Honeywell EN2H-0221GE51 R0808 service manual Bypass pump RBP

Hydraulic Components SDC / DHC

7.2.17.1Bypass pump (RBP)

Function The simplest way of controlling the return flow temperature is by means of a bypass pump. When the return temperature in the heat generator drops below the set boiler return minimum temperature limit, flow mixing is initiated by switching on a bypass pump parallel to the heat generator. As soon as the return temperature rises above the return minimum temperature plus the return switching differential, the bypass pump will be deactivated after the set delay time (extended pump running time "bypass pump"). As the mixing itself is not controlled, the bypass cross sections must be taken into account for the system layout.

When the switch-off condition is reached, the bypass pump is switched off with a time delay in accordance with the set value.

NOTE To avoid intermittent operation of the bypass pump, the return sensor must always be positioned downstream of the mixing point for this mode of return temperature control.

7.2.17.2Return maintenance through controlled feed water addition

Function If the control unit is equipped with a mixed heating circuit output, this output can be programmed for controlled flow mixing.

In this mode of return control the programmed mixed heating circuit adjusts the return temperature to the return temperature setpoint. The adjustment is independent of the status of any start- up protection of the heat generator. The return sensor for this function is connected at the sensor input of the respective mixed heating circuit (e.g. flow sensor 1 for mixed heating circuit 1).

The mixed heating circuit pump operates like a boiler circuit pump without boiler start-up protection for this purpose.

160 EN2H-0221GE51 R0808