# 480volt single phase issue



## HighVoltage1 (May 20, 2014)

Hi everyone,
I got a call today to check out a problem at the local golf course. The irrigation pump was working this morning, then the guys shut it off to go for coffee. After coffee they went to switch it back on....nothing. 

I got there and tested the voltage at the disconnect. It was 470v across L1-L2. 470v from L1-Gnd. 2v from L2-Gnd. When I turned on the disconnect and checked the voltage at the contactor and disconnect and my voltage was 25v L1-L2. 470v L1-gnd. 470v L2-gnd. I turned the disconnect off.
I was checking the fuses and then I checked the voltage again and now I was reading 240v from L1-L2 for some weird reason. So I took the golf cart to the step up 240v-->480v transformer to check the voltages and I have 484v from L1-L2.
I went back to the pump disconnect and still only 240V. 
I don't know if the transformer is messed or why my voltages are changing.

I hope I explained this right.
Hope someone can help!
The motor is a 30hp 480volt 1phase beast.


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## chicken steve (Mar 22, 2011)

Is this UG HighvoltageOne...?


~CS~


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## CFL (Jan 28, 2009)

Be more specific on where you tested voltage, i.e. line side of disco, load side, etc.. It seems like one of your fuses is blown.


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## CFL (Jan 28, 2009)

Also, I don't think I've ever seen a 480 volt single phase motor.


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## HighVoltage1 (May 20, 2014)

I got 240v on the line side of the disconnect. 480v on the HI side of the transformer but at the other end of the wire is only 240v


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## chicken steve (Mar 22, 2011)

Meg it HV

~CS~


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## HighVoltage1 (May 20, 2014)

I tried disconnecting the motor from the contactor just to see but it didn't change anything. The contactor will not engage.

P.S. I don't think i'm the same person you are thinking of


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## CFL (Jan 28, 2009)

There was a problem with your original voltage check when you read 470 L1 to L2 and 484 at the xfrmr. 14 volt drop with no load is not right. You might have a damaged wire or loose connection somewhere along the line.


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## CFL (Jan 28, 2009)

Do you think you may have been looking at this backwards? The disconnect you checked at first was line side of a 480 to 240 volt step down transformer feeding a 240 volt motor? What does the motor nameplate read?


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## JRaef (Mar 23, 2009)

Off the top of my head I'd think you have a high resistance ground fault INSIDE of the disconnect mechanism itself, likely on the L2 pole.

For the benefit of others, people make custom 480V single phase motors all the time for rural farm applications, because the PoCos don't want to run 3 wires or even 2 out to a farm that doesn't use a lot of power all of the time (no revenue for them). So they feed them with a Single Wire Earth Return (SWER) system that uses a single 12.7kV line, and they hook up a transformer that is 12.7kV Line to Ground on the primary, 480V line to line on the secondary.


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## CFL (Jan 28, 2009)

JRaef said:


> Off the top of my head I'd think you have a high resistance ground fault INSIDE of the disconnect mechanism itself, likely on the L2 pole.
> 
> For the benefit of others, people make custom 480V single phase motors all the time for rural farm applications, because the PoCos don't want to run 3 wires or even 2 out to a farm that doesn't use a lot of power all of the time (no revenue for them). So they feed them with a Single Wire Earth Return (SWER) system that uses a single 12.7kV line, and they hook up a transformer that is 12.7kV Line to Ground on the primary, 480V line to line on the secondary.


I didn't say they don't exist, but I've never seen one. In this case though, he says they're stepping up to 480. It's just unusual to me. But I've only seen a little bit of what's out there.


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## HighVoltage1 (May 20, 2014)

Thanks everybody!
I will head back there tomorrow and get some better numbers for you guys. I'm really second guessing myself.


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## Ultrafault (Dec 16, 2012)

There is an underground run from the tranny to the disconnect? 
I you think you may have a high resistance fault in your underground run.


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## JRaef (Mar 23, 2009)

CFL said:


> ... In this case though, he says they're stepping up to 480. ...





> So I took the golf cart to the *step up *240v-->480v transformer to check the voltages and I have 484v from L1-L2.


You're right, I missed that, but also referring to the LOAD side of a step-*up* transformers as "L1 and L2" is confusing to me. I would have said H1 and H2 (or as labeled)

Very odd that they would do that, then go have a custom 480V 1 phase motor made. Trying to get around a voltage drop issue maybe by boosting the voltage to 480 thus reducing the current? I know that golf course people can get really picky about locating electrical equipment.


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## Big John (May 23, 2010)

Unless this is hacked together (and because it's a golf-course water feature, there's about a 99% chance it is), it's possible your L-G measurements are fine because one leg of your 480V transformer should be grounded. You need to confirm if this is actually the case.

That said, I think you have a broken feeder conductor. 


 It would provide a solid ground on one leg and explain the 0V to ground, and still allow 480V L-L.
With the disconnect on, if the resistance of the earth was in series with the load, you'd have low current flow, and low voltage drop, and it would explain the 25V L-L. But you shouldn't have 470 L-G on both legs.
If you do have a ground fault with a changing impedance, it would also explain why your L-L voltage kept changing.
But there's other stuff there that's a little out-of-whack, too, like the voltage drop at no load. These voltages are a little suspect, I'm guessing your using a high impedance meter? Get a wiggy and take your measurements again.


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## HighVoltage1 (May 20, 2014)

*Broken feeder conductor*

I just wanted to say thanks to everyone for your help and you guys guessed right it is a broken feeder conductor. Now we need to find someone with that fancy locating tool to tell me where the break is. 

I snapped a pic of the motor nameplate: but I don't know how to attach it without getting a "too many character error".
here is the info:
Manufacturer: Written-Pole
synchronous ac motor
30hp
480v
1 phase


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## JRaef (Mar 23, 2009)

The fancy locating tool you are likely thinking of is called a TDR, Time Domain Reflectometer.

Written pole... those are really odd ducks.


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## Big John (May 23, 2010)

HighVoltage, I'm still curious about some of the measurements you had. What kinda meter were you using, and did you ever try a wiggy?


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## Ultrafault (Dec 16, 2012)

Make sure the transformer has been bonded on the secondary.


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## HighVoltage1 (May 20, 2014)

The Secondary is bonded, Thanks!

I am using a fluke multimeter. I've never heard of a wiggy until yesterday.
My measurements were a little weird. At one point yesterday I had 480v-gnd on L1. And 480 L1-L2. Which makes sense that L2 was the culprit. When I left yesterday, at the tranny I had 480v on H1-H2. 240v from H1-gnd and 240v from H2-gnd. At the line side of the disconnect I had 240v Across L1-L2, 240v from L1-gnd, 2.5v from L2-gnd. 
Today my numbers were the same. So I disconnected the H1 and H2 from the tranny and had my apprentice hold L1 and L2 together at the disconnect and I checked for continuity from the transformer and there was nothing. Then he held L1 to the white wire of the underground triplex (ground) and at the other end I checked for continuity and I had it. Then we tried L2 to the white ground and nothing! 
So i'm pretty confident that L2 is busted.

You guys are the best!

Now I just need to get my hands on that TDR!


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## CFL (Jan 28, 2009)

HighVoltage1 said:


> The Secondary is bonded, Thanks!
> 
> I am using a fluke multimeter. I've never heard of a wiggy until yesterday.
> My measurements were a little weird. At one point yesterday I had 480v-gnd on L1. And 480 L1-L2. Which makes sense that L2 was the culprit. When I left yesterday, at the tranny I had 480v on H1-H2. 240v from H1-gnd and 240v from H2-gnd. At the line side of the disconnect I had 240v Across L1-L2, 240v from L1-gnd, 2.5v from L2-gnd.
> ...


From this it sounds like you have a center tapped secondary that is grounded and your L2 conductor is probably broken and faulted to ground.


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## CFL (Jan 28, 2009)

Take two pieces of copper wire and bend them and then walk along the probable path, holding them like a couple of pistols. When you cross the fault they will touch each other.

That sounds like bs but i saw someone do it and he was dead on. The damaged wire was more than two feet deep. 

I would never really try that myself.


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## HighVoltage1 (May 20, 2014)

CFL said:


> Take two pieces of copper wire and bend them and then walk along the probable path, holding them like a couple of pistols. When you cross the fault they will touch each other.



I feel my business might suffer if someone saw me do this.:laughing: 
On the other hand we might find oil!


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## sparkywannabee (Jan 29, 2013)

CFL said:


> Take two pieces of copper wire and bend them and then walk along the probable path, holding them like a couple of pistols. When you cross the fault they will touch each other.
> 
> That sounds like bs but i saw someone do it and he was dead on. The damaged wire was more than two feet deep.
> 
> I would never really try that myself.


Are you sure. I thought that was how they figured out where to dig a well and hit water.


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## Legacyelectric (Sep 9, 2012)

Divining rods! I've met people that swear by that. Seems like a multi tool... Water, oil, electrical faults,


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## Hmacanada (Jan 16, 2014)

I use them to locate underground pipes and such that you just can't find any other way.
I wouldn't risk my life on them but have had good luck .
For a few yrs when they first started using plastic for underground gas they didn't require a tracer cable so it a big pain in the arse trying to find them without breaking it.

Never heard of using them for finding faults though.

Sent from my iPhone using electriciantalk.com


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## don_resqcapt19 (Jul 18, 2010)

HighVoltage1 said:


> ...
> Now I just need to get my hands on that TDR!


If you don't know the routing of the underground cable, you will need more than a TDR. The TDR will give you the distance to the fault, but you have to know the route of the cable to measure the distance and find the fault.


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## don_resqcapt19 (Jul 18, 2010)

CFL said:


> Take two pieces of copper wire and bend them and then walk along the probable path, holding them like a couple of pistols. When you cross the fault they will touch each other.
> 
> That sounds like bs but i saw someone do it and he was dead on. The damaged wire was more than two feet deep.
> 
> I would never really try that myself.


The first time I ever saw anyone do that is when we hired a guy to do some underground locating for us. He first checked the area with an electronic locater and then he got out his "bent wires". I was kind of giving him a "what the heck" and he said he sometimes finds things that the locater can't.

His company also sells the electronic locater and teaches classes on their use. He always talks about the "bent wires" in his class. He says at the beginning of the class almost no one believes him, but at the end most do and some of the class members can even make it work. He had the short end of the "L" wire in a small brass tube that he held in his hands to limit his hands from making the wires cross.

I have tried it a few times and found what I was looking for, but other times they wires crossed and when we dug we did not find anything. You also have to look up, because the will cross when you are using them and you walk under overhead lines. 

All of the science says it is impossible for the wires to work, but I have talked to too many who use them successfully to say that they can't work.


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## walkerj (May 13, 2007)

don_resqcapt19 said:


> The first time I ever saw anyone do that is when we hired a guy to do some underground locating for us. He first checked the area with an electronic locater and then he got out his "bent wires". I was kind of giving him a "what the heck" and he said he sometimes finds things that the locater can't. His company also sells the electronic locater and teaches classes on their use. He always talks about the "bent wires" in his class. He says at the beginning of the class almost no one believes him, but at the end most do and some of the class members can even make it work. He had the short end of the "L" wire in a small brass tube that he held in his hands to limit his hands from making the wires cross. I have tried it a few times and found what I was looking for, but other times they wires crossed and when we dug we did not find anything. You also have to look up, because the will cross when you are using them and you walk under overhead lines. All of the science says it is impossible for the wires to work, but I have talked to too many who use them successfully to say that they can't work.


We have a locater but I still verify with wires. 

I located a water line in my yard using nothing but 'witching sticks'


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## don_resqcapt19 (Jul 18, 2010)

walkerj said:


> We have a locater but I still verify with wires.
> 
> I located a water line in my yard using nothing but 'witching sticks'


And I have seen the "witching sticks" work on empty PVC conduits...something that an electronic locater can't do.


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## ElectricianJ (Apr 3, 2013)

Could just be a bad connection. Had something similar happen where I work. Read 120 to ground on both lines, but nine volts in between the two. Check to see if anything is loose


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## walkerj (May 13, 2007)

don_resqcapt19 said:


> And I have seen the "witching sticks" work on empty PVC conduits...something that an electronic locater can't do.


You know this already probably but if you push a fish tape in an empty conduit you can use the locator on that.


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## don_resqcapt19 (Jul 18, 2010)

walkerj said:


> You know this already probably but if you push a fish tape in an empty conduit you can use the locator on that.


But then the PVC conduit is no longer "empty"


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