2

GE seems to make two variants of their arc-fault breakers for use in their residential panels:

(also similar models for 20A which are THQL1120AF / THQL1120AF2).

I can't figure out what the differences between these two models are. The product info pages (linked above) seem to read almost identically, as does the packaging:

enter image description here enter image description here

I don't have any physically at hand to inspect for some obvious difference.

My first impression was that the -AF breakers might be an older model than -AF2, but since they still seem to be sold that doesn't seem to be the case.

4

It's a generational design difference

The early generation AFCIs (all branch/feeder units, and the earlier combination-type units) relied on a ~30mA differential (equipment protection ground fault) trip to detect arcs to ground. While some still do this to the best of my knowledge, this does mean that you need two-pole AFCIs for shared neutral/multi-wire branch circuits, and that's not something that people "get", so to speak, leading to quite a bit of befuddlement and false tripping.

So, the GE engineers went back to the drawing board, and figured out how to make an AFCI that can detect arcing to ground using the arc detection logic, eliminating the need for a ground fault trip. This allows a pair of handle-tied single-pole breakers to be used on a two-pole circuit, and is the design change denoted by the "AF2" suffix (vs "AF") in the catalog number + the "MOD 3" designation, as per this GE appnote.

  • I knew you'd know! – Harper Jun 9 '18 at 19:29
  • Fab answer and research! – DaveInCaz Jun 10 '18 at 10:47
  • Follow-up thought ... in a non-shared neutral situation would there be any downside to the older design of these AFCIs? – DaveInCaz Jun 10 '18 at 10:49
  • One other follow-up: what is the reason you want both legs to break when there was presumably a fault only on one of them? – DaveInCaz Jun 10 '18 at 10:51
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    @DaveInCaz -- the main downside to GF tripping in an AFCI is that people don't expect it, and it leads to confusion and perceived nuisance trips. As to the reason for common trip, it's because in a situation where you have both 120 and 240V loads on a circuit (think dryer or range), the 240V loads can backfeed the tripped leg from the good one through the 240V load impedance, re-energizing the fault and thus creating a hazardous condition. (It does mean that the AF2s can't be used on circuits with combined 120/240V loads, but those are typically not seen at the 15/20A level) – ThreePhaseEel Jun 11 '18 at 0:05
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This forum discussion includes the following statement describing the differences between the two breaker models - which may or may not be accurate:

The ... older [THQL1115AF] AFCI breakers contain an EPD device. It's the same concept and technology as GFCI except the current imbalance threshold is 30 mA instead of 5 mA. Newer GE AFCI breakers [THQL1115AF2] have omitted this.

I'm adding this as an answer here but comments are welcome to improve / clarify this answer (or post your own obvs).

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