If One Valve is Good, Two Must Be Better

The client had a problem with two zones going on at the same time.

I had already diagnosed this in my mind as a cut/shorted wire.

I was correct on that part but they had another confusing thing. The resistance on one station (at the clock) was about half of the value of each of the other stations.

It was because they had Two Valves on one station. Both of them needed to be on to allow the water to flow. They just wired them together.

One clue was that there was one more solenoid/valve than there were stations.

Remember class…

Resistors in Series, add values.

Resistors in Parallel, add them up and divide by the number of resistors.

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The Wrong Way to Do This

I got called to replace a cracked PVB. They didn't get their system blown out in time.
The Client said that another company had started to replace it but couldn't finish it.

 

I don't know how the heck they got as far as they did.