Protect old ungrounded circuit with GFCI outlets or GFCI breakers?

[brycenesbitt]

do you have an insulation tester? That be best bet, I hear horror stories about these old wiring constantly tripping afci/GFCI breakers.
been doing for 5 years on my own, lots of changes and I think only had one bad time and was with only a couple circuits.

Mixed up neutrals in K&T can cause headaches and trips, but once it stable seems stable here.

 

[chi]

Can you elaborate? I've read it's fine as long as the wiring is to local code and the expected loads are within the breaker's spec. Typically you pigtail the circuits to the breaker, not jam them both on there if the breaker was not designed for 2 like a SQD. Why would this be any different than a junction box combining 2 circuits to one outside the panel?

Without being pretentious in any way and to be elaborate as you are asking, it is poor workmanship to connect two circuits together.

 

[ptonsparky]

I would hazard a guess that K&T predates Art 300.3. We used AFCI often enough on combined old K&T circuits. Never an issue with tripping. Granted we were dealing with homes that only had two circuits to begin with and the load they now serve were general lighting only.

Yeah, when I am doing a panel change, in the old fusebox/panel as I unland each neutral (ok grounded circuit conductor ) I do a continuity test from the now detached neutral to the neutral bar to see if there is a parallel path to ground remaining, you need to store the unlanded neutrals back in their slots until your done of course.
GFCI breaker or not a indication of a parallel path would indicate a prior code violation that might not be 'grandfathered' becasue of the all the conductors of a circuit rule (300.3)

 

[Fred B]

Without being pretentious in any way and to be elaborate as you are asking, it is poor workmanship to connect two circuits together.

What's wrong with it if you only have a very small load on either and wiring is sized correctly to combine to one circuit? Done that with lighting expansion that the closest location to bring it together was the panel box, was like 2 light here and 2 light there, no need for 2 circuits for 4 LED lights.

 

[brycenesbitt]

I would hazard a guess that K&T predates Art 300.3. We used AFCI often enough on combined old K&T circuits. Never an issue with tripping. Granted we were dealing with homes that only had two circuits to begin with and the load they now serve were general lighting only.

Yes, that's a great approach. The old K&T wires enter the lighting boxes through a pretty janky mechanism (nothing like the tubes). Adding AFCI to the K&T MWBC after the big loads (kitchen, bath, laundry) have been done with modern circuits makes for a good result. It does momentarily confuse the insurance companies, but many have reported success with eventually working out that issue also.

 

[chi]

What's wrong with it if you only have a very small load on either and wiring is sized correctly to combine to one circuit? Done that with lighting expansion that the closest location to bring it together was the panel box, was like 2 light here and 2 light there, no need for 2 circuits for 4 LED lights.

The OP answered his own question. He had two solutions, and then he took a turn and suggested that he could always cheap out!
What if one circuit has an unforeseen problem, so adding another circuit does not make sense unless you want to cheap out and then go ahead?
Why do something like that? It is bad practice in my book. To my knowledge, by reading the post this is old wiring.
I do not see any purpose in debating whether or not to do something that raises a red flag, for crying out loud.