I’m trying to do a routine for controlling solar heating of my swimming pool. The idea is to have three states for a pump and a valve (stop, run, auto). The pump auto is a timer, and the valve auto is two PT100 (T1, pool water and T2, solar heater) which opens if T2 is more than T1 and closes if T1 is more than T2. I also have some safety with one leakage sensor and one pressure sensor. The leakage sensor sends a signal if there is a water leakage on the floor, and the pressure sensor (analog 4-20mA) should stop the unit when over or under the on/off thresholds. So far so good.

I think I got the most of it right but I have a few problems. When T1<T2 the valve opens, when T1>T2 the valve closes, but when T1=T2 there is no signal at all. I want the valve to close at T1=>T2. There should be no state where the valve is without a signal. Any ideas on how I should do? I am a total newbie so you have to explain like to an ***... ;) I have no idea what gain, offset and so on means.

I haven’t got the pressure guard to work. I have a on/off threshold that works but the function has to be delayed some way because right when the pump starts the pressure is zero and that should cause the system to stop, which is no good . The pump must run for 30s before the pressure check kicks in and if the pressure then is OK the pump keeps on running. If the pressure goes under or over the limits the system should halt and not restart before it is reset manually.

I have just tested a little bit In the demo of V6.1 since I haven’t got my ordered unit yet. If you take a look on the diagram I’m sure you experts will understand what I’m looking for. Any tips and ideas on how to make it better are gratefully received.

Regards D

Thank you so much! My inputs might look a little bit confusing. I’m thinking about using “three way switches” with On-off-auto for both pump and valve. That way it won’t be possible to have inputs for on and off at the same time. But one should probably build in protection for that anyway. I will try to use the “off position” from the pump switch to reset the pressure control. I will merge your two examples and try to learn something at the same time. Thanks again!

I have merged the two examples and it works the way I wanted it to do. But when I think of it I get more and more ideas. I’ve been trying this morning to get this time delay on the pump to work all the time, also when the pump is up and running. What I mean is that when valves are shifting, when someone connect the cleaning hose or whatever, the pressure can rise or fall temporary without cause for the pump to stop. If I have a buildup time for the pump of 10s when I start the first time, I would like this time to apply every time the pressure changes even if the pump has been running for hours. The pressure shall be allowed to change outside the boundaries for a time. I have tried to change the initiation flag to something in the process, extra time delays and so on, but I don’t know how I should approach this. Any idea on where I should start?