What the h**l is going on?

[Bill Verburg]

I have 2x 20Amp circuits buried in conduit going to my garage. Wed 3PM all is working fine, Wed evening I notice that the automatic area lights are not working.

After tearing everything apart today I find that 1 circuit has the proper 120vAC, the other has 120vAC in and 34vAC at the other end.

How does something like that happen? There is only a continuous wire from the circuit breaker to the garage junction box, 3 ground wires in the same conduit all have proper continuity, and 1 of the 2 hots as well, Only the 1 hot line seems to have developed an internal resistance causing the voltage drop.

[red-beard]

I would say broken wire.

[carambola]

when the wire was pulled, some of the insulation burned or rubbed off. the conduit filled up with water and corroded the wire until it broke. long story short.

[Zeke]

That's a lot of ground wires. Are they insulated? If so, I'd tape one up black and use it for a hot lead.
Your weak hot probably isn't going to get well.

[URY914]

Originally Posted by carambola

when the wire was pulled, some of the insulation burned or rubbed off. the conduit filled up with water and corroded the wire until it broke. long story short.

Or a long story of a short.....

[SXSMAN]

Originally Posted by URY914

Or a long story of a short.....

Oye-vay........

[svandamme]

Originally Posted by carambola

when the wire was pulled, some of the insulation burned or rubbed off. the conduit filled up with water and corroded the wire until it broke. long story short.

sure, but wouldn't that trip the amp loss breaker? (dunno how you would call it, it's a breaker that measures the difference in amps between the 2 wires.. anything goes into the ground, difference, breaker trips).
or don't you guys use those?

My entire house won't permit any loss over 400 milliamps..

I would think that a wet wire in the ground would surely cause amps down in the ground, triggering an amp loss breaker?

[pete3799]

Lost a bunch of circuits in my house a few years ago.
Checked the entrance panel and only had 120 on one side of the box.
Went out to the meter box on the pole and found the bus bar had rotted off on one side.
My vote is you have corrosion on that feeder line somewhere.
How long a run is it? Can you pull a new wire?

[Joe Bob]

Pull new wires.....also consider testing the breaker.

[RWebb]

Originally Posted by carambola

when the wire was pulled, some of the insulation burned or rubbed off. the conduit filled up with water and corroded the wire until it broke. long story short.

besides pulling new wires, maybe there is a way to pressure test the conduit??

that might either give you some assurances re flooding possibilities in the future or let you know you need to rent a backhoe

[masraum]

Oh Yeah! Bill is going to be "laying some pipe" soon!! Go Bill V!

[murphyjp]

As one of my old electronic instructors used to say, what goes in must come out. If you have 120 in but not out then the problem must be in the middle. Swap one of the other wires for the hot, or run a temp external. You can also switch the wires between circuits at the box to rule out everything.

Pulling new wires through conduit should not be too much hassle if it comes to that. Tie the old and new wires together and let er rip.

[Joeaksa]

Would be really careful about touching things around the conduit. Pull the power then you are safe...

[jyl]

Zeke's suggestion seems like a nice pragmatic way to handle it.

[Bill Douglas]

Originally Posted by jyl

Zeke's suggestion seems like a nice pragmatic way to handle it.

Agree. No point in doing it the expensive way first. My bets are on water having got into the phase wire and the current leaking into the ground (dirt!).

[wdfifteen]

The symptoms sound familiar. Too familiar.

I Hate these things

[Bill Verburg]

If there were any connections anywhere in the line I would say yes, bad connection, but there are none, it is a 200ft run of solid conductor wire, w/ no connections. 120vAC at the breakers out and 34vAC at the garage end.

If the insulation were damaged and there was a short to ground of any sort the GFI would trip, it does not.

I'm guessing that to replace the 1 wire I'll have to pull all 5(2 hot, 2 white ground and i insulated green ground), then repull through the conduit.

What a PIA, I still don't understand how after 10yrs of service 1 wire car build up so much resistance as to cause such a large voltage drop. I've seen new housing where there is a large voltage drop between the breaker and the outlet but always because of some post installation insult to the wire, a nail or staple or such. In this case there is no way the wire could be physically damaged subsequent to initial installation.

[pete3799]

What does the insulated green wire connect to?
Could you do as Zeke suggested and use it as a hot lead?

[Zeke]

GFCI's, if present, measure the difference in current between the neutral and ground.

I had a hot go to ground in the same way as Bill's and it did not trip the breaker. It went to an outside light fixture underground. The light did not work but I could hear buzzing in the box if I switched it on. I did not test the wires at the other end. I could not pull new wires either it was so corroded, so I abandoned the whole thing.

[Bill Verburg]

Originally Posted by pete3799

What does the insulated green wire connect to?
Could you do as Zeke suggested and use it as a hot lead?

In modern AC circuits there is 1 hot and 2 grounds, 1 is whit and one is green. The green is usually not insulated but they both go to the same bus in the breaker box.

The outdoor circuits in my hose are in conduit and are all individually/separately insulated from each other it's not like common Romex or BX wire


So just fo giggles I wired the 2 hots together and measured the resistance in the wire. There is a definite resistance in the wire as there are no connections other than the ends which a wired together.

another funny thing yesterday I was getting 34vAC in the bad line today 49vAC, maybe it will heal itself

i'm still very confused as to how something like this can happen out of the blue and also how it can change from day to day