What exactly is a 20 amp dedicated line?


My electrician was over this morning installing Porter ports. I had him install 20 amp dedicated lines a while ago. The wall outlets have two places for plugs. It was my impression that a 20 amp line was a separate line for each plug. However, he stated that a 20 amp line was for the double plug instead of the single plug. Luckily I only have one amp plugged into each double outlet. However, If I decided to plug two amps into an outlet with two plugs, wouldn't it negate the 20 amp line? Your comments would be greatly appreciated.
Ag insider logo xs@2xaaronmadler
now the really important question is what's a Porter port? Drawing a slack jawed zero over here!
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If you are trying to get 2 dedicated lines with one romex I'm assuming he is speaking of using 12/3 with ground. or 10/3 ...(same)...If you keep each hot on the same Phase in the Main Elect. panel then at your point of contact to your receptacle (in the J-box, at the stereo) there would be no way of accidentally ending up with 220 volts. Wiring is No Hobby, Call a professional. And I'm not trying to be a smart-ass with that comment either...
Hcbravesfan,

If you use a 3 wire with ground romex (NM-B) for the purpose of creating 2 circuits what you end up with is a multi wire branch circuit.

With a 3 wire multi wire branch you will have 2 separate circuit,(not 2 dedicated circuits), with a shared neutral conductor.

The 2 hot conductors must be fed from opposite Lines, legs, of the electrical panel.

When a multi wire branch circuit is fed from a single phase, split phase, secondary winding of a transformer only the unbalanced load of the loads connected to each separate circuit will return on the neutral conductor.

Example, if a connected load of exactly 5 amps each is connected to each 120V separate circuit, 0 amps will return on the neutral conductor to the source. The two 5 amp 120V loads are in series with one another.

Example, if 5 amps of load is connected to one 120V separate circuit and 2 amps of load connected to the other separate circuit, then 3 amps (the difference of the two) will return on the neutral. The balanced 2 amps will be in series with one another.

It is obvious why audio equipment should not be fed from separate circuits whether connected together by ICs or not.

Why would you want to series hash from digital equipment right out of the power cord right back into the power supply of an analog preamp or phono preamp.

With true dedicated branch circuits that have their own hot, neutral, and equipment ground conductors the dedicated circuits should be fed from the same Line, leg, from the panel when the equipment is linked together by ICs. I would even go so far to say HDMI cables as well. Though I have not read any info on such regarding HDMI cables..... Must be something out there.

Added note.
Per NEC, the 2008 edition, all multi wire branch circuits shall be fed from a multi pole common trip handle breaker.
Jea48, Just to clarify,

Did you mean to write "seperate legs" of the power box, when you wrote 'It is...not be fed from separate circuits...

Thanks