Frequency Of Starts And Stops - Grundfos LSV Montage- Und Betriebsanleitung

9.1.4 Flow rate
Minimum flow rate
The pump must not run against a closed outlet valve as this will cause an increase in the temperature or
formation of steam in the pump. This may cause shaft damage, impeller erosion, short life of bearings, damage
to stuffing boxes or mechanical shaft seals due to stress or vibration.
The continuous flow rate must be at least 25 % of the flow rate in the best efficiency point.
Maximum flow rate
The maximum flow rate must not exceed the value stated on the nameplate. If the maximum flow rate is
exceeded, cavitation and overload may occur.
Operating at reduced flow and/or head
Do not operate the pump at a flow rate below 10 % of the maximum flow rate stated on the nameplate or with
the outlet isolating or throttle valve closed. Operating the pump under such conditions may involve the risk of the
pump being overheated. To prevent possible damage, use protective devices such as liquid temperature relay,
bearing temperature relay, inlet pressure monitoring, etc.
If a pump is operated at reduced head, the flow rate will increase and the motor will consume more current than
normal. This will result in overheating of the motor. In such situations, throttle the valve on the outlet side
instead. If an automatic throttle valve is installed, this can be done automatically.

9.1.5 Frequency of starts and stops

The recommended maximum number of starts is 3 per hour for complete pumps with a motor supplied by
Grundfos.
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