoming water temperature.
= Outgoing water temperature as selected at the remote
Gas input # .
=
= Thermal efficiency*.
= Water flow in litres per minute.
- 16 -
T
OUT - IN) x 60 x Q
Calculation
T T
IN x TE = ( - ) x 60 x Q
OUT IN
45000 x 0.8 = (60 - 15) x 60 x Q
36000 = 45 x 60 x Q
36000
= 60 x Q
-------------- -
45
800 = 60 x Q
800
= Q
-------- -
60
13.3 L/min
Issue 2 - 5/07/04 ©Rinnai