For everyone's info, and because it could help someone else, here is the actual answer in my case.
While I had connected the white wire coming out of the AFCI to the ground bar, I hadn't connected the neutral from the circuit to the AFCI. In my case it was because I didn't realize the extra screw terminal was actually there and the documentation wasn't helpful.
Bottom line: If you install a combination AFCI and connect the hot but not the neutral, it will not pop until there is a load. After the fact, that actually makes sense. This is like a ground fault from the AFCI's point of view because it can't see the current going back through its neutral port.
Residential Kitchen
In a dwelling unit (residential), GFCI protection is only required for kitchen receptacles that serve the countertop surfaces. There's no requirement to GFCI protect receptacles that serve a refrigerator. Unless the fridge is plugged into a countertop receptacle.
National Electrical Code 2014
Chapter 2 Wiring and Protection
Article 210 Branch Circuits
I. General Provisions
210.8 Ground-Fault Circuit-Interrupter Protection for Personnel. Ground-fault circuit-interrupter protection for personnel shall be provided as required in 210.8(A) through (C). The ground-fault circuit-interrupter shall be installed in a readily accessible location.
(A) Dwelling Units. All 125-volt, single-phase, 15- and
20-ampere receptacles installed in the locations specified in
210.8(A)(1) through (10) shall have ground-fault circuit interrupter protection for personnel.
(6) Kitchens— where the receptacles are installed to serve the countertop surfaces.
Garages, Unfinished Basement, and Other Locations
If the refrigerator is in a garage, boathouse, or unfinished basement. All the receptacles are required to be GFCI protected, so the fridge will have to be plugged into a GFCI protected receptacle.
Why does the fridge trip the GFCI?
Any inductive load when switched off, can produce electromagnetic interference (EMI). This interference can, and often does, trip GFCI devices. Most vapor compression refrigerators have a few inductive loads, any of which could cause the trip.
Is there anything that can be done?
There are devices called snubbers that can be used to reduce, or eliminate the effects of EMI. Installing one between the fridge and the GFCI device, could prevent nuisance trips. The best solution though, is to connect the fridge to a non-GFCI protected circuit.
If that's all it takes, why isn't there already one built in?
While most (all) manufacturers are aware that refrigerators can cause nuisance tripping of GFCI devices, most (none) seem willing to provide a solution. It would be complete speculation for me to try and tell you why they don't care, so of course I'll go through a few possibilities.
- Cost.
Plain and simple, it costs money to implement a solution.
- Warranties and Operating Conditions.
Most refrigerators are designed to operate in a kitchen. Running them in dusty, dirty garages and basements could lead to more warranty covered repairs.
Best Answer
The refrigerator outlet being shared with countertop outlets is fine, and very common in older houses. However, there are some advantages to having the refrigerator be on a dedicated circuit. The primary advantage is that you're at no risk of some other device tripping the breaker, and you don't turn it back on right away for whatever reason, not realizing that your food is spoiling. The other advantage is that if you ever install a backup power source, such as a generator, it's much easier to wire that to keep your food save through power outages. It's up to you whether this is worth breaking out the drywall for or not.