Submersible pump motor keeps failing

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  #1  
Old 04-12-11, 01:41 PM
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Submersible pump motor keeps failing

I have a 1hp 2-wire 240V submersible 4" pump installed in a PVC-cased 6" well. It was installed 6yrs ago. The original pump/motor was a red jacket grizzly with Franklin motor. After 3yrs it failed (locked rotor) and when I pulled it out the case was visibly corroded with holes in it. The pump itself looked fine

3 year old well pump motor case corroded so badly it seized up?

I replaced the Franklin with a same-sized Grundfos which operated fine until I turned it on last weekend for the first time since winter. No water. I pulled it out and it also had a locked rotor and the same case corrosion.

3yr old SS pump motor corroded AGAIN

The well is connected to a lawn irrigation system and has plenty of sulfur that you can smell and see the residue. I measured the pH at the top of the water table and it was 7.3.

After seeing pics of the corrosion the pump guys thought this should be posted in an Electrical forum as well.

I really really really need to keep this from happening again.

Pics of the 3-yr-old failed Grundfos:








Pics of the 3-yr-old failed Franklin:

[URL="http://www.wichitaracing.com/pics/wellpump/wellpump 001.jpg"][/URL[URL="http://www.wichitaracing.com/pics/wellpump/wellpump 002.jpg"]][/URL]
http://www.wichitaracing.com/pics/we...llpump 004.jpg
http://www.wichitaracing.com/pics/we...llpump 005.jpg
http://www.wichitaracing.com/pics/we...llpump 006.jpg
http://www.wichitaracing.com/pics/we...llpump 007.jpg
http://www.wichitaracing.com/pics/we...llpump 008.jpg
http://www.wichitaracing.com/pics/we...llpump 009.jpg
 
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  #2  
Old 04-12-11, 02:38 PM
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Hmm, how close is your well to the transformer in the yard? Could you describe the site plan pointing out the relative locations of the house main electrical panel, transformer, and irrigation well?

What size wire feeds this pump? Approximately how far is it from the panel to the well head, then to the pump depth in the well?

If you have a multimeter or ohmmeter, set the meter to the lowest ohms scale or to continuity mode. Test between the metal pump housing and the ground wire feeding the pump for continuity or ohms.

additional: also this is only the irrigation well? Do you also have a potable well and how does it differ from this well?
 
  #3  
Old 04-12-11, 03:18 PM
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The other poster is thinking it may be electrolisis.
Looks more like a lightning strike to me, does your pump have lightning protection built in like one of these?
http://www.midwest-pump.com/dw.html
 
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Old 04-12-11, 03:32 PM
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That pump does have lightning protection. The big hole in the bottom could be lightning, but all the pitting along the side of the pump shell looks like a slow etching / corrosion process.
 
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Old 04-12-11, 04:04 PM
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I will check some things and update this more when I get home.

Originally Posted by ibpooks View Post
Hmm, how close is your well to the transformer in the yard? Could you describe the site plan pointing out the relative locations of the house main electrical panel, transformer, and irrigation well?

What size wire feeds this pump? Approximately how far is it from the panel to the well head, then to the pump depth in the well?

If you have a multimeter or ohmmeter, set the meter to the lowest ohms scale or to continuity mode. Test between the metal pump housing and the ground wire feeding the pump for continuity or ohms.

additional: also this is only the irrigation well? Do you also have a potable well and how does it differ from this well?
The well is probably 25ft from the transformer in the yard (at least I think that one of the two boxes is the transformer). I will draw up a rough sketch to show the relative locations.

The wire from the panel to the relay, and then to the switch on the side of the house, and then to the well head is 18ga I believe. I will check when I get home. The wire into the well is whatever submersible wire I got at Lowes, probably 16 or 18ga. Will check when I get home.

It's around 100ft from the panel to the well head and the pump is about 85ft deep.

Is the ground wire the same as the common wire? There are 2 wires going to the well; 2 hot and 1 common (I think???). Does that sound right?

The pump is out of the ground right now and I cut the wires. I can hook it back up and do that check. Will it still tell you something if it's not in the water?
 
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Old 04-12-11, 04:26 PM
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Originally Posted by Weez View Post
at least I think that one of the two boxes is the transformer
It's usually a green metal or fiberglass box, a couple feet on each side.

head is 18ga I believe....16 or 18ga. Will check when I get home.
That wire size would be pretty small for 185', check to make sure.

Is the ground wire the same as the common wire?
In a 240V circuit there is no common, two hots and a ground. The pump doesn't need to be in water or hooked to the circuit to measure it.
 
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Old 04-12-11, 09:01 PM
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OK, that's the transformer. I did this from memory b/c I haven't even been home yet. If it needs updating I'll redo it tomorrow night. The wienerdogs are spot-on accurate though and I'm sure somehow they're the source of my problem.



I was way off on the wire gauge; it's 2/12.

I'll measure that continuity ASAP.
 
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Old 04-13-11, 07:27 AM
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It looks like electrolysis to me. That means there is a "ground" current flowing thru the pump case. Just a guess, but I suspect that the ground voltage potential at the well is different than that of the house supply, causing a current the flow, which will take out any metal, even a corrosion resistant metal like stainless. It is not a corrosion mechanism.
I would actually drop back in the existing motor (even though its bad) and wire it up, but do not apply power. Now, break the ground connection to the motor at the supply panel, and measure the ground current.
WHere I'm going with this is that maybe the POCO transformer 25' away has some stray ground current nearby. Maybe even an unground feeder fault.
 
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Old 04-13-11, 08:31 AM
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Originally Posted by telecom guy View Post
It looks like electrolysis to me. That means there is a "ground" current flowing thru the pump case. Just a guess, but I suspect that the ground voltage potential at the well is different than that of the house supply, causing a current the flow, which will take out any metal, even a corrosion resistant metal like stainless. It is not a corrosion mechanism.
I would actually drop back in the existing motor (even though its bad) and wire it up, but do not apply power. Now, break the ground connection to the motor at the supply panel, and measure the ground current.
WHere I'm going with this is that maybe the POCO transformer 25' away has some stray ground current nearby. Maybe even an unground feeder fault.
I will try this ASAP. Will the fact that the motor is now fried skew the results of this test? (I.e. the tests shows a ground issue now, but if the motor was not damaged it would not have shown a ground issue?)

If it turns out to be the ground issue you are theorizing, what would be the fix?
 
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Old 04-13-11, 08:47 AM
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A locked rotor won't skew the test. What we are measuring is a difference in ground potential between the well and the panel at the house. If there is one, it could be one of several culprits, including a defective neutral at the house, a bad electric water heater, a few others.

To be clear on the experiment: connect the 12/3 at the motor end, and lower the motor into the well, normal depth. At the breaker panel, turn the well breaker OFF. Disconnect the 12/3 ground wire at the panel. With a voltmeter, measure AC voltage between the disconected wire and the ground/neutral bus. Make sure the rest of the house is ON, even make sure the water heater is on (if electric) and any others that involve the water system. If you measure a voltage, put in a AC ammeter in that ground circuit and see how current is flowing down that motor circuit. Any current here is likely flowing thru the metal motor case, to water, causing electrolysis.

It would also be prudent to test the panel for line unbalance/neutral trouble. With some load on ONE line side, measure the AC voltage from L1 to panel ground and then L2 to panel ground. They should be close, within a few volts.
 
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Old 04-13-11, 09:15 AM
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Originally Posted by telecom guy View Post
A locked rotor won't skew the test. What we are measuring is a difference in ground potential between the well and the panel at the house. If there is one, it could be one of several culprits, including a defective neutral at the house, a bad electric water heater, a few others.

To be clear on the experiment: connect the 12/3 at the motor end, and lower the motor into the well, normal depth. At the breaker panel, turn the well breaker OFF. Disconnect the 12/3 ground wire at the panel. With a voltmeter, measure AC voltage between the disconected wire and the ground/neutral bus. Make sure the rest of the house is ON, even make sure the water heater is on (if electric) and any others that involve the water system. If you measure a voltage, put in a AC ammeter in that ground circuit and see how current is flowing down that motor circuit. Any current here is likely flowing thru the metal motor case, to water, causing electrolysis.

It would also be prudent to test the panel for line unbalance/neutral trouble. With some load on ONE line side, measure the AC voltage from L1 to panel ground and then L2 to panel ground. They should be close, within a few volts.
How much current should I prepare for? Will my little multimeter be sufficient?

How much voltage is OK? If it reads .5V do I need to continue on with the current test?

When I do this test, what do I with the pump start relay that is beside the pane? Does it need to be energized?
 
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Old 04-13-11, 09:28 AM
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A buddy of mine who is in the oil industry had this to say about it:

Originally Posted by GarrettW View Post
Tim, based on your comments in that other thread related to the sulphur smell from your well it's pretty apparent that you have dissolved sulphides in the water either from naturally occurring sources or sulphate reducing microbes. This will commonly cause extensive corrosion on steel, even stainless. The pitting and cracking you have is a telltale for this, as well as the black corrosion (as opposed to the more common red rust). This little page details it fairly well for the microbial case but the naturally occurring case works in a similar fashion: Corrosion

Again, like I said in my previous post, I think your only real recourse is to do some sort of cathodic protection. Either by using a sacrificial anode or by using impressed current. I would highly recommend the first option; impressed current is overly complicated for what you are trying to do and will require a bunch of additional equipment that you will have to buy and maintain. We run into the same problems on our pipelines at my company. We use a combination of anticorrosion coatings and impressed current to protect our underground steel pipe. And just to back up my conclusions here I actually ran your problem by our corrosion engineers at work (I'll bill you later) and they agreed that it looks strongly like sulphide corrosion.
 
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Old 04-13-11, 09:52 AM
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I agree totally with your friend. I think you have a combination of sulphur in the water which is pretty bad for steel and some electrolysis due to your grounded well pump motor being so much closer to the transformer than the house GEC.

Basically the neutral current from your house mostly flows back to the transformer on the neutral wire feeding your house, however a small amount flows back through the earth. Since your pump is essentially very well grounded and also close to the transformer, I'm guessing you're having an above-average amount of current flow through the pump housing. In most wells this isn't a big issue because you can just bond the metal well casing to the house ground and the well casing will take the current instead of the pump housing. As you have a PVC well, all of the current is flowing out through the pump. Some other types of malfunction with the power company's system can cause this too, so I wouldn't completely rule that out yet either.

Your friend is probably right about getting some type of sacrificial anode set up for the well. I don't know anything about the details of such a job though. Perhaps you can find a company that makes an all-plastic well pump?
 
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Old 04-13-11, 10:13 AM
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Originally Posted by Weez View Post
How much current should I prepare for? Will my little multimeter be sufficient?

How much voltage is OK? If it reads .5V do I need to continue on with the current test?

When I do this test, what do I with the pump start relay that is beside the pane? Does it need to be energized?
a few AC amps. over that, I'd be surprised. Voltage: maybe 10 or less. <.5 is desireable. Pump start relay may stay unenergized, its the ground path that needs to stay intact.

When the electrical end of this is measured OK, then its time to look at that Sulphur issue!
 
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Old 04-13-11, 12:03 PM
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I think that I would start with the local rep of the pump company. It is possible he or she has seen this problem before and has some answers. Myself, I think it is a combination of chemical and stray current corrosion.
 
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Old 04-13-11, 06:19 PM
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Originally Posted by telecom guy View Post
It would also be prudent to test the panel for line unbalance/neutral trouble. With some load on ONE line side, measure the AC voltage from L1 to panel ground and then L2 to panel ground. They should be close, within a few volts.
How do you suggest I put a load on it?

I'm not sure what you mean by putting the load on one line side. Do you mean I check that side, then switch the load to the other side and check that one?

If this helps, when the pump was still in the water and I was testing it for power at various locations in the circuit both lines had ~120V. But this was with the pump load on BOTH lines.
 
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Old 04-13-11, 08:29 PM
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OK, I lied about the distance. The well is more like 15-20ft from the transformer box.

I checked resistance from the ground wire to the motor case (from the end of the motor pigtail) and there was only about 2ohms. Which makes sense because the ground is actually screwed to the case. (Somebody asked this question in one of the threads I think).

The pump/motor is back in the well.

The voltage between the disconnected ground wire and the ground bus bar in the panel is about 0.5V (but the meter read 0.2V before I even touched the bus bar).

The current running through it is about 80mA.

I did not get to try the balanced load tests.
 

Last edited by Weez; 04-13-11 at 09:17 PM.
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Old 04-14-11, 06:50 AM
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OK, good progress. Let me double check. Are all these voltage and current readings AC? Doesn't the meter read 0.0v AC with its probes shorted together? Open wire readings on a voltmeter don't count. Is your ammeter direct wired or clamp on? Does it read 0mA when not connected?
2 ohms from a short wire to the pump case is high. What does the ommeter read when its leads are shorted? S/B about .2ohms or so, hopefully less. I'd expect your bonding/grounding wire to show way less than one ohm for this test.

the line balance test is conveniently done with a space heater or similar, high load 120v device. ID an outlet on L1, then a different outlet on L2. Make sure the line voltage is similar for both tests, when loaded.

So, if the 80mA is real, we would have to estimate if that is significant, assuming it goes 24/7. Also, it would be helpful if you can insure the water heater is on (drawing current) for this measurement, is it electric? That could remove another possible culprit.
 
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Old 04-14-11, 10:06 AM
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The voltage readings are AC. The meter (a cheap Craftsman) reads 0.001VAC with the probes shorted.

What I was saying about the meter showing 0.2VAC before connecting the probes was this: I clipped one lead to the ground wire coming from the pump. The other probe I touched to the ground bus bar. However, as I approached the panel with that probe the meter started reading a voltage, which was 0.2VAC before I touched it to the bus bar. I guess it's picking up some induced voltage from magnetic flux or something???

About the ground to the motor case: I'm not sure how well the plug is making contact with the ground screws which also hold the plug in the jack on the motor. The small metal collar plate aroung the plug is used to screw the plug down to the motor. That collar is the part that makes ground contact with the motor. It is badly corroded (the pic is the wrong angle - if you saw it from the top it would show that the collar is less than half there, and the surface is very poor. I cleaned it up the best I could without destroying it so much that it is no longer works at all.



My ammeter is actually my multimeter which I of course had wired in series. If this is not sufficient I can attempt to get my hands on a dedicated ammeter (not sure if I know anybody though). I know I can get my hands on a calibrated Fluke multimeter at work, which should be more accurate than my Craftsman. I've just never seen anybody use a dedicated ammeter (I work in aircraft).

I will try the load balance test ASAP.

The water heater was not on. It is gas powered. I could get it to run by taking measurements right after I take a shower.

Also, I lied about the pump head being shiny. It's dirty, but no signs of corrosion on the case. One of the screws attaching the plastic wire shroud was a little "fuzzy" like a car battery terminal I think, but just a little.

 

Last edited by Weez; 04-14-11 at 12:23 PM.
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Old 04-14-11, 10:45 AM
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If it's gas fired, then it is not an issue.
 
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Old 04-14-11, 12:12 PM
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What about running the air conditioning?
 
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Old 04-14-11, 12:19 PM
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Originally Posted by Weez View Post
The voltage readings are AC. The meter (a cheap Craftsman) reads 0.001VAC with the probes shorted.

What I was saying about the meter showing 0.2VAC before connecting the probes was this: I clipped one lead to the ground wire coming from the pump. The other probe I touched to the ground bus bar. However, as I approached the panel with that probe the meter started reading a voltage, which was 0.2VAC before I touched it to the bus bar. I guess it's picking up some induced voltage from magnetic flux or something???

About the ground to the motor case: I'm not sure how well the plug is making contact with the ground screws which also hold the plug in the jack on the motor. The small metal collar plate aroung the plug is used to screw the plug down to the motor. That collar is the part that makes ground contact with the motor. It is badly corroded (the pic is the wrong angle - if you saw it from the top it would show that the collar is less than half there, and the surface is very poor. I cleaned it up the best I could without destroying it so much that it is no longer works at all.

My ammeter is actually my multimeter which I of course had wired in series. If this is not sufficient I can attempt to get my hands on a dedicated ammeter (not sure if I know anybody though). I know I can get my hands on a calibrated Fluke multimeter at work, which should be more accurate than my Craftsman. I've just never seen anybody use a dedicated ammeter (I work in aircraft).

I will try the load balance test ASAP.

The water heater was not on. It is gas powered. I could get it to run by taking measurements right after I take a shower.
I think your test process is OK. Ben and I don't think the gas WH is a factor.
So, we are left with a unenergized system that draws .08 Amps thru the water; caused by 0.5v AC in ground potential difference between the load center and the water around the pump. We don't know if the 80mA will vary much for the house or not. I would surmise that the more unbalanced the load there is in the house, then that number will rise. It might be good to keep that ammeter in the circuit for a few days and monitor it. I tend to think we have not found the smoking gun, as long as these numbers don't go much higher.
I'd get the water analyzed for content.

As a side note. I'm in the electronics development business. Right now, I have a product that turns gold plated battery charge contacts black with exposure to salt water. It happens in about 10 minutes of exposure. Longer exposure will eat away enough precious and base metal to cause a hole to form. Its a DC system, but the current is on the same order as your 80mA.
 
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Old 04-14-11, 12:25 PM
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Thanks guys.

I added a couple pics to my previous post that I accidentally left out.

I can leave that meter wired up and check it periodically. I'll have to get some aligator clip leads because for some reason I only have 1.

I found out that I do have access to clamp-on type ammeters here at work that I can check out and take home. Do you think that's worth doing?

Also, I could borrow a nice Fluke multimeter. Do you think that is worth doing?

Why is my meter reading values before I even connect it to the bus bar?

I have a feeling that if the ground connection at the motor wasn't in such poor shape that the current reading might be larger. I wish I had measured it before I disturbed the connection.
 
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Old 04-14-11, 12:35 PM
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Originally Posted by Weez View Post
Also, I could borrow a nice Fluke multimeter. Do you think that is worth doing?
Yeah, I think it makes sense to test with a good meter.

Why is my meter reading values before I even connect it to the bus bar?
It can pick up some electromagnetic fields from the area around the charged wire, from your body or it can just be error within the tolerance of the meter. The better meters have lower tolerance and will produce a more reliable reading.

I have a feeling that if the ground connection at the motor wasn't in such poor shape that the current reading might be larger.
Well the fact that the corrosion is so bad around the ground terminal connection is a strong indicator to me that this is at least part of the problem.
 
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Old 04-14-11, 09:09 PM
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OK, I brought home a calibrated Fluke multimeter from work.

I tested the following conditions tonight:

Electric washer and dryer both running: 110mA @ 720mVAC.

Just the electric dryer: 75mA @ 500mVAC

Both dryer and washer shut off: 75mA @ 545mV

I didn't get to try the load balance test.
 
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Old 04-21-11, 12:01 PM
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I finally got a heat gun that I'm going to use to try the load balance test.

I went ahead and ordered a new pump with Franklin motor. I also ordered a couple aluminum anodes from a marine supply place that they normally attach to propeller shafts. I intend to connect the anodes to the motor case, and I will pull the pump every so often to check it out.
 
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Old 05-06-11, 01:20 PM
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Well here's the new pump with the anodes wired up. I'll pull it up at the end of the summer to inspect.

 
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