Rinnai REU-2007W, Service Manual

Page: 37 / 69

Infinity REU-2007,2008,2408,2424 - 32 - ©Rinnai
In the case of the 2007, there is no direct connection between the mechanical water flow control
device with water flow sensor and the PCB, therefore, there could be occasions when the input
required to heat the water exceeds the capacity of the appliance, and water at a temperature lower
than that requested on the remote control is produced. In this case, annually reducing the water flow
at top will increase the temperature.
Once hot water is flowing the water temperature thermistor senses the outgoing water temperature.
The PCB continually makes adjustments in order to maintain a constant temperature; [adjusting both
the gas input and water flow in the case of the 2008 and 2408, where necessary.] It also continually
monitors the combustion fan rpm adjusting the gas rate to match.
When the hot water tap is turned off, the water flow sensor stops revolving, and the magnetic pulse
ceases, indicating to the PCB that there is no water flowing, in turn the PCB closes the gas valves.
The combustion fan continues to operate for 65 seconds. This is to provide quicker ignition when
the tap is turned on and off in rapid succession, as it removes the need for a pre-purge cycle, and
allows the burner to re-light immediately when a hot water tap is opened again.
The PCB stores data on the calculated incoming water temperature, ready for when the hot water is
turned on again. The data is used to calculate the initial gas flow.