GX developer: I don't understand this pump starting logic...

parky said:

That is why I did the top rung as one of the alternatives, this allowed to start/stop the pump manually without the need for an Auto/Man selector so gave him both options, it still works in auto so will stop when reaches low level but does not need to be at high level to start it manually, as for not being able to start the pump at high level is ridiculous as it would auto start anyway if not in manual. if it was above high level surely you would want to be able to start the pump to lower the level.
You are unlikely to get information about the whole process as it appears that either the original supplier or the company he works for are reluctant to divulge too much.

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I prefer the top rung idea, to be honest, but operator wants a manual/auto selector. Also I like your idea of a manual/auto toggle in which the associated text changes from "auto" to "manual" because , for me, space is limited on the HMI screen....I was going to have a toggle button with a lamp next to it which takes up more space.

Ah.. thought that might be, did a lot of work for RR many years ago, even worked on the RB211 test bed at Hucknall.
As a matter of interest do you need a Auto/manual selector or just a way for the operator to start & stop the pump based on above low level
Edit: you replied at the same time as me lol.

Don't know if it would be useful, but I did a system where using the same start button the operator could empty the vessel completely, this was done simply by putting the Start bit onto a timer i.e. 3 seconds, so the operator had to hold the button for 3 seconds before it would override the low level, run for a short time then lock out to allow the tank to completely drain, the time after completely empty was only short so no damage to the pump as they will run for a while because the pump seals are still wet.

parky said:

Don't know if it would be useful, but I did a system where using the same start button the operator could empty the vessel completely, this was done simply by putting the Start bit onto a timer i.e. 3 seconds, so the operator had to hold the button for 3 seconds before it would override the low level, run for a short time then lock out to allow the tank to completely drain, the time after completely empty was only short so no damage to the pump as they will run for a while because the pump seals are still wet.

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Interesting - might end up doing something like this. At the moment we're taking a cautious approach and emptying out the last remnants of water with a small portable bilge pump, the sort you might find on a canal boat or similar.

Here is a simple way, providing the system is in manual & the operator holds the button for 3 seconds (could make it longer) then providing the operator holds the button after 3 seconds it will run the pump maybe not what you want & does rely on the operator not holding the button for very long periods with a dry pump but that is unlikely unless they are trying to break it, also under normal operator starting the pump they just push it like normal not hold it so it only runs until low level or stop is pressed, alternatively, you could set a bit on the timer timing out with a one shot then use this with another timer to do the drain time. so to repeat the process the operator would need to press & hold it again if it did not drain first time.

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