Couple of quick questions....

[Master Brian]

Can a 12/2 wire, currently acting as a dedicated circuit for a dishwasher be on a 20amp circuit? The reason for the question is that my understanding is a single 15amp receptacle isn't "code" on a 20amp circuit with 12/2 wire. It has to be duplex. I have absolutely no idea what this dishwasher is rated for. If I am correct on the single recept, wouldn't (if not why?) it be wrong for a 15amp rated appliance to be alone on the circuit? Trying to learn a bit!

A little background on why I ask....

I was under a small box out for my kitchen. The dishwasher currently sits above this box out. In any case, I found a 12/2 wire, which was eventually traced to the dishwasher. Over about 2-3' of this wire had various black, golden brown and melted looking sections.

Obviously this isn't a good thing, so I killed that breaker and cut out the wire. I ran a new 12/2 wire back to the panel, then directly to the dishwasher. I left the wire long as it will eventually be a new supply for that wall in the kitchen, when I have the kitchen remodeled in hopefully the next 6months. At that point I want it to be on a 20amp breaker as it will feed 3-4 duplex receptacles on that wall. I had an open/spare 15amp breaker, so not being positive, I wired it to that spot, but if it can be on 20amp, I'll move it to a "spare" 20amp spot, so it doesn't have to be moved later.

At first I thought this wire was melted by a torch, by someone doing plumbing or something, as when I peeled back a small section of the sheathing, the insulation on the wires looked ok. When I went into the dishwasher to make the connection, I found that whoever installed this used a wire nut on the neutral wire, but just taped the hot wires together. Nice huh? I then found a spot on the dishwashers junction box cover where one of the wire had arched and left a mark on the cover. My guess is that this probably happened more than once, which is what caused the wire to overheat. What are your thoughts? Why wouldn't this trip the breaker?

Then the rest of the questions:
To save time and not to get into the entirety (sp?) of this mess, the wire I replaced, eventually went to a juntion box which has old silverish looking "romex" and "armored" cable. How do I tell visually what gauge wires these are? The white romex said 12/2, the grey/silver and the armor wire doesn't. I belive the grey/silver is from the 70's? and that the armor is from te 50's?. At least that's what I thought the electrician said.

All this mess is on a 20amp circuit, should I downgrade it to a 15amp circuit, until I can get it replaced??

**I should note, on the 12/2 romex I pulled out, of about 15-20ft of cable only the 1st few feet had burn/melt marks on it. I am hoping this means the rest of the wire in the circuit is ok. Thoughts??? Am I better killing the entire circuit?? I obviously can't peer into the armored cable...

 

[Jadnashua]

A dishwasher, even with a water heater, probably doesn't use more than 7-8A or so max...maybe a bit more when the motor starts. If the receptacle is a single, I THINK it must match the breaker (somebody with the code book would know). It is possible to have a duplex 15A receptacle on a 20A circuit. The (maybe?) easier thing would be to replace it with a 20A version, and leave it at 20A. Or, leave that, and put the wires on a 15A breaker. Either one should be plenty for the DW.

A CB doesn't trip on momentary over-current unless it is above a certain point (more than the sustained value). This curve varies, but as long as it wasn't a solid short that lasted long enough, it wouldn't trip the breaker. Now, an AFCI would probably have tripped, as arcs that don't trip a normal breaker is exactly what they are designed to detect. Frequent arcs can overheat things.

 

[Sponsor]

 

[Master Brian]

There is no receptacle in there. Direct wired. So far, sounds like my logic is correct.

I am guessing it was probably many, multiple arcs. What I can't figure out, is why someone would place a wire nut on the neutral and not the hot. If I only had only one, it would definately be the hot wire that gets it first. Of course, I'd be at the hardware store buying another one before finishing!!

 

[Jadnashua]

The current flows equally through both the hot and neutral, so unless both are well connected, you'll have problems. When directly wired, as long as the breaker is not larger than the wire connecting it to the load, you can make the wire any size you want (i.e, the wire can be larger, but not smaller than what is called for on the breaker).

 

[Drick]

It is not to code to have a single 15 amp receptacle protected by a 20A breaker.
It is not to code to have a single 15 amp duplex receptacle connected to a 20A breaker.

In both these cases you should use a 20A receptacle.
It is ok to connect 2 or more 15A receptacles to a 20A breaker.

I would run 12/2 with a 15 or 20A breaker for the dishwasher although 14/2 with a 15 amp breaker is probably adequate. Check the nameplate for the amps. If unsure of the amps wire with 12/2 and try a 15A breaker first. Most likely the old wire melted from arcing. Be happy you caught it before you house turned into a pile of ash. Arcing will not necessarily trip a breaker, although given enough time and the condition you described the wire in you would think it would have eventually tripped on one occasion or another. Consider introducing that breaker to the trash bin and buying a new one.

As you concluded the damage is probably limited to the beginning of the cable. In the unlikely event the armored cable is damaged it will short circuit against its metal sleeve and trip the breaker. That is one advantage armored cable has over romex. In older armored cable the wire gauge is not marked, however 12 gauge wire is noticeably thicker than 14 gauge. Strip yourself a short piece of #12 and a short piece of #14 from your new stock and compare it to the armored cable's conductors. If you are still in doubt assume it to be #14. Also the dates you were given for the old wiring sound about right. Also old residential wiring was very rarely anything other than #14 back before the 70s unless the circuit was for a large appliance. I would be suspicious of it being #12 just based on its age.

-rick

 

[Thatguy]

http://www.wholesalesolar.com/pdf.folder/Download folder/Power-table.pdf

 

[Lakee911]

It is not to code to have a single 15 amp receptacle protected by a 20A breaker.
It is not to code to have a single 15 amp duplex receptacle connected to a 20A breaker.

In both these cases you should use a 20A receptacle.
It is ok to connect 2 or more 15A receptacles to a 20A breaker.

If I'm not mistaken, a duplex receptacle is considered more than one and is therefore allowed. I can dig out a code ref if you/I/we need it.

 

[Lakee911]

My guess is that this probably happened more than once, which is what caused the wire to overheat. What are your thoughts? Why wouldn't this trip the breaker?

Circuit breakers are only guaranteed to be good once. They're there to stop the over current situation and once that happens, all bets are off for next time. I have seen properly sized wires melt before old breakers trip. Sure, most of the time it works, but if you have a breaker that trips over and over, replace it.

Jason

 

[Master Brian]

It is not to code to have a single 15 amp receptacle protected by a 20A breaker.
It is not to code to have a single 15 amp duplex receptacle connected to a 20A breaker.

Will note, this does seem to be debated in a later thread though. Doesn't matter to me either way, if I run 12 gauge wire and one receptacle, that receptacle will be 20amp. When I did my garage, I ran 12/2 wire to a 20amp GFI, then to 15amp receptacles, unless I thought I might need a 20amp receptacle somewhere else. That is off subject though....

I would run 12/2 with a 15 or 20A breaker for the dishwasher although 14/2 with a 15 amp breaker is probably adequate. Check the nameplate for the amps. If unsure of the amps wire with 12/2 and try a 15A breaker first. Most likely the old wire melted from arcing. Be happy you caught it before you house turned into a pile of ash. Arcing will not necessarily trip a breaker, although given enough time and the condition you described the wire in you would think it would have eventually tripped on one occasion or another. Consider introducing that breaker to the trash bin and buying a new one.

I figured 14/2 would be ok, but in ~6months, I want this wire to service all the receptacles on this wall. At that point the dishwasher will be moved to a different area. Sooo, I ran the 12/2, so it can be used as a 20amp circuit later. Again, currently it is on a 15amp breaker, but sounds like I can go ahead and switch it to a 20amp next time I'm in the box.

As you concluded the damage is probably limited to the beginning of the cable. In the unlikely event the armored cable is damaged it will short circuit against its metal sleeve and trip the breaker. That is one advantage armored cable has over romex. In older armored cable the wire gauge is not marked, however 12 gauge wire is noticeably thicker than 14 gauge. Strip yourself a short piece of #12 and a short piece of #14 from your new stock and compare it to the armored cable's conductors. If you are still in doubt assume it to be #14. Also the dates you were given for the old wiring sound about right. Also old residential wiring was very rarely anything other than #14 back before the 70s unless the circuit was for a large appliance. I would be suspicious of it being #12 just based on its age.

-rick

It never tripped these breakers, that I know of, so should I still replace the breaker it was on? I don't think the breaker failing to trip caused this issue. It could have been there with the old panel...

As for the rest of the wire, to me it doesn't look like 12 guage, just from the overall size of the metal housing and comparing the overall size of the romex sheathing, but in order to confirm that with a comparison test, I'd be deep enough in that I might as well replace the circuit all together. Those wires look fragile and I'm afraid to mess with them more than necessary. I'll just plan on eliminating them ASAP!!

Thanks for the replies.