How unsafe is running #14 off a 20a circuit?

The question about sticking a 20a breaker on an overloaded 15a circuit got me to wondering.
Last year I installed an invisible dog fence. The only outlet in the garage already had an extension cord in it that ran to the garage door opener. So, I ran #14 from the existing outlet (which I replaced with a GFCI) and put a new outlet on the ceiling for the garage door opener.
When I was actually connecting up the wire, I realized the existing wire #12; I checked the breaker and sure enough it was a 20a. I was fooled since it was a 15a outlet, and code required a 20a outlet on a 20a circuit since it was the only outlet on the circuit. (at least that is my understanding) Since I didn't want to redo what I had already done, and I couldn't image why I would ever need 20a on the circuit, I replaced the 20a breaker with a 15a.
Did I go to an unnecessary expense? Should I have just left the 20a breaker? I can't think of a single situation where leaving the 20a breaker would have been unsafe. Nothing but the garage door opener will ever plug into the ceiling outlet (with the #14), and it is all exposed to the air, so it is unlikely to overheat dangerously even if I did. Whatcha think?
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"Toller"

understanding)
This doesn't sound correct, but there are lots of codes out there. There is little physical difference between a 20A and 15A outlet - only the existance of the hortizontal spade is different. The codes related to these outlets are basically there to prevent putting a 20A appliance on a 15A circuit.

I would have installed a 15A breaker based soley on the existance of 14ga wire in the circuit. You'd probably be fine, but why ever bother questioning all the safety and research that sits behind these codes? You never know what someone will do 10 years after you sell the place. That said, I use 12 ga wire for both 15 and 20 A circuits. It just isn't that much extra work and money.
- Nate
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Canada requires 20A recepticles on 120V/20A circuits, but USA generally allows 15A for general purpose circuits w/ multiple recepticles?

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This is only true if you have complete control over the garage and never let anyone in it for any reason (like a contractor doing maintenance or repairs etc) _and_ you never sell your house. As soon as you sell your house, it's a problem.
Downgrading the breaker is safe. Upgrading to a GFCI is also a good idea (required by code where I live - all garage and outdoor recepticles).
Mike
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I think you knew the answer or you wouldn't have replaced the breaker. And since nothing will ever be plugged in except the opener, I assume that means you'll live in the house until you die, preventing anyone from using the outlet for anything else, and have the house bulldozed upon your death, correct?
Jeff
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Of course I know the code requirement; that is why I changed it. To be dangerous though, someonw would have to use the ceiling outlet, they would have to have a 20a appliance with a 15a plug on it, and the wire would have to overheat despite being exposed. All of these are unlikely; together they are nearly impossible. So why should it be dangerous? (I also had a 22a water heater running on #12 for 20 years, until I found and replaced it. I didn't check to see if it got hot, but it never started a fire.)
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Or plug two 12A items into it and run them simultaneously. I can do that easily with power tools.
Mike
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- Michael Daly -

- Nehmo - Then maybe the breaker will trip.
Codes require a rated outlet to have a circuit (breaker, wires, etc.) big enough to accommodate it. A higher rated circuit can have a lower rated outlet on it. Lots of 20 A circuits have 15 A outlets on them. And that doesn't mean you should load every outlet to the max. Since a single branch circuit can have several outlets, you can overload almost any breaker without overloading its outlets.
This site discusses some of the issues: http://www.codecheck.com/numberoutlets.htm
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* Nehmo Sergheyev *
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Or, they could simply have a 5 amp appliance on a 15 amp cord/plug that shorts internally, causing the slightly corroded connection at the original box to overheat and draw 19.5 amps, setting a fire and never tripping a breaker.

Well, it's not my house and hopefully never will be, so follow your instincts to whatever end you reach.
Jeff
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