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Schlominator 10-01-2011 03:28 PM

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

Code05 10-01-2011 04:09 PM

Quote:

Originally Posted by Schlominator (Post 739640)
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?

a7ecorsair 10-01-2011 04:12 PM

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.

whatsup 10-01-2011 04:16 PM

Quote:

Originally Posted by Schlominator (Post 739640)
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.

Sunny B. 10-01-2011 04:17 PM

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?

whatsup 10-01-2011 04:25 PM

The reading of 70 volts and 160 volts is a dead give away for neutral problem.

Sunny B. 10-01-2011 04:47 PM

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?

Schlominator 10-01-2011 04:54 PM

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.

whatsup 10-01-2011 09:30 PM

ok check your driven ground rods, look for loose or broken ground wire
 
Quote:

Originally Posted by Schlominator (Post 739692)
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.

Jim Port 10-01-2011 09:35 PM

Quote:

Originally Posted by Sunny B. (Post 739667)
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.

a7ecorsair 10-01-2011 09:40 PM

Quote:

Originally Posted by whatsup (Post 739932)
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 10-01-2011 09:50 PM

Quote:

Originally Posted by Schlominator (Post 739692)
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.

whatsup 10-01-2011 09:54 PM

Quote:

Originally Posted by a7ecorsair (Post 739941)
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?

Jim Port 10-02-2011 08:15 AM

Quote:

Originally Posted by whatsup (Post 739954)
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.


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