Electrical Short Issues

[onocoffee]

I have an issue developing that I wanted to ask the minds here. Two outlets have developed shorts and that’s reflected in the plug which has also shorted. Each of these duplex outlets carries a 20A load and the extension cord runs into the garage to power all my woodworking tools.

The outlets come from a six space panel being fed with 50A line from the main panel. The tools being powered are all my Festool tools, a Ridgid vac, bench top jointer, a 9” and 14” delta bandsaw and the array of Festool tools through the CT MIDI. However, only one of any of these operates at any one moment (well the Ridgid or MIDI will work with the other tools).

I was planning on tearing it all apart today to see what is going on but other stuff came up and I’ll have to get to it tomorrow. But have any of you seen similar? Trying to troubleshoot it and wondering what I should be on the lookout for.

Thanks!

 

[Mike Goetzke]

Be careful - something is definitely wrong. I googled and found this: An electrical plug melts on one side due to issues like a loose connection in the outlet or plug itself, arcing between conductors, a worn-out outlet, an overloaded circuit, or defective wiring. These problems increase electrical resistance, generating heat that can melt plastic and cause a fire hazard, necessitating an immediate call to a licensed electrician.

Those outlets are not 20A rated from the looks of them. Make sure the wires are tight. Get one of those outlet testers. - call a professional

 

[tjbnwi]

You have a neutral issue. My guess is you will find a loose connection. The neutral is a current carrying conductor. I know two electricians who were electrocuted by open neutrals, they are far more dangerous than the line side of the circuit.

I’m going to assume all of the wiring including the cord are 12 ga. minimum.

To start with use a 20 amp commercial grade receptacle (5-20R) and plug (5-20P). The wipes are heavier than the standard grade you are using. Get the ones that have clamps for the wire connections.

Make sure the breaker to the circuit is turned off and locked out before you begin working on the system.

Tom

 

[Muttley000]

That looks like a field wireable plug, I’d start by safely taking that apart and inspecting.

 

[onocoffee]

Be careful - something is definitely wrong. I googled and found this: An electrical plug melts on one side due to issues like a loose connection in the outlet or plug itself, arcing between conductors, a worn-out outlet, an overloaded circuit, or defective wiring. These problems increase electrical resistance, generating heat that can melt plastic and cause a fire hazard, necessitating an immediate call to a licensed electrician.

Those outlets are not 20A rated from the looks of them. Make sure the wires are tight. Get one of those outlet testers. - call a professional

Thanks. I think you're right. They look like 15A to me. The loose connection thing makes sense. These outlets are a good 20 years old.

 

[onocoffee]

You have a neutral issue. My guess is you will find a loose connection. The neutral is a current carrying conductor. I know two electricians who were electrocuted by open neutrals, they are far more dangerous than the line side of the circuit.

I’m going to assume all of the wiring including the cord are 12 ga. minimum.

To start with use a 20 amp commercial grade receptacle (5-20R) and plug (5-20P). The wipes are heavier than the standard grade you are using. Get the ones that have clamps for the wire connections.

Make sure the breaker to the circuit is turned off and locked out before you begin working on the system.

Tom

Got it. The current wires are 12ga and I'll be replacing these outlets with the commercial grade ones. And the nice thing is that I can fully disconnect all of this to work on it. Thanks!

 

[onocoffee]

That looks like a field wireable plug, I’d start by safely taking that apart and inspecting.

That's tomorrow morning's task. Thanks!

 

[tjbnwi]

Got it. The current wires are 12ga and I'll be replacing these outlets with the commercial grade ones. And the nice thing is that I can fully disconnect all of this to work on it. Thanks!

Check the wire and cable for any “stiffness” the heat may have affected the insulation, cut back as needed.

Tom

 

[luvmytoolz]

Check the wire and cable for any “stiffness” the heat may have affected the insulation, cut back as needed.

Tom

We had our entire house and sheds rewired late last year, and the condition of the wiring that "looked good" was really pretty scary. Very little handling was required for the insulation to crumble off. The original cloth covered cabling was even worse.

I sleep a lot better now not worrying about the wiring.

 

[Vtshopdog]

Are the two outlets on individual breakers or do they share a single circuit? Looks like box in first photo has 3 cables and assume it is in series with other outlets or lights??

 

[onocoffee]

It's morning so I finally got to tearing the panel apart and seeing what is what. The different outlets are singed on the same spade from the extension cord, which is the load side. But everything upstream is clean and in good order.

As I was thinking about it last night, I was sure that the load on the line was within 20A, so I started listing the equipment I use and their amp ratings:
Ridgid Shop Vac - 11A
Cutech Jointer - 10A
Delta 890 - 8A
Milwaukee 5625 - 15A
Freud FT2200 - 15A
DeWalt 735X - 15A
CT MIDI - 10A
SawStop CTS - 15A

In most cases, I will use the Ridgid as the dust collector for the tools, which means that peak load could be as high as 26A - however, I never start the vac and the equipment at the same moment. It's usually one then the other - mainly because I use a remote switch for the vac.

Prior to the last couple months, I had been running two separate 12ga extension cables from the two different outlet sides (each group of outlets is wired to its own 20A circuit). But this summer, I started running the one cable from the outlet to a power strip and then connecting the tools to the power strip. This has led me to think that this melting issue is being caused by overloading the outlets (which are 15A rated outlets).

So my battle plan for today is to get upgraded commercial 20A outlets and a new plug for the extension cable and rewire it all. The wiring from the outlets to the panel look clean and are 12/2 so I think they should be good.

If you have any thoughts on this, I'd appreciate hearing about them. Thanks!

 

[Cheese]

Just looking at the black main feed cable, what gauge is that because it's a lot larger than the wire that goes to the individual outlets. The wires appear to be 12 Ga & 14 Ga respectively. Also, the 2 receptacles (img 5396), are all on the same electrical leg...just so you know if you're plugging multiple items into the outlets and using them at the same time.

Here's what you need if you want to use 20 amp rated spec grade receptacles. Heavy duty screw connections...back-stab connections not available. These are being installed in the garage along with some 15 amp spec grade receptacles.

 

[tjbnwi]

The neutral wire on the plug came loose causing the problem. Get better plugs that will accept the proper gauge wire.

Tom

 

[onocoffee]

@Cheese - I don't recall what the main line is but it was properly sized to the 50A outlet it is plugged into. The 50A line goes into the panel and then it's distributed to the outlets. All of the wiring is 12/2 - here in the United States, they changed the regulations years ago to color code the Romex wires. 10ga is white, 12ga is yellow and 10ga is orange. The feed line is stranded cable instead of a Romex type wire which is why it has black sheathing.

Today, I ran out to grab some parts and reassembled the distribution panel. New Eaton 120v/20A commercial outlets, new 240v/20A breaker, checked all the wiring and changed the extension cable plug (after inspecting the wiring inside the cable). The plug was well toasted and the outlets were pretty well singed. While it could be looseness of the plug in the outlet, I also think that I might have been overloading the circuit a bit - which is why I split the outlets into their own separate circuits, so each duplex will (eventually) have their own breaker - though I did forget to grab those breakers today and will get them later this week.

Energized it a little while ago and everything seems to be in good order.

 

[luvmytoolz]

@Cheese Unless I'm mistaken, the one you're pointing to as 12GA looks like it's bare copper?

 

[grbmds]

Could it be the plug itself?

 

[tjbnwi]

@Cheese - I don't recall what the main line is but it was properly sized to the 50A outlet it is plugged into. The 50A line goes into the panel and then it's distributed to the outlets. All of the wiring is 12/2 - here in the United States, they changed the regulations years ago to color code the Romex wires. 10ga is white, 12ga is yellow and 10ga is orange. The feed line is stranded cable instead of a Romex type wire which is why it has black sheathing.

Today, I ran out to grab some parts and reassembled the distribution panel. New Eaton 120v/20A commercial outlets, new 240v/20A breaker, checked all the wiring and changed the extension cable plug (after inspecting the wiring inside the cable). The plug was well toasted and the outlets were pretty well singed. While it could be looseness of the plug in the outlet, I also think that I might have been overloading the circuit a bit - which is why I split the outlets into their own separate circuits, so each duplex will (eventually) have their own breaker - though I did forget to grab those breakers today and will get them later this week.

Energized it a little while ago and everything seems to be in good order.

There is no way the feeder to that sub panel is a 6 gauge cable which is required by the NEC for a 50 amp circuit. A 6 gauge copper wire is just over 1/4” in diameter (0.262).

Again the heat damage is isolated to the neutral side of the circuit. I believe from looking at the plug and connections on the plug the neutral wire came loose.

@Cheese any conductor out of yellow jacket NM (Romex) is 12 gauge.

@luvmytoolz the bare conductor is the ground conductor. It is not a current carrying conductor, no insulation necessary.

Tom

 

[tjbnwi]

@Cheese - I don't recall what the main line is but it was properly sized to the 50A outlet it is plugged into. The 50A line goes into the panel and then it's distributed to the outlets. All of the wiring is 12/2 - here in the United States, they changed the regulations years ago to color code the Romex wires. 10ga is white, 12ga is yellow and 10ga is orange. The feed line is stranded cable instead of a Romex type wire which is why it has black sheathing.

Today, I ran out to grab some parts and reassembled the distribution panel. New Eaton 120v/20A commercial outlets, new 240v/20A breaker, checked all the wiring and changed the extension cable plug (after inspecting the wiring inside the cable). The plug was well toasted and the outlets were pretty well singed. While it could be looseness of the plug in the outlet, I also think that I might have been overloading the circuit a bit - which is why I split the outlets into their own separate circuits, so each duplex will (eventually) have their own breaker - though I did forget to grab those breakers today and will get them later this week.

Energized it a little while ago and everything seems to be in good order.

Sorry, double post.

 

[tsmi243]

Could it be the plug itself?

It's definitely this. If the entire circuit were undersized, but the plug in good shape, you'd have all the thermal effects spread across the entire length of the circuit (and thus much lower intensity). That's not what this is.

Those "plug it yourself" thingies are always suss. Don't count on them lasting forever. Especially if no ferrules are used- and I'm the only person I've met in real life who uses them. Maybe you did, maybe you didn't.

Open neutrals- Tom's right about the danger, but the danger is in the unpredictability. It just means you'll have hot voltage where you're not expecting it. It won't cause the damage to be greater when a fault occurs. That's also not what's wrong here. This is a current path that was established, but then a physical connection problem that degraded the conductive path caused a runaway "thermal event" (which is a nice way to phrase it in front of customers....)

 

[rvieceli]

@onocoffee i’m with Tom on the feeder size. Double check that the feeder is 6 gauge and that the outlet you are plugging the feeder into is connected to the main with 6 gauge.

It also appears that you have a 40 amp 240 breaker that feeds with 12 gauge wire if you actually need 40 amps that requires 8 gauge. If you don’t need 40 amps then change the breaker. It looks like a 20 amp outlet. 10 gauge wire might be better choice

Ron