orthomead OP28 posts
12-21-2019
2:36pm
I think I’m getting somewhere here thanks to y’all. Jim, the PowerPaper you referenced indicated that there were two sheathing options-aluminum or steel and the article further references the aluminum sheathed hospital grade cable. Of these 3 options, what would you currently choose? Are all your components plugged directly into the wall or do you use a power strip and/or conditioner/regenerator?
@ orthomead
MC aluminum armored cable is more widely used than steel. Aluminum will help shield from RF noise but not AC magnetic fields. The steel armor helps reduce AC magnetic fields. Though the twisting of the current carrying conductor does most of that. The steel armor will help protect the conductors of the MC cable from close near by parallel running NM cables from induing an AC voltage, AC noise, onto the conductors of the MC cable.
If aluminum armor MC cable is used it should be kept, spaced, from other branch circuit wiring probably a safe distance would be 8" to 12" or so. 8" would be enough but 12" would be safer. (Within reason after getting out of the electrical panel and starting the parallel runs, of the dedicated branch circuits, as well as any existing parallel running NM (Romex) branch circuits, as they are being installed to the audio room and down the wall to the outlets.) (With Romex you need to pay more attention to cable separation.)
FWIW.
(I am not a fan of 4plexs, 2 duplex outlets (for two dedicated branch circuits), sharing the same outlet box. Kind of defeats the purpose of dedicated circuits separation. Also worth mentioning if wall warts are used, depending on the physical size of the wall wart, it blocks part of the outlet on either side of it.
If you want to use the steel armored MC cable I wouldn’t be surprised if the electrical contractor will have to special order it. I suppose it depends on amount of usage of steel armored MC cable in your State, area, though.
As for hospital grade MC armored cable it has two equipment ground wires. One bare ground that runs along side the spiraled twisted circuit conductors, (to bond, connect, the equipment grounding conductor to the steel outlet box). The other grounding conductor is a green color insulated wire for an IG, (Isolated Ground) type outlet). (This insulated green wire is tightly held in place and twisted in a spiral together with the black and white current carrying conductors.)
You don’t need to use IG outlets in a single family dwelling house structure. IG outlets aren’t used that much anymore and when they were used they were used in commercial and industrial facilities where branch circuit steel conduits are fastened to other steel objects. The theory is AC noise is traveling all over the place through the interconnecting steel and other electrical steel conduits.
Of these 3 options, what would you currently choose?
This is a question you really need to have with the electrical contractor you are working with. He has been on site and is better qualified to assess your situation. For one thing can he keep the 4 dedicated MC armor cables separated from one another after he gets out of the electrical panel, as well as other parallel running branch circuit wiring. As for me, I would go with the aluminum armor MC cable.
ONE THING FOR SURE! Make sure you tell the contractor you want #10awg SOLID wire. Not Stranded wire...... Make sure he understands you want solid.... Don’t let him try to talk you out of it. He will tell you the ampacity rating is exactly the same, and yes it is. Your audio system won’t sound the same though. Solid wire only.
Are all your components plugged directly into the wall or do you use a power strip and/or conditioner/regenerator?
Yes directly plugged into the wall outlet. No power conditioner.
And again, I used NM (Romex) cable. Your situation may be different than mine though. I didn’t feel the need to spend the extra money for the MC armored cable.
If you don’t mind having a sub panel installed in your audio room you may want to go that route. One factor to consider though is resale of the home.
Best place to Install it is in the new wall you will be building. Speaking of the new wall you may want to consider building a double wall with staggered studs. Leave a slight space between the two framed walls. A 1/2 inch to an inch would probably be plenty.
Per the NEC, and I’m pretty sure the AHJ (Authority Having Jurisdiction) in your city, the electrical panel must be readily accessible and have a clear working space in front of the panel. Your electrical contractor can tell you what the minimum front and side distance measurements are.
If you decide to have a sub panel installed, because of the cost of the installation, (material and labor), you should add plenty of a fudge factor for future. It’s a lot cheaper now than later if you decide to buy bigger amplifiers.
I would wire sub panel for 120/240V. With your present audio equipment you can still feed all the 4 dedicated circuits from one Line, leg. With both Lines, Legs, available you have the option to easily move the dedicated branch circuits to the Line, leg, for what ever reason if you so choose.
Sub Panel Feeder:
If it were me I would feed the sub panel with at least #4awg copper or #2awg aluminum conductors. I would oversize the equipment grounding conductor as well.
If the electrician used #4 copper, (or #2 aluminum), he could use a 2 pole 70 amp, or a 2 pole 80 amp, breaker at the main electrical panel. Code only requires a #8 copper for the equipment grounding conductor. I would probably bump it up to a #6 copper wire.
Overkill? Yeah, probably...... But consider you want four 120V 20 amp dedicated circuits, using #10 wire, to feed an audio system that draws around 7 amps.
Combined wire gauge calculator.
https://www.wirebarn.com/Combined-Wire-Gauge-Calculator_ep_42.html
Enter 4 for the number of wires.
Enter #10awg for wire gauge.4 #10s = #4awg.
Jim
