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15 amp circuit sufficient? My results........


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15 replies to this topic

#1 of 16 OFFLINE   JimmyK

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Posted August 04 2003 - 03:05 AM

I've read many posts regarding this topic. It seems many prefer to hook up their system to a dedicated 20amp circuit to meet their system's demands. Looking at my system, I became concerned that my 15 amp circuit wasn't sufficient. My system contains a Pre/Proc, three high current 2 channel amps (two Hafler DH200's, one Parasound HCA75) powering 5 speakers of average efficiency, a Yamaha DSP-1 sound processor, one DVD player, one CD player, one VCR, one MD player, 40" 16x9 rear projection HD ready TV, SVS 16-46PC+ powered sub. ( I think I mentioned everything). Total room volume is approx 5500 cubic feet (room has high ceiling). All these components are powered through a single 15 amp outlet. I decided to see how much current my setup draws under real world conditions. After all, it's extremely unlikely that all my components would be drawing maximum power at the same time. Armed with a amp meter, I put in on the hot lead in the breaker box, turned on all my components, put in Lord Of the Rings, and cranked it up as loud as I could stand it (which was VERY loud! The battle scenes sounded spectacular!) The result? Maximum draw was only 4.7 amps. I was very surprised, and glad, that it was this low. Looks like in my situation, a 15 amp circuit is plenty. It would be interesting to know if those of you who installed 20amp circuits actually tested to see it was really needed. JimmyK PS - My applogies if this post is in the wrong section.

#2 of 16 OFFLINE   Yogi

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Posted August 04 2003 - 04:00 AM

I have a 15 amp circuit but I always knew I wouldn't be drawing anywhere near even 10 amps so I am totally at ease knowing that my HT equipment is more than adequately powered with my 15 amp circuit.
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#3 of 16 OFFLINE   Jason.Soko

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Posted August 04 2003 - 04:34 AM

We can only hope this 20amp circuit obsession will end with more results like this. Highest I've ever seen a system go was a full mcintosh system running at like 6-7amps.
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#4 of 16 OFFLINE   alan halvorson

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Posted August 04 2003 - 05:08 AM

I used to own a Krell 200 watt/channel class A stereo amplifier. According to the spec sheet (I didn't measure it), it drew 15 amps continuous! The thing ran hotter than blazes (as all true class A amps do) - in the winter, I had no need for any other heat source in the room. A couple years ago I was playing the remastered Iggy Pop cd, Raw Power, as loud as I could stand - actually, louder than I could stand. I was trying to see how loud I could get my system. My amp at the time (still is) was a Crown Macro Reference rated at 760 watts/channel that drove a pair of Legacy Focus speakers (higher than average efficiency). I don't recall on which song, but my 20 amp circuit breaker tripped. I have not played anything near as loud since. So, it all depends on the equipment you're using, how hard it's driven, and what else is on the line.
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#5 of 16 OFFLINE   Wayne A. Pflughaupt

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Posted August 04 2003 - 10:46 AM

Great info, Jimmy. Always happy to see someone “put to the test” some of the things passed around as fact on these forums. I for one would have expected to see that much equipment (and especially that many amps) pulling close to max in a load test, especially in a room as large as yours. That said, I think it’s easy to explain the popularity of 20A circuits. It’s widely held that a dedicated circuit is the preference for a serious home theater system (and I happen to agree). Since most house wiring is 12ga., “upgrading” from a 15A to a 20A circuit is as easy as changing the breaker. Regards, Wayne A. Pflughaupt
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#6 of 16 OFFLINE   Jason.Soko

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Posted August 04 2003 - 11:11 AM

I won't argue the need for a dedicated line to reduce power noise. But higher amperage is not necessary.
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#7 of 16 OFFLINE   MikeNagy

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Posted August 04 2003 - 12:25 PM

Are you guys talking about a dedicated electrical circuit in your house? As in, your HT system has its own breaker switch? Never thought about doing that before.....

#8 of 16 OFFLINE   kevitra

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Posted August 04 2003 - 04:12 PM

I ran one (15A) because when my amp turns on my lights would dim for 1/2 second. If I turned on the amp and lights at the same time the breaker would blow. It doesn't sound like a big deal, but I have X10 in my house and my family room lights turn on when my system is turned on (if I want them to turn on). I figured it would be nice to keep the lighting off of the same path as the HT for noise issues, and stop blowing the breaker.

#9 of 16 OFFLINE   DaveHo

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Posted August 05 2003 - 06:53 AM

Current is measured by putting the meter inline with the hot wire. How did you measure current without disconnecting the hot wire from the breaker? Maybe I misunderstood something you wrote, but it sounds to me like you did not measure correctly. -Dave

#10 of 16 OFFLINE   JimmyK

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Posted August 05 2003 - 06:59 AM

[quote] That said, I think it’s easy to explain the popularity of 20A circuits. It’s widely held that a dedicated circuit is the preference for a serious home theater system (and I happen to agree). Since most house wiring is 12ga., “upgrading” from a 15A to a 20A circuit is as easy as changing the breaker. [quote]

I would also prefer a dedicated circuit for my system. However, due to several reasons (floor plan, house on slab, 14 gauge wire used on 15 amp circuits) it would have been quite a project to install a dedicated circuit in that room.

Fortunately, I'm in good shape with the existing circuit and can stop worrying if the circuit will trip during a movie or if I'll see flames start shooting out!Posted Image

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#11 of 16 OFFLINE   Wayne A. Pflughaupt

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Posted August 05 2003 - 07:25 AM

[quote] However, due to several reasons (floor plan, house on slab, 14 gauge wire used on 15 amp circuits)... [quote] 14ga. is within spec for 15a circuits.

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#12 of 16 OFFLINE   JimmyK

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Posted August 05 2003 - 07:53 AM

[quote] 14ga. is within spec for 15a circuits. [quote]

Correct. But is not up to spec for 20 amp, hence, the reason I could not just switch out the breaker. Because of the location of my living room/HT room, installing a dedicated circuit, whether 15 amp or 20 amp, would require new wire run to a room that is not easily accessable.Posted Image

Fortunately, I do not suffer any noticeable negative effects (ie- noise, distortion, etc) from my system sharing a circuit with other lighting, and I am well within the load capability of that circuit. So, at least in my case, it doesn't make sense to go through any great trouble to install a dedicated circuit.Posted Image

Perhaps in my next house...... Posted Image Posted Image

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#13 of 16 OFFLINE   Chu Gai

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Posted August 05 2003 - 02:06 PM

15 or 20 is not a big thing and if you've got 12 ga wiring, we're talking a couple of cents for the breaker differential.

#14 of 16 OFFLINE   Ron-P

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Posted August 08 2003 - 09:32 AM

I have two 20 amp dedicated lines. I went with 20 amp breakers because I got them at the same price as the 15's.


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#15 of 16 OFFLINE   Trevor_J

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Posted August 11 2003 - 04:09 AM

I've got 1 dedicated 20 amp circuit for my equipment rack, the rest of the room is on a seperate 15amp breaker. I went with 20 amp b/c I was/am building the room from scratch and figured the cost of the wiring and breaker was worth the piece of mind. In my old theater, the basement was already finished so I had to use what was available. I noticed that with the lights on and a movie playing, the lights would dim during bass intensive scenes.
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#16 of 16 OFFLINE   Shiu

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Posted August 11 2003 - 12:25 PM

Without measuring the actual currents with a "clamp-on" meter, using the formula Power=VoltageXCurrentXP.F., assuming P.F.=0.8, maximum power you can input to an amplifier at 110V, 15A is 1320 Watts. Even if we assume a an efficiency as low as 50%, a 15A circuit will still allow an amplifier to provide an output in excess of 650 Watts continuously. Most high power amplifiers would dim lights (just a brink) on the same circuit, or even on different circuits, when it is switched on. The reason is that the start up "surge/or transient" current of a power transformer is much higher than its steady state full load current. Depend on the type of the transformer and the time of switching (i.e., at which part of the sine wave), the start up surge current could be higher than 10 times that of the steady state full load current. So if you have a 1000 VA transformer, the surge current could approach 100A (again, it depends on a few things)! albeit for an extremely short duration, but long enough to dim the lights. The current will decrease to its steady state momentarily. The lights should not dim after that, unless the music content occasionally demands extremely high transient currents. Even then, I would think that those huge capacitors commonly found in high power amplifiers should be able to take care of such transient loads.




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