Electical conundrum - 30A subpanel or (2) 20A lines - AVS Forum
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post #1 of 11 Old 01-16-2013, 09:35 AM - Thread Starter
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I'm trying to decide if I should use an existing, unused 60' 30A 10/2 run from the main breaker box to the attic, or to just run new 12/2 lines.

Option A:
The subpanel would be about:
5' from the projector
10' from the equipment rack (HTPC, PS3, AVR4311, Parasound HCA 2200II, Cable Box)
20' from the networking panel with the cable modem and router
40' from the sub amps (2xEP4000)

Option B:
Alternatively I could run two new 12/2 lines from the main breaker:
(1) for 20' to the sub amps (2xEP4000)
(1) for 50' to the projector, then 15' to the equipment and 15' to the cable modem and router.

Option C:
Run a new line for the sub amps, and use the 30A line for a subpanel in the attic.
(1) 20' 12/2 line to the sub amps
Attic subpanel for the rest.

Option D:
Tap into the 10/2 wire at the subs (it goes right past the subs), and use a single 10/2 run for the entire system. Problem: There are no 30A 120v receptacles that I can find anyway. I'd be worried about burning out the contacts on the plugs that are rated only for 20A on a 30A line.

I already have 250' of 12/2 wire, a subpanel, and plenty of breakers -- so no $$ saved by not using them. I"m looking for the solution that gives the best result for clean power with no ground loop hum.

I'm leaning towards the 30A subpanel and from there run a 20A line back to the subs and a 20A line for the rest of the equipment, to keep everything on a single breaker back at the main breaker box. But I'm concerned that I'll be driving the Behringers pretty hard at 2ohms/ch stereo, so they'll occasionally need all 20A of that line. That leaves only 10A for the rest of the equipment, which is probably fine but it's close.

Any advice is greatly appreciated. I'd like to do this in the next few days.
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post #2 of 11 Old 01-16-2013, 10:05 AM
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Well I'm no electrician, but I would think that taking 2 circuits directly from the original panel is the best and most straight-forward way to go. I ended up wiring my basement theater to a sub-panel because I had to install one anyway. My entire basement necessitated an additional panel, so it made more sense to wire in the new circuits into that panel rather than re-routing a bunch of circuits from the original panel into the sub-panel just to free up space for the theater. I guess what I'm trying to say is, if you have the room in your original panel and don't need room for anything else, why not just use those spaces for the theater. If you're really worried about good, stable, clean power you'll use a power conditioner anyway.
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post #3 of 11 Old 01-16-2013, 11:06 AM
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Would vote for the 30 A subpanel. However, the 30A panel should be 240 V, but you indicate that the #10 wire is 2 conductor (no neutral), so it would not work for that. If you have a Neutral conductor, you can make it a 120/240V panel, and then you get plenty of power (120 V 60 A).

Shorter runs, and shorter grounds, are always better to avoid ground loops.
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post #4 of 11 Old 01-16-2013, 11:16 AM
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Quote:
There are no 30A 120v receptacles that I can find anyway. I'd be worried about burning out the contacts on the plugs that are rated only for 20A on a 30A line.

If your load doesn't draw 30 Amps, you won't be burning the contacts.
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If you're really worried about good, stable, clean power you'll use a power conditioner anyway.

That's funny.
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post #5 of 11 Old 01-16-2013, 11:39 AM - Thread Starter
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Thanks for the tip. I asked that wire to be installed by the solar guys and they did it as a courtesy. Turns out I should have made it 4-wire even though I have no need for 240v. Bummer. So back to the drawing board.

So now if I want to do a subpanel it will require a new run to the attic. I have 75' of 8/3 laying around that I was saving for a hot tub, but guess I could use that instead. Then I could easily run everything from the subpanel.

Alternatively, I could use the 10/2 That's already there and put a 20A breaker on it for the HTPC / Equipment rack. It's a pretty long run anyway and could probably benefit from the heavier wire. Then it's just a two more 12/2 runs -- a short one for the sub amps, and a longer one for the projector. Well maybe one more as well -- I'll want to add another for the TV downstairs as well, as I'll be running an HDMI cable down there as well and don't want ground loop noise from the power down there. Running a separate circuit to the networking panel is probably overkill. I guess I could run an extension cord from the projector area to the networking panel for the cable modem (part of the RG-6 chain) if I still had some ground loop noise.

I'm going to have to take a look and see exactly how much room I have left in the main panel. I'm talking about adding four lines now. Is it OK to use single pole double throw switches (two lines in a single slot?)

Thanks again for your advice to both of you guys.
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post #6 of 11 Old 01-16-2013, 12:24 PM
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Quote:
Originally Posted by zacjones View Post

Is it OK to use single pole double throw switches (two lines in a single slot?)

Thanks again for your advice to both of you guys.

That depends on the panel installed in the house. Some panels are designed to allow these breakers and some are not- the only way you can tell is by either the model number or a diagram in the panel box. Tandem breakers are supposed to only work in panels designed to accept them since they have a different connector for the panel bus. IF there is no diagram showing allowed tandem breakers then get your model No and google it or call the manufacturer to see if it would accept tandem breakers and where those breaker slots are on your panel.
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post #7 of 11 Old 01-16-2013, 03:49 PM - Thread Starter
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Sorry let me clarify -- there are plenty of double pole breakers in the panel already -- I'm just verifying that there's no reason not to use them from an A/V standpoint.
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post #8 of 11 Old 01-17-2013, 04:12 AM
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They're single pole breakers....some may be ganged together, some may be half sized allowing for more breakers in the box, but they're all single pole devices.
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post #9 of 11 Old 01-17-2013, 07:22 AM
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Quote:
Originally Posted by zacjones View Post

Sorry let me clarify -- there are plenty of double pole breakers in the panel already -- I'm just verifying that there's no reason not to use them from an A/V standpoint.

You should be fine as long as the panel properly supports tandem breakers. The reason I say this is that some manufacturers make a tandem breaker that does not have the modern "rejection" feature- it's called non-CTL replacement breaker and is meant for use in older panels that allow tandem breakers but don't have the built in rejection feature on the bus. Trust me- I bought a house 5 years ago and the home inspector totally missed that the previous homeowner had placed these non-ctl tandem breakers in the panel box. The panel box itself was not rated for tandem breakers and they still fit in there. It wasn't until I had a new furnace installed that the electrician raised the flag. I needed new 200 amp service any way so I had him put in a 42 breaker panel. So- regardless of whether there are existing tandem breakers, I am suggesting that you confirm that your panel is rated for these.

Now, if it is properly rated panel then you should be fine. There isn't any real difference between the function of the breakers if they are tandem or not. They will still trip if there is an overload on the circuit. As long as the panel is designed to allow them then the power supplied through the circuit is no different than a regular breaker as far as I know. However, the breaker itself should be listed as CTL if you have a CTL panel so you don't stick it in the wrong slot (meaning a breaker slot not meant to take a tandem breaker). Panels that do allow tandem breakers only allow them in specific places.

Sorry for the belabored response and I hope I don't sound like a jerk as that is not my intent. I have learned the hard way during the last 5 years of renovating a 110 year old house that just because something is there doesn't mean it is right. I'd hate to be the guy that says "yeah go ahead" and then later find out you had a fire or fried your $$$ AV equipment.
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post #10 of 11 Old 01-17-2013, 09:38 AM
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Just to clarify -- you don't use a double-pole breaker unless you are connecting a 240 V load.

There are also what I call "piggy-backed" breakers, where you have, for example, 2 single-pole 15A breakers that fit into a single slot. These are used where you have run out of full-sized slots.
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post #11 of 11 Old 01-25-2013, 01:18 PM
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I'm way late to the party, but:
I would run a 120V circuit, using the 10/2 from the main breaker box to a small breaker box in or adjacent to your A/V room. Then two or three 20Amp circuits to your equipment. Try to locate the small breaker box so the all the 20A runs are short.

Kevin
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