Customer called recently with afci breakers tripping randomly in remodeled basement probably done several Yrs ago before new residents moved in, house aprox 10-20 yrs old with no AFCIs up stairs in living quarters. Basement circuits are all on AFCIs , office, sump pump/ with small printer plugged in, play room plugs and lights and gas furnace ( don’t need that on afci) and should be removed. Customer said breakers would randomly trip for example: something running on one circuit would trip furnace off or using a vacuum would trip a different circuit ect. Nothing made sense so replaced all the old AFCIs to rule out bad AFCIs (4) but customer said a few days ago breakers are still randomly tripping so only thing I can think of is to either take AFCIs out and replace with normal breakers or do a megohm test to see if something is really going on or just some kind of weird wire talk making AFCIs randomly think arc is present ( if that’s even possible ) customer is reluctant to remove AFCIs but wants answers and I haven't seen anything quite like it , usually it’s one circuit the randomly trips and we usually are able to change breaker or look for ground fault and go on our way. I haven’t heard any inspectors comment on removing afci when can’t find any fault.
If anybody wants to share insights it may help bring this to a close I would greatly appreciate it.
Regardless of what I personally think of AFCI's, I often get sent out to figure out why stuff like this is happening.
I have successfully done this for over 12 years.
All I can say is I have resolved every case to date, there is no need for you to give up.
Some get very expensive to resolve, so you need to get clear on the budget.
In your case I would remove the furnace from the AFCI and put it on its on 15A circuit.
I have a custom solution for old vacuums.
This is a cut and paste of my basic outline:
AFCI troubleshooting procedure:
1) Visit the site and gather as many facts as you can about the trips.
A. Find out who has done what wiring recently, even low voltage.
B. Document all recent alterations, construction, renovations.
Did someone install,repair or replace a deck, shelving, roof, foundation or plumbing ?
C. Create a detailed panel schedule noting each breakers loads, function and amps.
D. Visually inspect the service for obvious problems.
E. Note which breakers were tripping.
F. Provide the system user a notebook to log the time of a trip and what appliances on those circuits were on.
2) Electrical operational test: Turn on all lighting and appliances, demonstrate that all equipment, is connected and in working order.
A. Note any flickering buzzing or other irregularities.
B. Check the temperature of the breakers in the panel during this test.
3) Electrical polarity and voltage drop: Test with an 'Ideal Sure Test' the permanently wired lighting, equipment and receptacle outlets to determine that connections have been properly made and voltage will not be less than 108V at any 120V equipment under
A. 12 Amp load test for 15A circuits
B. 15A load test for 20A circuits.
C. 20A load test for 30A circuits.
D. Note any 10% or higher voltage drop.
E. In no case should voltage drop be above 14% for systems running 120-127 Volts. (ANSI-C84.1)
4) If the AFCI trip cannot be reproduced during a site visit setup a data logger to record voltage to ground, and 3 CT’s that record miliamps on the Hot, Neutral and ECG of the affected circuit.
5) Affix a identification label or color dot to the 'problem' breakers indicating their position number in the panel.
A. Remove the breakers and replace with same amperage GFCI breaker 30ma Class B.
B. Run ‘Electrical operational test’ again with a 30ma Class B GFCI breaker installed.
C. If the breakers don't trip leave them in place for 30 days with the data logger.
6) Dielectric Strength Test. This tests the branch circuits, remove all devices such as GFCI’s, dimmer’s, regular switches are to remain. Completely remove all light bulbs lamps, disconnect LED and fluorescent fixtures.
A. The wiring of each AFCI circuit shall be subjected to a 1-minute, 1000 volt, dielectric strength test (with all switches closed) between live parts (including neutral conductor) and the grounding electrode conductor.
B. Listed luminaires or appliances shall not be included in this test.
C. This test is outlined in NEC 550.17(A).
7) Single point grounding Test; Switch the service off, disconnect the service neutral, MBJ and or GEC from the neutral bar, test the neutral bar for continuity to the GEC with the megger on 250 Volts. There should be no parallel paths to ground.
Note more than one path to ground can give stray voltages from power-line,lighting, or ham radio a path thru the building.
