Sunday, April 27, 2008

Sprinkler System Electrical Problems

I got this email from Lisa. I love emails. They give me something to post about!

Hi Craig,
We currently have a 7 zone sprinkler system and only zones 1-3 are "working" (they run when the controller tells them to and the water actually comes out of the sprinkler heads).
I have googled so many articles and adds regarding troubleshooting and I have done all the readings etc.. needed to check voltage and ohms, but nothing we have done appears to fix our problem.
We have an older system that only has 16 gauge wiring (red and white) which runs out to 7 different valves (spread out all over our yard). When testing voltage at the controller (with the zone turned on) we get the following zone readings:
  1. 28.0
  2. 27.9
  3. 28.0
  4. 29.5
  5. 29.5
  6. 29.5
  7. 29.5
When checking ohms (at the controller with the zones off), on our multimeter, we selected "20K" and it produced the following readings:
  1. 0.04
  2. 0.08
  3. 0.04
  4. 0.00
  5. 0.00
  6. 0.00
  7. 0.00
We replaced the controller with a Rain Bird 9-zone controller so I do not believe it is the controller since the system is still doing the same thing as when we had the other controller in place.
Is there anything else you can recommend we try to get zones 4-7 working?
I appreciate any help you can offer.

Okay Lisa, the voltage looks good, but the ohms are a different story.

What an ohm meter does is send a very tiny amount of electricity through the circuit to determine how difficult it is for the electricity to flow back to the meter. This is known as resistance.

I have used an auto-range multimeter for so many years, and have not needed to set the meter range, that I'm going to assume that the 20 K setting (20,000 ohm setting) is what has thrown the reading out of whack on the working circuits, one through three. Set the range to the lowest setting. Zones one through three should read between 20 to 60 ohms. Most solenoids read in the high 20's. Rain Bird solenoids tend to read higher, around 54 ohms.

Zones 4 through 7 read zero, known as infinity , i.e. infinite resistance. No circuit, no electrical flow. Because all the zones read this way, we can make an educated guess that it is the common wire that is causing the problem. Because everything is underground, it is a guess. It is possible that all the wires are bad, however this is unlikely. To find the valves without a valve locater read this article on finding buried lawn sprinkler valves.

My approach would be to find the first valve electrically down stream of the last working valve and check the common connection. This is the typical culprit. If re-splicing that common at the valve doesn't work, without a wire tracker to tell you where the signal got lost, things get more difficult.

Can you run a new common from any working valve to any non working valve? There is a good chance that this could solve the problem of all the non working valves. Has there been any digging on the property? New TV cables run? Dog wire or fencing? Is there a plastic box right by the controller or where the wires come out of the garage? Did some bone head splice the rain sensor to the common wire in the ground instead of in the controller. These are all things to consider.

When I get the time and the money (camera guy's are expensive) I will be adding more video about advanced electrical troubleshooting of lawn irrigation on my site.

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