residential outlet tailing wire size

[eric stromberg]

I do not even know if I have ever held a 20 amp plug in my hand. What sorts of 120 volt single phase devices use a plug that would not fit into a 15 amp receptacle, but that would fit into a 20 amp receptacle?

Charlie,
A 20 Amp cord cap is quite common on Audio amplifiers. Manufacturers try to get the maximum that they can out of an audio amp. For a 20 Amp circuit, 1920 Watts is the maximum for a single cord and plug connected device. For a 15 Amp circuit, it's 1440 Watts. Let's round the 1920 figure on up to 2000 for the sake of conversation. Let's also estimate that audio amps are about 70% efficient. 2000 Watts input becomes 1000 Watts per channel. At 70%, the output that is available is 700 Watts per channel. This is why there are so many amps on the market that are around 700 Watts per channel. There are some amps that are still connected to a 20 Amp circuit that have higher ratings than this, but these are peak ratings that depend on stored energy in the power supply of the amp.

Eric Stromberg, P.E.

 

[celtic]

....such as an incandescent luminaire that only allows a 60 watt bulb maximum.

What..incandescent lamps greater than 60W have a different sized base or something?

Celtic, I suspect that this post was intended to be in the "tongue in cheek" line. I am sure you know (though others in the industry and homeowners might not know) that the 60 watt limit (i.e., 1/2 amp limit) is not based on ampacity. Rather, it is there to prevent too much heat from being generated by the bulb itself.

Actually, my post was tongue in cheek

While many fixtures may have the "60W max" notation, I'm sure we have all seen CF's and the like with 100W lamps (x3 or x4 ) in them....but fixtures are another post

:wink:

 

[still-learnin]

hey....

why 'tail out' with #14 when you can just land 2 sets of #12 under the screws and crawl to the next recep??

I will tail out to ring out the circuits to verify i don't have a problem with the wiring, drywall screw,etc.

I am glad that my question is now get more peoples thoughts and ideas on the reasoning to the NECs stance on this.
I don't see heat build-up as a problem in the application with romex in a box and the tails being removed from the sheathing and with an outlet and cover allowing some of the potential heat to disipate. I do understand that application of #14 in conduit with other conductors, some of which could and would be continuous duty type circuits.
Well, I guess i am still looking for that explanation that is going to make me feel all warm and fuzzy inside.
Thanks for all the responses. Well, almost all the responses..............

 

[iwire]

It does not have to make sense to us.

We don't need to know why.

It is the code we agreed to follow when we got our licenses or chose to become electricians. 8)

Why is NM required to be supported every 4.5' why not 5' etc.?

If a lug is rated for one stranded 14 AWG to 6 AWG why can't I use it for two stranded 10 AWGs?

How does the lug 'know' the strands it is clamping are from one or two conductors?

The only reason is 'because it's the code'.

 

[Pierre C Belarge]

Bob
Just because it is a "lug" doesn't mean it has no feelings...be nice to the lug. :wink:

 

[dlhoule]

Bob, quit buying the cheap dumb lugs, buy the more expensive intelligent lugs!

And when you find them, let me know where.

 

[still-learnin]

Bob, you stated that you often use #10 for tails at receptacles. why is that?
Do you feel that it makes a more sound connection at the receptacle? I have never seen this and am curious to the reason.

 

[iwire]

Bob, you stated that you often use #10 for tails at receptacles. why is that?
Do you feel that it makes a more sound connection at the receptacle?

Fair question.

The answer is no.

I think 14, 12 and 10 can all make sound connections on the receptacles we use.

Many of our jobs have specifications that require us to use 10 AWG on longer 20 amp circuits. We generally run MC cable which in this area comes with solid conductors just like NM.

Anyway when the guys cut the MC into the boxes they use the left over scraps they cut off to make the pigtail. The company I work for has a policy of pig tailing everything on the rough.

So the short answer is we use the 10 because it is in our hands at the box anyway. If the MC is 12 AWG we pigtail with that.

Keep in mind all our boxes are 4" deeps with plaster rings so we have more space to fold the conductors into the box. :wink: