New construction - 20amp outlets and 240V outlets

rawhitSeptember 24, 2013

we are building a new house and being a hometheater buff I would like to install some separate 20amp lines with minimal interference with rest of the electrical system. Is this something we should get done right now through the builder or something that can be easily done later?
Also same question regarding adding some 240V (50 hz?) outlets to be able run european equipment. Are there any concerns we should be aware of if installing these?


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Ron Natalie

It will always be cheaper and easier before the drywall goes up. Just have them run directly from your media room to the main panel.

You can do the same for 240 if you wish, however in my experience most equipment these days uses switcher power supplies that don't care squat about frequency and operate over a wide variety of input voltages.

    Bookmark   September 24, 2013 at 5:50PM
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I am not sure how you are going to get 50 Hz cycle frequency though, even if you install the correct outlets.

As for the outlets, I would have them run with an independent ground, and not shared, that will minimize the interference from other devices. Independent circuits would accomplish this and would be cheaper and easier done early.

    Bookmark   September 25, 2013 at 7:03AM
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Thanks for the replies.
240V circuits it seems may not required except for some equipment which can draw in excess of 2200W (don't have any such equipment now) are explicitly designed to work only for 240V (max safe limit for 120V 20amp circuit would be around 2000W?)

thanks for the suggestion on independent ground. Will discuss that with the builder. I guess my question about 50hz shows how clueless I am :)
I am guessing its not possible to do 50hz without some additional transformer etc. My primitive understanding is that 50 vs 60 hz may not be important as most equipment are able to tolerate that variation in freq.

I guess I will go with one 20amp line for the rooms where dry wall is being put up now should be able to add additional 20amp outlets when we finish the basement later?

    Bookmark   September 25, 2013 at 9:42AM
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Ron Natalie

The word is "isolated ground" but unless you have metal conduiting or subpanels in the path between the receptacle and the main panel, there's your ground is already isolated as good as it's going to get.

    Bookmark   September 25, 2013 at 10:10AM
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That is correct, and is most useful in factories and such with lats of florescent lights and/or motors.

What I was trying to convey was for the stereo equipment, he should run dedicated circuits. Homeruns without daisy-chaining multiple outlets. Granted this may be a negligible improvement, but compared to cryogenic treated power cords, it is cheap.

    Bookmark   September 25, 2013 at 12:42PM
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Ron Natalie

I agree on dedicated circuits. Isolated grounds were derigeur when we were doing sensitive computer or medical stuff in conduit, but for NM and plastic boxes, there's just no difference between the case ground and the isolated one.

    Bookmark   September 25, 2013 at 4:27PM
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You could put in 240V outlets if you wish. But if it is a dedicated circuit, you could make it 120v now and convert at the panel later(switch from one breaker to two). I'm guessing that any Euro stuff you might buy is going to be less than 20 amps, unless you're talking about a gonzo power amp.

    Bookmark   September 27, 2013 at 9:20PM
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... that would be one intense household amplifier.

My PA is 1500W, and setting it up in my livingroom causes pain in the majority of my houseguests. If you need more than 20A @ 240V you can forget about a timely recovery!

    Bookmark   September 30, 2013 at 1:21PM
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Thanks for all the responses!
So if I get it right I need dedicated circuits but need not do anything for isolated ground?

My current speakers are very efficient and wouldn't need anywhere near 1000W. I am more concerned about the subwoofer (link added). I would definitely have one sub and if required a second one later.
The spec tab says "2500 W RMS short-term"

Here is a link that might be useful: JL Audio F113

    Bookmark   September 30, 2013 at 1:56PM
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Ron Natalie

"Shortterm RMS" heh That's sort of a non-sequitor. The thing has a 15A 120V plug on it. There's no way that it's consuming more than 1800W input power. I suspect it's only temporarily exceeding 1500W by the fact that it's stored up energy in big power supply caps.

    Bookmark   October 1, 2013 at 9:26AM
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