Priming; Checking The Direction Of Rotation; Startup - Grundfos NK Serie Montage- Und Betriebsanleitung

10.3 Priming

Closed systems or open systems where the liquid level is
above the pump inlet
1. Close the discharge isolating valve and slowly open the
isolating valve in the suction pipe. Both the pump and the
suction pipe must be completely filled with liquid.
2. Loosen the priming plug in order to vent the pump. Once liquid
runs out, tighten the priming plug.
Warning
Pay attention to the orientation of the priming hole to
ensure that the escaping water does not cause
personal injury or damage to the motor or other
components.
In hot-liquid installations, pay special attention to the
risk of personal injury caused by scalding hot liquid.
In cold-liquid installations, pay special attention to
the risk of personal injury caused by cold liquid.
Suction operation with non-return valve
The suction pipe and the pump must be filled with liquid and
vented before the pump is started.
1. Close the discharge isolating valve and slowly open the
isolating valve in the suction pipe.
2. Remove the priming plug, M.
3. Pour liquid through the hole until the suction pipe and the
pump are completely filled with liquid.
4. Fit the priming plug, M.
The suction pipe may be filled and vented via the priming plug.
See fig. 28. Alternatively a priming device with funnel can be
installed before the pump.
Open systems where the liquid level is below the pump inlet
1. If an isolating valve is fitted on the suction side of the pump,
the valve must be fully open.
2. Close the discharge isolating valve and tighten the priming
and drain plugs.
3. Connect a manual venting pump instead of a priming device
with funnel.
4. Install a slide valve between the venting pump and the
centrifugal pump in order to protect the venting pump against
excessive pressure.
5. Once the slide valve at the manual venting pump has been
opened, vent the suction pipe using short, rapid pump strokes
until the liquid runs out on the discharge side.
6. Close the valve at the venting pump.
E Drain plug
M Priming plug
Fig. 28 Drain and priming plug
24

10.4 Checking the direction of rotation

Warning
The pump must be filled with liquid when checking
the direction of rotation.
The correct direction of rotation is shown by arrows on the pump
housing. Seen from the pump end, the direction of rotation must
be counter-clockwise. See fig. 28.

10.5 Startup

Before starting the pump, completely open the isolating valve on
the suction side of the pump and leave the isolating valve on the
discharge side almost closed.
Start the pump.
Vent the pump during startup by loosening the air vent screw in
the pump head/cover until a steady stream of liquid runs out of
the vent hole.
Warning
Pay attention to the orientation of the vent hole to
ensure that the escaping water does not cause
personal injury or damage to the motor or other
components.
In hot-liquid installations, pay special attention to the
risk of personal injury caused by scalding hot liquid.
In cold-liquid installations, pay special attention to
the risk of personal injury caused by cold liquid.
When the pipework has been filled with liquid, slowly open the
isolating valve on the discharge side until it is completely open.
If the pump is fitted with a motor with an output
selected on the basis of a specific maximum flow
Caution
rate, the motor may be overloaded if the differential
pressure is lower than anticipated.
Check for overload by measuring the motor current consumption
and comparing the value with the rated current stated on the
motor nameplate. In case of overload, throttle the valve on the
discharge side until the motor is no longer overloaded.
Always measure the motor current consumption during startup.
At the moment of start, the input current of the pump
Note motor is up to six times higher than the full-load
current stated on the motor nameplate.