Loose Ground Wire?

[Paul Fitzgerald]

Last weekend I had an electrician put in a single 220V outlet for my new DC. I had him run a duplex 110V outlet into the same two gang box.

Unfortunately, I couldn't locate an appropriate cover plate, so I ordered a duplex 220V outlet to replace the single 220V outlet. When I went to replace the single 220V outlet today, I noticed the ground screw was loose. I'm 100% sure it was tight when he installed it because I was watching him like a hawk.

Then, I went to install a new light fixture in my kitchen and its ground screw was loose too. Again, I'm 100% sure it was tight when it was installed because I'm the one that installed the old one and I'm very anal when it comes to electrical work. I just don't want to have to deal with an electrical fire.

So... what the heck!? This is the first time I've ever seen a ground screw "work itself loose"... and to see it twice in one day on two different connections... what the heck!?

Anyone ever see this?

Paul

[Rob Russell]

I've never seen it happen in any of my wiring.

[Duncan Horner]

Copper wire?

[David G Baker]

The possibility of the screw being loosened when the receptical was pushed into the box if there was pressure on the wire. Other than that I can't imagine anything else causing the wire to loosen.
By ground wire you are talking about the green wire and not the neutral wire right?

[Paul Fitzgerald]

It was bare copper. 10AWG on the 220V outlet and 14AWG on the light fixture.

Paul

[Duncan Horner]

All I can think of is insufficient torque on the screw. The reason I asked about copper wire, is because due to the different coefficient of expansion of Aluminum wires, they tend to loosen when used with the wrong terminals.

I always use the largest flat blade driver I can find, or a nutrunner if one fits. It also helps a lot, especially for stranded wires, to wiggle the attached conductor and then retighten the screw. Widely considered mandatory for heavy gauge service wires.

[Paul Fitzgerald]

Sounds reasonable. I'll be more careful next time.

Just for my information... how bad is a loose ground? Overheating? Risk of fire? Anything else?

Paul

[Ken Fitzgerald]

In 40 years of electronics, I have never seen a ground wire work loose. I have seen some loose because the ground screw was overtightened, stripped the threads on the hole and thus overtime, the tension on the wire cause it to pop out but...the hole was stripped and that's what caused it. Unless the connection was submitted to some some very serious vibration (like the magnetic field of gradient coils in an MR scanner) I can't imagine what would cause ground wires to back out. JMHO and worth everything you paid for it.

[Bob Wingard]

Brass screw + copper wire .. both very soft, malleable materials. If he cranked down too much with the torque, he may have caused a condition where the wire compressed under load and the screw stretched. Most electricians these days use a preset torque-limiting screwdriver to get it just right. Many times, the local inspector will even ask the tradesman what the setting is on his screwdriver as part of the inspection, if he's on the job at the time.


<<<__Bøb__>>>

[Duncan Horner]

Many times, the local inspector will even ask the tradesman what the setting is on his screwdriver as part of the inspection, if he's on the job at the time.<<<__Bøb__>>>

Interesting, never came across that where I was, but good points.

No hazard of fire if the ground is loose, unless you have a larger problem in the circuit. In fact it shouldn't ever see current if all is well. Still needs to be kosher however, because when you need it, you *really* need it.

[Chip Lindley]

Two loose screws in ONE DAY? Wanna try for 3?? Peek at a few other recepticles to assure yourself this was just a freak occurance!

In the event every ground screw in the house is loose, you will know you have a Pre St.Patty's Day Gremlin who loves un-tweaking those pretty green screws! Far as I know, the only CURE is a visit from the *Green Hornet* or downing several cans of *Popeye Spinach*....hmmm

[Paul Fitzgerald]

Two loose screws in ONE DAY? Wanna try for 3?? Peek at a few other recepticles to assure yourself this was just a freak occurance!

In the event every ground screw in the house is loose, you will know you have a Pre St.Patty's Day Gremlin who loves un-tweaking those pretty green screws! Far as I know, the only CURE is a visit from the *Green Hornet* or downing several cans of *Popeye Spinach*....hmmm

Before too long, we'll be replacing all the outlets and switches in the kitchen. If any of those are loose, I'll have to track down that pesky Pre St. Patty's Day Gremlin and let him know it's not nice to mess with a fellow Irishman.

Paul

[Lee Schierer]

I suspect torque on the wire caused the loosening when the receptacle was pushed into the box. I was taught to make a z fold in the wires prior to pushing the receptacle into the box this keeps excess stress off the terminals. #10 wire, even copper is pretty stiff and if the torque was in the direction to loosen the screw it can happen.

Here's a test: Retighten the screw moderately tight and then grab the wire and rotate it around the screw shaft in the direction to loosen the screw. Most likely the screw will move.