Well pump pressure switch blowing

We recently lost water pressure from our submersible well. Upon inspection I found the pressure control switch to be completely blackened by soot. I assumed a bad switch, so I replaced it. The new switch cut in fine, but at cutout the switch started arcing rapidly, followed by a big flash and bang. So that's what happened to the old switch! Pressure settings are correct, bladder pressure is correct, tank has been drained, etc., but very rapid cycling at cutout pressure remains. Any ideas? Bad controller, low water, leak in pipe?
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mustang wrote:

Run the pump till pressure gets near where it would cut off. Flip the breaker OFF just before so that the pressure switch doesn't trip.
Run water and see how much water is consumed before the pressure drops to where the switch would normally trip On.
This will tell you if the bladder accumulator is functioning right.
Arcing might be due to Start winding not opening, but would not account for the rapid cycling.
Jim
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If the air pressure is correct, 1-2 psi less than cut-in setting, with no water in the tank, then you have serious blockage between the switch and pump, or an electrical problem.
Do you have any filter or shut off valve before the pressure tank/ switch?
Do you have a control box for the pump, usually on the wall and the electric line from the switch goes to it and then on to the well/pump?
Are absolutely sure the pressure tank is totally empty of water after draining it? Wobble it, it should be light and no water above the bladder sloshing around. You don't get water or water vapor out of it when you spritz some air out of it?
If no to all that, then call a pump guy, well driller or only a plumber that can service and pull a submersible pump (most don't/ can't).
Gary Quality Water Associates
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On Mon, 18 Jun 2007 10:34:31 -0700, Gary Slusser wrote:

If the OP is having those kinds of problems with the switch he could have a short of the electric cable going to the submersible, sometimes caused by the loss of the support of the pump and the cable getting stretched over the top of the well casing. Happened to me once.
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Meat Plow wrote:

That's unique one... :) "Loss of support" of the pump would be a complete break of the discharge line and there would be no water discharge in any installation I've had. How is your pump supported?
I agree from symptoms OP's problem almost has to be electrical. At least I can think of a way to get a real pressure fluctuation to cause such a rapid cycling of the pressure itself. Deadhead or full bladder cause the cutoff, certainly, but what can cause such a rapid pressure loss that isn't readily apparent is the problem I'm having...
Don't suppose there's some bizarre way corrosion in the pressure-sensing line could cause it? OP ought to check that for sure, anyway, though one would presume that would have been done when replaced the switch.
Oh, another diagnostic would be what did the indicated pressure do during this episode? (Assuming OP had the presence of mind to notice while watching the spitzen-sparkzen... :)
--
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On Mon, 18 Jun 2007 13:05:10 -0500, dpb wrote:

The nylon support rope broke (also wore thru over the side of the casing) and the electric supply cable supported the pump. Had no idea until it wore thru the insulation and shorted on the casing. The discharge line and tubing remained intact. Pretty crummy install job which was corrected many years ago. I now use the well for outside water, we've long since switch to city provided water.

I doubt it, the OP was probably consumed watching the pretty blue sparks. :)
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Meat Plow wrote: ...

I'm still curious how that is...why wouldn't pump be hanging on the discharge pipe w/ a snubber around the bottom pipe section against the casing wall? I can't figure how the pump can drop lower than the length of the discharge pipe which should be much less "stretchy" than the feed cable.
Inquiring minds and all that... :)
--
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On Tue, 19 Jun 2007 07:58:17 -0500, dpb wrote:

I can't tell you for sure it was long ago maybe 1974 and I was in my teens. I just remember the well guy finding the pump being held up by the tubing and elec supply line and the nylon rope broke. The pump was pulled and things were redone, maybe even the pump was replaced like I said it was 33+ years ago.
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I've talked with several local experts, who can't figure this one out. As a last resort, I installed another pressure switch (the third one in 30 days) and it is working normally for the moment. We'll see what happens next. Thanks, folks.
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Stumps me too. If the pump was reaching cut-out pressure but the switch then started arcing....Shouldn't be a pump problem causing that (not to say that you might not have a pump problem). Hard to think of why a new switch wouldn't just shut off if it did truly reach cut-out other than a defective switch.
Harry K
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On Mon, 18 Jun 2007 11:20:14 -0700, mustang wrote:

Well (no pun intended) report back if you find something. If you blew a couple switches you've got pump or electric supply line problems. The first downhole pump I had was suspended by a thick piece of nylon rope when over a period of ten years cut through from the torque of the motor twisting it. That allowed the electric supply line then to become the support and shortly thereafter grounded out one leg of the 220v. But at first it was intermittent and I went through a couple switches over a period of a month before calling someone out who discovered the problem. No telling if you have the same setup because you haven't described it but you might want to take this into consideration unless it's been ruled out already.
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If it blows again, you really need an amp meter on your pump line.
The amps will tell whether you likely have a shorted winding in your motor or a shorted line.
wrote:

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