We are getting a bit off track on how wiring affects audio ... so feel free to skip this post ,.. i.e. "these are not the droids we are looking for ... move along".
12/2 is code in the states.
The gauge of wire is dependent on two things ... amperage and length. Since I don't know the code for this I can just tell you what I have in my house (built last year).
Most if not all 120V outlets are wired with 12/2. Most if not all 120V lighting was done with 14/2 and 14/3.
I'm not sure if 12/2 was required as a minimum for all 15A outlets or if it was just easier to use it for all outlets without keeping track of the run length.
Don't run an arc fault breaker or outlet unless it's a bedroom. They have a tendency to trip. Ground fault is overkill unless you just want the extra protection. Arc faults have to be on bedroom outlets now and ground faults in the bathroom and anything above the counter in the kitchen in addition to outdoor outlets.
That's interesting. The electrician said they were required in kitchens too ... at least in Massachusetts. Unfortunately the inverter in our microwave kept blowing it. I ended up just getting a different microwave. Less often, I have the same problem with my shop lights. Not sure why I have an arc fault on them ... perhaps because the downstairs bedroom light is also on it? I'm pretty sure they would not have used one if code didn't require it ...be nice to know the reasoning ...
Commercial grade outlets are more than enough for audio outlets. We did not use any residential outlets in our home build. Bulk buying is the cheapest route if you need several. We wired the HT on dedicated circuits but probably not necessary with the new building codes.
From what I understand the difference between commercial grade and residential grade is durability. Outlets like all connectors are only guaranteed for a limited number of swipes before they wear out. (I.E. Swipes on Residential grade << swipes on Contractor grade.)
I do not know if the contact resistance is any better ... but it has to be reasonable on all outlets otherwise they would be a hazard. It does make sense that if the outlet is worn thin then you'll have a higher resistance. So in places where you are constantly plugging in and out stuff, like the kitchen, you'd definitely want the higher grade ...
On contact force ... guess I should qualify that this is educated reasoning rather than hard facts ... just applying what I know about connectors to stuff I know about outlets ...
Once you reach a force that wipes the contacts clean (so you get a good connection) extra force may just result in extra wear. So there are trade offs. Hospital grade outlets have a high contact force mainly to keep the plug from being accidentally pulled out. I'm sure they are designed for long wear too (probably by having a thicker layer of contact material) making it more expensive (but not necessarily better)
Also, in the states we were required to use tamper proof outlets with the new codes.
We have no tamper proof outlets ... most likely it's a state requirement.
