Home Improvement → Re: is 12/2 really necessary?

Sorry to say, but for some reason this thread is full of amateur opinion & mis-information. Unfortunately, the OP doesn't know who the professionals are here & who to trust. Little I can do about that.Nonsense? Now who is trolling. Its obvious from your post that you don't understand this subject the way a professional does. You say a compressor can draw more than 15A under some conditions? No. It draws more than 15A under all conditions. Its a short term condition called in-rush and will not heat up the wire. Meeting the NEC code requirements for breaker size and wire size is more than good enough - its safe under all proper wiring installations - with a safety margin to boot. Circuit breakers are designed to work with their respective wire sizes, to trip under overload conditions, before the wire is damaged. This includes when the wires are grouped together as allowed, inside of thermal insulation. As quite a few people here have said there was something else wrong with the circuit you described; perhaps a poor connection or bad breaker.Pretty much accurate. 14AWG wires can carry 20A without issue. However, the NEC limits 14AWG wiring to 15A, because of certain issues, mostly poor residential installation practices, where the crappy installer doesn't follow the other provisions in the NEC. (Think a few wires bundled together in an attic reaching 130 degrees F in the summertime. The NEC would require this to be derated. I have yet to see any typical homebuilder take that into account.)Then you are buying your materials in the wrong place. The cost of both 20A receptacles and breakers are usually the same price or just slightly more than 15A devices. And there is almost no need for 20A receptacles on 20A circuits, with the exception of a few appliances that require dedicated 20A circuits, anyway. Seriously, I think you should start to consider the use of a qualified electrician. Sorry to say, but your questions make me wonder how qualified you are to do the actual wiring.Its not. 14AWG is permissible in quite a number of circuits, just not receptacles wired with type-NM cable.There is no 'de-rating' as you discuss in data centers or anywhere else. You are mistakenly confusing the requirements for continuous vs. non-continuous loads. This is not de-rating the circuit. It also has absolutely nothing to do with the wire - just the breakers. Where thermal-magnetic breakers are used - which are not 100% rated for continuous loads - the load must be multiplied by 125% in the calculation. This is for the breaker to work properly. If you could buy a 100% rated breaker, the wire would not have to be increased. Individual wires in conduit have much better heat disipation than type-NM cable. Any multiple circuits have to have de-rating applied whether its in conduit or cable. This has nothing to do with the other points discussed here. Sorry, but there is nothing in your statement that is not wrong.

Even if we did know who is who anyone can claim anything they want online. The only safe assumption is NO ONE here is a professional. I mean even the so called PRO's here are wrong all the time. A compressor can pull 12-13A when it starts normally but when dirty it pulls 15-17A. That just happened less then a year ago for me. It was verified by TWO licensed electricians as well. Once the coil was clean the compressor was back in the 12-13A range when it started. In this instance the compressor was hanging trying to kick over so it was sticking at that level until it popped the breaker which took a few minutes each time. I don't buy anyones professional opinions on the forums here without supporting info to back it up. No one has went as far as to prove anything either way just posting opinions.

first of all, you haven't read my posts very clearly. i asked a specific question: is there a tangible, quantifiable benefit to wiring a 15A circuit with 12/2?

i NEVER said that i think that all outlets in a house NEED to have 20A receptacles on 20A breakers. the thread got a little off track and veered into the cost and utility of later upgrading a circuit wired with 12/2 to 20A receptacles and breakers. i quoted prices from home depot, not exactly an unusual or obtuse place to buy materials for home renovation. not everyone has access to wholesale prices, nor do they want to purchase 5000 feet of cable or 500 devices to get the wholesale price.

when you say that the prices are "usually" nearly the same for 15A and 20A devices, where do you shop?

i appreciate the input from many people on the safety of various wiring configurations. i also understand that there is not universal agreement on the best approach. the default position is from the NEC (plus/minus local code additions) but clearly many professionals and experienced people have practices that exceed the NEC.

i believe i am qualified to do this job and i don't buy your logic that buying materials from home depot automatically makes someone incapable of performing the work. i have an extensive background in science/physics and a lot of practical experience (growing up with a dad who completed 3 old house renovations himself as well as 5 years of habitat for humanity builds). this house has a pretty simple layout with almost no complexity. in fact, there is only one 3-way switch in the entire house, that is the limit of the complexity. furthermore, the work will be permitted and inspected.

Interesting opinion from someone that just joined a whole month ago.

FYI, there are some VERY experienced pros on this board (whizkid3 is one of them) that can not only quote the NEC chapter and verse, but know and understand the physics behind the requirements. It's pretty clear you don't have the understanding they do, so I'd advise that the best course of action is to read and learn.Actually, the compressor motor almost certainly momentarily pulled well over 30 A when starting normally. Not at all a big deal, motors do that, but that would still be fine for a 15 A breaker. Any damage caused by overheating wires are almost certainly due to defective connections or hardware.

Did your electrician note how the outlet to the AC was connected? it sounds like it was back-stabbed, a UL-approved method of connection that is notoriously well known for arcing and poor connections. I suspect that was the issue in your case, not the slow AC start (that would be protected by a properly working 15 A breaker).

An incorrect assumption, but understandable considering your notably short membership existence on this site.

Those of us who have observed bit more water pass under the bridge can clearly understand who is the pro and who just wants to be. Clarity of information, good use of citations to reliable data, and discussions with examples offered that are obviously based on first-hand experience. Yeah, you really can separate the wheat from the chaff.