advice on dedicated line

Al,

Here is a white paper of a 2012 seminar by Bill Whitlock.

http://centralindianaaes.files.wordpress.com/2012/09/indy-aes-2012-seminar-w-notes-v1-0.pdf

Check out grounding, starting on page 31.

Note page 35, for those that have to use metallic conduit for the branch circuit wiring. MC cable with an aluminum armor is the best. Conduit runs with loosely randomly installed wires pulled in the conduit is the worst for ground loops.

I would have liked to have seen Bill comment on the effects of multiple dedicated branch circuits sharing the same conduit raceway addressed.

Also check out pages 200 through 212.
.
Jim

I assume, though, that modern code doesn't permit installation of conduit containing only two conductors. Am I correct about that?
02-11-14: Almarg

Al,

As for NEC 2011 Code, Rigid, IMC (intermediate Metal Conduit), EMT (thin wall), are reconized as an equipment grounding conductor.
Flexible metal conduit 6' or less in length is also acceptable for use as an equipment grounding conductor provided the connectors are Listed for use as equipment grounding means, and the branch circuits is 20 amps or less.

Remember NEC Code is bare minimum. The AHJ (Authority Having Jurisdiction) in the area a person resides may not allow the above metal conduits to be the sole equipment grounding conductor. The AHJ may require an equipment grounding wire to be installed in the conduit with the other branch circuit wires.

The problem I have with using any metal conduit for the equipment ground is the continuity integrity of the couplings and connectors to maintain a good conductive electrical connection over the passage of time. Not to mention how well the conduit installation, fittings tightness, was to begin with.

As for the white paper....
I was glad to see actual testing done for an equipment grounding conductor sharing the same raceway or cable as the current carrying conductors of a branch circuit.

I always thought a voltage could be induced from the current carrying hot and neutral conductor over onto the equipment grounding conductor on a long branch circuit run. We now know why many audio enthusiasts recommended using NM-B cable, (Romex is a Trade name of NM-B), for audio equipment branch circuits.

One thing for sure, conduit runs where the wire is installed after installation is the worst thing for audio. And to repeat what I have said in the past, dedicated branch circuits should not share the same raceway, conduit, with other branch circuits.

For those out there that have to use conduit I suggest MC cable with aluminum armor and solid core conductors. MC can be bought with solid or stranded wire conductors.
MC Cable
http://www.afcweb.com/product-category/mc-metal-clad-cables/
.
.
**Just an added note.
Old homes built before around the middle 1950s and earlier may be wired with old BX cable wiring. Construction of the cable is 2 insulated cloth covered conductors with a steel spiral armor cover around the conductors.
The receptacles back then were the old 2 wire type.

The armor on this BX cable should not be used as an equipment grounding conductor. Not only is the steel armor not an effective ground fault path for fault current, neither is the electrical connection of the BX to box connectors.

NEC 1959 Code required AC/BX cable to have a continuous bonding strip installed under the armor so the cable could be used as an equipment grounding conductor. Just guessing the BX to box connectors were still the same old connectors. By NEC 1962 Grounding type receptacles were required.

Here are a couple of Links.

http://www.inspectorsjournal.com/forum/topic.asp?TOPIC_ID=10144

http://www.dslreports.com/forum/r26797846-using-BX-cable-as-a-ground-

Jim

For what it's worth I have two 20 amp dedicated lines for my 2 channel system. I ran #10-2 with ground NM-B cable. (Romex is a trade name of NM-B cable). Each run is about 75' each. Digital equipment on one line, analog on the other. My system is dead quiet.

Al, Your last post was right on IMO.
.

Here is a post by the late Robert Crump.

Quote.
"Posted by rcrump (M) on February 5, 2004 at 07:15:55
In Reply to: Re: Why solid over stranded??? posted by Jwm on February 3, 2004 at 06:20:47:"

"Solid core Romex has an absolute ton of inductance and you can use that to roll off the digital backwash and end up isolating your analog from digital with yards of the solid core Romex in the walls. Romex is insulated with PVC and, again I will say that PVC is what you want rather than anything faster as you just want to pass 60hz and attenuate anything above that.....Stranded wire, especially a twisted lay, will pass high frequencies better, exactly what you don't want to do with 60hz AC.......
http://www.audioasylum.com/audio/cables/messages/8/88644.html

Most of the AC noise/hash on the mains of our audio equipment is connected to is caused by the power supplies of the audio equipment.
Dedicated branch circuits will decouple audio equipment power supplies from one another.

http://www.middleatlantic.com/pdf/PowerPaper.pdf

Jim

Excellent post Jim. Thanks. That's exactly where I'm heading. I may go for 2 or 3 dedicated Romex circuits. A 15 amp job for my CDP. A 15 or 20 amp line for just the amp, although I suspect 15 amps would be major overkill since the amp pulls about 800 watts (or 7.5+ amps when driving a heavy load). And a 3rd line for the rest of the my gear.
02-09-14: Bifwynne

Bifwynne,

Install only 20 amp dedicated branch circuits. Wire size #12 solid core copper bare minimum. Per NEC Code a 20 amp NEMA 5-20R receptacle can only be installed on a 20 amp circuit. A NEMA 5-15R 15 amp duplex receptacle can also be installed on a 20 amp branch circuit.
Porter Ports are NEMA 5-20R 20 amp duplex receptacles.

How long are the runs from the electrical panel to your equipment? Don't forget to figure up and down, over and around, when figuring the lengths.

Tell the electrician to try and keep each branch circuit length the same. Do not mix wire sizes. Make all dedicated branch circuits either #12 or #10 wire.
Jim