Start-Up; Before Start-Up; Venting The Pump - Grundfos ALPHA2 L Series Installation And Operating Instructions Manual

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Do not start the pump until the system has been filled with liquid and
vented. The required minimum inlet pressure must be available at the
pump inlet. See and
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Venting the pump

The pump is self-venting. It need not be vented before start-up.
Air in the pump may cause noise. This noise ceases after a few minutes
running.
Quick venting of the pump can be obtained by setting the pump to speed
III for a short period, depending on system size and design.
When the pump has been vented, i.e. when the noise has ceased, set the
pump according to the recommendations. See .
The system cannot be vented through the pump. See
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