Multiple dedicated 20A circuits for AV equipment closet or ??? - AVS Forum
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post #1 of 17 Old 10-08-2013, 05:53 PM - Thread Starter
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When my home was built I had the electrician run three dedicated 20A outlets to my AV equipment closet under the stairs. At the time I requested this with the assumption that I would need that many outlets to power my equipment and that having them dedicated would allow for more robust power hungry equipment to be run, and therefore "future proof". The basement was unfinished but the outlets are in place. I'm currently building my dedicated HT and am wondering if I was wrong to do the electrical this way...

Should I have just done one dedicated 20A outlet and used a power conditioner/UPS that has one connection to a single wall receptacle with multiple outlets on the unit for the equipment?

Should I add or change anything to my existing circuits? I'm not concerned about battery backup but would like to eliminate the potential for ground loops/hum within my speakers... My house doesn't have a whole home surge suppressor or anything...
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post #2 of 17 Old 10-10-2013, 02:32 PM
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That was a good call.  Of course it depends on what kind of equipment you are installing as to the draw requirements but more is always better.  Bad news is you will want a power conditioner in front of each line you are using.  You could just install one good conditioner and run an AV receiver, sources and control system no problem and never exceed to capabilities of the line or conditioner.  Only if you decide to run multiple high current amps will you need to use some of the other outlets (and conditioners).  The biggest draws on current are typically the AV Receiver, the sub(s) and the display.  The sub and display are usually across the room so they don't even come into play with your equipment room (usually).  Conditioners even out the line voltage (clean power is a good thing) but they don't do much about hum.  Usually hum happens because your source and display are on two different phases.   When a house is wired they service entrance brings in 240v two phase.  At the main breaker panel the electricians break this out to run one phase to one side of the house and another phase to the other.  If your AVR is on one phase and display on the other then you can get hum.  Fixing that is usually trial and error and involves things with wire cutters that I probably shouldn't mention..   Easy way to avoid the problem is to run TV or projector power back to the equipment room and then there's zero chance of hum typically.

Sorry for the brain dump.. it's been a long day

-Rob

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post #3 of 17 Old 10-10-2013, 03:29 PM
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+1 on the good planning, I have 2x30A and 2x20A circuits feeding the HT equipment in the basement which then feed the in room equipment and the projector so everything is on the same phase but spread across the circuits.
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post #4 of 17 Old 10-10-2013, 03:46 PM
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They're on the same leg, not phase. The whole breaker box is the same phase, with two different legs. Unless, of course, your house is some mansion with a 3phase panel, which is somewhat rare.

Amps = watts/volts or watts = amps x volts


So really you can wager an educated guess as to whether or not a single 20amp circuit will do. Remember too, the chances you'll run at peak wattage or amperage is slim to none.
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post #5 of 17 Old 10-10-2013, 04:54 PM
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Quote:
Originally Posted by jbcain View Post

They're on the same leg, not phase. The whole breaker box is the same phase, with two different legs. Unless, of course, your house is some mansion with a 3phase panel, which is somewhat rare.

Amps = watts/volts or watts = amps x volts


So really you can wager an educated guess as to whether or not a single 20amp circuit will do. Remember too, the chances you'll run at peak wattage or amperage is slim to none.

Not true.  The two hots in the breaker box are out of phase relative to each other.  That's why X10 devices require a phase coupler to bridge the two sides.

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post #6 of 17 Old 10-10-2013, 05:38 PM
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Bud, I'm a journeyman lineman and posses an electrical engineering degree. Let me explain a couple things; the SINGLE phase transformer outside of your house is just that, a single phase of either a Wye system or delta. While it may have two actually phases to it, merely to obtain voltage, it is a true single phase in a vector. Now, if I could visually show you how a vector works, this would be a simple lesson, but I hate referring to source material of other's websites so ill verbally explain the best I can. Most common these days is a single phase padmount transformer. It is single phase high side and therefore contains a single vector line. To obtain your 120/240 aka 110/220 your secondary vector line too, only contains a single vector line, but if you take that line and draw a dot in the middle of it, and one at each end, from center dot to either end is 120volts and end dot to end dot is your 240, all while still being the same single.phase vector line. These individual legs are not phases, they are legs of the same single phase.
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post #7 of 17 Old 10-10-2013, 06:11 PM
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I think we're dancing around two different concepts and calling them the same name (blame my working knowledge and ignorance of the theory).  No matter what the mechanism to get power in your house when it gets there you have two hot lines and a neutral.  Each of those hot lines are out of phase with each other.  Those are split up to divide the load of the house.  Put a TV on one line and put a bluray player on the other line and connect them with an HDMI cable.  More than likely you will have rolling purple bands across the screen due to the phase difference between the two lines.  As a bonus you probably now have 60htz hum coming from your speakers too.  I deal with this daily and usually solve the problem intelligently (as opposed to the wire cutters method).

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post #8 of 17 Old 10-10-2013, 07:05 PM
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Considering I use my journeyman ticket on a daily basis, i'd like to consider myself hands on since I've been doing it for 10 years. Don't confuse me with some guy sitting behind a desk, i went to school to get my EE while i was an apprentice. While the two LEGS are 180 degrees "out" from each other, they are still not phases. Your terminology is inaccurate in any field dealing with electricity and may be confusing for people that don't know any better.
REAL "phases"


a SINGLE phase transformer with two hot LEGS and a neutral on ONE secondary phase winding (center tapped neutral and far tapped legs)
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post #9 of 17 Old 10-10-2013, 08:19 PM
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Hey, I'm not arguing with you.. (much)  ;-)   when you say "out" that's short for "out of phase" as in the sine waves are opposing.. I know it's pedantic, but from a low-voltage guy that's pretty much the definition of "out of phase".  We're losing sight of the intent of the thread though.  Point being, More Romex = Better.  Better still if the electrician on site is your buddy and wires all of your AV stuff in purpose.  FWIW, I had 9 20A dedicated lines for my theater and I still ran out...

 

 

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post #10 of 17 Old 10-11-2013, 04:58 AM
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Now THAT'S a thing of beauty...
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post #11 of 17 Old 10-11-2013, 10:16 AM
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I plan to deal with this issue by installing a 230 V 30 A feed to the equipment closet, and using an isolation transformer to give me 60 A 120 V 5 kVA in several 20 A circuits (Exactpower Powercore EP5). Not inexpensive, but it addresses all the issues about common grounding, everything on the same "phase", etc. This is the method recommended by the Erskine Group.

In my last (current) theatre, I installed a small (60A) panel in the equipment closet, and carefully grounded everything to a common point in that panel. That worked well to prevent ground loops and hum. Short runs to the common ground and common power bus are helpful in preventing ground loops.
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post #12 of 17 Old 10-11-2013, 01:51 PM
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Quote:
Originally Posted by LeBon View Post

I plan to deal with this issue by installing a 230 V 30 A feed to the equipment closet, and using an isolation transformer to give me 60 A 120 V 5 kVA in several 20 A circuits (Exactpower Powercore EP5). Not inexpensive, but it addresses all the issues about common grounding, everything on the same "phase", etc. This is the method recommended by the Erskine Group.

In my last (current) theatre, I installed a small (60A) panel in the equipment closet, and carefully grounded everything to a common point in that panel. That worked well to prevent ground loops and hum. Short runs to the common ground and common power bus are helpful in preventing ground loops.

Sounds like a good plan.  That was our intent at first but quite frankly we ran out of time.  We had an engineer in California that specialized in grounding ready to fly out and work with out electricians and install an isolation transformer but like I said, time was against me.  Had to settle for the 20A lines (all of the amps ran on 240v).  In total I had 3 300Wx2 amps, 4 700Wx2 amps and 2 250Wx7 amps.

 

(pardon the mess)

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post #13 of 17 Old 10-14-2013, 07:34 AM
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Quote:
Originally Posted by robertintemple View Post

Sounds like a good plan.  That was our intent at first but quite frankly we ran out of time.  We had an engineer in California that specialized in grounding ready to fly out and work with out electricians and install an isolation transformer but like I said, time was against me.  Had to settle for the 20A lines (all of the amps ran on 240v).  In total I had 3 300Wx2 amps, 4 700Wx2 amps and 2 250Wx7 amps.

(pardon the mess)




Temple! you guys sound like your very knowledgable on the very latest problem I'm having. I've got a pretty nice setup , my theater is dedicated and I have the flexibility to do as I need. You can see photos in my profile, I wish that I could isolate a hum in my room. I've disconnected just about every thing and can't find the source. When I turn my avr off I can still here a hum, I have all separate amps,if left on the amps still have a hum even with the avr turned off. I hope you can chime in and give me some help.
Thanks very much for any assistance .





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post #14 of 17 Old 10-14-2013, 08:18 AM
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I had the exact same problem at another media room I did.  I had an AVR (Integra) running as just a pre/pro.  Had some separate CAT amps running the speakers.  It was a large rack (well, 2 actually..  2 54u racks) and I had 4 Panamax MB1500 conditioners.  The AVR was on one conditioner and each CAT amp was on a separate conditioner.  I had a small but noticeable hum at all times.  It wasn't the HDMI to the tv (which was my first thought since it was on a dedicated circuit) so I kept fiddling.  Eventually I found the problem... I made a short grounding cable and grounded the chassis of the CAT amps to the same conditioner the AVR was plugged into.  Hum disappeared immediately.  YMMV but it's a good place to start.

-robert

 

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post #15 of 17 Old 10-14-2013, 09:45 AM
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Robertintemple thanks for the information. I will certainly try this and keep looking for the source, you got me thinking about the phase you guys are talking about, and separate lines. I only have two that go to my room everything is hooked up to the same 20amp circuit. That includes lights,projector and all six crown xls 1500 amps. Three amps bridged (1550) watts for the lcr's and three amps for surround duty at 525 watts x six. Also five Rythmik subs, two dual 15" (600)watts plate amp for each cabinet times two at the front and one dual 15" (800)watts plate amp at the rear along with two separate single15" (370)watts each flanking at the rear. Total of eight identical subwoofer drivers.
Thanks





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post #16 of 17 Old 10-14-2013, 10:18 AM
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Wow, nice setup.  As you might glean from my profile I'm a big fan of the More Subwoofers=Better club.  What pre/pro are you using?  Are you connected XLR to the amps?  The Integra I was using as a pro/pro didn't have a grounded plug.  If I connected the Integra and the CAT amps to the same conditioner I got hum until I ran a ground wire from the grounding post on the Integra to the chassis on the amp.  But, when I had them on different conditioners (on separate circuits) grounding the Integra to the amp caused MORE hum.  Final solution was to ground amp chassis to the conditioner the Integra was plugged into (and like I said, the Integra power cord didn't have a ground connection on it).  Ground loops are the most squirrelly problems to fix.

-robert

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post #17 of 17 Old 10-14-2013, 12:46 PM
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Quote:
Originally Posted by robertintemple View Post

Wow, nice setup.  As you might glean from my profile I'm a big fan of the More Subwoofers=Better club.  What pre/pro are you using?  Are you connected XLR to the amps?  The Integra I was using as a pro/pro didn't have a grounded plug.  If I connected the Integra and the CAT amps to the same conditioner I got hum until I ran a ground wire from the grounding post on the Integra to the chassis on the amp.  But, when I had them on different conditioners (on separate circuits) grounding the Integra to the amp caused MORE hum.  Final solution was to ground amp chassis to the conditioner the Integra was plugged into (and like I said, the Integra power cord didn't have a ground connection on it).  Ground loops are the most squirrelly problems to fix.
-robert


I'm following your thread on the very hi-end build very cool! Yeah the idea of more subs the better I like it, all about balance with that many subs. I use a denon 4311ci none of it's amps, and no XLR on the denon. The amps have XLR and can at some time use a different pre/pro but for now I'm looking to change my projector first real soon. Anyway i'm gonna hookup a new circuit box I ran out of circuits on the main box just need to do some more research before I DIY it not sure how many I should go with. Concerns about phase as you talked about earlier. I've done electrical many times before with due safety,however I always get as much information before doing such a project. Wish me
Luck.




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