Other breakers use ground fault CTs and will not work with shared neutrals
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I have never been impressed with the AFCI technology and taking out the ground fault CT is a huge step backwards, in my opinion. The GE document is correct that neither the NEC nor the UL AFCI standards require the ground fault detection CT,but, it is my opinion that the majority of the AFCI trips, both real and nuisance are from the ground fault detection circuit. I expect that GE removed this part of the device for a number of reasons, 1) cost...it is not required by the standard, 2) to improve market share by permitting the use of multiwire circuits, and 3) to reduce nuisance trips.
Give the fact that an AFCI cannot directly detect the heat from a poor connection (glowing connection, series arc, or whatever you want to call it), the removal of the ground fault detection part of the AFCI removes a lot of the actual fire prevention for the device. An AFCI that does not have a ground fault CT can only detect this type of fault when the heat has caused enough insulation damage that the fault becomes a parallel arcing fault. The AFCI does not look at the arc signature of parallel arcing faults unless the arcing fault current exceeds 5 amps (or maybe unless it exceeds 75 amps, depending on what information you are reading). The AFCI with the ground fault CT will open the circuit when there is enough damage to the insulation to cause 30 to 50mA of ground fault current. Where the AFCI is installed on a circuit that has an EGC, the AFCI will open the circuit much quicker if it has the ground fault detection.
