Circuit finding Tool Question

[Greatwhitewing]

Short version- had a new main service panel (main breaker is outside so technically a distribution panel) installed over a year ago with an upgrade to 200 amp service. A microwave oven circuit I installed years prior on a dedicated 20 amp breaker now seems to share a breaker with another circuit in spite of a breaker labeled "microwave" but the oven is NOT on that breaker.
I know because suddenly the oven tripped and it was on a bedroom outlet circuit that must be spliced in the panel?

I have seen circuit breaker finders but I think I want to find which wire in the panel coming from the outlet (not the breaker) is closer to what I need.
A wire is connected to the breaker labeled "microwave" but I shut it off and nothing appears unpowered. All has been inspected, signed off and no chance of getting original electrician back due a long story not pertinent to this thread.

I am comfortable working in a panel and can shut off all power to diagnose but I am not a electrical tech and just looking for tool advice to trace from an outlet to a wire over the insulation.

A whole different related topic is once I turned off the surge protector breaker, test the oven and turned back on no more oven tripping which is what started the whole investigation.

 

[wyliesdiesels]

plenty of options out there... how much money do you want to spend?

Amazon.com : breaker finder

i use this one. works well

https://www.amazon.com/dp/B07VLP4LY6/?tag=atomicindus08-20

 

[LXCam]

Well look up circuit tracer(s) and see what fits your budget. Heck if you're in AZ, you can borrow one of the three I have.

The easiest solution as long as you don't have some kind of unknown piece of equipment that better not get shutdown is to individually turn off and on each breaker and see which one kills the microwave.

I base my next guess on your description. Sounds like there might be some circuits tied together that aren't supposed to be tied together. If individually shutting off the circuits (one at a time) does not de-energize the microwave circuit, that's the case.

 

[SlappyWhite]

Cheapest way, two people and a lamp. Plug the lamp into the outlet, turn it on and turn breakers off one at a time with some yelling back and forth. Can be done with one person, you just get more exercise and it takes longer.

The fancy tools are great for an electrician as it saves time and money...and they do this more often.

 

[FredWanaker]

we took a small anything that plugs in, two people with two phones and went switch to switch and receptacle to receptacle including areas under the counter like dishwasher, garbage disposal, outside lights, doorbell etc. I had pages of notes that I put into a spread sheet and printed it. I can tell you which breaker controls every item. One thing we learned is that the outside receptacle by the back door came from the bathroom circuit which was GFCI. That is why it, also a GFCI would trip randomly or the bathroom would trip randomly. My electrician put a non GFCI receptacle in outside that runs off the bathroom one, and neither has tripped randomly since. Just figure where everything goes, and you will be good to go.

 

[alfredeneuman]

A real low tech way that you can do alone...... Get a radio and plug into the recp.
Turn off all the 15 and 20A breakers in the panel.
One by one turn them on until the radio plays.
To find out if it's fed by more than 1 breaker turn off the breaker that powered the radio and check the rest.

 

[sparky 1971]

I use this one. It works well on modern panels. The old Federal's, Zinsco's, and Bulldogs, not so much.

https://www.testequipmentdepot.com/ideal-electrical/test-measurement/electrical-testers/circuit-breaker-finder-61534.htm

In my house I know which breakers serve the dryer, water heater, AC, sub panel (used to be the main panel), furnace, and dishwasher because I put them in. That's all. Maybe someday I will get around to labeling, but that's not likely. In the shop I know there are (2) two pole 30's. One is for the welder and the other the air compressor, but I don't know which is which and I have no clue about the 120 breakers because I forgot to mark them when I wired it.

 

[Jim greengo]

Plug a radio into the outlet,then start tripping breakers.

 

[Terry D]

I have the expensive greenlee one.

 

[FredWanaker]

Easier with two people. Too much a problem to map the house with one person running back and forth. Finding one circuit is fine if you are an electrician working on someone else's home, but for your own home you should map all the receptacles and breakers. Takes about an hour to do and another hour to type up a spread sheet. I have it in a printed copy. Can go to it and determine which breaker needs to be involved. In some cases there are too many lines to copy onto a small label next to the breaker.

Example:

 

[ToddG]

I've seen a bunch of old houses that have a microwave or hood wired off of a leg of the 240v circuit to the stove. Not safe at all but cheap....

 

[Zeke]

Why do you say you think it's spliced in the panel? The receptacle that the MW is on could simply be on a circuit that powers the bedroom, etc. It could very well be in the middle of the circuit.

What I like to do is flip all the breakers off, then one at a time go locate every device that is on any given breaker. That's what Fred is saying. It can go pretty fast using a non contact tester to quickly get into the general area and then start checking with a plug in circuit tester and turning on wall switches. You may have some fire alarms hard wired so don't forget about those. Use some making tape or labels as you go so you aren't checking the same devices more than once. Gives a good visual idea as well.

Don't know what to tell you about the MW. Maybe you can get a new cable to that recep.

 

[nadogail]

A button flasher and a high wattage incandescent lamp plugged into the same circuit will be easily found with your clamp on amp meter