Low Volt Wiring Btwn 2 Sprinkler Controls & Well

wneumanJune 30, 2010

I have two 12-sprinkler line automatic controllers, each of which allows 24 Volt wiring to a well solenoid that turns on or off the well. Currently I have only one of the controllers wired to the well, to the effect that a sprinkler line on that controller must be on for the well to also provide water to any sprinkler line on the other controller. Can I connect the well outputs from the two controllers together, so that if either controller were on, it would send 24 volt power to the well solenoid, and if both controllers were on at the same time, they would each be sending 24 volt power to the well solenoid? My question is if both are on at the same time (each sending 24 volt power) would that damage either the solenoid or the controllers?

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Without seeing a schematic diagram of the actual controllers you are using, it's really impossible to answer your question and then even with seeing a schematic it is still difficult to say for sure.

The controller would need to switch the 24 VAC to each station, as well as the master valve output, and while I've never designed one, I think the most logical choice would be to use a triac to control each output. The problem I see with paralleling the two outputs is the 24 VAC from each controller must be in the same phase or your control voltage cancels out and most likely will damage the controller or at the very least blow the internal fuse.

I'm not sure if you are switching a master valve or pump start relay but I would be inclined to just parallel two valves or relays to isolate the controller outputs. You'd think that this would be a fairly common problem so I Googled "pump start relay isolator" but only found one product available.

As a no cost alternative, you could use the first controller for the master control for both controllers. Just don't use the last output (#12) of the first controller but set #12's on-time to be the same as the duration of all the second controller's outputs. Just check to make sure the clocks stay in sync - of course this also assumes that there's a pressure switch in line to the pump as well.

    Bookmark   July 1, 2010 at 8:20PM
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This sounds the same to me as line valves in hot water heating. I had 6 valves at 16v? and any or all could turn on the pump for the system.

I think if both controllers are hooked to the same transformer there is no way you could send more than 24v to the pump.

    Bookmark   July 1, 2010 at 10:08PM
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