Don't add up amps, it's not the way its done. I count 5 circuits for audio, one for lights and one for AC. Usually you assign 360 VA (watts) to each receptacle plus air conditioning plus lights. The AC (11 amps at 240 volts) is 2,640 VA. The lights are 1,500 watts at most. That adds up to 5x360 + 2,660 + 1500 VA = 6,000 VA. That's only 25 amps because you're bringing in 240 Volts to the subpanel. You're barely going to draw half that under normal circumstances.
Even if you maxed out all circuits at 1,800 VA per dedicated line, that's still (5x1800+2640+1500)/240 or 55 amps at the ridiculous most you can possibly plug into.
Use a 100 amp subpanel with a 60-amp main breaker. At the main panel in the house, pop in a 2-pole 60-amp breaker and run the appropriate wire size (use 100-amp #2 wire @ 60 C) with the appropriate feeders, mind your grounding, and you'll be fine.
Inside, use 20-amp breakers for the receptacle circuits, 15-amp for the lighting circuit and check the manufacturers literature for the maximum breaker size for the AC unit (important at 240 volts).
Finally, put trust only in your electrician. Good luck and have fun towards your new project.
BTW - you'll have enough power this way for a well-stocked woodworking shop. Would add a ton of value to your house. |
Lissnr, You did not mention how far from the house the garage is. Distance from the house main electrical panel, to the new audio room sub panel? You may need to take into account voltage drop. You stated the new sub panel feeder will be buried 18" below grade. Direct burial cable or PVC conduit with single conductors? I would recommend PVC conduit over direct burial. Copper or aluminum feeder conductors? Copper will cost you an arm and a leg..... And I hope you are not thinking of an isolated dedicated equipment ground rod. The equipment grounding conductor shall occupy the same raceway or cable as the feeder conductors and shall terminate in the same panel as the feeder conductors, NEC. I'm expecting the main breaker on the house side of it to probably only be 100 amps? as well as the main breaker on the sub panel to only be 100 amps too... mostly because First off you do not need a main in the sub panel, that is unless your local code requires it. If your local code does not require a main then all you need is a main lug only panel. The sub panel and sub panel feeder will be protected by the breaker at the main electrical panel for the new feeder. As for the sub panel what brand are you looking at? I would use a panel with copper bus. If you have the money I would go with a Square D NQOB panel board. The bus is copper and the breakers are bolt on. I'm expecting the main breaker on the house side of it to probably only be 100 amps? as well as the main breaker on the sub panel to only be 100 amps too... mostly because the 100 amp breaker is 1/3 the $300 cost of the 125 and I can't imagine I'd be drawing that much current all at one time? I do not believe you could install a 125 amp breaker in the main 200 amp electrical panel anyway. It might fit but the panel is not approved for that large of a breaker. Curious, did the electrician say he could? |
Thank you both for your replies, between my electrician's visit today (I picked his brain for well over an hour) and the info. I'm getting from both of you, I'm learning a lot more than I've ever been aware. The biggest lesson I now understand is that a subpanel rated at a certain amperage (ie 125A) can have many more breakers on it, simply to dedicate the individual items, than the total of all the breaker amp ratings combined. This opens up considerably more flexibility regarding lights, A/C, dedicated audio lines, etc.
Gs5556: I will do the breaker designations as you described, namely 5x20A dedicated audio, [probably] a 20A for the A/c unit, and a 15A for the lighting. I also mentioned to my electrician that I was considering the possibility of adding a 1/2 sized refrigerator (like the ones in hotel rooms/college dorms) and he said I should put another 20A breaker dedicated for it alone... (I thought I'd mix it on the A/C line and he said the A/C should have its own circuit...) If I took this whole concept to the max, so to speak, does that mean I could conceivably add one more 20A breaker for "future potential" home theater items such as a surround sound receiver/amps, projector or big screen LCD TV, etc??? This is the time to ask right? No, I can't think of anything else...That would make a total of :
1x15A lights
1x20A A.C
5x20A dedicated audios
1x20A refrigerator
1x20A home theater
and thanks again for the kind words : I hope it does add value to the house!
Jea48: the house panel to garage distance is only about 40' in a straight line BUT I don't have the option of digging that trench for the cable straight due to trees and a patio in the way. My electrician recommended that I run the main (indoor type) wire from the house panel along inside my patio soffit for a distance of 65' until I get to the corner of the house where I can THEN run a junction box of sorts to another 45' of the heavy duty outdoor direct burial cable in an unobstructed trench to the sub-panel placement point. I am not looking forward to delving into a perfectly neat soffit to do this but I think I'm out of options. All cable will be copper.For a few $$$ more you'd recommend housing the direct burial cable in PVC? OK, can you estimate what I.D. PVC I will need? I don't know what size breaker he said he'd mount at the house panel... it won't take a 100A? He kept trying to talk me into exactly what Gs5556 advised: a 2 pole 60 amp breaker... maybe I should listen to the experts instead of carrying on like I think I know what I need....(but if I add the home theater and small refrig options as above is the 60A breaker still OK?)
As for grounding, I asked him if I could run a grounding bar (or two) from the grounding point on the sub panel (yes, I am looking at the Square D QO series... I think it's the
QO11224l125G which I initially picked out on-line). He said I could run 1 or 2 if I wanted, spaced 8' apart both on the same bare copper cable (did he say 8G or 6G???-I'll ask again...). I did not mention to him that I wanted to run Hubbel 5362 I/G's and run each ground wire individually back (to the sub-panel I assume??) using individual 10G solid copper wire for each and every terminal [and that's what's going to the grounding rods] [from the sub-panel]. I know it's labor intensive but from what I read on these forums it's supposed to be worth it and I was going to do all that wiring myself, then the entire job would be inspected by the town inspector (who my electrician notifies for me once he's checked all my work first). This is what I'm hoping... maybe he will let me run the Romex through the studs but won't let me make the actual connections? I'll find out later... right now it's "part 1: get the power to a sub-panel". Input/comments/help/corrections = highly encouraged! and thanks already for all your help fellas. Best regards... |
Hello again, Jea48: OK, I'll tell my electrician that a 2 pole 70A breaker at the main box is good. When you say that the 2 hots and neutral on the main feed from the house should all be 2AWG copper and the ground should be #6AWG, for a total of 4 individual cables from the house panel to sub-panel? I didn't even realize that the ground wire was supposed to return to connect to the main house panel!!
"The sub panel will have a separate equipment ground bar bonded, connected, to the metal panel enclosure."
What do I know? I thought we were going to run a ground wire from the sub-panel via a #6G bare copper wire to an 8'-10' pole hammered into the ground at least 8' from the garage and that was THE ground... Do I still do that, even with the #6G returning to the main house panel [underground and in the soffit] along with the 2 hots and 1 neutral #2G's? BTW, if I use a PVC tube to encapsulate the underground wires will that be a different type of wire/can it be the same as the "in-house/soffit type" as compared to an "underground feeder cable"? I was checking prices on #2AWG copper cable and we're up to at least $2.50 per foot! Does that mean 65' + 45' = 110'x3 runs (2hot,1neutral) for a total of 330' x $2.50ea = $825 plus the 110' of #6 ground @ $xx? per foot? WOW...
Also, when you say the dedicated branch circuit will have 1hot,1neutral,1gnd... you are referring to the individual wire of 12/2 or preferably 10/2 Romex which attaches to the outlet? When you say "No sharing of neutral" what does this imply? I was thinking of running 2 x 5362 Hubbels next to each other 9for a total of 4 plug in points0 per 20A dedicated line... and I was going to place 3 of these on the wall behind my speakers to hook up all the amps, subs, etc, with therefore 2 add'l outlets per 20A line... Does this work in theory? Thanks for all your help. |
I didn't even realize that the ground wire was supposed to return to connect to the main house panel!! Yes it does, as per NEC. I thought we were going to run a ground wire from the sub-panel via a #6G bare copper wire to an 8'-10' pole hammered into the ground at least 8' from the garage and that was THE ground.. Have your electrician read NEC 2005 250.54 Supplementary Grounding Electrode. Page 70-103 Do I still do that, even with the #6G returning to the main house panel [underground and in the soffit] along with the 2 hots and 1 neutral #2G's? BTW, if I use a PVC tube to encapsulate the underground wires will that be a different type of wire/can it be the same as the "in-house/soffit type" as compared to an "underground feeder cable"? I was checking prices on #2AWG copper cable and we're up to at least $2.50 per foot! Does that mean 65' + 45' = 110'x3 runs (2hot,1neutral) for a total of 330' x $2.50ea = $825 plus the 110' of #6 ground @ $xx? per foot? WOW... I said it would cost you an arm and a leg..... You could use aluminum. You would need to increase the size to #1 awg, and the equipment ground wire to a #4 awg. The wire from your main electrical panel in your home to a junction box mounted on the house above the earth could be insulated THHN/THWN copper installed in 1 1/4" EMT metal conduit. You could use 1" EMT per code but trust me it is a bitch pulling 3 #2 and a #6 in 1".... From the JCT box through the earth to the new sub panel XHHW insulated copper wire in 1 1/4" PVC conduit. Also, when you say the dedicated branch circuit will have 1hot,1neutral,1gnd... you are referring to the individual wire of 12/2 or preferably 10/2 Romex which attaches to the outlet? When you say "No sharing of neutral" what does this imply? Multi wire branch circuits. You can have two 120V separate branch circuits sharing the same neutral. Each Hot conductor must be connected to opposite Lines, legs, in the sub panel. One on L1 the other one on L2. With this wiring configuration only one neutral conductor and one equipment grounding conductor are required. Two separate circuits..... But not two dedicated circuits. I was thinking of running 2 x 5362 Hubbels next to each other 9for a total of 4 plug in points0 per 20A dedicated line... Sounds fine. Many will recommend using plastic rough-in boxes instead of metallic. |
Jea48 You have been a guiding beacon in all this. Due to the absurd costs of running 110' of wire through the soffit/underground route I have decided to bite the bullet and attempt the direct route under/beside the trees and under the patio... it's going to be a lot of digging but the soffit looks far too complex to pull apart, not to mention the direct route will save $$$hundreds. I haven't measured the exact distance but it should be between 40' and 50'. As per your recom. I'll probably make it all XHHW #2 insulated copper wire all the way (No need to bother with a junction box just to save a few bucks on the 10'-15' or so that's inside) and then place the external/underground section into 1 1/4" PVC to the sub-panel location. The rest of your advice is very very helpful too (running multi outlets off of each dedicated line), I'll keep you updated. Thanks very much! Best regards and happy Lissn'n. |
Hi guys, Just an update. So far my electrician has scheduled me for the middle of next week. I made some purchases today after listening to more advice from everyone and my electrician as well. GS5556: as per your rec, and my electricians (you both said the same thing) I decided to go with one step up from what you 2 said (2 poloe 60 amp main breaker) and purchased a 2 pole 70 amp instead... I did this because I've decided to go with 8x20A dedicated (bought these breakers today) as well as 3x15 amp breakers (also bought today). I bought the Square D panel which I noted above (12 spaces) and I also bought the optional ISOLATED grounding bar for it. I bought 8x Hubbell 5362 IG's and 2x5352IG's (for 2 of the 15A dedicated lines, I'll be short by 1 terminal for now (remember I have 3x15A breakers) , but this is more than I need to start. The most serious deviation from all our discussion is that because I'm only running a 70Amp main breaker (into the 125A panel) my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service so I shouldn't waste my $$$ on the 2G and just get the 4G... which, although I was hesitant not to continue with "over-overkill everything"... I decided to do the 4G. But, I didn't skimp on the quality : it's the good heavy duty burial designated cable -referred to as XLP cable (supposedly doesn't need to be PVC encapsulated) though I will OF COURSE be running it through PVC anyway. I also didn't skimp on the ground for it... while everyone told me the ground cable can be one size smaller than the main ones, I didn't do that, I simply had an identical as the other [3] 4g cable made to use as the ground.I figured I owed the system this much at least, considering I didn't go for the 2G. It looks like the 4 pcs of 4G will probably fit 1" PVC but I think I'll use the 1 1/4" instead for ease of use. I'll also run a separate 3/4" PVC for my RPG6 cable (isn't that the cable TV designation cable?) How far away in the 18" deep trench should this cable TV cable be from the main power contained PVC to ensure no interference? If the main power is 18" down can I put the TV cable about a foot or so above it? Jea48: I was looking at the grounding screw on the 5362 Hubbells and while the main hot/neutral leads will accommodate 10g cable (probably an equivalent of a 10/2 Romex). the ground screw sure looks like a lot of work for a 10G ground wire... could I get away with a 12G ground wire there or must it be 10G? What if I ran 12/2 Romex and a 12G ground? I know it's designed for that (into a 20A receptacle) but I always hear talk on these threads that 10G is worth stepping up to. Any opinions, anyone? Thanks again guys, and I'll keep you updated. Happy Lissn'n. |
I also bought the optional ISOLATED grounding bar for it. Why? An isolated ground bar will serve no purpose. I imagine the panel enclosure will be mounted to wood studs and the branch circuit wiring will be NM-B cable. (Romex is an example of NM-B). How does your electrician plan bonding the panel enclosure to the main electrical systems equipment ground? Is he going to install two equipment grounding conductors from the main electrical panel to the sub panel? One for the isolated equipment ground bar and one for the panel enclosure? The most serious deviation from all our discussion is that because I'm only running a 70Amp main breaker (into the 125A panel) my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service so I shouldn't waste my $$$ on the 2G and just get the 4G... which, although I was hesitant not to continue with "over-overkill everything"... I decided to do the 4G. NEC 2005 Table 310.16 #4awg 60 C is good for 70 amps, not 100...... Because of the distance from the main electrical panel to the sub panel I would have stuck with the #2awg minimum. my electrician and the guys at the electric supply store told me 2G wire is way overkill and that 4G can handle 100A service The guys at the electrical supply store are not electricians. Did you ask to see your Electrician's Electrical License? You are not installing an electrical service. You are installing a feeder and a sub panel. NEC does allow # 4awg for a 100 amp electrical service. But in most cases the service entrance conductors are less than 25 ft. In your case the larger feeder wire is for voltage drop due to the air conditioning load, small refrigerator, as well as the dynamic demand your audio system's Power Amp/s may present on the feeder. You want the voltage not to fluctuate with load changes as much as possible. I also didn't skimp on the ground for it... while everyone told me the ground cable can be one size smaller than the main ones, I think they confused the neutral, (The Grounded Conductor), with the equipment ground, (The Grounding Conductor). NEC 2005 Table 250.122 Minimum Size Equipment Grounding Conductors for Grounding Raceway and Equipment. 70 amp breaker - minimum #8 awg copper. I said go with a #6 but I think for an audio system a larger wire would probably be better. |
Uh oh? The term "Voltage drop" can send shivers down my spine...Assuming this 4G wire couldn't possibly be returned, as it's already cut, it sounds like I can do at least 2 things to minimize the voltage drop:
1) "Pre-cool" the room w/ the A/C before I go in to listen (which is what I normally do anyway due to the noise)as my amps are warming up (about 1/2 hour which should be plenty)
2) Forget about the small refrigerator completely (I shouldn't be promoting liquids in the room anyway!) (or, worst case, have a plastic beach cooler instead).
"...as well as the dynamic demand your audio system's Power Amp/s may present on the feeder. You want the voltage not to fluctuate with load changes as much as possible."
The overall [cable length] distance from main box to sub panel will be about 50' (twice the 25' you had mentioned)...W/ no A/C [or refrigerator running] can I feel pretty confident that I won't have a noticeable drop (if any at all) in power to my system at this distance/scenario? At this stage of the game, if I have to consider $400 of cable (I bought extra extra length to be sure not to have underestimated) a worthless stack of novice blunder...then pay an additional $4-500 for the right stuff (the 2G)...now's the time to do it. I'll bite the bullet if I have to... especially if this is fundamentally critical to the best sound my system can deliver...In the big picture of things, it's like getting stuck with a new I/C or P/C that didn't synergize with your system but simply can't be returned (or ever re-sold!) ouch!! (but I'd really rather not!)
As for the separate ground...I'll ask my electrician (who came highly recommended from a contractor friend of mine)and who claims to be fully licensed...what I will do there. The Hubbell I/G outlets can still be used anyway, yes? Even if they're simply grounded back to the sub panel's standard grounding bar?
Yes, the sub panel will be affixed to 2 sheets of 3/4" plywood attached to the wood walls (I'm using 3 sheets of 5/8 drywall on all the main walls for sound proofing purposes and I need the 2 pieces of 3/4" ply to get the cover of the panel out enough to be about even with the drywall).
Needless to say, I'm anxiously awaiting your advice.
Pensively. Thanks again. |
At the beginning you mentioned installing dimmers. Dimmers are bad for RFI. I'd recommend just using lower watt bulbs and/or more light switches to turn on seperate lights for progressively more lighting. Possibly even use low voltage lighting when listening for a softer ambient feel. |
The overall [cable length] distance from main box to sub panel will be about 50' That's a far cry from 110' you posted earlier...... If the run is only a total of 50' then #4awg copper should be fine. As for the separate ground...I'll ask my electrician (who came highly recommended from a contractor friend of mine)and who claims to be fully licensed...what I will do there. Ya, post back his response if you would. The Hubbell I/G outlets can still be used anyway, yes? Even if they're simply grounded back to the sub panel's standard grounding bar? Unless you just like the orange color of the receptacle why did you spend the extra money for isolated ground receptacles? Isolated ground receptacles are used in commercial and industrial facilities where EMI noise on conduit, metal studs and steel are a problem. I assume you will be using wood studs with MN-B cable and plastic rough-in boxes. Essentially the non IG Hubbell will work just as an IG ground type in your instance. For the Power Amp/s I personally would go with the Hubbell HBL8300H ("H" stands for non plated) |
I would recommend "Lutron" Dimmers! |
Whew!! I feel much better.... 50' shouldn't be a problem w/ the 4G. Thank you!
Should I still minimize the use of A/C while listening I guess?
I looked up those Lutron dimmers... they look great. They'll all be on a separate dedicated 15A line so I don't expect an impact of their use on my main system??? (as this is mainly why I'm going separate lines in the first place).
I'll let you know what my electrician says about the isolated grounding bar/from the I/G outlets. Thanks again. |
I'll let you know what my electrician says about the isolated grounding bar/from the I/G outlets. Thanks again.
Lissnr It is a Myth that the earth has some mystical magical power that sucks RFI/EMI noise from an audio system. Though I do not advocate lifting the equipment ground , no equipment ground for an audio system seems to be the best. More and more audio equipment manufactures are building their equipment with double insulated AC power wiring thus eliminating the need for the safety equipment ground. . |
Jea48,
Wow thanks for this info and link to presentation paper from Whitlock. An excellent summary. My personal experience matches this exactly.
1) Items not plugged into the same breaker/mains socket but coupled together sometimes give problems hum/hiss - it can be a significant issue, pain in the @#$%!.
2) I have found XLR balanced is by far the way to go for the least troubles - but this is sometimes not perfect - now I know why - real world imbalances.
3) If I ever get a nasty hum/hiss problem I now know to look for a Jensen transformer such as the ISO-MAX® PI-2XX. |
