# Well pump meggering



## Lone Crapshooter (Nov 8, 2008)

To start with disconnect the pump wiring from the VFD. Then connect the megger between any one of the phase wires and the ground wire going to the pump.
Apply twice the operating voltage to the pump motor with the megger. 
If you have a megger that shows output voltage of the megger the output voltage should be very close to the voltage selected if it is not then there is something wrong in the pump motor circuit.
If you feel that there is something wrong in the pump circuit then you should pull the pump and disconnect the motor megg only motor and see what kind of readings you get if they are the same as before then the motor is bad.
If not megg each conductor to ground if you get better readings than before that tells you that the problem is in the motor.
If the readings are worse then the problem is in the wiring to the motor.
For a 208 volt motor the lowest reading that I would accept is 1.25 megg That formula to determine lowest acceptable reading is 1 megg / 1000volts +1 megg. IN this case I used 250 volts to make it easier to figure.

Another thing I would test is the winding resistance phase to phase. 
No one can tell you what that reading should be but they all should be the same. It is not uncommon for motors to have winding resistances less than 1 ohm. I can tell you this that the larger the motor the less winding resistance.

LC

Listen Think Solve


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## micromind (Aug 11, 2007)

The above post is right-on. Just make sure that all 3 wires are disconnected from the VFD, or the megger will wreck it. 

According to the Franklin book, the winding resistance for a 5 HP 3 phase 200 volt motor is 0.74-0.91 ohms. If you're measuring it at the VFD, you'll need to add the resistance of the wire down the well. 

The current of this motor is 18.3 amps, the SF (service factor) current is 20.5 amps. The locked rotor amps is 122.

Most submersible pumps operate into the service factor, but with a 3HP wet end, I'd be suspicious of any current over 18 amps at 60 HZ. 

The fact that it hunts at more than 60HZ could be a lot of things, including well capacity or pump design. One thing to try would be to adjust the VFDs carrier frequency up or down a notch. Sometimes this will result in more stability, especially at higher speeds.

Rob


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## Zog (Apr 15, 2009)

Lone Crapshooter said:


> That formula to determine lowest acceptable reading is 1 megg /volts +1 megg. IN this case I used 250 volts to make it easier to figure.


That formula has not been used in any standard since it was removed from NAME in 1979.


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## MDShunk (Jan 7, 2007)

Zog said:


> That formula has not been used in any standard since it was removed from NAME in 1979.


Save for the fact that this is still printed in the instructions for many well pumps.


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## Lone Crapshooter (Nov 8, 2008)

We use that formula all the time at work . What formula should we be using?

LC

Think Listen Solve


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## leenah (Mar 27, 2010)

Well thanks for the reply, 

The test that you mention using the megger on the test with the pump aqnd pimp wiring:

spot test,
time resistance test

since there is no formal data i guess both these would be a good idea?
and then a ohm check on the windings them selfs. which someone kindly gave me those numbers..thankyou

so if im finding bad readings at the VFD end ( testing pump and pump wiring , with the VFD disconnected), pulling the pump is the next step? checking the pump itself and the wiring to the pump seperatly?

The VFD on has two settings on it 60/80hz. so i cant bump it up slightly. Do you think the Hunting could be caused by a breech in the wire some where?

thanks


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## Jlarson (Jun 28, 2009)

leenah said:


> I have come across a 3 phase, 5HP 208v well pump install that is acting up. When i showed up onsite the pump tech's were there and the VFD had just blew off the wall...


 What do you mean by it blew off the wall, overheat, overload, caught fire? 
That is information that could be helpful to know. 

Besides that I might be able to give you a couple of helpful tips, having done more well work than I care to think about. 

1. match the motor and wet end and run the VFD a 60Hz, most manufactures of pumps and motors recommend it.

2. Use a VFD that you can program and has control inputs, the VFDs from well manufactures that come in little gray boxes are trash. If you use a good VFD you can program use it to ramp up to 60 on start up and ramp down on shut off, especially if its a really deep well. 

3. When you pull a faulty pump megger the cable as it comes up and watch for changes also after you get the cable out string it out on the ground and clean it with a towel and inspect every inch and megger wire to wire. 

4. megger the pump as soon as its out of the well and then let it sit in the sun for a couple of days and then megger it again, if the readings go up there's a faulty seal 

5. *when you put the pump back in do the splices your self*, if you want I can post my custom splicing procedure. Well guys are really bad at it most of the time

6. Have the well guys use spiders when they put the pump back in, spiders are rubber things that go on the drop pipe and keep it centered in the casing and won't let the cable rub going down. 

7. If you can swing it have the well videoed when the pump is out this will tell you what is going on water level wise and if there are any other problem with the well itself 

8. Follow the other advice other have given you on using the megger 

9. This is a really important one, especially if your company is pulling the pump, *BE CAREFUL SO YOU DON'T LOSE THE PUMP DOWN THE WELL*, trust me I know. 

Sorry for the really long post, hope it helps. If i think of anything else I will post it.


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## leenah (Mar 27, 2010)

Jlarson said:


> What do you mean by it blew off the wall, overheat, overload, caught fire?
> That is information that could be helpful to know.
> 
> Besides that I might be able to give you a couple of helpful tips, having done more well work than I care to think about.
> ...


Yes all of this information is GREAT, i am so getting my head around these systems before i go out and start testing. Thankyou!

Just a couple of more things i would like to run past you guys

This is not a typical deep well system although all the information so far is relitive

This system feeds a group of seven houses on the lake, with two pumps 
Pump 1, is not in question ( pumps water from the lake to the pump house resivior)

Pump 2, feeds the seven houses through a two 1250 gallon underground tanks( joined together), the pump sits in a horizontal position in the tank.
I just learned today that it had a cooling sleve on it for the past 8 months. When the system broke down (VFD blew, and the 2" T/A on the discharge pipe was cracked) the pump techs pulled the pump and found that the sleve over the pump/motor was not true on the pump, it was crooked in relation to being centered over the pump, thus they took it off and replaced the VFD and are now running the pump without the sleve. 

The only check valve on the system is in the pump it self, so the tech says. 
My reading articals suggest a check valve be in the system to pervent water hammer and other bad operations in the system. is this good enough?? check valve at the pump not down the line further? 

The houses the system is feeding is higher in elevation then the tanks. 

I know for a fact aswell the grounding and circuits going from panel to VFD are not sized properly, which i will fix.

And yes data in the testing of the blown VFD would be nice and i am working on getting that from Franklin..

another long post.. thanks again and again, your inputs are great..


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## leenah (Mar 27, 2010)

sorry i did not answer your question, the cover of the VFD blew off.. all the high voltage circuits where fried. When I showed up on site a week ago, the pump tech showed up to fix the broken 2"T/A in the tank..

and then they said they fixed it and turned it on and the VFD blew???? umm..

so needless to say not sure what happened, they pled that they just turned it on after the fix. which is what just might of happened, dont know.

i would think the VFD would protect the system from all sorts of faults.

And yes it just one of those low end ones

the new VFD is a 
*CentriPro BF50*
*and those splice notes would be handy to have if i have to repair*


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## Jlarson (Jun 28, 2009)

This assumes 4 wire pump cable, if they ran a separate ground to the pump tell me because that can screw things up, learned that the hard way. 

parts list 

- uninsulated barrel crimp connectors and a good crimp tool
- heat shrink with adhesive inside to cover each crimp 
- large heat shrink to go over all the wires make it a long piece and twice as big as you need to shrink onto the wires 
- hot melt glue sticks
- good heat gun

Slide the big piece of heat shrink over the cable then slide the small pieces of heat shrink over each individual wire then make up the crimps and slide the small shrink over each crimp and shrink until you see the glue come out each side. Slide the big heat shrink over the splices and make sure its centered on the splice and stuff in the hot melt glue sticks get as many in there as you can on all sides. Heat that until the glue comes out each end and let cool.

About the horizontal mounting, that puts lots of stress on the bearings it works but you will get the best life out of the pumps and motors if they are mounted vertical especially if they are run past 60 Hz. Try to see if you can mount it vertically. Also put the cooling sleeve back on and I would put in a spring check valve at the pump so it doesn't have to work as hard when it starts


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## Zog (Apr 15, 2009)

Lone Crapshooter said:


> We use that formula all the time at work . What formula should we be using?
> 
> LC
> 
> Think Listen Solve


THis is what ANSI, NEMA, IEEE, and NETA all use as a spec. 

The dielectric absorption ratio or polarization index shall not be less than 1.0. The recommended minimum insulation resistance (IR1 min) test results in megohms shall be corrected to 40° C and read as follows:​ 
1. IR 1 min = kV + 1 for most windings made before 1970, all field windings, and others not
described in 2.2 and 2.3.
(kV is the rated machine terminal-to-terminal voltage in rms kV)​ 
2. IR 1 min = 100 megohms for most dc armature and ac windings built after 1970 (formwound
coils).​ 
3. IR 1 min = 5 megohms for most machines and random-wound stator coils and formwound
coils rated below 1 kV.​ 
NOTE: Dielectric withstand voltage and surge comparison tests shall not be performed
on machines having values lower than those indicated above.​


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## leenah (Mar 27, 2010)

thanks for all the help


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## doc (Mar 30, 2010)

Yeo Leenah, excelent question, I have come accross this myself, and like you have looked deeper into this than many, more to come, thank you Doc~


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## Lone Crapshooter (Nov 8, 2008)

I was looking through some notes and found this. According to my notes it is a IEEE standard for minimum insulation resistance for rotating equipment.
This as I recall I read it in a magazine about 12 to 15 years ago.

KV X 11= Minimum insulation to ground

480----5.2M 
2400---264M
4160---4576M
13.2KV---145,200M
LC

Listen Think Solve


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## leenah (Mar 27, 2010)

*motor test results*

out side temp 10 degrees celsius
megger tested motor leads at VFD ( VFD disconnected from motor leads)
motor/pump submerged in tank
VFD - Motor distance aprox:40'
1 splice in motor wires
splice submerged
wire tested: 4 wire ( Green,yellow,black,blue
motor 208v 5HP 3ph

Megger set: 500v/200Mohm 30 SEC

L1-Ground O.L. (over limit)
L2-Ground O.L.
L3-Ground O.L.

Megger Set: 1000v/ 2000Mohm 30 SEC

L1-Ground 540. M ohm
L2-Ground 538. M ohm 
L3-Ground 560. M ohm

OHM test with multimeter

L1 - L2 1.2 ohm
L2 - L3 1.2 ohm
L1 - L3 1.2 ohm


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## Lone Crapshooter (Nov 8, 2008)

Looks good to me

LC


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## leenah (Mar 27, 2010)

The motor is still in operation, and running good, i think the issue with the system is mechanical, very good thanks for all the reply


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## Zog (Apr 15, 2009)

leenah said:


> out side temp 10 degrees celsius
> megger tested motor leads at VFD ( VFD disconnected from motor leads)
> motor/pump submerged in tank
> VFD - Motor distance aprox:40'
> ...


 What was the winding temp at the time of test????? Worthless data without tempatures. What was your 1 minute and 10 minute readings? Hard to calculate DAR and PI without the other readings


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## micromind (Aug 11, 2007)

Those numbers look good. If there was anything at all wrong with the motor or wires, it'd show up in the tests you ran.

Rob


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## leenah (Mar 27, 2010)

Zog said:


> What was the winding temp at the time of test????? Worthless data without tempatures. What was your 1 minute and 10 minute readings? Hard to calculate DAR and PI without the other readings




The temp of the motor submersed in the water i did not get.

I did not do the other tests with longer duration


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## Zog (Apr 15, 2009)

leenah said:


> The temp of the motor submersed in the water i did not get.
> 
> I did not do the other tests with longer duration


Tempature makes a huge difference, now with your 500M readings on a LV motor you should be good no matter what but the readings are useless for trending in the future without the tempature. What happens in a year or 2 when you test this motor and the tempature is different? The most valuable info you get from an IR test is not so much what it is today but what the trend is over time for predicting failure. 

A spot test only measures one if the 3 insulating properties of insulation so you are only getting part of the story. DAR is key info for a LV motor.


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## leenah (Mar 27, 2010)

is there a reference manual to show reading values for different motors? 

ie, baldor, franklin, goulds, etc?


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## Zog (Apr 15, 2009)

leenah said:


> is there a reference manual to show reading values for different motors?
> 
> ie, baldor, franklin, goulds, etc?


Not by manufacturer but by type, size, and vintage. I posted all the specs earlier in this thread (#12)


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