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Chnodomar

Unregistered

1

Tuesday, January 10th 2012, 8:25am

Changed valves to solenoids, now I'm having unexplainable pressure problems

Hi all,
I've got a bore in my backyard. The bore is powered by a 440V three phase motor driven pump.





I don't know much about pumps, so I can't say what kind of pump it is. I've got a simple switch in the house to switch the pump on and off.

Pump Switch (opened up)


The zoning is simple: one zone for the front, the other zone for the back of the house. To switch between the zones I used manual 50mm ball valves.



The system worked fine for the 2 years I've lived in the house, and probably for many years before that.
Now I've decided to automate the system. I started by buying 2x 50mm solenoids. I cut the old valves out and replaced them with the new solenoids. I've also added a pressure relief valve to protect my pump.

The old and the new valves


New valves installed


The next day, when the PVC glue was dry, I went to test my new system. The controller isn't installed yet, so I used the manual switches to turn the solenoid for the front garden on and the back yard off. Because I didn't want to get wet, I've put the pressure relief valve to a very high threshold (200 psi), with the plan to open it slowly when the pump is running to see at which pressure level it starts opening.

When I started the pump, my pipes started shaking. Then I could hear water going through to the front yard. The sprinkler heads popped up - everything seemed fine.

After about 10 or 20 seconds, I could hear a rattling noise in the pipes. Then the water stopped. I could still hear the motor running, but there was no water coming out the sprinklers.

I switched off the pump and started trying all sorts of diffent valve combinations, repeatedly switching the pump on and off - with very strange results. In one of the tries, I changed from front to back yard and put the relief valve to a very low setting (50 psi). Then I switched the pump back on. Everything went ok. Backyard sprinklers working fine.

I played a bit with the flow control, to see how that effects my sprinklers. When I had the flow control almost closed, the sprinklers shut off and the relief valve opened - as planned.
With the pump still running I opened up the flow control again, but the sprinklers wouldn't come back. So I switched off the pump, waited for a few seconds and switched it back on.

What happened now I can't explain, yet I could reproduce the problem a few times. When I switched the pump on, my front yard sprinklers started up - even though that valve was closed! My backyard stayed off, even though the valve was open. Again, after a few seconds the pipes started rattling and the front yard sprinklers would turn off again, leaving only the relief valve running.

I could repeat this several times. I even asked my wife to come and check my valve settings, because I stopped trusting my senses.

I'm completely puzzled. Does anyone have any ideas what could be wrong?

Thanks
Chno

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

2

Tuesday, January 10th 2012, 2:13pm

Seems you should have simplified things at the beginning by running the pump to an open zone, or even an open pipe. You want to do that now, so you can confirm the pump is undamaged and capable of normal operation. It would have made sense to have installed the electric valves in a parallel configuration to the old ball valves.

Chnodomar

Unregistered

3

Tuesday, January 10th 2012, 4:19pm

I have done that, too. I've removed the relief valve entirely and left the pipe open. Then I closed both solenoids. The water came out of the pipe that led to the relief valve - so the pump seems to be working fine.

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

4

Wednesday, January 11th 2012, 11:31am

I have to backtrack a bit - 440 volt three-phase power is heavy-duty stuff in the States, but perhaps less so in Australia. If the electric diaphragm valves are in good order, they should allow the water to pass without problems, if the solenoids are energized, or the valves manually set to be open. Note that with air still in the valves, they can be noisy.

In general, it is better to have something like a constant upstream pressure on these valves, for reliable opening and closing. That would mean adding a pressure switch and a pressure tank to the supply, just as if you were feeding a house with this water. This can be a critical addition to some (not necessarily yours) systems, because some pumps need something for them to "push against" and the pressure tank gives that.

Mitchgo

Supreme Member

Posts: 502

Location: Seattle

5

Wednesday, January 11th 2012, 7:38pm

One theory is.. These valves require a small amount of back pressure in order to have them closed. If your relief valve is set low this can cause the pressure on the main line to drop enough to actually open the electric valve. Thus why it runs for 10-20 seconds before it closes when turned on.

Chnodomar

Unregistered

6

Friday, January 27th 2012, 8:45pm

Just to close this off: the mystery is solved.
As long as the solenoids weren't connected to the control system, the manual opening of the valves didn't work properly. They shut off by themselves after a few seconds. I don't really know why, but that's what happened. To make sure the valves stay open I had to open the bleed screw - that worked fine. Once I had the control system connected, the current kept the valves open. Now the system works perfectly.

Wet_Boots

Supreme Member

Posts: 4,078

Location: Metro NYC

7

Saturday, January 28th 2012, 10:29am

What make and model of valve?

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