Should it be balanced?
Ha Ha, everybody knows, that there is no surch thing, as balanced AC currant!!
Whatever you get from your power grid, that’s all you’re gonna get!!
In the US and CAN, you do not have a choice: our 240v is balanced (120+120). Our 120 is simply one leg of the balanced 240, therefore unbalanced. One of the cool byproducts of the first Power Plant was that the 120v was balanced, IIRC, with 60v+60v
“It doesn’t cost that much to run it”. From an electrician, “it does!”. You want to run 1 circuit to your listening room, price $X. You want 3 circuits, multiply by 3 and so on.
A dedicated circuit is not a big problem, if you use 12 gauge wire and 20 amp outlets with the appropriate circuit breaker.
The reason electricians have a problem with larger wire is that it is a violation of the national electric code to connect standard duplex outlet’s that are only rated at either 15 or 20 amps, to 10 gauge wire. When you go to 10 gauge wire that is rated at 30 amps, all devices in that circuit must be rated for 30 amps. A 30 amp receptacle is a totally different configuration. You could do it by changing to a 30 amp outlet, but then you would have to change the plugs and wiring to your devices. That’s where the expense comes in, not to mention a circuit that would be unique from normal house wiring, which could lead to legal issues. There are other solutions, but then again, requiring unique circuits.
I do not agree and there are many Code commentaries that state the opposite of what you say about receptacles. I have read, debated, written commentaries and edited sections of the NEC for clients. The NEC and its stated wire gauges are a minimum standard. Upgrading wire gauge is commonplace, due to resistance, line length or the customer just wants bigger. No house ever burnt down due to larger wire.
Nothing in the NEC requires 30 amp rated receptacles on a 10 gauge line. Further, the current limiting device (breaker) is rated to protect the wire, not down stream outlets. Again, there nothing prohibiting using a smaller breaker on a larger wire gauge. Receptacles are rated to handle there use or throughput of the device, not the wiring it is attached to.
That said, it is common place with using 10 gauge romex to power a 120v circuit, to use a 20 amp current limiting device (breaker), while a 30 amp would be permitted.
I stand corrected. Yes, with a 20A breaker feeding the circuit, there is nothing wrong with using the 20A receptacle on 30A wiring.
If your listening room is on the opposite end of the house from the breaker box, would it be beneficial or cheaper to run 1 line and add a second breaker box in the listening room and have all the outlets dedicated to that breaker box? Also, would that have any effect on the sound vs home runs to the main breaker?
Great question. I have always been a fan of sub panels. But that is for pure convenience and safety. And for high current devices are involved: i.e. welders in the garage panel, and table saw in the workshop panel. SAFETY NOTE: Subpanels require special care in their wiring so that its neutral – white pole is not bonded to the ground as in the main service panel. If what I said makes no sense to you, PLEASE research or get help from an electrician. There are many great articles on installing subpanels and bonding requirements.
For 120v hifi equipment, there is no particular benefit for a sub panel, other than cost, installation hassle and convenience. I would hazard a guess that potentially, several home run 12 gauge romex lines from your music room to the main panel – service panel could produce cleaner power than say, 50 amp breaker on your main panel, feeding an 8 gauge cable to your new sub panel, another main breaker in the sub panel, and then 20 amp breakers to each circuit, and lines from each 20a breaker. By using the sub panel, and breakers, you are introducing a bunch more connections and terminations. Not an issue with table saws, but with hifi, each connection is a possible corrosion point. With home runs from your music room directly to the main service panel, you eliminate an extra breakers and connections and terminations.
As Paul stated, nothing sounds as good as a heavy gauge home run (10 or 12g) directly from new commercial grade receptacle feeding the hifi equipment, without any splices, to a dedicated NEW breaker for that line in the main service panel. Fewest connections possible.
Note that most a/c wiring comparisons have been between a dedicated home run, with new 12 or 10g versus simply plugging in your stuff into an existing 15 or 20 amp branch circuit with a bunch of other outlets. In that case, everyone finds the dedicated 12g homerun superior in both listening and measurement.
Hope that helps and I did not confuse you.
At least in Canada, the National Electric Code only requires a MINIMUM wire gage for a given breaker. Thus a 20A breaker needs minimum of 12 ga, but there is no problem running 10Ga. on a 20A circuit. In my strange house (a former country store) it had an unused 60A 240V sub panel that was once used for gas pumps. It had a 4 Ga. connection back to the main panel. I ran six (!) 20A circuits with 10 Ga. from that sub-panel to three separate rooms, one on each floor. Two were for the home theater room on the main floor, two for the stereo in the living room on the second floor, and two to my dedicated “man cave” listening room on the third floor. Yes, I am a little spoiled!
Your electrical receptacles with “isolated ground” (and similarly hospital grade receptacles) are designed such that that a 4 conductor cable like a three shielded inside cables in a metal conductor (like the old armored cable or metal conduit) with an internal ground wire clad with an insulator be used. The outer armor (or metal conduit) is attached to the metal receptacle box and the Main breaker box, and the inner clad green ground be attached to the pin terminal of the receptacle, and not the metal box. The pin terminal on the receptacle is not to be connected to the receptacle box, but is connected only to the to the “green ground wire”. At the main box the green wire is connected to the main box ground, not the ground bar that gets the neutral (white) wires. Do you advise using this wiring or just ignore the isolated ground aspect of the receptacles and choose them only for the stronger internal contact with the plug?
Great question Shenefelt. Executive Summary: YES, use real hd commercial outlets or hospital grade outlets for strong internal pin clamping and do not worry about the isolated ground in home use with poly boxes and Romex wiring..
Let me give you some background.
When I designed the PS receptacle, I spoke a lot with engineers from Hubbell. Boy did I learn alot and they corrected lots of my misnomers. I always thought the Hospital Grade plug was the dogs bollocks (my wife is English) for hifi. Not exactly. What I learned was that hospital grade receptacles are made first, second and third to withstand maximum abuse, such as: have a janitor ram a floor polisher into it every night; having blood, toxic chemicals spilled in it, staying connected to life saving equipment under crappy conditions. Hence, thick steel frame, very heavy duty pure nylon body, rhodium plating on special brass alloy clamping mechanisms.
True heavy duty commercial grade plugs (costing $10 up and not the light grade commercial $5 ones) AND isolated hospital grade plugs (usually $15 or so) have the same SPECIAL clamping mechanisms inside to give a death grip. YES, we recommend them. Yes, they are worth it! The number TWO problem with receptacles is the clamping mechanism loosening up over time. Number ONE problem, by the way: corrosion on crappy brass alloy inside of cheap outlets.
And the isolated ground is used in hospitals due to the very sensitive electronics and bizarre emf and rfi that does occur all the time in a hospital. Think massive MRI, X rays. In a hospital and most commercial structures, receptacles outlets are wired through metal conduit, metal studs, metal clamps to metal panels, and metal receptacle boxes – and all are bonded (electrically connected). As you pointed out, a hospital and isolated ground receptacle isolates the “grounding pin” from the outlet’s frame, the metal box it sits in and the metal conduit. By having the receptacles grounding pin connected ONLY to other receptacles grounding pins and then going to the main service panel, this safety grounding circuit is not as polluted with all the rfi, emi picked up by the massive array of metal conduit running through the building, touching metal studs, girders, rebar, etc. The conduit system in a hospital must be a kick ass antenna.
In almost all homes, we do not have those issues. Most have the poly or nylon receptacle boxes (smurf blue) with only Romex wiring. Hubbell explained that in home use, isolated ground really has no benefit because we do not have a grounded conduit array (1) with its own and different electrical grounding potential and (2) acting as a massive RFI EMI antenna.
THE GOOD NEWS:
Home Runs for hifi give you Isolated grounds for Free! If you use a 10 or 12g home run from your wall receptacle near your hifi directly to (without stopping at go) the MAIN service panel (called service equipement by the NEC) you in essence have created a true isolated ground, using a standard HD commercial receptacle. The grounding pins on the receptacle go straight to the service panel with NO interuptions, connections, splices, etc.
SO, yes use the very heavy duty commercial receptacles. They do not have to me hospital grade or isolated ground. UNLESS, of course, you ram a big ass floor polisher into your outlets very often. 🙂
You must be logged in to post a comment.