Are you feeding the sub panel with 120V only or 120/240V?
If 120/240V every other breaker down each side is the same Line, leg. Hmmm...good question. When the electrician scouted the job, he took a quick look at the panel. He said that he would use one of the two vacant slots in the panel to tie the feeder line to. Don't know if he specifically checked the info on the panel door or not, but it was he that came up with the recommendation for a 100 amp sub panel. He told me specifically that I'd need to get a 100 one-way amp breaker for the main panel. (I take it that he meant a single pole 100 amp breaker.) He also said that I should have a 100 amp main breaker in the sub instead of a lug only load center. But after thinking about it later, I couldn't see the need for it, so that's why I threw the question out here. I thought because he would be tying into only one place on the main panel...using only a single pole breaker...that this meant the feeder line was tied to only one leg, and therefore only 120v. On the other hand, he did specify the feeder line needs to be a 3 conductor wire, so perhaps he does intend to feed 120/240V? If so, I'll be sure to use every other breaker in the sub panel in order to keep everything on the same phase. I think my next step is to work out some of the above details with the electrician that's going to do the job. No need to expect folks here to take up anymore of their time to help fill in gaps that I can run down by other means. However, I couldn't have got this far without the help of Jim (Jea) and others who provided guidance. Nice thing about forums with decent search engines like this one is that threads like this can help other folks down the line for a long time to come. I think I've learned that while there's a strong argument for using only one dedicated circuit to feed all interconnected equipment, others find advantages in having all analog and all digital on separate circuits. If a single dedicated line isn't practical, it would seem adviseable to at least branch all lines for interconected components from the same panel in an effort to avoid ground loop issues. Wiring phase for both the lines and the equipment is an important part of the equation and needs to be checked. And finally...in spite of what smattering of knowledge a laymen might gain, wiring in additional electrical capabilites is serious business that's best left up to a certified pro. I'm sure there are several other points others have made that I failed to mention. I'm also sure there are a dozen other aspects that haven't been brought up, so if anyone wants to chime in with other pointers, I'm certainly willing to listen. |
One question I haven’t nailed down as yet: Do I need to buy both a 100 amp (or, perhaps the 60-70 amp you mentioned) breaker for one of the two available slots on the main panel AS WELL AS a 100 Amp main breaker at the sub panel?
The sub panel does not need a main breaker. Buy a main lug only load center. BTW, thank you for your tip about making all the wiring for the circuits off the subpanel the same AWG. I had thought about using 10/2 for the mono amp circuits and 12/2 for the rest. Your advice about not using a mixture of AWG is appreciated.
That was someone else but I agree..... As short as your branch circuit runs are you could use 12-2 W/G for all the branch circuits.The electrician would probably give you a big hug as well.... 8' to 20' branch circuit runs, call me cautious but I would try to keep them with in a couple of feet of each other. No coiling up though... A couple of final questions if you don’t mind…with a 100 amp subpanel in mind, the electrician had recommended a #3 AWG copper cable for the feeder line. I assume this means a 3 conductor solid core cable with safety ground wire…right?
Per UL for sizing the over current device,(breaker), for #2 awg wire and smaller use the 60* C column. #3 awg THHN/THWN copper wire is good for 85 amps. If you look inside your 200 amp panel some where on the side you will see an info label. The label will say what the maximum allowable size branch circuit breaker that can be installed in the panel. Just guessing 80 amp. Check your panel. In most cases the lug size on a 60 amp breaker is for a maximum size wire of #4 awg. You would have to use at least a 70 amp breaker for #3 awg wire. The maximum lug size for a 70, I believe, is #2 awg. #3 awg wire will be stranded. As far as trying to keep everything in the sub panel on the same leg is concerned…since it is being fed from only one leg off the main panel, does this mean that each and every breaker row in the sub panel is therefore also on this same leg? In other words, there’s no need to skip breaker rows in the sub to ensure the all the audio gear is fed from the same leg?
Are you feeding the sub panel with 120V only or 120/240V? If 120/240V every other breaker down each side is the same Line, leg. Future? I would probably feed the panel 120/240V 2 hots, 1 neutral, 1 equipment grounding conductor. Jim |
Swampwaker…Thanks for pointing out the wording in that section. It made me think about exaclty how the equipment is loaded in my rack. Each piece is, in fact, not bolted to the rail. However, each piece is pushed up against a custom cut metal face plate that MA sells. These faceplates are then bolted to the rails. I started out using the insulating washers, but they were somewhat "fiddly" to deal with, so I wound up with just a few of them. I'll now probably go back and make sure they are installed on each one.
And…just to provide a little more assurance against a ground loop from forming, I think I’ll abandon the idea of trying to use the existing branch circuit coming off the main panel to power the non-audio gear. Seems like it would be better to simply install an additional circuit or two off the sub-panel.
Jea...no, I wasn't planning an isolated grounding scheme. However, just out of interest I read up a bit more on the subject last evening and have a better understanding of its commercial application. I see now that MA's white paper is, as you pointed out, geared more toward that type of install.
The 80' back to the panel is the up, down, and around estimate. Estimate includes some slack, so the feeder wire could turn out to be shorter. For the circuits off the sub panel, I estimate the longest run to be about 20', shortest run could be as little as 8', depending on cross stud placements we encounter in the wall. That is…unless there is an audible or electrical advantage to keeping the runs the same length?
The deal I have with the electrician is that I will buy and have on hand all the materials. Consequently, I’m doing my own research on what all will be needed. Concerning the sub panel… I started out thinking a Square D QO product, but think I’ve instead settled on a 100 amp Cutler Hammer CH panel. According to their product literature, the CH series uses a “Single-Piece Silver Flash-Plated Copper Bus”
My main panel is a CH 200 amp box. I have only two-breaker slots left available on this panel, which is the reason for the sub-panel decision. I have 20 amp breakers in the main, and I plan to use 20 amp breakers in the sub panel also.
One question I haven’t nailed down as yet: Do I need to buy both a 100 amp (or, perhaps the 60-70 amp you mentioned) breaker for one of the two available slots on the main panel AS WELL AS a 100 Amp main breaker at the sub panel?
BTW, thank you for your tip about making all the wiring for the circuits off the subpanel the same AWG. I had thought about using 10/2 for the mono amp circuits and 12/2 for the rest. Your advice about not using a mixture of AWG is appreciated.
A couple of final questions if you don’t mind…with a 100 amp subpanel in mind, the electrician had recommended a #3 AWG copper cable for the feeder line. I assume this means a 3 conductor solid core cable with safety ground wire…right? That is, when I give the big-box store man my order, I shouldn’t have to specify much else? In other words, I don’t need to purchase a separate ground wire also?
As far as trying to keep everything in the sub panel on the same leg is concerned…since it is being fed from only one leg off the main panel, does this mean that each and every breaker row in the sub panel is therefore also on this same leg? In other words, there’s no need to skip breaker rows in the sub to ensure the all the audio gear is fed from the same leg? |
Unfortunately, I think your opinion lines up with mine and gives me reason to believe that a multiple circuit (dedicated or not) might cause more issues than it would solve. BTW, I noticed your comments were specific to equipment connected via IC's. What about the notion that in a metal rack, ALL the equipment loaded into it is interconnected...whether interconnects are present or not? Or am I reading too much into, or not properly understanding,this publication from Middle Atlantic? Not really.... My comments are in regards to using the existing 80 ft 20 amp dedicated branch circuit and branch circuit/s from a sub panel with an 80 ft feeder to feed equipment that would be connected together by ics of equipment fed from the two different fed power systems. Has nothing to do with rather the equipment is rack mounted or not. >>>>>>>>>>>>>> Isolated ground power strip in a non-isolated rack (cont.) A problem will exist due to the fact that all equipment with a 3-prong (grounded) plug has the power cord ground conductor bonded to
the chassis. When this rackmounted equipment is screwed to the rackrail, an inadvertent ground connection will be present, defeating
the isolation!" In the above quoted info the author is talking about commercial building power wiring situations. Problems a person would not normally encounter in a single family dwelling unit, imo. You are not going to use an isolated ground system are you? If you install a sub panel, as you said, about 10 ft from the rack I see no problem. Branch circuit runs will be short, less than 20 ft. (Figuring up and down or around.) 80 ft? Is that straight as the crow flies? Did you figure up, down, and around? In the sub panel you will have an isolated neutral bar and an equipment ground bar. Sizing all conductors the same will a sure both the neutral bar and the ground bar will be at the same ground potential. So if you are worried about the possibility of the neutral conductor and equipment grounding conductor not being at the same ground potential at the sub panel make all the feeder conductors the same size.... Minimum size feeder wire I would recommend, #4 awg copper. Breaker size 60 or 70 amp. Electrical panel, copper bus only..... No aluminum bus. |
Shutterman- the critical words are
"When this rackmounted equipment is screwed to the rackrail,..."
So in an all metal rack, with power cord grounded to chassis, IF every chassis is screwed [aka grounded] to rack, they will all be grounded to each other. OTOH, if you do not rack mount the equipment (or use plastic washers between the chassis and the rack and between the chassis and the screws) they will not be grounded to each other, unless the interconnects make the ground connection. |
Thanks for weighing in Jea, as I know from your posts that you've been around the block a time or two with this sort of thing.
Unfortunately, I think your opinion lines up with mine and gives me reason to believe that a multiple circuit (dedicated or not) might cause more issues than it would solve.
BTW, I noticed your comments were specific to equipment connected via IC's. What about the notion that in a metal rack, ALL the equipment loaded into it is interconnected...whether interconnects are present or not? Or am I reading too much into, or not properly understanding,this publication from Middle Atlantic?
http://www.middleatlantic.com/pdf/PowerWhitePaper4_07.pdf
One blurb that jumped out at me (pg 29): "A problem will exist due to the fact that all equipment with a 3-prong (grounded) plug has the power cord ground conductor bonded to
the chassis. When this rackmounted equipment is screwed to the rackrail, an inadvertent ground connection will be present, defeating
the isolation!" |
The existing branch circuit (which will continue to feed the cable box installed in the rack, the plasma TV in the other room, the wall wart devices, etc.) is terminated and grounded at the main panel 80 feet away. The dedicated lines would terminate, and I assume be grounded at, a subpanel less than 10 feet away.
09-17-09: Shutterman If you are going to install a sub panel, feed all audio equipment that will be inter connected by ics from the sub panel only. Any thing fed from the 80 ft branch circuit and connected by ics to equipment fed from the sub panel will surely cause ground loop hum, jmo..... |
"The trick to eliminate ground loops is to run all of the lines powering your equipment to the same phase (leg) of ground in your fuse box. It is also a good idea to isolate all of the "noisy" lines on the other phase from your equipment. Your electrician should understand this readily."
Understood. However, in the configuration I've detailed above...wouldn't the fact that I'd have interconnected equipment (via the metal equipment rack) on a mixture of a branch circuit plus dedicated curcuits still not cause an issue?
The existing branch circuit (which will continue to feed the cable box installed in the rack, the plasma TV in the other room, the wall wart devices, etc.) is terminated and grounded at the main panel 80 feet away. The dedicated lines would terminate, and I assume be grounded at, a subpanel less than 10 feet away.
I understand that the subpanel itself is then grounded back to the main panel, but wouldn't I still essentially end up with interconnected components (via the rack) sharing two different circuits...circuits that are initally gounded at two different places? If so, wouldn't this establish a large ground loop?
As far using the same phase or leg is concerned...as long as I tie the sub panel to the same leg that the branch cucuit is on, will everything in the sub panel then be on the same leg? Or should I alternately space the wiring(i.e., skip a breaker row) within the sub panel? |
LOL, Bigamp. Quick, name ONE universally accepted answer in audio. I have two dedicated 20 amp lines and usually try to separate the analog and digital. Despite having 2 BPT power strips I usually have too many of one to segregate them. Perhaps there is a valid theoretical answer, perhaps not; but the best application will very with your system, try it as many ways as you can and see what works the best for you. |
Interesting post, and timely. I am involved in a very similar scenario at the moment. There seem to be two conflicting lines of thought here. The first says put everything on one circuit. The second says separate out digital and analog. And what if you have two channel system combined with an HT system? This seems to compound the issue -- do you put your receiver, cable box, and DVD player on the "digital" circuit or does this taint your hi-end CD player's circuit? Seems like there should be a universally-accepted answer on this issue. |
Two factors to consider:
1) Done properly, it is good to run analog and digital components on different lines on the same phase of the fuse box.
2) How much current does your amp(s) draw? If it is a high power model, it will benefit from having its own 20 amp line.
If you want to isolate your analog equipment from the digital (without a power conditioner) and your amp really needs its own dedicated 20 amp line, then you will need 3 lines!
I have not used the Belkin units but I strongly suspect that you will find after installing dedicated lines that your system will sound best without them (it probably will sound better without them now).
If surges are your concern, then use the blue whole house unit that has been recommended numerous times on Audio Asylum.
If you must use a power conditioner (don't just assume that you do), you are right to only consider the SOTA: Synergistic Research Powercell 10SE, Audience aR6-T, etc. You would want to run all of your components through these for maximum benefit (only need one "strong" 20 amp line).
Running two lines is indeed not significantly more expensive that running one as others have said. If it works out the your system works better through a single line, you really haven't lost much money.
The trick to eliminate ground loops is to run all of the lines powering your equipment to the same phase (leg) of ground in your fuse box. It is also a good idea to isolate all of the "noisy" lines on the other phase from your equipment. Your electrician should understand this readily.
Minimizing ground leakage as perfectly described by Inline phil is also a worthwhile exercise. |
"The more components you connect in this fashion, the more ground loops you create. For this reason, it is best to use one lare circuit to feed your system rather than several smaller ones. If you use a line conditioner - as you should - buy one that will handle all of your equipment and run a dedicated line to that. Then plug everything into it."
This is certainly the impression I too have come away with in my readings. This is probably why I don't have any ground hum issues with my current setup. While it is not a dedicated line per se, all the equipment IS plugged into one circuit.
Your comments and the link Danielk provided to BAT Technologies FAQ page (thanks, Danielk!) have started me thinking that using one line to feed everything might be the best solution in my case...especially since the metal equipment rack interconnects a good portion of the gear.
However, my difficulty in doing this is that I have the mono amps in one room, and the rest of the equipment in another. |
"I'm not aware of any "downside" to using dedicated lines.
I do, however, suggest installing two lines -- not much more trouble really -- and then you can separate components as you wish - i.e: front end/amps, digital/analog, motors/electronics, etc."
Well...the downside is the increased potential for ground hum or noise as stated in my post, so I'm not sure I fully understand what you mean. Are you saying that you don't believe such potential exists? If so, I'd certainly like to believe you are correct. However, based on posts from the archives here and on articles posted other places, I came away with the impression that the potiential increases in configurations as the one I cited above.
Regarding the recommendation for two lines...yes, as I stated, plans are for at least two. I would have to have at least two as the amps are in one room while the rest of the equipment is in another. |
You are correct in your concerns. Improper grounding creates ground loops not only internally to the circuit but also from component to component. Fortunately today, most high end equipment manufacturers have learned what the medical industry has known since the introduction of electronic scalpels in the 1960s.
A ground loop is any grounding scheme that can take more than one path to reach earth. So if your preamp and power amp both use a 3-wire grounded plug and you plug them into different electrical circuits and then you ground them to each other with your interconnect cables, you have by definition a ground loop.
The more components you connect in this fashion, the more ground loops you create. For this reason, it is best to use one lare circuit to feed your system rather than several smaller ones. If you use a line conditioner - as you should - buy one that will handle all of your equipment and run a dedicated line to that. Then plug everything into it.
Now this assumes that the transformers inside each piece of equipment have been properly tested and wired for lowest line leakage (properly phased) upon assembly by the manufacturer. Easy to check. Unplug everything from the component and lift the ground wire from that component by using what's called a "cheater" plug. Plug the cheater into the wall outlet and measure the voltage from the ground wire to earth ground inside the wall outlet. Then reverse the polarity of the cheater plug in the wall outlet and measure this voltage again. If the voltage lowers in the reverse direction, the power transformer phase inside that component is wired improperly and should be reversed. Do this for each component and all will be well in OZ.
Even those components using two-wire plugs can have this phasing problem. A similar scenario can be used to test ground leakage voltage by measureing from a circuit ground of the component to the wall outlet (use a ground pin on the component or the shield of an RCA plug).
Balanced component systems have an advantage over single-ended (RCA style) systems here in that they use additional electronic wizardry (called the common mode rejection ratio) to again lower the influences of ground loops and other stray electrical influences imposed on the interconnect cables. |
"You may run into a ground loop hum. If you do purchase a www.jensen-transformers.com/ isolator. I had hum from a powered subwoofer and the cable tv cable"
Thanks...appreciate the link. I knew there were other humbusters out there, but I just didn't think about Jensen. My impression is they make some quality stuff, so this will be a nice link to hang on to. However, I'm hoping to find a way to do the dedicated lines and end up not having the need for something like this. |
Here's an alternative view, from the BAT website.
They prefer one strong (20 amp) line to your entire system.
Click on FAQs:
http://www.balanced.com/ |
I'm not aware of any "downside" to using dedicated lines.
I do, however, suggest installing two lines -- not much more trouble really -- and then you can separate components as you wish - i.e: front end/amps, digital/analog, motors/electronics, etc.
Doak |
You may run into a ground loop hum. If you do purchase a http://www.jensen-transformers.com/ isolator. I had hum from a powered subwoofer and the cable tv cable |
