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 10-01-2011, 03:28 PM   #1
Newbie
 
Join Date: Oct 2011
Location: Houston, Texas
Posts: 3
Share |
Default

Garage subpanel problem


Hi everyone. I found your forum searching for some answers to this problem.

All the outlets and lights in my garage are wired to a subpanel connected to the main breaker box. The outlets read 120v on a multimeter until something is turned on or plugged in. Then some outlets read 240v and some are dead. That is with everything unplugged. When the house sprinkler control was plugged in, then some lines read 70v and others read 160v. I checked all the connections in the sub panel and all looked ok and felt tight. All the outlets seem to be wired properly. a three light tester showed no open neutrals in the outlets. There are some fluorescent lights wired into the line and I haven't opened all of those yet. Any ideas of what to look at next? thanks.

Larry

Schlominator is offline   Reply With Quote
Old 10-01-2011, 04:09 PM   #2
Member
 
Code05's Avatar
 
Join Date: May 2009
Location: Easton MD
Posts: 1,841
Default

Garage subpanel problem


Quote:
Originally Posted by Schlominator View Post
Hi everyone. I found your forum searching for some answers to this problem.

All the outlets and lights in my garage are wired to a subpanel connected to the main breaker box. The outlets read 120v on a multimeter until something is turned on or plugged in. Then some outlets read 240v and some are dead. That is with everything unplugged. When the house sprinkler control was plugged in, then some lines read 70v and others read 160v. I checked all the connections in the sub panel and all looked ok and felt tight. All the outlets seem to be wired properly. a three light tester showed no open neutrals in the outlets. There are some fluorescent lights wired into the line and I haven't opened all of those yet. Any ideas of what to look at next? thanks.

Larry
You have a bad neutral somewhere. What readings do you get at the main panel?

Code05 is offline   Reply With Quote
Old 10-01-2011, 04:12 PM   #3
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Default

Garage subpanel problem


Test the volt output at the breaker in the main panel that feeds this sub. Across the breaker you should always read 240 and from each leg to neutral you should read 120. Have someone turn on stuff in the garage while you test at the main panel.
a7ecorsair is offline   Reply With Quote
Old 10-01-2011, 04:16 PM   #4
Newbie
 
Join Date: Oct 2011
Location: south carolina
Posts: 9
Default

Garage subpanel problem


Quote:
Originally Posted by Schlominator View Post
Hi everyone. I found your forum searching for some answers to this problem.

All the outlets and lights in my garage are wired to a subpanel connected to the main breaker box. The outlets read 120v on a multimeter until something is turned on or plugged in. Then some outlets read 240v and some are dead. That is with everything unplugged. When the house sprinkler control was plugged in, then some lines read 70v and others read 160v. I checked all the connections in the sub panel and all looked ok and felt tight. All the outlets seem to be wired properly. a three light tester showed no open neutrals in the outlets. There are some fluorescent lights wired into the line and I haven't opened all of those yet. Any ideas of what to look at next? thanks.

Larry
Is service wire from main panel 3 conductor or 4 conductor? Is the garage seperate and detached? Does house exhibit any of the same symtoms? Neutral /ground issue.

Last edited by whatsup; 10-01-2011 at 04:19 PM. Reason: misspell
whatsup is offline   Reply With Quote
Old 10-01-2011, 04:17 PM   #5
Member
 
Join Date: Sep 2011
Posts: 218
Default

Garage subpanel problem


Quote:
Originally Posted by Code05

You have a bad neutral somewhere. What readings do you get at the main panel?
But he is getting 240. How is a bad neutral the cause of this?
Sunny B. is offline   Reply With Quote
Old 10-01-2011, 04:25 PM   #6
Newbie
 
Join Date: Oct 2011
Location: south carolina
Posts: 9
Default

Garage subpanel problem


The reading of 70 volts and 160 volts is a dead give away for neutral problem.
whatsup is offline   Reply With Quote
Old 10-01-2011, 04:47 PM   #7
Member
 
Join Date: Sep 2011
Posts: 218
Default

Garage subpanel problem


Quote:
Originally Posted by whatsup
The reading of 70 volts and 160 volts is a dead give away for neutral problem.
I don't have too much troubleshooting experience, that's why I asked. But when you have a bad neutral, its possible to read a higher voltage?
Sunny B. is offline   Reply With Quote
Old 10-01-2011, 04:54 PM   #8
Newbie
 
Join Date: Oct 2011
Location: Houston, Texas
Posts: 3
Default

Garage subpanel problem


I tested the main breaker that feeds the sub and got 240 across and 120 to neutral or ground. I will do it again with something connected and have someone plug it in and out in garage and see if it fluctuates.

I'm getting 120 through each line in the sub, but don't know how to test the neutral between the sub and main. Could it be a break in this line? It is underground and we have had a lot of ground shifting due to drought and finally a little rain.

It is a 3 conductor from main to a detached garage. No problems noticed in the house.

I get 240 or 120 when nothing is plugged in or turned on in the garage. Lower voltage when something is on, but not working.

I have been looking for a bad neutral in the garage but don't know how to track it down.

Thanks again, all.
Schlominator is offline   Reply With Quote
Old 10-01-2011, 09:30 PM   #9
Newbie
 
Join Date: Oct 2011
Location: south carolina
Posts: 9
Default

Garage subpanel problem


Quote:
Originally Posted by Schlominator View Post
I tested the main breaker that feeds the sub and got 240 across and 120 to neutral or ground. I will do it again with something connected and have someone plug it in and out in garage and see if it fluctuates.

I'm getting 120 through each line in the sub, but don't know how to test the neutral between the sub and main. Could it be a break in this line? It is underground and we have had a lot of ground shifting due to drought and finally a little rain.

It is a 3 conductor from main to a detached garage. No problems noticed in the house.

I get 240 or 120 when nothing is plugged in or turned on in the garage. Lower voltage when something is on, but not working.

I have been looking for a bad neutral in the garage but don't know how to track it down.

Thanks again, all.
Ok You should Have A seperate driven ground rod at each panel (main and sub) Your readings are good, but,once a load is applied they fluctuate, right? check your ground connections at driven electrode, loose or broken? Also check if garage panel neutral is bond to ground.
whatsup is offline   Reply With Quote
Old 10-01-2011, 09:35 PM   #10
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,314
Default

Garage subpanel problem


Quote:
Originally Posted by Sunny B. View Post
But he is getting 240. How is a bad neutral the cause of this?
You will notice a shift between the two legs when the neutral is bad. The neutral is the reference point. As the one leg voltage goes up the other leg will go down by the same amount. For example, one leg goes to 160 the other drops to 80.
__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is online now   Reply With Quote
Old 10-01-2011, 09:40 PM   #11
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Default

Garage subpanel problem


Quote:
Originally Posted by whatsup View Post
Ok You should Have A seperate driven ground rod at each panel (main and sub) Your readings are good, but,once a load is applied they fluctuate, right? check your ground connections at driven electrode, loose or broken? Also check if garage panel neutral is bond to ground.
Ground circuit has nothing to do with current flow.
a7ecorsair is offline   Reply With Quote
Old 10-01-2011, 09:50 PM   #12
I=E/R
 
a7ecorsair's Avatar
 
Join Date: May 2010
Location: Minnesota
Posts: 2,052
Default

Garage subpanel problem


Quote:
Originally Posted by Schlominator View Post
I tested the main breaker that feeds the sub and got 240 across and 120 to neutral or ground. I will do it again with something connected and have someone plug it in and out in garage and see if it fluctuates.

I'm getting 120 through each line in the sub, but don't know how to test the neutral between the sub and main. Could it be a break in this line? It is underground and we have had a lot of ground shifting due to drought and finally a little rain.

It is a 3 conductor from main to a detached garage. No problems noticed in the house.

I get 240 or 120 when nothing is plugged in or turned on in the garage. Lower voltage when something is on, but not working.

I have been looking for a bad neutral in the garage but don't know how to track it down.

Thanks again, all.
Your garage panel should have three wires coming in from the house. Two hots from the house panel breaker and one neutral from the house panel neutral bar. You need to check the lug at the main panel where the neutral from the garage is connected. Turn off the main breaker before using a screw driver inside the main panel. Loosen and tighten this lug a couple of times.
Then do the same in the garage panel. Loosen and tighten the neutral lug a couple of times.
a7ecorsair is offline   Reply With Quote
Old 10-01-2011, 09:54 PM   #13
Newbie
 
Join Date: Oct 2011
Location: south carolina
Posts: 9
Default

Garage subpanel problem


Quote:
Originally Posted by a7ecorsair View Post
Ground circuit has nothing to do with current flow.
Really,next time your working on an energized circuit grab hold of hot wire and ground potential. See how that works for you! just kidding,What purpose does the ground rod serve?

Last edited by whatsup; 10-01-2011 at 09:57 PM. Reason: clarity
whatsup is offline   Reply With Quote
Old 10-02-2011, 08:15 AM   #14
Licensed electrician
 
Join Date: Sep 2007
Location: Maryland
Posts: 7,314
Default

Garage subpanel problem


Quote:
Originally Posted by whatsup View Post
Really,next time your working on an energized circuit grab hold of hot wire and ground potential. See how that works for you! just kidding,What purpose does the ground rod serve?
Grounding electrodes are for high voltage events like lightning strikes.

__________________
Answers based on the National Electrical Code. Local amendments may apply. Check with your local building officials.
Jim Port is online now   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
Garage Subpanel matt151617 Electrical 7 09-13-2011 09:17 PM
Detached Garage Subpanel + Generator Back Feed insaneirish Electrical 3 09-06-2011 02:09 AM
Wiring Subpanel off Subpanel brgmgb Electrical 2 08-29-2011 04:18 PM
correct garage subpanel wiring lawsklsux Electrical 14 11-14-2010 10:54 PM
Garage Wiring issues jimmyfloyd Electrical 20 06-08-2009 02:57 PM




Top of Page | View New Posts

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