7.4.1 Cleaning the bypass check valve
1. Turn off the electric power and gas supply to the combi boiler.
2. Isolate boiler circuit and drain.
3. Bypass circuit check valve access is by a bayonet plug on the left-hand side of the On-Demand
DHW block (see inFigure 46
4. Lightly push the bayonet knob, rotate counter-clockwise a quarter turn, and pull to remove.
5. Flush clean with water and replace.
7.4.2 Replacing the bypass actuator
1. Turn off the electric power and gas supply to the combi boiler.
2.
The actuator ( inFigure 46 is located immediately behind the flow sensor and can be
removed without isolating the water. Unplug the control wire from the bypass valve
actuatorFigure 46
3. The actuator slides to the left out from its base for inspection or replacement.
4. Reinstall by sliding the actuator rightwards back into its base and reconnect control wire.
7.4.3 Removing the flow sensor
1. Turn off the electric power and gas supply to the combi boiler.
2. Isolate DHW circuit and drain.
3.
Remove flow sensor ( inFigure 46 ) wiring harness.
4. Sensor is retained by a fork-shaped clip. Caution: this may be sharp to the touch. Use needle-
nose pliers to squeeze the clip prongs together; when prongs disengage from their secured
position, pull the clip out to the left.
5. Grasp the flow sensor by its central nub and pull straight forward to remove.
6. The underside of the sensor is a paddle wheel. This should show no erosion nor fouling, and
when blown at should spin easily. Clean or replace as necessary.
7. Reinsert sensor such that the harness pins are oriented to the right side. Slide retainer clip until
it clicks in place, and reattach wiring harness.
7.4.4 Cleaning the water strainer / flow restrictor
1. Turn off the electric power and gas supply to the combi boiler.
2. Isolate DHW circuit and drain.
3. Water strainer / flow restrictor access is by a bayonet-mount plug on the right-hand side of the
On-Demand DHW block (see inFigure 46
4. Lightly push the bayonet knob, rotate counter-clockwise a quarter turn to unlock, then pull
forward to remove a black cyclinder. Note that on the end of the cylinder there is an white bar:
grasp bar to remove the strainer from the cylinder. Backflush strainer / flow sensor to clean as
7.4.1 Cleaning the bypass check valve
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