This installment requires certified personnel to perform. If you don't possess the experience and training then hire the right person.
Read on for my replacement of existing thermal magnetic breakers to afci.
Step 1: Opening the Panelboard.
There are two types of electrical faults: arcing and bolted. Standard thermal magnetic breakers will pick up only the bolted type where two live or a live and neutral/ground make a solid connection. Afci combination breakers like what I purchased from Amazon.com will handle both types of faults.
Step 2: Replacing the Air Conditioning Breakers.
First I turned off the main breaker, the 70adp. I verified the conductors de-energized with my multimeter. I disconnected the motor protectors and removed the breakers.
Next I wired the load wires to a single motor protector. The motor protector I wired to the afci breaker. The white neutral wire I connect to a lug on the neutral bus. I socketed the afci into the panelboard and verified tightness of all connections.
I ran all 3 air conditioning units at their lowest temperature for half an hour and took thermal images. All temperatures on the breaker, motor protector and wire connection are good.
Now a single 20adp afci breaker and motor protector handles the 3 air conditioning units very well and within code requirements.
Step 3: Replacing 2 Single Pole Breakers.
Here it is important to identify the neutral wire for each breaker and connecting that neutral wire to the respective afci breaker neutral output lug.
Using my clamp ammeter I located each neutral wire by switching on and off the breaker for each. I swapped out to afci one at a time.
Again I applied maximum load to both breakers after verifying tightness of all wire connections. The load for these breakers are very small and the thermal image reveal nothing of consequence.
Step 4: Completion
With new afci breakers in my panelboard I feel a bit safer should any electrical faults occur. This is a worthwhile upgrade for safety in any home!
There are many cases of nuisance tripping of AFCI however when I tested on my home devices using motors with brushes, they all worked perfectly. Perhaps it is the newer combination AFCI models I have at home but they have been reliable so far. IF you have nuisance tripping then thorough inspection of the building wiring and end devices should be performed before judging the AFCI as defective.
Monthly testing of each afci breaker will be performed as per manufacturer instructions. This is simply pressing the test buttons of each, resetting the breaker and confirming the led indicator of the type of fault.