[Roger123]

This is a story of my poor trouble shooting skill. I purposely left the s off of skills because that may indicate that maybe there was more than the half skill I have.

Well anyway, call from homeowner that microwave tripping the circuit breaker. Square D, QO 15amp breaker on 14awg wire, with general lighting & microwave loads. Circuit is over 20 years old and was running fine for that time until recently. First thing I checked for was overload on breaker. Turn on all lights and micro. Found 18.6amps on breaker. Breaker opened after a couple of minutes. Hmm, I didn't buy the overload. Something was telling me why was this circuit running so long like this. What changed. So, I installed a 20amp new breaker. Second test, same load of 18.6amps., breaker opened again but again after a couple of minutes. Feeling good now after discounting an overload. Third, was to check bus stab for heat buildup. Stab in pristine condition. At this time owners advise that the breaker only trips with micro running. Hmm, now looking for a shorted connection. Remove micro from this circuit and tested it on another circuit. Unit runs fine, no problems. OK, take the microwave receptacle out and replaced it with a new one. Reconnect micro and circuit holds good with no problems. I inspect and take apart the old recpt. because I couldn't believe that it cause the breaker to open. The old recpt. is also in pristine condition. Hmm, Now it was time to really scratch my ass. Here is what I missed. One, the couple of minutes it took to trip the breaker. Two, when I replaced the recpt. I notice that there was no outer covering on the NM wire in the NM Connector. Three, the box was steel and was grounded. Four, I pulled the wires apart in this box looking for compromised insulation. Seeing none I installed new recpt., keeping the wires apart as far a possible. Well I think you guys know what went wrong now......... The insulation on the NM wire in the NM connector got compromised over the years and after warning up for a couple of minutes with a load of 13amps, shorted together. Apparently after the wires cooled the micro would run again for another couple of minutes. I pulled in a couple of inches of wiring in the box, which was surface mounted, repaired compromised insulation and AMF. It appeared that the clamp on this connector crushed the insulation.

I learned much from this repair, and I hope this story helps another electrician. One day I hope to include the "s" in my trouble shooting skill!

 

[HARRY304E]

This is a story of my poor trouble shooting skill. I purposely left the s off of skills because that may indicate that maybe there was more than the half skill I have.

Well anyway, call from homeowner that microwave tripping the circuit breaker. Square D, QO 15amp breaker on 14awg wire, with general lighting & microwave loads. Circuit is over 20 years old and was running fine for that time until recently. First thing I checked for was overload on breaker. Turn on all lights and micro. Found 18.6amps on breaker. Breaker opened after a couple of minutes. Hmm, I didn't buy the overload. Something was telling me why was this circuit running so long like this. What changed. So, I installed a 20amp new breaker. Second test, same load of 18.6amps., breaker opened again but again after a couple of minutes. Feeling good now after discounting an overload. Third, was to check bus stab for heat buildup. Stab in pristine condition. At this time owners advise that the breaker only trips with micro running. Hmm, now looking for a shorted connection. Remove micro from this circuit and tested it on another circuit. Unit runs fine, no problems. OK, take the microwave receptacle out and replaced it with a new one. Reconnect micro and circuit holds good with no problems. I inspect and take apart the old recpt. because I couldn't believe that it cause the breaker to open. The old recpt. is also in pristine condition. Hmm, Now it was time to really scratch my ass. Here is what I missed. One, the couple of minutes it took to trip the breaker. Two, when I replaced the recpt. I notice that there was no outer covering on the NM wire in the NM Connector. Three, the box was steel and was grounded. Four, I pulled the wires apart in this box looking for compromised insulation. Seeing none I installed new recpt., keeping the wires apart as far a possible. Well I think you guys know what went wrong now......... The insulation on the NM wire in the NM connector got compromised over the years and after warning up for a couple of minutes with a load of 13amps, shorted together. Apparently after the wires cooled the micro would run again for another couple of minutes. I pulled in a couple of inches of wiring in the box, which was surface mounted, repaired compromised insulation and AMF. It appeared that the clamp on this connector crushed the insulation.

I learned much from this repair, and I hope this story helps another electrician. One day I hope to include the "s" in my trouble shooting skill!

How many hot dogs did you cook while testing?:laughing:


Good work..:thumbup:

 

[Wirenuting]

We all learn from past exposure to problems.
If you want to try and become a better troubleshooter do this,
1) draw out what you have
2) test at 1/2 the distance to problem, keep cutting the drawing, ie circuit, in half until you find the problem
3) draw out what it should be and make repairs.

 

[sbrn33]

This is a story of my poor trouble shooting skill. I purposely left the s off of skills because that may indicate that maybe there was more than the half skill I have.

Well anyway, call from homeowner that microwave tripping the circuit breaker. Square D, QO 15amp breaker on 14awg wire, with general lighting & microwave loads. Circuit is over 20 years old and was running fine for that time until recently. First thing I checked for was overload on breaker. Turn on all lights and micro. Found 18.6amps on breaker. Breaker opened after a couple of minutes. Hmm, I didn't buy the overload. Something was telling me why was this circuit running so long like this. What changed. So, I installed a 20amp new breaker. Second test, same load of 18.6amps., breaker opened again but again after a couple of minutes. Feeling good now after discounting an overload. Third, was to check bus stab for heat buildup. Stab in pristine condition. At this time owners advise that the breaker only trips with micro running. Hmm, now looking for a shorted connection. Remove micro from this circuit and tested it on another circuit. Unit runs fine, no problems. OK, take the microwave receptacle out and replaced it with a new one. Reconnect micro and circuit holds good with no problems. I inspect and take apart the old recpt. because I couldn't believe that it cause the breaker to open. The old recpt. is also in pristine condition. Hmm, Now it was time to really scratch my ass. Here is what I missed. One, the couple of minutes it took to trip the breaker. Two, when I replaced the recpt. I notice that there was no outer covering on the NM wire in the NM Connector. Three, the box was steel and was grounded. Four, I pulled the wires apart in this box looking for compromised insulation. Seeing none I installed new recpt., keeping the wires apart as far a possible. Well I think you guys know what went wrong now......... The insulation on the NM wire in the NM connector got compromised over the years and after warning up for a couple of minutes with a load of 13amps, shorted together. Apparently after the wires cooled the micro would run again for another couple of minutes. I pulled in a couple of inches of wiring in the box, which was surface mounted, repaired compromised insulation and AMF. It appeared that the clamp on this connector crushed the insulation.

I learned much from this repair, and I hope this story helps another electrician. One day I hope to include the "s" in my trouble shooting skill!

All I got out of that was that you put a 20 amp breaker on 14. With a load of 18 amps. Why did you think this was the proper course of action?

 

[EBFD6]

All I got out of that was that you put a 20 amp breaker on 14. With a load of 18 amps. Why did you think this was the proper course of action?

He did it temporarily to see if the breaker was tripping due to an overload or short circuit. Since the 20 amp breaker also tripped at 18 amps he was able to determine that it wasn't due to over current.

Not how I would have done things, but it was effective for him in this situation. I would have meggered the circuit most likely.

 

[Roger123]

He did it temporarily to see if the breaker was tripping due to an overload or short circuit. Since the 20 amp breaker also tripped at 18 amps he was able to determine that it wasn't due to over current.

Not how I would have done things, but it was effective for him in this situation. I would have meggered the circuit most likely.

You are correct. That is why I did that temporarily. I figured it was easier than disconnecting all the other loads on the circuit.

 

[wcord]

I give you points for figuring out the compressed insulation.
BUT, putting a 20 amp breaker on #14, in my book, that's looking for trouble and I mean in causing a potential fire.
Meggering would have been the right method, and in the case of not having a megger, than as previously mentioned, split the circuit up till you find the cause of the overload.

 

[EBFD6]

I give you points for figuring out the compressed insulation.
BUT, putting a 20 amp breaker on #14, in my book, that's looking for trouble and I mean in causing a potential fire.
Meggering would have been the right method, and in the case of not having a megger, than as previously mentioned, split the circuit up till you find the cause of the overload.

Let's not overreact here. Putting a #14 on a 20 amp breaker for a few minutes while troubleshooting is not going to cause a fire. A #14 can carry 20 amps for quite a while without any ill effect.

 

[bobelectric]

This is a story of my poor trouble shooting skill. I purposely left the s off of skills because that may indicate that maybe there was more than the half skill I have.

Well anyway, call from homeowner that microwave tripping the circuit breaker. Square D, QO 15amp breaker on 14awg wire, with general lighting & microwave loads. Circuit is over 20 years old and was running fine for that time until recently. First thing I checked for was overload on breaker. Turn on all lights and micro. Found 18.6amps on breaker. Breaker opened after a couple of minutes. Hmm, I didn't buy the overload. Something was telling me why was this circuit running so long like this. What changed. So, I installed a 20amp new breaker. Second test, same load of 18.6amps., breaker opened again but again after a couple of minutes. Feeling good now after discounting an overload. Third, was to check bus stab for heat buildup. Stab in pristine condition. At this time owners advise that the breaker only trips with micro running. Hmm, now looking for a shorted connection. Remove micro from this circuit and tested it on another circuit. Unit runs fine, no problems. OK, take the microwave receptacle out and replaced it with a new one. Reconnect micro and circuit holds good with no problems. I inspect and take apart the old recpt. because I couldn't believe that it cause the breaker to open. The old recpt. is also in pristine condition. Hmm, Now it was time to really scratch my ass. Here is what I missed. One, the couple of minutes it took to trip the breaker. Two, when I replaced the recpt. I notice that there was no outer covering on the NM wire in the NM Connector. Three, the box was steel and was grounded. Four, I pulled the wires apart in this box looking for compromised insulation. Seeing none I installed new recpt., keeping the wires apart as far a possible. Well I think you guys know what went wrong now......... The insulation on the NM wire in the NM connector got compromised over the years and after warning up for a couple of minutes with a load of 13amps, shorted together. Apparently after the wires cooled the micro would run again for another couple of minutes. I pulled in a couple of inches of wiring in the box, which was surface mounted, repaired compromised insulation and AMF. It appeared that the clamp on this connector crushed the insulation.

I learned much from this repair, and I hope this story helps another electrician. One day I hope to include the "s" in my trouble shooting skill!

Could you repeat that? I fell asleep.

 

[markore]

Could you repeat that? I fell asleep.

Never underestimate the utility of a good old line break/new paragraph. :thumbup:

Maybe throw in a little bold or something here and there...

In other news, I'm moving to Dayton, OH. Lets make some toast! Harry's bringing the hotdogs.

All around the country and coast to coast.
People always say, "What do you like most?"
I don't want to brag, I don't want to boast
I always tell them that I like toast

 

[Ultrafault]

Let's not overreact here. Putting a #14 on a 20 amp breaker is not going to cause a fire. A #14 can carry 20 amps forever without any ill effect.

Fify.

 

[FrunkSlammer]

Yeah in my code book #14 copper could be good for 25amps.

 

[Deep Cover]

If the circuit was shorting to ground or neutral, wasn't there a nice arc mark on either the conductors or box?

 

[Roger123]

in other news, i'm moving to dayton, oh. Lets make some toast! Harry's bringing the hotdogs.

 

[brian john]

Quote:
All around the country and coast to coast.
People always say, "What do you like most?"
I don't want to brag, I don't want to boast
I always tell them that I like toast

With butter and honey or real preserves peach, strawberry, blackberry ,raspberry………

 

[Roger123]

With butter and honey or real preserves peach, strawberry, blackberry ,raspberry………

Yeah Toast!!!

 

[erics37]

Yeah Toast!!!

Dada dada dum, dada dada dada dum

 

[leland]

I give you points for figuring out the compressed insulation.
BUT, putting a 20 amp breaker on #14, in my book, that's looking for trouble and I mean in causing a potential fire.
Meggering would have been the right method, and in the case of not having a megger, than as previously mentioned, split the circuit up till you find the cause of the overload.

I meggerd a ckt once, and there was a 'rogue' rec. out there and I blew up a nice stereo.

 

[Roger123]

I meggerd a ckt once, and there was a 'rogue' rec. out there and I blew up a nice stereo.

After thinking about it, I'm not sure a Megger would've found the said fault.

 

[Big John]

Sounds like you did good finding it. Those types of intermittents are the worst pain-in-the-ass. I often find myself just wishing it would break 100% so I could at least locate the part that wasn't working.

This is a story of my poor trouble shooting skill. I purposely left the s off of skills because that may indicate that maybe there was more than the half skill I have....

And I got a pretty good laugh out of this.