Irrigation Pump Issue ... Electrical?

[Norm K]

Yesterday, out of the blue and on its own, my irrigation pump turned on. The panel where I typically turn it on (with the various zones) was in the "Off" position. I moved it to the "On" setting, then turned it back off. The pump kept running.

Went up to the main electrical panel and switched the 30 amp double pole breaker off. The water flow stopped. Switched it back on and ... nothing. Moved the zone panel switch back to "On" but still nothing. Walked down to the dock where the sub-panel is located and switched the 20 amp d-pole breaker off, then back on. Walked back up to the house and switched the 30 amp one on again. The pump came on, but with very little pressure.

With my healthy fear of 240 volts firmly in-hand and foremost in mind, I removed the inner panel of the sub-panel and probed around with my multi-meter. I'm getting 120v across the wired terminals and 120V across where the other end of the breaker snaps into place.

Here's what's throwing me: I'm getting 120 volts on of the the wired terminals to the bus bar, but no voltage from the other side to the bus bar. I'm trying to hear a difference in my mind's ear between how the pump sounds now versus how it sounded yesterday (when everything was working properly) but have to admit to being uncertain. It'll spit water of out a couple of the heads nearest the lake, but nothing any higher than that. Will the pump run at half power if half the circuit breaker isn't producing?

Ideas welcome!

_

[Zeke]

Some motors will, yes. It's not a good idea of course, so you need to restore that 2nd leg.
It's a bit of a mystery why the pump turned on by itself. If I was there I'd know more. What you can check is to make sure any 3rd wire or conduit (equipment ground) is not energized.

[Arizona_928]

+1^^^

Pull amps across the hots.

I have a 3 phase well pump that bit the dust and it was pretty obvious the windings took a dump measuring the current.

[1990C4S]

A sketch of what you measured might help...

[Norm K]

It's been 24 hours so my 67-year-old memory might be faulty, but this is what I recall ...

A-B = 120v
A/B-C = 120V
A-D = 120V
B-D = 0V

A & B are where the wires come into the breaker, C is where the breaker snaps into place and D, as noted, is the bus bar.

[greglepore]

I suspect one side of the contactor to the pump is shot...
If it was running without an on command, something in the contactor failed allowing it to close, or in the control panel.
Why you don't see continuity to ground on one side of the circuit is beyond my feeble knowledge.

[Norm K]

The contactor is a good thought. If the electromagnet somehow got energized that would certainly start the pump.

I remain stumped, though, by the feeble pressure exhibited when I re-started the pump after turning the sub-panel 20 amp breaker off, then back on.

I'll replace the breaker first (it was cheap) and if it's not the issue I guess I'll have a spare.

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[Zeke]

Originally Posted by greglepore

I suspect one side of the contactor to the pump is shot...
If it was running without an on command, something in the contactor failed allowing it to close, or in the control panel.
Why you don't see continuity to ground on one side of the circuit is beyond my feeble knowledge.

I don't think you're feeble. That's a mystery and a dangerous one. I suspect the answer will become apparent when the dropped leg is fixed. Then no more mystery.

A continuity check on the whole system is in order. Fortunately radio type testers are pretty cheap now. IDK how far the run is but if there is some scrap wire of any nature available that will reach (even some lengths tied together) the system can be checked with the aforementioned meter. Hopefully it's in one panel or the other.

However, I suspect it's not.

What kind of pump motor is this? Brand and model please.

[Norm K]

Took but a few minutes to replace the breaker and upon first start water was gushing out of a hose bib just as it always has.

Shut the system down at the control panel and closed the hose bib, confident that the issue had been resolved. Upon manual re-start of the zone closest to the pump though, all I got was a very weak stream from one sprinkler head and some gurgling from one or two others (typically runs five heads no problem). So I shut it down again, re-opened the hose bib, re-started things and the Vesuvius-like gusher I'd witnessed but a couple of minutes before was gone, replaced by a lazy stream.

I hate chasing parts, but I gotta think there's something to the bad contactor theory.

_

[Norm K]

Originally Posted by Zeke

What kind of pump motor is this? Brand and model please.

[1990C4S]

Originally Posted by Norm K

It's been 24 hours so my 67-year-old memory might be faulty, but this is what I recall ...

A-B = 120v
A/B-C = 120V
A-D = 120V
B-D = 0V

A & B are where the wires come into the breaker, C is where the breaker snaps into place and D, as noted, is the bus bar.

Something is not right here... A-Neutral and B-Neutral should be 120VAC.

A-B should be 240VAC.

And C should be two plates, 240VAC between them...

Post a pic of the contactor and the breaker please.

[Norm K]

I removed the contactor and did a couple of tests.

Manually engaging the contacts resulted in fluctuating resistance readings between three of the four Lines and Terminals: ranging from maybe 5-45 ohms. Only one of the four consistently read zero to point one.

I applied power to the 120V connection and the unit immediately activated. Resistance readings on two of the three still fluctuated, but not as greatly. The third one that had been fluctuating now read from .01 to .03 Ohms. The one that had read zero continued to do so.

When I measured voltage between the Line and Terminal connectors however, I got no readings (???).

_

[Norm K]

Originally Posted by 1990C4S

Something is not right here... A-Neutral and B-Neutral should be 120VAC.

A-B should be 240VAC.

And C should be two plates, 240VAC between them...

Post a pic of the contactor and the breaker please.

As I noted, my recollection is probably flawed. Everything is disassembled, so no pic available at this time.

_

[Zeke]

Originally Posted by 1990C4S

Something is not right here... A-Neutral and B-Neutral should be 120VAC.

A-B should be 240VAC.

And C should be two plates, 240VAC between them...

Post a pic of the contactor and the breaker please.

Yeah, that drawing is not right. Best to disregard. Greg brought up a contactor. Now there is a contacter in the system, but not on the drawing. I'm guessing the zone control is also the energizer for this contact device.

Whatever, as stated A-B has to be 240v ahead of any switching. I'd take the zone control out of circuit and troubleshoot from there. That or I don't understand what all this is.

I plead feeble.

[greglepore]

OK, so the contactor has 4 terminals, which means its breaking both hot and ground (assuming-some just break hot side so 2 in/2 out).
I suspect that with one terminal disengaged the induction of the motor being on the circuit is allowing you to see 120v on the "dead" leg of the 240v circuit (again, an assumption as I'm not an engineer-but Choo Choo Charlie was an engineer).
Contactors are cheap, suspect your issue is there as one leg shows no continuity. Sometimes they weld themselves together in failure mode and when you cycled the coil current it shook loose.
Or the motor is bad and burned out the contactor.
But I'd start with the contactor if you're going to continue to diy this.
Not an electrician, but I stayed at a super 8 motel once.

[greglepore]

One other thing-forgeting voltage, is there continuity between B and the side of the buss bar it clamps to?
And yes, A to B needs to be 240. Try troubleshooting the panel with the leads to the breaker disconnected to eliminate downstream from the equation.

[Norm K]

Back to my hand sketch for a moment:



The readings below are as of a few minutes ago, double and triple-checked. I took them because when I energized the system (after installing a new contactor) I immediately got the desired gusher from the hose bib but, once again, as soon as I tried to activate one of the zones it became a relative trickle.

* A-C and B-C both have good continuity

Voltages are as follow :

* A-B 123V
* A-C 123V
* A-D 0-.117V
* B-D 123V
* B-C 0V


Here's a photo of the inside of the sub-panel (surprisingly, no spiders found)...



And here's one of the new contactor I installed this morning, wired exactly as the original. The two connections you can't see are A-1 (white wire) and A-2, which is jumpered to L3.



I checked carefully for any loose connections at A, B, C and D and found none. I hate chasing parts (fortunately only about $30 so far) and I really don't want to pay a sprinkler guy if I can help it but temps are rising and I have to have sprinklers if I want a lawn.

I think my next step might be trying to test the system (zone) control panel, as I'm not sure how best to proceed otherwise.

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[greglepore]

What do you see at the 30 amp breaker FEEDING the sub panel. You should see 220v across the two breaker terminals, and 110v from each to the respective leg of the buss bar.

[Norm K]

I'll check that later, thank for the idea.

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[greglepore]

The other thing is, from the photo of the subpanel, I only see one leg on the buss bar. Normal 220 practice is red and black wires are the two phases and white is neutral. All I see is a black wire on the buss bar. Not saying the other phase isn't there but I don't see it.