I've spent about 8 hours of my own time trying to figure this out and for some reason I'm not getting it.
We have a customer that has several very large orange groves. The groves irrigation is supplied by a system of canals and pumps. We recently just got this account.
I do most of the control work for the company I work for so I got sent out to figure out why the auto setting on their motor control is not working. The system consists of 2 75hp motors driving two pumps, the system can be controlled manually or automatically. The way it WAS controlled automatically is in my opinion extremly hazardous so I will not put it back that way. The way it was controlled is as follows:
Four wires run from the control panel to the irrigation canal, they are only using three. Two of the wires carry 120 volts and one wire is the control wire going back to the control panel, these wires are placed in a 6" conduit placed vertically in the canal. The control wire has a large split bolt attatched to it, the two other wires are connected to these electrode looking things, they are using the water within the conduit to make the connection from the two hot wires to the signal wire. Obviously all of this stuff was home made, it's been this way for 30 years. The 120v starter is not energized unless both 120v leads are in the water, this threw me off so I put 120v to one wire and tested what I had coming back, it was 57v, due to voltage drop and the resistance of the water, this is why there are two 120v wires out there.
While the system is very hazardous in my opinion I also thought it was pretty ingenius
My problem is I need a way to energize the 120V coil on the starter when the water is low, deenergize when the water hits a certain level and not reenergize until the water is at a level between the low and high water sensors.
It's done this way so when the pump kicks off from hitting the high water it doesn't cycle on and off due to water turbulence ETC. I need to keep this as low tech as possable. I have found small float switches from Grainger but I am having major problems trying to figure out how not to kick the pumps back on until the water reaches a level lower than the high water level.
I also need to do the same thing on the feeder canal but this is to shut the pumps off in case of a low water situation so the pumps don't run dry and burn up.
I keep drawing it out with three floats and three relays but I'm just not getting it.
