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Discussion Starter #1
This afternoon I went into my shop to work on some woodworking projects and tried to start my 220 volt tablesaw. I could hear the starter but the saw did not start. After checking the wiring at the saw's switch, I checked the current at the receptacle. I found that the voltage was reading about 150 volts. I checked the other 240 volt receptacles and found the same voltage readings. I then checked the voltage at the main breaker at the sub panel and found the same reading. Later, i checked the voltage at the breaker on the main panel and found that it was reading 248 volts.

I'm afraid that I know the problem, but is it possible that there is a problem with the main breaker in the sub panel, or has the main feed wire been compromised and will have to be replaced?
 

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??

Check hot to hot voltage and hot to ground hot to ground voltage.

If you have panel cvr off same thing. Check hot to hot. Hot to ground hot to ground.
 

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depends if you measured before or after the breaker. problem could be a bad breaker connection or a bad connection on wires feeding the breaker. That could be in the meter can, at the weatherhead, at the POCO transformer.
 

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I'm sorry, I forgot to post that. Hot to hot was 150 volts, one hot to ground was was 123 volts, and the other hot to ground was only about 45 volts. I found about the same at the main breaker at the sub panel.
 

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Maybe a lost neutral.
Turn the power off until you find and fix the problem.
 
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Discussion Starter #7
We turned off the main breaker and checked the voltage. Hot to hot was 249 and both hots to ground were 124 each. We turned off the main panel breaker to the shop earlier.
 

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An open neutral shouldn't affect your 240v readings. Lack of neutral will lead to wacky readings across 120 legs but those readings should add up to 240v even if 150v and 90v.

I would check your hot leg connections.
 

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Discussion Starter #9
I'll check the hot connections in the morning when I have some light. Some things I should have mentioned in my original post: The main feed wire to the shop is 4 awg aluminum, and it is run under ground about 90 feet into the shop. It is also probably about 30 years old.
 

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If it is direct buried, 30 years old is probably past the life expectancy of it.

A common place for you to find damaged conductors is where it exits or enters at the underground. Other places are near any fence posts, footings or other conflicts with the cable route.
 

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Always learning something new here. I didn't know direct burial cable had a life expectancy.

Moms post lite is fed with uf. I'm guessing it's been there 45 or 50 yrs??
Guess they got the good stuff for that install. :)



(Hope I didn't jinx anything mom)
 

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Well, I'm used to high voltage cable which does. I'd imagine you'll get longer life in a dry location. Back in the '70s they allowed DB services on new homes. While many are still going, many have been repaired. Many replaced. Moisture finds a way. Tree roots love trench lines. Many installed along property lines and past back yard fences, thus the references regarding posts and footers. I can't tell you how many 3x3x4' deep holes I've dug. Sometimes finding a phone co repair right above. But yeah, there isn't an always and forever cable that I know of. The power in the hot legs will work to find that ***** in the insulation.
 

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As a side note and earth (dirt) conductivity. The way you locate a bad spot in direct buried wire is by use of a tool dubbed the "earth ground gradient fault locator." Or something close to that. What you do is isolate the bad cable connect a thumper (Hi-pot tester) to it and a ground to a probe (large screwdriver) shoved in the dirt. Every few seconds he thumper pulses a dc voltage, usually set to 600v ,to the wire which is touching earth. You use 2 probes spaced along the path of the cable. The meter connected to each probe deflects towards the one that sees the voltage first. Move along the path until there's no deflection. Mark the spot. Repeat at a 90 degree angle. Mark the spot. There you go. Dig away. ImageUploadedByTapatalk1418606042.058785.jpg ImageUploadedByTapatalk1418606055.205006.jpg ImageUploadedByTapatalk1418606062.829007.jpg

We have both these models
 

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As a side note and earth (dirt) conductivity. The way you locate a bad spot in direct buried wire is by use of a tool dubbed the "earth ground gradient fault locator." Or something close to that. What you do is isolate the bad cable connect a thumper (Hi-pot tester) to it and a ground to a probe (large screwdriver) shoved in the dirt. Every few seconds he thumper pulses a dc voltage, usually set to 600v ,to the wire which is touching earth. You use 2 probes spaced along the path of the cable. The meter connected to each probe deflects towards the one that sees the voltage first. Move along the path until there's no deflection. Mark the spot. Repeat at a 90 degree angle. Mark the spot. There you go. Dig away. View attachment 97674 View attachment 97682 View attachment 97690

We have both these models
THANKS CLW...... I learned something NEW....... that is interesting.:thumbsup::thumbsup::thumbsup:
 

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The first pic looks like a GFL3000. About $800-900.

For residential work, I would just start digging. And this time, put it in conduit.

Locating the fault and slapping a temp repair on an old cable makes sense for a utility. They usually schedule a permanent replacement in the near future.
 

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The first pic looks like a GFL3000. About $800-900.

For residential work, I would just start digging. And this time, put it in conduit.

Locating the fault and slapping a temp repair on an old cable makes sense for a utility. They usually schedule a permanent replacement in the near future.
Yes we are a different animal. Just thought I'd share. Actually a repair done right can last ages. Some though, the wire is too compromised. I prefer the a-tronics one.

As far as scheduling a future permanent repair, no not really. Even if you have your own dirt crew it's pretty pricey.

As far as the OP, that's why I mentioned common places for failure. Easy to find and might get lucky. Gophers are another cause here. But that's trickier.
 
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