The wire in the conduit is unlikely to be the problem. The problem is almost certainly at a termination or with one of the loads. You need to identify all the outlets on the circuit. First, remove all the loads, and then examine the connections.

If that doesn't find it, then you'll likely have to "divide and conquer," disconnecting parts of the circuit until you find where the fault is.

There's not anything particularly special about it being a MWBC in this regard.

Ok just to clarify I should shut off breakers check all outlet connections as a first step. I have noticed that the outlets are all backstabbed so I’ll use the screws and reinstall. That does seem as it may be a likely location for a short. Should I check the switches?

Backstabs usually fail open. I'd be looking for missing wire nuts and excessive ground wires that may be touching another wire, etc... By the way, the neutrals on a MWBC whould **NOT** be connected using the device itself (be it the screws or backstabs) but connected together then pigtailed to the device.

Is this by any chance a Ground Fault or Arc Fault breaker?

I found an outlet that fell apart when I removed the cover. Literally came out in pieces. I bet is was a long time failing however the breaker is still tripping at a box where I connected through to put the dishwasher on a dedicated circuit. The DW works great but maybe I made a wiring error. I’m including a picture and hoping your trained eyes might spot a problem. Thanks so much for directing me to the outlets. One small problem still to go.

I see no picture.

Check now. Thanks

I thought this might be a better picture.

When you get this resolved, you need to put an extender on that box. It looks like it far exceeds boxfill standards.

Ron, help me out here. Do I recall correctly that a MWBC is supposed to be connected to a double pole breaker, not two single pole breakers?

Also, Gallagher, check the installation manual for the dishwasher and make sure it doesn't specify that the dishwasher has to have its own circuit.

In any case, by code, you can't connect a dishwasher (or anything else) to the counter receptacle circuit, if that's what you're trying to do here.

Depends on which code applied when the house was built. It used to be that the NEC only required a handle tie (or two pole breaker) when the two halves served the same device yoke. This was later changed to be required all the time.

I agree about the box fill.

DavidR's last point is incorrect. There's no such thing as a "counter receptacle circuit." The "SMALL APPLIANCE" receptacle circuits are to serve all 120V 15/20A receptacles in the kitchen area. This includes any such receptacles that are not on the countertops, including those for cord-and-plug-connected appliances. The only exceptions are the refrigerator and a clock. Indeed, other than these receptacles, no other outlets (lights, rooms out side the area, etc...) are permitted.

You still haven't answered if this is a GFCI circuit. What happened to the wire nuts in the second picture?

No GFCI circuits. I removed the wire nuts of the like colored wires to try find the fault. Even with that the breaker still tripped. Can you explain in some detail how to do the divide and conquer approach. Thanks for sticking with me through this.

Thanks for the correction, Ron!

You find the first junction box after the panel, disconnect things there. If not, then move along to the next device/junction box. Since your wiring method uses the conduit for grounds, I'd pay careful attention at devices touching the box or possible ground pigtails from the boxes touching the hot side.

I'd also make sure that the proper fittings to join the conduit to the boxes are used. You notice that the ones like in the box you have open that there are smooth shoulders where the wires come out of the fitting so they wont cut in. Also note well the metal knockout in the top of the box. Make sure that if there are any installed the other way around (with the sharp points inside) that they're nut cutting into any wires.

Generally, any sooty marks on wires or devices indicates that something may have touched at some point.

Well I have an update. After checking some connections to fluorescent lights I noticed that some are very poor and one nonexistent. The wirenut held only a few strands of AL wire. Probably enough to trip the breaker. I still have several more connections to check but is it possible the breaker trips because the thinner aluminum wire can’t carry the load? The lights work fine however. Question: I have a Ge panel, what 2 pole 240 volt breaker with GFCI and or AFCI 15 amp would you recommend?

The wirenut held only a few strands of AL wire... is it possible the breaker trips because the thinner aluminum wire can’t carry the load?

Nope, sorry. Doesn't work that way. It IS possible that stray uninsulated strands could short to ground, however.

I've seen stranded AL wire down to AGW 8, but not often. More commonly it's used in larger sizes, around AWG 4 and larger.. And if you actually found AL wire in an ordinary wirenut, I'd guess that you're looking at a real hack job there.

As K says, it could be stranded tinned copper, but that would also be surprising -- unless you're talking about wires inside the fluorescent fixture, such as a ballast or switch pigtail. There it would make sense.

I have a Ge panel, what 2 pole 240 volt breaker with GFCI and or AFCI 15 amp would you recommend?

For a GE panel, there's no recommendation. You have one choice for a 2-pole 15 amp AFCI, a GE THQL2115AF.

Are you sitting down? Look here or here or here.

Please don't take offense, but you seem to be spinning your wheels here. It might be time to consider calling for a tow, er, I mean calling in a pro.

No, breakers won't trip because of too thin wire or wires not in the wirenut unless they touch something else.

I'm fairly sure you will need GE breakers to go into a GE panel.

Weed is right, the only breakers approved for a GE panel are GE breakers. Don't think GE makes any dual function two-pole breakers, so you'll have to go for either AFCI or GFCI.