Warm Outlets: How Warm is Too Warm?

[tommygdawg]

Hey all,


Basic question. Running a light off a 20 amp circuit. Light draws 14-16 amps continuous. The area surrounding very near to the wall plug (like within a couple inches at most of where I plug the light in) gets slightly warm after running the light for 30-60 minutes. Warm as in, warm enough to feel a difference when I put my hand up a few more inches, but not hot by any means. Is this normal? Or does it mean that the wires inside the wall are dangerously hot and I'm only slightly feeling it on the outside?

Thanks!

[IanB]

What country?

[tommygdawg]

USA. I've measured at multiple outlets in my house and it typically comes out between 118-122 volts.

[uncle_bob]

Hi

Wall sockets wear out. They wear out faster if you do crazy things pulling cords from them. They wear out faster if you buy the ones that (for some odd reason) are on sale for 1/10th the price of a name brand.

The reason you have electricians that understand all this is so you can call them up and say "can you come take a look at this?". If its a concern, give the guy a call. It might cost you a few bucks. He'll look at all your sockets and (if he's honest and most of them are) give you a pretty good idea of what you should do throughout your dwelling.

That said, a little warm (as i define a little warm) is not unusual at 3/4 load. Pulling 3/4 load from a single outlet is considered "unusual" by most of the rating agencies.

Bob

[djacobow]

The reason you have electricians that understand all this is so you can call them up and say "can you come take a look at this?". If its a concern, give the guy a call. It might cost you a few bucks. He'll look at all your sockets and (if he's honest and most of them are) give you a pretty good idea of what you should do throughout your dwelling.

My experience with electricians is that they understand very little and operate largely by rules of thumb and "something an older electrician told them one time."

That said, though I personally would not first call an electrician to diagnose a problem like this, if you do not know what you're doing, you absolutely should do so. Nobody here -- myself included -- wants to bear the responsibility of your house burning down.

[IanB]

In the USA, wall sockets can be manufactured at cost of 5 cents and sold for 50 cents, especially when homes are being built and the things are being installed by the thousands.

In my home, for example, they used sockets where the wires were just pushed into holes in the back and you hoped they didn't fall out. Also, the plugs would sometimes just fall out of the front as well because all spring tension was lost on the contacts. You can imagine how these things could overheat on heavy loads.

I replaced them with higher quality sockets and made sure the wires were attached with solid screw terminals done up tight.

[Delta]

Get a proper mains voltage, son....

120v?  Pah!  😁

[uncle_bob]

Hi

I guess we all have had our own experiences along the way. I do my own electrical work. If the house burns, it's my own darn fault. I could do the HVAC and plumbing, I prefer not to. Even for the electrical, I occasionally have to make a call. (It's tough to replace a switch in the US when you are Japan). My experience with all the guys I've dealt with has been positive. What they have suggested has made sense and none of it was over the top. It's possible I've just been lucky or I live in the right place..... There is the *slight* possibility that they are pretty good a figuring out who they can BS.

Bob (the 6'4" 300 lb guy you probably don't want to piss off ...)

[uncle_bob]

Get a proper mains voltage, son....

120v?  Pah!  😁

Hi

Did we mention that it's 60 Hz and not 50

Boy, the opportunity to use "real British" wall plugs ... neat-o ....

Bob

[Delta]

Get a proper mains voltage, son....

120v?  Pah!  😁

Hi

Did we mention that it's 60 Hz and not 50

Boy, the opportunity to use "real British" wall plugs ... neat-o ....

Bob

Best in the world though mate!  (Let's not go there....! Although you will not find a domestic plug anywhere in the world that can induce as much pain into a bare or socked foot as an upturned BS1363!)

[uncle_bob]

Get a proper mains voltage, son....

120v?  Pah!  😁

Hi

Did we mention that it's 60 Hz and not 50

Boy, the opportunity to use "real British" wall plugs ... neat-o ....

Bob

Best in the world though mate!  (Let's not go there....! Although you will not find a domestic plug anywhere in the world that can induce as much pain into a bare or socked foot as an upturned BS1363!)

Hi

Well we wouldn't be running a thread about a BS1363 getting warm at 2KW would we?

Bob

[djacobow]

I guess we all have had our own experiences along the way. I do my own electrical work.

Indeed. My last experience with a sparky was when I wanted to have a backfeed outlet installed for an emergency generator. They need to be installed with a physical interlock that keeps the backfeed from being closed while the main breaker is also closed. (They sell special hardware for this purpose for many common panels.) He claimed to have never in his 30 years seen a residential generator installation, and was unfamiliar with the rules. He declined the job.

A time before that, I had built a small shed to be an electronics workshop and ham shack. It is a good 50' from my house and double that from the main panel. I had dug a 2' deep ditch for the conduit from the house to the shed. I told the guy I wanted 40 amps to a subpanel in the shed and I'd take it from there. Too much work for a an hour or two and $300 and not enough for a longer period. I think he wanted to bill all the time for the wiring in the walls and outlets. He also didn't want to work with PVC, even underground, even though it is perfectly legal in this jurisdiction. (Must be sch 80 above ground). In the end he didn't bid or even return calls.

Regarding the BS thing. Yes, it would be a fun "sting" operation to call electricians with canned electrical problems, with different actors: a man, a woman, etc.

[tommygdawg]

Thanks much for all the responses, everyone. I'll pull the socket out of the wall and check the wire gauge as well as see if it gets hot when it's not in the wall. I will say the breaker is rated at 20amps for that socket and it's labeled as a 20a socket (it's a GFCI), so I doubt they'd use 12 gauge wire on that. But you never know.

Alternatively, could this be caused by the light? The actual plug for the light got warm as well.

[djacobow]

Thanks much for all the responses, everyone. I'll pull the socket out of the wall and check the wire gauge as well as see if it gets hot when it's not in the wall. I will say the breaker is rated at 20amps for that socket and it's labeled as a 20a socket (it's a GFCI), so I doubt they'd use 12 gauge wire on that. But you never know.

Alternatively, could this be caused by the light? The actual plug for the light got warm as well.

#12 is ok for 20A. It's #14 or smaller that is an issue.

For $20 you could also just replace the outlet. At the least, tighten the screw, and if it is the push in back-wire type of connection, consider removing the wires and screwing them down ye olde fashioned way.

I've seen GFCI's self-destruct. It happened in my house the other day when I wasn't home. Wife reported one of our outlets started buzzing like a solenoid buzzer and died. I don't know why caused it to start to fail, but the coil that holds the contacts closed was cooked by the time I got home and pulled it.

[tommygdawg]

Thanks much for all the responses, everyone. I'll pull the socket out of the wall and check the wire gauge as well as see if it gets hot when it's not in the wall. I will say the breaker is rated at 20amps for that socket and it's labeled as a 20a socket (it's a GFCI), so I doubt they'd use 12 gauge wire on that. But you never know.

Alternatively, could this be caused by the light? The actual plug for the light got warm as well.

#12 is ok for 20A. It's #14 or smaller that is an issue.

For $20 you could also just replace the outlet. At the least, tighten the screw, and if it is the push in back-wire type of connection, consider removing the wires and screwing them down ye olde fashioned way.

I've seen GFCI's self-destruct. It happened in my house the other day when I wasn't home. Wife reported one of our outlets started buzzing like a solenoid buzzer and died. I don't know why caused it to start to fail, but the coil that holds the contacts closed was cooked by the time I got home and pulled it.

I guess I just like to make strong choices and put #10 on everything

That GFCI sounds terrifying! Glad it didn't cause any additional damage. Have you experienced anything like that before?

[Primus]

The reason you have electricians that understand all this is so you can call them up and say "can you come take a look at this?". If its a concern, give the guy a call. It might cost you a few bucks. He'll look at all your sockets and (if he's honest and most of them are) give you a pretty good idea of what you should do throughout your dwelling.

My experience with electricians is that they understand very little and operate largely by rules of thumb and "something an older electrician told them one time."

That said, though I personally would not first call an electrician to diagnose a problem like this, if you do not know what you're doing, you absolutely should do so. Nobody here -- myself included -- wants to bear the responsibility of your house burning down.

Understand very little? I understand you're talking "in general", but I really don't understand how anyone would think this. I've only got 8 years of experience in the field, but the depth of knowledge required for this type of work is not trivial. With industrial/commercial you have everything from VFDs, motor controls, switching controls, back-up power generation and the related transfer switches. My mentors have been very knowledgeable and it requires just as much to learn this line of work as it does my electronics hobby.

Any electrician worth their salt knows the basics about electricity, included the requisite trig and algebra... no, we're not pulling out calculus reference sheets in the fields or calculating anything that requires a physics major. But, just for example... what if you need to know the load of an unbalanced 3-phase panel neutral, well, you need a little at least a working knowledge of vectors and how to add/subtract the vector components. So, basic electricity, basic physics, basic math skills and a mechanical aptitude and you have a decent apprentice electrician.

This isn't mentioning the full gamut of wiring techniques, materials and just pure amount of things you will never, ever learn from a book, you simply have to practice it under knowledgeable people.

As for the OPs question, the energy you feel radiating from your could be some voltage drop across the lights extension cord, but you really shouldn't be having too much drop from your branch-circuit conductors or the outlet itself. It really just depends on how hot it's getting as to whether it's an issue; remove the cover and do a visual inspection, check for any discoloration of the wiring or device. We call them "glowing joints" in the trade, and it's a very common troubleshooting annoyance for us, and I've seen many a melted things in my time, including receptacles.

[djacobow]

That GFCI sounds terrifying! Glad it didn't cause any additional damage. Have you experienced anything like that before?

I have not. But my house was brought up to 2008 code before I bought it and as a result, about 1.2 zillion GFCI's were installed -- they're not just for garages and bathrooms anymore. So the chance of a GFCI failure has certainly increased.

It's educational to take one apart. The are surprisingly complex devices. They have a current transformer wound with two primaries to detect differential current on the neutral and hot lines. The secondary feeds some electronics which, in turn, drive a solenoid that holds a mechanical contact in place as long as the unit is in the "untripped" state. When you push in the reset button of a GFCI you are actually forcing the contacts back over and re-energizing the ckt, which also drives the holding coil so that the circuit stays latched -- unless there is a fault, in which case it won't latch. Anyway, there is a good reason they cost $15-20 rather than the $0.75-$3 of a typical outlet.

ALL that said ... I don't think this fault would have resulted in a fire, as ultimate the unit died open. I was not there to see whether there was heat, spark, fire, flame, but inspecting the unit, I only saw the burnt solenoid wire.

By the way, regarding your question about warmth on the appliance side. I think -- but am not sure -- that the rules for gauge of the cords that feed appliances are more lax than the in-wall requirements. So, for example, a 15A tea kettle that is only designed to be on for a few minutes at a time, could be wired with thin wire that heats noticeable. In fact, my kettle is just so. Anyway, a little warm on the plug and cord side is a little less worrisome since you can observe it directly, and you don't have to worry about heating someplace hidden like your wall.

[djacobow]

Understand very little? I understand you're talking "in general", but I really don't understand how anyone would think this.

I'm sure it varies. People doing industrial practice might be a little more up on their game than some of the residential guys I've run into. Also, there is a lot of the NEC that one can avoid knowing precisely by just using rules of thumb that "round up" safely. Why consult a fill table when you can just be super conservative and use bigger or more parallel conduits? Residential customer won't know the difference and it's allowed.

[Primus]

Thanks much for all the responses, everyone. I'll pull the socket out of the wall and check the wire gauge as well as see if it gets hot when it's not in the wall. I will say the breaker is rated at 20amps for that socket and it's labeled as a 20a socket (it's a GFCI), so I doubt they'd use 12 gauge wire on that. But you never know.

Alternatively, could this be caused by the light? The actual plug for the light got warm as well.

#12 is ok for 20A. It's #14 or smaller that is an issue.

For $20 you could also just replace the outlet. At the least, tighten the screw, and if it is the push in back-wire type of connection, consider removing the wires and screwing them down ye olde fashioned way.

I've seen GFCI's self-destruct. It happened in my house the other day when I wasn't home. Wife reported one of our outlets started buzzing like a solenoid buzzer and died. I don't know why caused it to start to fail, but the coil that holds the contacts closed was cooked by the time I got home and pulled it.

Yeah, I have a collection of about 200 different types of GFCIs I've dissected. It's pretty interesting to see all the different ways electrical equipment fails! And yeah, just say no to using the stab-lock terminals on an outlet - simple stuff like that has made me a lot of money over the years.

Understand very little? I understand you're talking "in general", but I really don't understand how anyone would think this.

I'm sure it varies. People doing industrial practice might be a little more up on their game than some of the residential guys I've run into. Also, there is a lot of the NEC that one can avoid knowing precisely by just using rules of thumb that "round up" safely. Why consult a fill table when you can just be super conservative and use bigger or more parallel conduits? Residential customer won't know the difference and it's allowed.

I've done my fair share of residential work, but yeah, residential only guys tend to be the least informed.

[djacobow]

Yeah, I have a collection of about 200 different types of GFCIs I've dissected. It's pretty interesting to see all the different ways electrical equipment fails! And yeah, just say no to using the stab-lock terminals on an outlet - simple stuff like that has made me a lot of money over the years.

Cool. I've only taken apart one. Do they vary much in design. I was surprised to see so much mechanical stuff, and just a lot of copper overall. Generally, a pretty beefy design.

I've done my fair share of residential work, but yeah, residential only guys tend to be the least informed.

It was unfair of me to paint the whole profession based on a few interactions. I'm sure it's like any profession, with folks who take it very seriously for their whole careers, those who slide by with the least knowledge possible, and lots of people in between.

:-)

[tommygdawg]

Thanks again for the thoughts! The cable/plug for the light does get warm, so it could very well be the heat generated from that radiating into the wall. The unit is a Chinese HID light. Perhaps it might be in my best interest to rewire it with a higher end cable. It claims it's rated for 15 amps, but that is right on the edge of what I'm drawing.

[rrinker]

 My old house, I replaced all the outlets, most of them wouldn't even hold a plug. I used the more expensive ones as replacements. This house - I have to do the same thing. One of the ones in the master bedroom literally fell apart, the surround of the top half came right off. And others are of similar dubious quality. So, next project, start replacing outlets around the house. Such a fun job - not.

[tommygdawg]

My old house, I replaced all the outlets, most of them wouldn't even hold a plug. I used the more expensive ones as replacements. This house - I have to do the same thing. One of the ones in the master bedroom literally fell apart, the surround of the top half came right off. And others are of similar dubious quality. So, next project, start replacing outlets around the house. Such a fun job - not.

Wow, that's a lot of work. How old were the two houses and their respective electrical systems before you did the work? My house is only around 10 years old so it should be fairly up to snuff.

[Paul Moir]

I guess I just like to make strong choices and put #10 on everything

Try making a reliable connection to an outlet with #10.  It can be a little tricky to pack a box even with #12.  If you read the back of your outlet, you'll find that the lugs are only rated up to #12 anyway.  Bigger ain't necessarily better.

[Richard Crowley]

At the very least, take the socket out of the wall box and check that the wire connections are tight.
If they are the push-in variety, replace with the screw-down type. Some plugs allow both kinds of connections.

You didn't mention the vintage of the house.  There was a period where aluminum wires were used.
During a time of very expensive copper, many houses were wired with aluminum.
Many (most?) of those aluminum wiring jobs have become loose because aluminum has a larger temperature expansion than copper.
So at the very east they need re-tightening.  ALL OF THEM! Up to and including the breaker panel.

OF COURSE you shut off the power while you are working on mains wiring unless you are attempting suicide or arson.

Remember that if THAT outlet is getting warm, there may be others in the house.
And some of them may produce conditions sufficient to start a fire.
You are lucky you got a warning before anything serious happens.