If you are a home builder and are building 50 homes, then you want to cut costs as much as possible to maximize profit. So 15 amp outlets where not required and as few as possible is the rule.
However if you are that same home builder building your own home, then 20 amp outlets everywhere and plenty of them (no 15 amp outlets)...
The key concern is overloads. Both 15 and 20 amp breakers will trip on direct shorts (if they are working properly).
There is a tradeoff.
20A circuits have a convenience factor with the ability to delivery a considerable greater amount of power to a given situation. A typical example today would be a home office with multiple monitors, printers, computers and accessories in addition to whatever other routine loads (vacuum cleaners, electric heaters, etc.) are placed on the circuit.That extra 5A capability might just be the difference between adaquate wiring or a long-term headache of a constantly tripping circuit breaker.
On the other hand, the subloads on a 20A circuit might (possible) pose a safety issue. The 18 gauge lamp cord example has already been mentioned.
The danger being that if the 18 g. wire is overloaded just enough for the 18 g. wire to melt, but not enough to trip a 20A breaker. (In such a case, a 15A circuit breaker might be more likely to trip than a
20A breaker, but not necessarily). This is the reason that most power strips contain their own internal circuit breakers. 15A circuits were standardized during a time when there where few constant electrical loads and the loads were generally light. (a few lamps, a fan, etc.).These days, many people have home entertainment systems, hefty audio amplifiers, air conditioners, computers, big-screen plasma tv's, monitors, laser printers, and a whole lot of loads that could not be imagined 60, 70 or 80 years ago.
In my opinion, this makes the argument favor the 20A circuits over 15A circuits, just for the added capacity and convenience.
Beachcomber
The CORRECT solution to this situation is a split 15 amp circuit.
15 amps to the top outlet, 15 to the bottom. Done by using 14/3 cable and double breakers. The legal way is a "tied breaker" which means if you blow one, it trips the other as well. This is to prevent half of the box being live. Untied breakers are often used for this reason.
If it the wire from the back was clamped when you screwed it down, that is the good "back wire" type connection. Less prep time and good solid connections, particularly good for stranded wire. Nothing wrong with these connections at all.
The "push wire" type have a hole with a flimsy little spring tab that grabs the wire and a little slot next to the hole where you insert a small screwdriver to release the tab if you want to remove the wire. These are the horrendous ones with tiny contact area, low contact pressure and frequent intermittent connections.
Doing that will also put the two outlets on opposite poles / phases, giving 240V between the upper and lower hot connections. I'm not sure how that works with the ratings of the break off tabs on a duplex receptacle. At any rate a hinky solution at best.
The truly correct solution is to just install more circuits in locations that need them. Basically instead of the all too common situation of every receptacle in a room being on a single 15A or 20A they should be individual circuits or at least two circuits alternated so any given location is within reach of both circuits.
The alleged safety concerns of 18ga lamp cord on a 20A vs. 15A circuit are pretty much all bunk. The wire is rated at less than half of what even the 15A circuit is rated at, the 20A circuit introduces no additional risk. In both cases the circuit breaker properly protects what it is designed to protect - the wires in the walls. In neither case is the circuit breaker supposed to be the protection for the lamp cord and the liklihood of a fault developing in the lamp cord that would trip a 15A breaker, but not trip a 20A breaker is virtually non existent.
I seem to recall seeing that the 2008 version of the NEC will require AFCIs on just about all of the 120Vac circuits, not just the ones for bedrooms.
No, this is not a hinky solution. It's called a splitwire or multiwire circuit, and has been the standard for kitchen counter receptacles in Canada for decades.
Having every receptacle on its own circuit is ridiculous overkill. Even having two circuits per room is overkill for many rooms. That said, there are some rooms (kitchens, home theaters, home workshops) that would benefit from more circuits, and just about any room would benefit from more receptacles.
Chris
So?
You're not sure how it works, but you're sure it's a "hinky solution." :-)
Actually, it's a perfectly fine solution.
How is having two circuits available at alternating receptacles any improvement over having two circuits available at *every* receptacle?
It's also quite common in office building environment. A variant of this is when you have 3-phase 208VAC available. You can run all three phases and a neutral in the conduit and use a different phase and neutral in each box. There are some issues with the size of the neutral, but I won't go into that here.
By using just one phase and neutral in each box, you avoid having higher than 120VAC available in one outlet. This can also be done with residential circuits, use alternating 'hots' in each successive box. So box 1, 3, 5, etc... is off of the first 'hot' and 2, 4, 6, etc... is off the second 'hot'.
There are many times I wish there were two receptacle boxes side by side in a 'quad-outlet' arrangement. Just because of the number of things to plug in, not the overall VA requirement. In a modern home office you might need a total of about 400 VA (about 1/3 of a 15A circuit capacity), but it's split into six or more 'plugs' (couple of watts for speakers, couple of watts for radio, couple of watts for cordless phone, 7-15 watts for CFL, rest for computer and printer).
Even my bedroom, with a reading lamp, wireless telephone, alarm clock for me, and an alarm clock for the Mrs., I end up needing an 'adapter' while the four other outlets in the bedroom are empty. Total load: about 11 watts (when the 7 watt CFL reading lamp is on).
daestrom
I'm sure the world will get right on adopting those superior Canadian electrical standards...
My kitchen has I believe four separate 20A circuits in it, and it was that way when I got here. I did have to replace the Federal Pacific Stab-Loc main panel incendiary device with a proper Square D QO panel however.
My shop is wired with a "quad" every 6', with a "quad" being a 4" square box containing a 20A GFCI duplex receptacle paired with a 20A regular duplex receptacle. Every "quad" is an separate circuit. All wiring is in surface mounted conduit for ease of additions / changes. 240V receptacles are located where needed. The walls are type X fire code sheetrock. I'm pretty happy with it for a home shop.
He's talking about splitting poles / phases on the upper and lower halves of a duplex receptacle, not using a different phase in successive box locations.
I'm good with cycling through the phases from box to box, but not splitting upper and lower of a duplex.
I wired my shop with all "quads", each one is a 20A GFCI receptacle paired with a 20A regular receptacle, and each "quad" is a separate circuit. The "quads" are spaced every 6'. The shop has a 125A 32 space Square D QO sub panel.
That's another issue, a zillion tiny loads in one spot. I have a power strip under my night stand for the table lamp, alarm clock, cordless phone charger, cell phone charger, bluetooth headset charger and weather radio (tornado alley).
It's hinky in my book, and I wouldn't wire it that way.
It avoids having 240V on a device where most people expect only 120V. I'm fine with cycling through poles / phases box to box, but I don't like it within a single box in a residential application where joe bozo might mess with it. People blow things up with some regularity in industrial environments with three phase "wild leg" delta service, and in an industrial environment they're supposed to have a clue. Give joe bozo homeowner an unexpected red wire in the box and he's likely to blow stuff up too. I think it's an unnecessary risk in a residential environment.
Good thing I did my electrical rebuild in 2006 eh? Actually it wouldn't have mattered since I'm outside city limits and per the city building department I didn't need any permits or inspections. I was a little worried about how the AFCIs for the bedrooms would react to the TIG welder and plasma cutter on the shop sub panel, but they seem to be fine.
It's called an Edison circuit. It's used all over. There's nothing "hinky" about it.
I don't agree, but even if there was zero workability difference, that wouldn't be a valid reason to spend even a nickel extra on a 12W circuit, or any low-power circuit. The only half-way reasonable argument I've heard for using 12 on low-power circuits is that it's more forgiving of bad workmanship. But anyone who needs that crutch shouldn't be doing electrical work anyway.
Lots of people (including me) waste money when they don't need to, but we shouldn't encourage the newbs to do that. Ask any question on Usenet, and far more people will tell you to overdo things than underdo them. If a guy with a normal budget started building a home, and followed the Usenet consensus on how to do it, he'd probably run out of money before he finished the foundation. :-)
Wayne
Fine, don't wire it that way -- but don't tell others it's a bad solution, just because you don't like/understand it.
So how, exactly, is that an issue? You can't plug a *single* device into both sockets of a duplex receptacle at once. Each socket has only 120V; that there is a 240V potential between the two hots is of no relevance whatever.
I'd love to hear your explanation of how this will "blow stuff up."
I see people below disagree with "hinky". I don't know the term. However, as the "Joe Blow" guy who messes with outlets occasionally, I would be quite unhappily surprised to discover by accident that I could get 220 between some wires on the same outlet. Yikes. Also, I've got some house intercoms that apparently don't work right when plugged into "different legs" of the 240. On the other hand, if I were doing it to my own house, it won't be a surprise so who cares? (just my 2 cents, etc...)
No, it is not called an Edison circuit, though it connects to one. Feeding separate 120V devices from a three wire feed is called an "Edison circuit", feeding upper and lower halves of a duplex receptacle from separate legs / phases is not in the definition of an "Edison circuit".
I understand it, and I recommend against using it in a residential environment for a good reason.
It has plenty of relevance. See below.
It has a decent potential to "blow stuff up", when Joe Bozo homeowner yanks on the vacuum cleaner cord, cracks the receptacle and goes to replace it. Joe Bozo homeowner who has no business being in the box to begin with and doesn't remember which wire went where. I've seen some pretty screwed up stuff like that and I see no good reason to add this risk when simply installing a separate box and outlet for the $2.50 will eliminate that risk.
Not "hinkey" Required by code in kitchen countertop applications in Canada. The breakoff tabs are there for that purpose. You remove them.
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