Rinnai B20 Manuel de service télécharger pdf (Page 25)

REU-2532W Series 25 Rinnai

5. Combustion Fan

Air for the combustion is supplied by a centrifugal fan

driven by a DC motor. After a pre-purge period of 0.2

seconds, the fan speed is controlled by the PCB to

provide the correct volume of air for combustion. The

calculation for the fan speed is based upon incoming

water temperature, water flow and the temperature

selected on the remote controls.

The actual speed of the motor is continuously monitored

by a magnetic pulse sensor.

This sensor emits (4) pulses per rotation of the fan. This is

the fan feedback or confirmation data processed by the PCB.

1. The fan speed is constantly correcting to provide optimum combustion conditions.

2. To determine the opening degree of the modulating gas valve, so that the gas rate always matches the volume

of air for combustion, as well as the input required to heat the water.

The reason for controlling the opening degree of the modulating gas valve based upon data from the combustion

fan is that, the gas valve is able to react much more quickly to a change in control signal than the combustion fan

is. Controlling the gas valve based upon data from the combustion fan means that combustion remains

satisfactory, even if there are sudden changes in input conditions.

1. Water Flow Sensor and Water Flow Control device

Water flow is detected by a turbine/magnetic pulse generating device. Water flows through the turbine/magnetic

sensor providing information to the PCB by generating a pre-determined number of pulses in proportion to the

water flow. These pulses are counted by the PCB – no pulse indicates no water flow. The frequency of the

magnetic pulses increases as the water flow increases, this enables the PCB to calculate the exact water flow, and

determine the water flow in gallons per minute. As soon as the required water flow is detected, the PCB activates

the combustion fan. The combustion fan speed is monitored by a magnetic pulse sensor. The output from this

sensor is processed by the PCB which opens the gas modulating valve to a degree proportional to the fan speed.

See above for further details on the combustion fan.

The water flow control consists of a plug and barrel valve which is rotated by a motor to increase or decrease the

volume of water passing through the heat exchanger.

REU-2532 units have an automatic water flow control device.

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Rinnai B20 Manuel de service Page 25