Hi Folks,

The set up:

Garage has a box and ground rod - 220V in with 2 110 circuits (lights and outlet respectively). Feed comes from house through a PVC pipe - 3 wire Romex - 30 amp breaker at house. The house ground rod is about 40 feet away.

The problem:

Whenever the ground gets saturated the breaker at the house to the garage trips whenever I flip the garage breakers to on. <<note that I'm not going to complain about the rain as I am in Texas and the drought is bad>>

More detail:

Today I started poking about and discovered that I'm getting @ 270 volt AC at the garage box.

I'm also getting tired of not having working electricity in my garage as it is Christmas break and I've lots of work to do.

Any thoughts?

Should I bump up the house to garage breaker to 40amp?

Note that I put this in myself and was being particularly safety conscious in placing the 30amp.

Still wondering what the dampness might be causing. I don't think I'm getting wet wire in the pipe as it was continuous from box to box.

Thanks in advance for your thoughts.

-Robert

 

Did you use romex or UF? If you used romex, it's insulation has probably deteriorated and when the pipe fills with water the water conducts electricity and the breaker trips.

 

Type NM cable cannot be used outside even if in conduit. I agree that the insulation has broken down and the moisture is allowing the voltage to bridge a gap and short out.

 

Bumping the breaker to a larger size is like tossing gasoline to put out a fire. The breaker is that size for a reason.

As the others have posted, it sounds like you have a short. Not sure why you are getting 270 volts but one thing at a time. Take a good meter, disconnect the feeders to the garage in the house AND garage panel. Measure resistance (ohms) between the two hots. You should get nothing. If you get a reading, you have a short and need to replace the feeders.

Just wondering, what size are the feeders?

 

I'll presume from your description that a 30 amp Feeder from the house supplies a circuit-breaker panel in a detached garage, and the garage panel has two circuit-breakers , possibly two 20 amp breakers , two 15 amp breakers , or one 20 breaker and one 15 amp breaker.

The problem occurs ONLY when the breakers in the garage are switched "On" .

Try operating the garage circuits with one of the "live" Feeder leads dis-connected from the 30 amp breaker. If the one "live" circuit in the garage operate "normally" , then dis-connect that Feeder conductor at the 30 amp CB and re-connect the Feeder conductor that was first dis-connected.

Now test the second garage circuit for "normal" opertion. By testing the individual Feeder conductors seperately , you may find one of them has a Groung-Fault.

 

First thanks to all who have replied and an update.

What I have done:

Went and purchased UF-B cable - pulled and replaced the Romex I had in the piping underground. There was definitely water in the pipe but no visible breaks or degradation of the wire. Rewired everything as before.

What is happening now:

The 20 amp outlet circuit in the garage will go on and hold. I can plug things in and then work. When I turn on the 20 amp circuit for the lights it will not work and cause the outlet circuit to fail - sometimes but not always it will trip the 30 amp feeder breaker at the house. This will happen even if all the lights are turned off and I've removed the bulbs. Sometimes I can turn off the garage 20 amp light circuit and the 20 amp outlet circuit will work again.

Question to PATTBAA -

Your 1st two paragraphs are correct. 30 amp at house supplies circuit breaker panel in detached garage each with two 20 amp breakers. The problem does occur ONLY when the breakers in the garage are switched "On".

I would like to try your suggestion in paragraph 3 but am uncertain of the mechanics involved. I think that what I would do is to remove say the "white" feed from the 30 amp house side (or could do this in the garage?).

Jumping forward - if I find that one of the circuits has a ground fault what is the solution? Sorry for the daftness here - just trying to resolve before I have to go back to work (need to get the garage operable again to work on kids science projects).

Thanks again for everybody's help.

 

Did you pull 10-3 or 10-2 UF? The 10-3 would have a black, a red, a white and a bare.

 

I am not convinced that your problem was ever the feeder in the pipe feeding the garage since the problem only occurred when you turned on breakers in the garage.

I think when you get around to checking all the wiring in the garage you will find the problem. Like pcboss, I am also interested in exactly what type UF cable you pulled. You should have 3 insulated conductors and a ground, total of 4 wires. Since it evidently was an older installation, you may have had 3 insulated conductors and no ground before.

 

The new wiring was UF-B 10-3 with 4 wires red / white / black and bare (ground) - same as the Romex I had before. I rewired it identically.

My garage box has the following wire connections - bare wire to ground on far left - red to left portion of central panel and black to right of central panel - white goes to the neutral on the far right.

When I measure across the red and black I get 264 V across black to white 131 V or red to white I get 131 V. The outlet also shows 131 V.

Both of the circuits I'm using are on the "Red" service. Thus removing the Red causes both circuits to fail (lose power). Removing the Black does nothing to the operable circuit.

My continuing problem is that flipping the light circuit (20a on the Red / White "service") will flip the 30amp breaker at the house. Even with the lights on the circuit turned off or bulb removed this occurs. Note also that there have been no changes to the wiring and it has worked for years (with the exception of the usual post rain house breaker problem).

Thanks

 

I think a pic might help.

 

Here is the garage box.

[IMG]e:\\home\garage_box.jpg[/IMG]

 

I don't know if that came across. It appears that I cannot post pics or place attachments.

 

http://www.doityourself.com/forum/li...-pictures.html

 

What kind of meter are you measuring the voltage with? What voltage readings do you get at the main panel in the house?

 

If the meter is digital replace the battery and try again.

 

First my thanks to all who offered help.

I discovered and fixed the problem. There was a switch to an external light that had gotten enough moisture in it to constantly be shorting out. I dried it out - cleaned and re-applied sealant to the joints and all is working.

Again my thanks.

 

Had you dis-connected the Neutral "White" conductor of the three-wire Feeder between the house and the garage you would have caused a very serious hazard because it's possibe there would be 180 volts across one load , say an electronic equipment, and only 40 volts across another load.

I recently had a customer who lost $500 in oil-burner controls , and a computor printer, because of an "open" Neutral connection .