Go Back   DIY Chatroom Home Improvement Forum > Home Improvement > Electrical

CLICK HERE AND JOIN OUR COMMUNITY TODAY...IT'S FREE!

Reply
 
Thread Tools Search this Thread Display Modes
Old 06-06-2012, 05:56 PM   #1
Newbie
 
Join Date: May 2012
Location: Alaska
Posts: 7
Rewards Points: 10
Default

voltage drop on one leg


ten years ago I ran three wires from one barn to the next about 100 ft away. I have used this set up for ten years and now this year one leg only has 80 volts at the main wire using my VOM. one shows 120V the other is only 80V. I checked where the wires came from and they are both 120V there. Can it be a bad connection would cause this drop? They are aluminum wires that where greased and it just seems funny that one end of the wire is 120 and the other is 80. if the wire broke it seems that it would be using a lot of electricity and its not. any ideas for me to try?

wjkrostek is offline   Reply With Quote
Old 06-06-2012, 06:00 PM   #2
Member
 
Join Date: Jan 2012
Location: IL
Posts: 823
Rewards Points: 698
Default

voltage drop on one leg


try switching off load items and see if the voltage pops back up to 120 as you switch things off. Try to localize if it is a single item causing the drop or just the total load.

curiousB is offline   Reply With Quote
Old 06-06-2012, 08:26 PM   #3
Member
 
Join Date: Jun 2007
Posts: 3,510
Rewards Points: 2,008
Default

voltage drop on one leg


What is the voltage across the two hot leads. Checking to ground is a mistake. Check line to line (hot to hot) and each line to neutral. Now what are you reading?
You never said anything about the circuit either. Is it a single 120 volt circuit or single 240 volt circuit?
J. V. is offline   Reply With Quote
Old 06-06-2012, 11:01 PM   #4
Member
 
joed's Avatar
 
Join Date: Mar 2005
Location: Welland, Ontario
Posts: 8,102
Rewards Points: 2,998
Blog Entries: 4
Default

voltage drop on one leg


Sounds like a damaged cable.
__________________
Do not PM with questions that can be asked in a forum. I will not respond.
joed is online now   Reply With Quote
The Following User Says Thank You to joed For This Useful Post:
J. V. (06-07-2012)
Old 06-06-2012, 11:11 PM   #5
Lic Electrical Inspector
 
electures's Avatar
 
Join Date: Dec 2009
Location: The Great Police State of New Jersey
Posts: 1,731
Rewards Points: 1,068
Default

voltage drop on one leg


I agree with Joed, damaged cable. Is it in conduit or direct burial?
__________________
All responses based on the 2011 NEC.
If you live in New Jersey click here. All other states click here.
Please check with local, county and state officials as laws may vary.
Sizing motors here. Online motor calculator here. Online calculators here.
electures is offline   Reply With Quote
Old 06-07-2012, 10:42 AM   #6
Member
 
Join Date: Nov 2007
Location: Nashua, NH, USA
Posts: 6,968
Rewards Points: 2,032
Default

voltage drop on one leg


If a ground hog or other animal chews the insulation, buried aluminum wires can rust out quickly thereafter.

A rusted out wire will result in either zero volts hot to neutral all the time, or voltage varying depending on the load (sometimes it could take more than 10 amps before there is a noticeable voltage drop).
__________________
Forget super sized fries. The Washington Redskins could promote healthy eating with First Lady Obama by choosing a (red skinned) turnip for a mascot.
AllanJ is offline   Reply With Quote
Old 06-07-2012, 11:54 AM   #7
Member
 
Join Date: Jun 2007
Posts: 3,510
Rewards Points: 2,008
Default

voltage drop on one leg


Quote:
Originally Posted by AllanJ View Post
If a ground hog or other animal chews the insulation, buried aluminum wires can rust out quickly thereafter.

A rusted out wire will result in either zero volts hot to neutral all the time, or voltage varying depending on the load (sometimes it could take more than 10 amps before there is a noticeable voltage drop).
Rust and aluminum should not be used in the same sentence.
J. V. is offline   Reply With Quote
Old 06-07-2012, 12:52 PM   #8
Member
 
Join Date: Jul 2008
Location: NW of D.C.
Posts: 5,990
Rewards Points: 2,000
Default

voltage drop on one leg


Quote:
Originally Posted by wjkrostek View Post
it just seems funny that one end of the wire is 120 and the other is 80.
There are several places to measure, with a load or without.
Each VOM probe on the end of the wire.
Each VOM probe on the connections at the end of the wire.

I have also had a case where the connection voltage measured depended on how hard I pressed the VOM probe against the connection.
Yoyizit is offline   Reply With Quote
Old 06-07-2012, 01:17 PM   #9
Electrical Contractor
 
rrolleston's Avatar
 
Join Date: Oct 2011
Location: Granville, NY
Posts: 1,941
Rewards Points: 1,000
Send a message via AIM to rrolleston Send a message via Yahoo to rrolleston
Default

voltage drop on one leg


What kind of wire was used and how deep with conduit or direct burial.
__________________
With Electricity there is the right way to do it and the dead way. Just because it works does not make it safe.
rrolleston is offline   Reply With Quote
Old 06-09-2012, 04:56 PM   #10
Newbie
 
Join Date: May 2012
Location: Alaska
Posts: 7
Rewards Points: 10
Default

voltage drop on one leg


I haven't made it over to my barn to check on all the thoughts you all have given me but I can answer some so your questions now. It's a o or double o cable that is under ground direct burial only about 1 or two ft deep and 100 ft long. its three cables buried, two carry 120 each and one is the neutral. none were in use at the time I checked them. I use only one at the time each to it's own 120 volt motor (1 hp) to run a fan on my grain bins. The one that reads 80 volts hasn't been used for a couple of years the other has been used until recently to air the grain. The way I found the problem when I was checking to see if the wires where hot so I didn't have to back to the barn to see it they where turned on. to my surprise I found one at 80 volts checked the other and it was 120. Didn't make sense to me so I asked here. I hope to make it back over there next week and I can check more. If the cable is corroded is there a way to find out where with out digging it all up? Seems like there would be a lot of loss to ground and arcing if it was leaking to ground? Any thoughts on that? I think it may be just the connections. But if in use that would make a lot of heat right? what do I do to get emails when some one responds. I was waiting and checked and there where answers but no emails. Thanks
wjkrostek is offline   Reply With Quote
Old 06-09-2012, 06:06 PM   #11
CDH
Member
 
Join Date: Aug 2009
Posts: 40
Rewards Points: 25
Default

voltage drop on one leg


Direct buried aluminum wire if the insulation is nicked will eventually allow moisture into the conductor itself and it will slowly oxidize into a powder, you will usually not notice this until it's almost oxidized itself into, you will not necessarily have higher light bills, there are fault locating machines but usually only power company's or electricians are gonna have one, but under most circumstances a fault can be located relatively easy and if as you said only 1' deep can be dug up and repaired in less than an hour, I've located hundreds of faults over the last 25 years and repaired them. Good luck.
CDH is offline   Reply With Quote
Old 06-09-2012, 06:50 PM   #12
Newbie
 
Join Date: May 2012
Location: Alaska
Posts: 7
Rewards Points: 10
Default

voltage drop on one leg


thanks, will it be very noticeable or do you need the bend the wire to find it? Would I be able to run some juice through it and feel for heat change? Or will having only 80 volts burn out my motor? If thats what I have, digging is not easy so while I have it up would it be better to slip it into some pvc pipe while and if I need to dig it all up and it's excisable?
wjkrostek is offline   Reply With Quote
Old 06-09-2012, 08:19 PM   #13
CDH
Member
 
Join Date: Aug 2009
Posts: 40
Rewards Points: 25
Default

voltage drop on one leg


Quote:
Originally Posted by wjkrostek View Post
thanks, will it be very noticeable or do you need the bend the wire to find it? Would I be able to run some juice through it and feel for heat change? Or will having only 80 volts burn out my motor? If thats what I have, digging is not easy so while I have it up would it be better to slip it into some pvc pipe while and if I need to dig it all up and it's excisable?
If one of the legs of your service is burning out and it sounds probable, if you want to verify swap the legs in the panel it's feeding out of and see if your still only getting 80 volts. Feeling for heat change I couldn't say, I'm in Florida and most services we dig up are a minimum of 36" deep and I have never heard of the heat change being used for locating an underground fault, in my opinion without using a fault locator you will be hunting the needle in the haystack and in my opinion if I was going that route I would bury new conduit and pull in a new service and abandon the old.

CDH is offline   Reply With Quote
Reply


Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off


Similar Threads
Thread Thread Starter Forum Replies Last Post
Long Run Voltage Drop i_need_help Electrical 10 02-05-2011 11:53 AM
2 - 900w tansformers on a 15A circuit? tonyBagadonuts Electrical 19 07-20-2008 08:15 PM
Will splice cause voltage drop? JPsAlias Electrical 6 05-19-2008 08:09 PM
Voltage Drop Issues sushiboy Electrical 12 04-03-2008 10:01 PM
Voltage Drop between switch and fixtures CaptMike Electrical 1 06-24-2005 10:30 PM




Top of Page | View New Posts

Copyright © 2003-2014 Escalate Media. All Rights Reserved.