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How does run dry protection works on ATV600?

Published date: 01 March 2019

According to manual (ATV600_Programming_Manual_EN_EAV64318_06), page 372 for using the function "Dry run monitoring" without no flow sensor (it means DRYM=power) it is necessary to define a curve that corresponds to No flow curve (with water in pipe system). The curve is defined by 2 points:
point A [NFLS, NFLP] and point B [NFHS, NFHP]
Point A is a point where pump is running at low speed NFLS (NFLS to be defined by user, can be equal to LSP for instance) with zero flow, but the the power NFLP is as minimal as possible that can be achieved with water in the pump. This situation corresponds to closed valve at the ouptut but with water in the pump. Lower power than NFLP is only possible when there is no water in the pump (DRY RUN PUMP) 
Point B is similar to point at but at different speed NFHS.

While NFLS and NFHS are used defined, the associated values of power NFLP and NFHP must be measured. Measuremet to be done with closed vale.
1. When pump is operated at NFLS speed with valve closed (water must be present on suction side), measure the power conumed by the pump. Enter this value to NFLP after that
2. Repeat the same at NFHS and measure power again. Value will be entered to NFHP

Now we defined the curve. Because this curve that defines border between no flow with water and no flow without the water may vary depending on water density temperature, etc. it make sense to define a kind of confidence level DRYX in order to avoid tripping (run dry trip) when water is still in the system (low flow stil with water).
Then the pump is run dry when measured power is below the curve defined by points A and B multiplied by DRYX. (blue dashed line in manual) 

If you additionally use low flow monitoring function it make sense to define PLFX which a a kind of border between low flow and normal flow. (to distunguish "low flow" from "flow greater than low flow"). Low flow is detected when measured power is below the curve defined by point A and B multiplied by PLFX (white dashed line in manual) 

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