OS 3.0 Low Voltage at the farthest station

[totnik]

Hi Ray,

I have one zone(24 AC Solenoid) that refused to turn on. On hooking up a multimeter to it I see the initial impulse voltage of only about 5VDC max.. It then settles down at about 1.8V after the initial impulse. This looks like it wouldn’t be enough to turn on the solenoid. The station is about 200 ft away from the controller with about a 16 AWG wiring between. Could the distance be an issue or are there other ways to troubleshoot whats going on. For what its worth, my other 17 stations work, including a station that is literally 2 feet from this one and I’ve made sure the solenoid itself works.

Any tips?

Thanks.

[Ray]

The voltage reported (5VDC initially and then 1.8VDC) is unusually low. There are two things to check:
– make sure you measuring DC (not AC) voltage (it seems you are, just to double check).
– remove power from the controller, and use multimeter to measure the resistance between COM (common) wire and the zone that has problem. Most 24VAC solenoids should have a resistance of somewhere between 20 to 50 ohm. If it’s too low, it indicates a shorting, either in the solenoid or in the wiring.

Another possibility is that the internal boost converter on the controller is not functioning properly. But judging from the fact that the other zones work, this is unlikely to be the case. Still, if you want to isolate solenoid issues with controller issues, you can do the following:
– remove the COM (common) wire from the terminal block: this will disconnect all solenoids from the controller circuit.
– Turn on the problematic zone for 1 minute, and while it’s running, measure the DC voltage between COM terminal and the zone port. This should give you a voltage that’s somewhat higher than the DC power adapter you are using. For example, if your power adapter is 7.5VDC, the voltage you measured here should be higher than 7.5, indicating the internal voltage booster functions correctly. Basically this is the voltage that the controller presents to the solenoid, before the solenoid is actually connected. Once the solenoid is wired into the circuit, and if the solenoid has a shorting, that will lower the measured voltage significantly (which could explain why you are only getting 1.8VDC).

[totnik]

Hi Ray,

It’s been raining pretty continuously out here and havent had a chance to go back to this till this morning. To answer your questions above:

1)Yes I measured DC
2)Resistance is right around 30 Ohms.. I went out and purchased a couple new 24AC solenoids as well and tested them with a solenoid tester and they do work
3) I disconnected COM and the measurement across COM and the Zone was right around 12V DC.

Here’s what I’ve done additionally as well:

Went out and purchased a Rachio to see if indeed it was a hardware issue.

1) Measure the V at the controller, it’s putting out a steady 28V AC
2) At the zone without the solenoid hooked up, I get about 8V AC..

So here too I’m getting some pretty significant drop in voltage.. Whether it be AC or DC. This leads me to believe there is an issue with the line itself.. Cannot for the life of me figure out what the issue may be now.

Any other suggestions?

[Author]

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