Never assume the job was done right from the beginning

[goldstar]

I went out on a service call yesterday to a residence where the 30 amp dryer receptacle burnt severely. At first look I evaluated the problem and determined that the receptacle and cord had to be replaced. I looked into the receptacle and viewing the wiring I noticed that the insulation had melted off. I pulled on the armored cable feed and I figured there was enough wire to re-cut the armor and install it into a new receptacle. Thankfully the supply house was less than a mile away. After removing the wiring I found that the armored cable was 12/3 instead of 10/3. The dryer draws 26 amps when drying. No wonder the receptacle burnt. But the HO said "It's been like that for 25 years" !!! Go figure. :slaphead: Another trip to the supply house.:roll: And yes, the Fire, Police and Building Depts. were there.

 

[jumper]

I would bet that a bad/loose connection probably caused the problem rather than the #12, but who knows.

 

[templdl]

I would bet that a bad/loose connection probably caused the problem rather than the #12, but who knows.

I agree with you that a loose connection are more apt to have caused the failure. However It should be given some consideration that the heating and cooling of the undersized wire may have resulted in the connections loosening because of expansion and contraction of the terminations.

 

[Ponchik]

If the terminations are done correctly and torqued to spec, I can not imagine why would the undersized conductor cause this.

IMO, even though on regular bases the #12 OCPD can not exceed 20Amps but #12 at 75 degrees can carry 25A, so I don't think it is a wire size issue but rather loose connection.

 

[kwired]

I went out on a service call yesterday to a residence where the 30 amp dryer receptacle burnt severely. At first look I evaluated the problem and determined that the receptacle and cord had to be replaced. I looked into the receptacle and viewing the wiring I noticed that the insulation had melted off. I pulled on the armored cable feed and I figured there was enough wire to re-cut the armor and install it into a new receptacle. Thankfully the supply house was less than a mile away. After removing the wiring I found that the armored cable was 12/3 instead of 10/3. The dryer draws 26 amps when drying. No wonder the receptacle burnt. But the HO said "It's been like that for 25 years" !!! Go figure. :slaphead: Another trip to the supply house.:roll: And yes, the Fire, Police and Building Depts. were there.

"the Fire, Police and Building Depts. were there." At the supply house? I would have just driven by and went to a different place to buy supplies

I have to agree a loose connection was the main cause of this meltdown. Undersized conductor may have had some contribution to it becoming loose though.

 

[goldstar]

I see all your points about a loose connection and it may very well be the case. I didn't take the time to investigate. Besides, the receptacle was so crusted over from the melted plug I didn't want to bother. This happens often on 15 and 20 amp receptacle circuits. Somehow, the breaker didn't trip. I guess the wires didn't short together before all the smoke filled the house. However, I'm sure we're all familiar with what happens when we over-lamp a light fixture. If the label on the fixture states that we shouldn't exceed 60 watts and we (or the HO) put 100 watt bulbs in it, the wire will heat up, the insulation will soften, then when it cools down everything goes back to normal (or so we think). IMHO, over time (probably years) that insulation will break down to the point that it will actually flake off the wire. Had this happened in this case I'm sure it would have tripped the breaker.

So, I believe your theories about the loose connection(s) are probably more sound than mine but either one could be plausible.

BTW, as luck would have it the original circuit WAS IN FACT a 10/3 AC cable. I only had to run about 10' to the JB in the bsmt. and not all the way back to the breaker panel. I'm sure this was a HO job.

 

[gadfly56]

If the terminations are done correctly and torqued to spec, I can not imagine why would the undersized conductor cause this.

IMO, even though on regular bases the #12 OCPD can not exceed 20Amps but #12 at 75 degrees can carry 25A, so I don't think it is a wire size issue but rather loose connection.

Even when torqued to spec, copper will cold flow over time, especially stranded copper. This can result in a loose(r) connection.

On new fire alarm panel installs where we typically use 14-18 AWG solid, when we come back the following year, all the connections at the panel will tighten up at least a touch.

 

[electricalist]

Ive seen many things undersized by the nec standard and I think electrically in the begening wiring may have been more about the needs of a given circuit. . I always give credit to those guys who wired it based on what it needs. Somebody knew thats all the dryer needed. I usually cover my butt and check breaker size and dryer nameplate . If it its close enough to say it aint my fault.im not gonna work on it. When they say it was working ..true but not anymore.

 

[jaylectricity]

Reminds me of a guy who asked me to come help him fix his dryer. He had ordered a new heating element and wanted some expertise on putting it in and making sure the wires were correct and whatnot. So I helped him out, we plug it in and it still doesn't work. It's just not getting hot. It almost feels like it wants to be warm but not quite.

So we call the manufacturer and the first thing he asks is, "Is there 220V at the receptacle?" I smack my head and test and sure enough it's only 110. I open up the receptacle and this guy has one hot to the ground, the other to the neutral, the ground to the other hot and the neutral to the ground.

 

[goldstar]

Reminds me of a guy who asked me to come help him fix his dryer. He had ordered a new heating element and wanted some expertise on putting it in and making sure the wires were correct and whatnot. So I helped him out, we plug it in and it still doesn't work. It's just not getting hot. It almost feels like it wants to be warm but not quite.

So we call the manufacturer and the first thing he asks is, "Is there 220V at the receptacle?" I smack my head and test and sure enough it's only 110. I open up the receptacle and this guy has one hot to the ground, the other to the neutral, the ground to the other hot and the neutral to the ground.

This is exactly the point I was trying to make with this thread. I approached this service call ASSUMING the receptacle was wired correctly never thinking that the wiring was undersized. Fortunately for me the supply house was close by.

 

[kwired]

I see all your points about a loose connection and it may very well be the case. I didn't take the time to investigate. Besides, the receptacle was so crusted over from the melted plug I didn't want to bother. This happens often on 15 and 20 amp receptacle circuits. Somehow, the breaker didn't trip. I guess the wires didn't short together before all the smoke filled the house. However, I'm sure we're all familiar with what happens when we over-lamp a light fixture. If the label on the fixture states that we shouldn't exceed 60 watts and we (or the HO) put 100 watt bulbs in it, the wire will heat up, the insulation will soften, then when it cools down everything goes back to normal (or so we think). IMHO, over time (probably years) that insulation will break down to the point that it will actually flake off the wire. Had this happened in this case I'm sure it would have tripped the breaker.

So, I believe your theories about the loose connection(s) are probably more sound than mine but either one could be plausible.

BTW, as luck would have it the original circuit WAS IN FACT a 10/3 AC cable. I only had to run about 10' to the JB in the bsmt. and not all the way back to the breaker panel. I'm sure this was a HO job.

Chances are your "further investigation" will not verfy loose connection, if it wasn't loose before it probably is now. It probably was loose connection, but question is was it one of the supply conductors, the plug to receptacle connection itself, or something in the cord cap?

You mention seeing this on 120 volt receptacles - I just want to put this in that AFCI claims to be able to protect against this, it is generally called glowing connection, and you can probably be assured in your instance something was probably glowing red hot at one time when that was trying to fail. There are some people that have tried to replicate this kind of failure with an AFCI in the circuit and it doesn't ever trip though

If you have more interest there are some threads with that topic, but can't recall any that are recent, but you can probably find them by searching for glowing connection.

 

[iwire]

Ive seen many things undersized by the nec standard

Can you name a few? I am curious. :?

 

[growler]

I'm sure we're all familiar with what happens when we over-lamp a light fixture. If the label on the fixture states that we shouldn't exceed 60 watts and we (or the HO) put 100 watt bulbs in it, the wire will heat up, the insulation will soften, then when it cools down everything goes back to normal (or so we think).

It's not the fixture wire or socket that's the problem when useing to large of a lamp. A 100W incandescent lamp puts out a lot of heat and turns the fixture into an "easy bake oven". These are normally enclosed fixtures with no way to dissipate the heat.

 

[goldstar]

It's not the fixture wire or socket that's the problem when using to large of a lamp. A 100W incandescent lamp puts out a lot of heat and turns the fixture into an "easy bake oven". These are normally enclosed fixtures with no way to dissipate the heat.

I'm sure there's some degree of validity to your statement. However, I've seen RX cable circuit wires burnt back beyond their entrance to the JB where a light fixture was installed. I know incandescent bulbs get hot but I can't imagine a light bulb producing so much heat that it would cause the insulation on the circuit wires to deteriorate to the point that they would flake off the wire (unless the fixture is over-lamped). I've seen instances where the scenario you cited causes an incandescent bulb to have a shorter life when the heat from the bulb in a fixture (with a globe) enclosing that bulb has nowhere to dissipate its heat. However, if the fixture is lamped to the spec of that fixture the life expectancy of the fixture (and all its components) is greater than if it is over-lamped.

Just my opinion.

 

[goldstar]

Chances are your "further investigation" will not verfy loose connection, if it wasn't loose before it probably is now. It probably was loose connection, but question is was it one of the supply conductors, the plug to receptacle connection itself, or something in the cord cap?

Not sure.

You mention seeing this on 120 volt receptacles - I just want to put this in that AFCI claims to be able to protect against this, it is generally called glowing connection, and you can probably be assured in your instance something was probably glowing red hot at one time when that was trying to fail. There are some people that have tried to replicate this kind of failure with an AFCI in the circuit and it doesn't ever trip though

Good point.

If you have more interest there are some threads with that topic, but can't recall any that are recent, but you can probably find them by searching for glowing connection.

Thanks KW. I'll look into it when I have some spare time. This is not Nebraska Cornhusker territory. Us contractors here on the East Coast are out there every day trying to earn a living.

Just busting your chops !!!

 

[kwired]

I'm sure there's some degree of validity to your statement. However, I've seen RX cable circuit wires burnt back beyond their entrance to the JB where a light fixture was installed. I know incandescent bulbs get hot but I can't imagine a light bulb producing so much heat that it would cause the insulation on the circuit wires to deteriorate to the point that they would flake off the wire (unless the fixture is over-lamped). I've seen instances where the scenario you cited causes an incandescent bulb to have a shorter life when the heat from the bulb in a fixture (with a globe) enclosing that bulb has nowhere to dissipate its heat. However, if the fixture is lamped to the spec of that fixture the life expectancy of the fixture (and all its components) is greater than if it is over-lamped.

Just my opinion.

Most of the time when lamp life of incandescent lamps seems to be short (even with properly sized lamp) is because of weak connection at the lampholder creating excess heat. This weak connection is usually loose conductor attachment to the lampholder, loose rivet or other hardware that connects the terminal to the center pin or socket shell, and with aluminum shells I even see stretched shells trying to pull away from the rivet that attaches them to the terminal, this from over-torquing the lamp when installing it. Some of those deterioration of lampholder conditions likely do come from excess heat if too high wattage lamp was installed before.

 

[electricalist]

Can you name a few? I am curious. :?

K you got me and I retract my statement. I have seen ungrounded 4/0 conductors with #4 neutral. So I wasnt saying the code book is wrong. My statement assumed that what I saw was undersized. I have no proof. Yes ill remeber to keep my commentd factual or stated as opinion

 

[kwired]

K you got me and I retract my statement. I have seen ungrounded 4/0 conductors with #4 neutral. So I wasnt saying the code book is wrong. My statement assumed that what I saw was undersized. I have no proof. Yes ill remeber to keep my commentd factual or stated as opinion

Ungrounded 4/0 with #4 grounded can be code compliant - all depends on how much load is on the grounded conductor, and to some extent if it is service or non service application, as for services the grounded conductor must be at least the same size as the required grounding elecrode conductor (T250.66) even if there is no neutral load at all, and for non service applications it must be at least the same size as the minimum required equipment grounding conductor (T250.122), but for non service applications you don't even have to run a grounded conductor if the load supplied doesn't utilize a grounded conductor, you still need an equipment grounding conductor though.

 

[goldstar]

I didn't want to start a new thread with the same title so this is more on the same subject (but a different job). I was doing a house remodel recently in a lake community where people did all their own work years ago (ALL trades plumbing, electric, etc.). This house was a disaster and a fire waiting to happen. It had been abandoned for over a year with the electricity shut off at the meter. Water was also shut off and pipes burst all over the place. While tracing wiring and circuits I found a very "neatly" installed receptacle in a plastic remodel JB. I pulled out the receptacle and found it was wired with NMB cable. However, when I went down to the bsmt. I saw only armored cables in that area. Soooooooo....I decided to pull out the entire JB and found this. As it turned out, the same craftsmanship was found in three other locations. The wiring in the metal JB was spliced and opening taped over with friction tape.:slaphead:

 

[mjf]

I didn't want to start a new thread with the same title so this is more on the same subject (but a different job). I was doing a house remodel recently in a lake community where people did all their own work years ago (ALL trades plumbing, electric, etc.). This house was a disaster and a fire waiting to happen. It had been abandoned for over a year with the electricity shut off at the meter. Water was also shut off and pipes burst all over the place. While tracing wiring and circuits I found a very "neatly" installed receptacle in a plastic remodel JB. I pulled out the receptacle and found it was wired with NMB cable. However, when I went down to the bsmt. I saw only armored cables in that area. Soooooooo....I decided to pull out the entire JB and found this. As it turned out, the same craftsmanship was found in three other locations. The wiring in the metal JB was spliced and opening taped over with friction tape.:slaphead:

Same guy has been up my way!!