Low voltage at subpanel

[Houlio45]

Hi:

I have a 100 amp subpanel in my garage that is fed by a 60 amp double pole breaker from the house via about 50 feet of buried Triplex 2-2-4 wire (Two insulated hot wires and a bare neutral). Here's my problem: One hot wire at the subpanel registers 120 volts while the other only registers 79 volts. Therefore I can only use one half the panel. Any ideas why that voltage is low?

 

[awdblazer]

whats the voltage at the main panel? could be a loose connection

 

[Kevin C]

Run a load on the low side and see if it goes to zero. A typical old school incandescent bulb should be enough. Odds are you have a complete open and the 79 volts you see is just an induced voltage from the other leg.

As AWDBlazer mentioned, the main panel is a good place to start.

A photo of each box is a good start.

 

[Aceman]

Hi:

I have a 100 amp subpanel in my garage that is fed by a 60 amp double pole breaker from the house via about 50 feet of buried Triplex 2-2-4 wire (Two insulated hot wires and a bare neutral). Here's my problem: One hot wire at the subpanel registers 120 volts while the other only registers 79 volts. Therefore I can only use one half the panel. Any ideas why that voltage is low?

Yes, it's most likely because you have the wrong cable installed underground. I'd be willing to bet the the aluminum wire is corroding and turning into a white chalk.

I wouldn't even waste time troubleshooting it. Start digging a trench, lay some conduit and install the right stuff.

 

[ishiboo]

Yes, it's most likely because you have the wrong cable installed underground. I'd be willing to bet the the aluminum wire is corroding and turning into a white chalk.

I wouldn't even waste time troubleshooting it. Start digging a trench, lay some conduit and install the right stuff.

+1.

Time to run some 2-2-2-4 MHF.

You've apparently got triplex service drop wire, which is supposed to be in the air. The neutral won't last underground and hasn't, and even the insulated hots will probably not last much longer.

 

[Houlio45]

Voltage coming off the breaker in the main panel reads 120 off each contact.

 

[Houlio45]

Thanks. Must be the wire is gone bad. The run has been underground encased in ABS hose for about two years.

 

[Houlio45]

Is 2-2-2-4 MHF my only option for wire? I do need 220 to run a compressor.

 

[Rookie2]

Put 120v and 240v load on the panel and recheck all voltage points that you just checked. There is a bad connection or maybe a bad breaker.

 

[Gary S]

And, definitely take Aceman's advice. BURY CONDUIT!!!

Then you don't have to dig another trench if something goes wrong.

 

[pattenp]

It is advisable to run 120V/240V. Also MHF is a good option because it can also be run inside the structure in conduit. You can run Quadruplex URD but it is rated for outside only. The URD needs to be terminated outside in a junction box where you can transition to SER for the run inside. Even though Mobile Home Feeder (MHF) and Quadruplex URD are rated for direct bury, it's best to put them in conduit.

Is 2-2-2-4 MHF my only option for wire? I do need 220 to run a compressor.

 

[CNGsaves]

Thanks. Must be the wire is gone bad. The run has been underground encased in ABS hose for about two years.

If you buried electric cable that has failed in just 2 years . . . . . . . we've just got to SEE that !!!!
Post up some pics !!!



Also, are there "special circumstances" that might have led to wire failure . . . . WHERE are you located . . . . . Area 51 in New Mexico ??

 

[wyliesdiesels]

Putting my money on the bare neutral failing! Agree with Aceman! Dont bother troubleshooting!

 

[ishiboo]

If you buried electric cable that has failed in just 2 years . . . . . . . we've just got to SEE that !!!!
Post up some pics !!!



Also, are there "special circumstances" that might have led to wire failure . . . . WHERE are you located . . . . . Area 51 in New Mexico ??

He said "bare neutral" which means it is an overhead, open-air wire NOT intended to be buried. It is simply a bare aluminum neutral.

 

[shamrock12]

A bare neutral buried underground? Yeah, I'd say the neutral is failing too, but I'd also suspect one of hot is failing too since you were able to read 120v on the other hot.

 

[MTW]

For this one, you probably don't even need a tester. During a soaking rain look for earth worms along the cable length, they will show you where the cable is leaking, by trying to get the hell out of Dodge. At the same time you might find your meter spinning furiously.

Just a thought.

 

[madosta]

Should have used steel or aluminum conduit, then you could have used that for your backup neutral.

LOL jk.

 

[awdblazer]

do you have a ground at your panel?

 

[Houlio45]

Well, pulled out the old wire -the neutral was corroded almost all the way through in two spots, and one of the hots was damn near corroded right through in one spot. Thanks for the sound advice.

 

[pattenp]

Some people make the mistake thinking that wire in conduit underground is protected from getting wet, but conduit underground is not a dry location. Condensation will collect and cause puddles of water that the wire will lay in and corrode. That's why wire needs to be rated for wet locations when in conduit underground.