My garage is electrically charged w/120v!!

[Reach4]

Still electrifies door, rails, and seemingly GDO.

As measured by .... touching the case and feeling a shock? Measuring with a high impedance voltmeter to ground?

 

[Yi3o8]

As measured by .... touching the case and feeling a shock? Measuring with a high impedance voltmeter to ground?

A no contact tester that beeps. I was trying the voltmeter at first but the tester is just easier.

I brushed my arm against the rails without shoes on. That's when I discovered the issue. It was a decent enough jolt. My arm was sore from it.

 

[Sponsor]

 

[Jadnashua]

A gfci will trip if the mismatch of in versus out current is >5ma. If you can get shocked and it’s gfci protected, something is really wrong and needs to be fixed before someone is severely hurt.

if the 3-way switch is miswired, things might look okay with it in one position and not when it is in the other.

 

[Reach4]

A no contact tester that beeps.

A no-contact tester can be too sensitive.

You might try shunting your meter leads with a resistor of maybe 100,000 ohms. Measure the voltage from a ground to your suspect conductors. You can the repeat the test.

Alternatively, read the AC current to ground. 5 mA is the lowest that could really hurt you when touched with your hand. There is a fuse in your meter probably. It may have been previously blown because somebody touched across a voltage source while the meter was in current range.

One question-- did you cut the ground off of the door opener plug or did you use a 2-prong adapter? Reversing the plug may change the symptoms. Consider that a workaround rather than a fix.

 

[Yi3o8]

A gfci will trip if the mismatch of in versus out current is >5ma. If you can get shocked and it’s gfci protected, something is really wrong and needs to be fixed before someone is severely hurt.

if the 3-way switch is miswired, things might look okay with it in one position and not when it is in the other.

The shock was before I installed a gfci. But I am surprised the door and rails are electrified without tripping it.

More surprised a long extension cord is making the difference.

 

[Yi3o8]

A no-contact tester can be too sensitive.

You might try shunting your meter leads with a resistor of maybe 100,000 ohms. Measure the voltage from a ground to your suspect conductors. You can the repeat the test.

Alternatively, read the AC current to ground. 5 mA is the lowest that could really hurt you when touched with your hand. There is a fuse in your meter probably. It may have been previously blown because somebody touched across a voltage source while the meter was in current range.

One question-- did you cut the ground off of the door opener plug or did you use a 2-prong adapter? Reversing the plug may change the symptoms. Consider that a workaround rather than a fix.

Someone had installed a 3 prong outlet without ground. A gfci without equipment ground is a workaround. But other than a previous suggestion that the GDO has a short, I can't wrap my head around it. And can't figure out why the long extension cord makes the difference between an electrified door and rails- there's nothing special about the cord.

 

[Reach4]

And can't figure out why the long extension cord makes the difference between an electrified door and rails- there's nothing special about the cord.

Is the hot-neutral reversed in that extension cord?

 

[Yi3o8]

Is the hot-neutral reversed in that extension cord?

Not according to my cheap tester that although simple works well enough. It's showing open ground. If the hot and neutral were reversed I believe it would show, even on an extension cord. Also, if it were reversed in the cord, it would mean the outlets in the house were also reversed. The tester shows they are wired correctly.

Although I'm baffled why the extension cord is making it safe for now. I'm going to see about replacing the GDO. If anyone has any ideas or insights. I'd greatly appreciate it.

 

[Yi3o8]

So I really appreciate everyone's comments. Instead of troubleshooting the electrical, I used the two extension cords I have to narrow it down to a short in the GDO.

I have a 50 ft with the male ground ripped off (by the kids somehow). And a standard 100 ft. orange extension cord.

The 50 ft energizes the door and rails even if hot neutral are reversed/unreversed. Hooked up to an ungrounded gfci in the garage or a grounded gfci in the house.

The 100 ft cord must lower the voltage enough to where the short in the GDO is unaffected. How this happens is a mystery and someone else might be better equipped to figure it out.

Thanks again. Although I'm still confused, I couldn't have guessed the orange cord was the thing making the difference.

 

[Reach4]

The 100 ft cord must lower the voltage enough to where the short in the GDO is unaffected.

The difference is that the door does not go up and down when powered by the long extension, regardless of which outlet powers that extension cord. Beyond that, is there any difference in symptoms?

No configuration trips the GFI, right?

 

[Yi3o8]

The garage door opener works fine with the long extension cord.

I think maybe it has enough ground wire to make a difference?

 

[DIYorBust]

I doubt a 50 ft extension cord has enouhg resistance to block a ground fault. There I said it. Could be a polarity plug issue. I don't know.

 

[Jadnashua]

Just having line voltage where it shouldn't be won't necessarily trip a GFCI until you touch it. The GFCI is measuring the in/out current. When they differ (i.e., flowing through something, and probably someONE rather than between the hot and neutral) by >5ma, then, it should trip.

FWIW, a GFCI will work just fine without a ground anywhere. There should never be any current flow through the ground wire unless there is a fault. It is there as a backup, safety path to help ensure that the breaker or fuse trips should power exceed the circuit limits imposed (and then, it generally has a slight delay unless the threshold exceeds a certain point or it exists longer duration). The neutral lead IS connected to ground at the power panel, and neutral DOES have current in it when the circuit is functioning. WHen there's a fault, power IS going through the ground path, since it's not finding its way via the neutral.

Non-contact voltage sensors are not necessarily all that accurate and a typical high impedance DMM can give some confusing measurements, too...voltage is relative to a reference...you MUST understand what that is. Remember working on a high voltage power supply one time. Was looking for five volts at one point, but if you measured it wrong, you got -4995 vdc, as the real reference point was at -5000v to ground, so it was actually +5vdc relative to the proper reference point. Not understanding what's going on could kill you.

 

[DIYorBust]

I think a possible move here would be to bond the rail to the ground system, and to be clear that means tying it into a properly wired grounding conductor on the same circuit as the GDO, not directly to the physical floor. That should make the situation much safer. I'd expect that the breaker will trip immediately after being reset due to the ground fault. The next step would be to identify where there is a short to ground, correct the condition, and reset the breaker.

 

[Stuff]

A lot of confusion with this. Time to fix or replace the garage door opener before things gets worse.

Note that a basic three light voltage tester can not tell if hot and neutral are reversed if there is no ground for reference. Depending on what wiring is touching the chassis it doesn't matter if the feed is reversed or not, the rails may still be hot, but possibly only when the motor is operating. There are lots of failure conditions and that is why a good ground saves lives.

A GFCI is designed to trip after 5 ma. Most people can feel a tingle way before it would trip.

I wonder if the 100' cord has its neutral and ground shorted? Test this by plugging the 100' into a receptacle, plug the 50' into it, and plug the GDO into to 50'.