Probably not what you are looking for however I thought I'd mentioned it:
Somewhere after the sub-panel but before the AC outlet you might consider the installation of an isolation transformer 5 KVA each per dedicated line. This would be dependent upon your logistics because the isolation transformers will generate some heat and 60 dB of hum.
In my basement, I had two isolation transformers in-between my main panel and sub-panel (feeding my sub-pannel) which gave me eight dedicated lines.
|
Have you tried or considered a Jensen line transformer between your source and pre or between your pre and power amp? I realize inserting such a device is taboo on this site because its installed "in the chain", but the Jensen devices are high quality, and inexpensive enough that you're not out much money if you decide it's not working.
|
Are you positive the noise isnt being generated by one of your components?
|
@winoguy17 , that's a good thought. My SS amp has high gain and was boosting the noise level previously on a shared dedicated line. Since I moved my system to a subpanel with a line dedicated to analogue, the noise floor has been greatly reduced.
As a test, I hooked up an old Kenwood amp with much lower power and the noise from the mains was still present.
@yakbob , I tried a Jensen transformer between preamp and amp, but I have an Atma-Sphere OTL pre and the transformer ruined the sonics. I've seen some comments by Ralph(atmasphere) where he says putting a transformer inline with an OTL device can have unpredictable or negative results.
@lak , I like the concept of the iso transformers and looked at how you've implemented them. That type of setup would work in my basement, but cost is a consideration. I will ask my electrician about it and show him your pics, thanks.
|
@lowrider57
How expensive was the surge protector with noise filtering? It would seem to be the right way to go, in my opinion.
B |
@lowrider57 One must look on eBay but you can find used ones at a reasonable price. That's what I did.
What State do you reside in? |
No need to filter at the breaker box! Buy a Chang LightSpeed Line Filter which you can plug all your audio equipment into. Has Digital and Analog AC sockets. Does not limit current inflow! Works great IMO! http://www.changlightspeed.com |
You may be right, gdnrbob. I think the surge/ noise reduction unit was about $700, but I have found some online for less. I get the feeling the electrician will only install the brands that his company uses. He had a binder showing the different units available.
However, he was fine with me providing the Romex and Hubbells for the installation.
@lak , I'm in Philly, PA (a row home). How did you determine the rating of the transformer (5 KVA) for your needs?
@don_c55 , thanks, but I've got a limited budget and I've already invested in Blue Circle and Brickwall PC's plus some Blue Circle line filters.
|
If you feel sure this is a mains noise level issue and not some kind of equipment thing going on, then I would recommend Alan Maher Designs, despite that most audiophiles have little or no experience with them. I’ve been dealing with Alan since 2010 with full confidence in what he says and what he does. I know for a fact he can reduce mains noise levels because this is essentially the kind of problem he handles all day every day.
I know the normal products he would recommend for ordinary standalone homes, but for a row house, you will need to contact Alan directly through his company site on facebook (Alan P Maher, or alanmaherdesigns.net and fb message him, he will respond to your q’s within a day). Don’t worry, he has grounding and noise-reduction expertise with electrical systems worldwide so a row house will not offer him any real challenge. For the said normal house, a good solution with his stuff would be around $300-$350, with always the option to expand from there if you liked what those changes did to the sound quality (the improvements of which being the real attraction to Alan’s approach...reducing electrical noise = much improved sound in all departments, not simply just a reduction in perceived background hiss or audible noise, of course).
Lots easier and just as effective in most cases as dealing with balanced transformers. Installation of the AMD stuff IME is a breeze although it usually takes about 30 days or so to fully come on song, but I’ve found everything I’ve ordered from him to work as advertised to say the least.
Some, or possibly even all, of the products he will recommend to you can be applied directly to the breaker box. |
Thanks @ivan_nosnibor , I'll look him up.
I don't believe it's component related, but tomorrow I plan on removing all power conditioning and surge protectors to eliminate extra circuits and cables.
I swapped the SS with a tube amp tonight and the same amount of noise was audible.
|
A friend suggested the 5 KVA because he knew it was large enough for most audiophiles systems and would not bottom out. Other than that I'm not sure how to figure the needs but I'm sure other more knowledgeable people on Audiogon could assist.
|
lak A friend suggested the 5 KVA because he knew it was large enough for most audiophiles systems 5KVA works out to 5000 watts - assuming you have a good power factor. That might be sufficient for a small system, but obviously undersized on even a 15A line. |
|
For $750 you would be done with the problem, rather than adding another component/layer. Even better if you can buy yourself for less.
Your electrician seems to be a good guy, if he lets you provide materials.
Though, if you let him install the brand he offers, then he will probably stand behind it should anything go wrong in the future. I'd ask him why he thinks his brand is better than the less expensive ones. |
The sub-panel is connected by the hot lead and has it’s own ground including a second grounding rod. Lowrider, my understanding is that a sub-panel should have hot, neutral, and safety ground all wired back to the main service panel, and safety ground (which may or may not be connected from the sub-panel to earth) should only be connected to neutral at the main panel, and NOT at the sub-panel. (Jim/Jea48, correct me if I’m wrong about any of that). Is that how your sub-panel has been wired? More relevant to your issue, though, have you tried powering the entire system from just one of the dedicated lines coming from the sub-panel? I realize that installing the sub-panel and using its two dedicated lines lowered the noise floor substantially. But using separate dedicated lines for digital and analog components, while certainly beneficial in many cases, in some cases can cause or contribute to ground-loop related noise. And perhaps the improvement the sub-panel installation provided occurred mainly as a result of the new wiring, rather than having separate dedicated lines for digital and analog. Especially if the type of wiring was changed when the sub-panel was installed, as there are several ways in which wiring type can affect noise issues. Best regards, -- Al |
Lowrider, my understanding is that a sub-panel should have hot, neutral, and safety ground all wired back to the main service panel
Al, that's what I thought. I asked the electrician about code, and he said it meets code and this is how he wired his house for a high-end HT system. He said not having a ground wire back to my circuit box containing old, poor quality wiring would cut down on noise. I thought, finally I found an electrician who appreciates good audio. One issue about my main circuit box is that it is a mix of new, updated wiring and old wire and breakers from the previous owners. Maybe @jea48 can weigh in regarding adding a subpanel. I'll try using only one line, that's a good idea. This is an upgrade for me and I wanted to get it right. I used Romex 12/2 with Hubbell 20A brass duplex receptacles grounded (not self-grounded). Romex was run from subpanel taking separate routes to the receptacles, same length. |
Get your Self a Industrial Power Conditioner IMHO, Nothing will beat a Elgar 3006.. Atma-Sphere Sells these Pre-conditioned and tested. The ones on Ebay are crap. You should speak to Ralph about this he can advise you on the matter.
|
I asked the electrician about code, and he said it meets code and this
is how he wired his house for a high-end HT system. He said not having a
ground wire back to my circuit box containing old, poor quality wiring
would cut down on noise.
We'll see what Jim (Jea48) says, as the expert on these matters, but that doesn't sound right to me. I assume neutral and safety ground are not connected together at the sub-panel, which would be a definite code violation and would create numerous potential safety hazards, and possibly noise problems as well. Given that assumption, the main purpose of a safety ground is defeated by the approach you've described. Especially if there is a significant distance between the ground rods of the two panels, and/or the soil in between them is dry. If a short to chassis were to develop in anything that is plugged into those dedicated lines, that is not "double-insulated" and therefore utilizes safety ground, the path for the resulting fault current would include the soil between the ground rods of the two panels. The corresponding resistance will likely be high enough to limit the current to too low a value to trip the breaker in either panel, resulting in a shock hazard. Best regards, -- Al |
almargLowrider,
my understanding is that a sub-panel should have hot, neutral, and
safety ground all wired back to the main service panel lowrider57Al,
that's what I thought. I asked the electrician about code, and he said
it meets code and this is how he wired his house for a high-end HT
system. He said not having a ground wire back to my circuit box
containing old, poor quality wiring would cut down on noise.
I'm certain this does not meet NEC and I'm with Al that this creates a safety hazard. @lowrider57 did you get construction permits for this project? Was the work inspected by your town's electrical inspector? |
Are we getting a little ahead of ourselves in
recommending iso and regen type power conditioners assuming the noise at
2 feet in front of the speakers is being caused by coupled or conducted
EM/RF
What if the electrician failed to bond the second ground
rod off the new sub panel to the main ground rod at the house's main
service entrance ... cable guys do this all the time = ground loop
What
if electrician didn't place both dedicated lines on the same phase in
the main panel box as he was only trying to be diligent and balance the
load evenly in the panel box = ground loop
What if electrician's
apprentice after consuming large amounts of Gin and Corn Chips for
lunch failed to tighten or fully insert the neutral wires into the
audiophile grade outlets Lowrider57 spent so much money on or if he was
careless in pushing those expensive outlets back in the wall and
loosened up the neutral wire = lack of continuity = major buzzing
What
if Lowrider57 switches interconnects and components frequently and has
broken a return lead in one of the ICs or has loosened up one of the
male chassis RCAs losing ground = Buzzing
What if Lowrider57 has lost a power supply cap or has a cracked solder joint in one of his component's = buzzing
Will a power conditioner of any type remedy any of this ?
I just lost a 4 year old premium Nichicon power supply cap in my amp and I'm still in denial = buzzing and crying :-(
Shouldn't the first step to problem solution be problem identification
Just saying Enter your text ... |
I assume neutral and safety ground are not connected together at the
sub-panel, which would be a definite code violation and would create
numerous potential safety hazards, and possibly noise problems as well.
Given that assumption, the main purpose of a safety ground is defeated
by the approach you've described. Especially if there is a significant
distance between the ground rods of the two panels, and/or the soil in
between them is dry. @almarg , Now I'm confused and will call the electrician tomorrow. As I understand it, the hot for the subpanel is connected to the main circuit panel. The neutral and safety ground are connected to the subpanel. The main panel has a 8' grounding rod into the earth, the subpanel has a ground rod into earth about 3 feet away. Here's what I can confirm; using only the amp and preamp plugged into the same dedicated line, I get loud 60Hz hum when I power on the Atma-Sphere UV-1 preamp. When using a cheater-plug, I hear low-level hum. This happens on both receptacles/dedicated lines. I have also used cheater-plugs on both components. BTW, no sources or power conditioners are being used. I checked for continuity with a multimeter between chassis and IEC connector safety-ground pin and connection is OK. Performed this on both the amp and preamp. This SE preamp has always caused hum with every amp I own. This is the noise/hum that I've been hearing. |
almarg 7,350 posts07-15-2017 1:27pmThe sub-panel is connected by the hot lead and has it’s own ground including a second grounding rod. Lowrider, my understanding is that a sub-panel should have hot, neutral, and safety ground all wired back to the main service panel, and safety ground (which may or may not be connected from the sub-panel to earth) should only be connected to neutral at the main panel, and NOT at the sub-panel. Al, you are correct. The sub panel feeder Hot/s, neutral, and safety equipment ground conductor are all fed from the same main panel. An Aux earth ground connection, example ground rod, can be installed and connected to the equipment ground bar in the sub panel in addition to the equipment grounding conductor. Again, in addition to the equipment grounding conductor from the main electrical panel, the sub panel is fed from. (I personally do not recommend the addition of an Aux earth ground. Lightning loves them.) The sub panel feeder neutral conductor/neutral bar can not be bonded, connected to the sub panel metal enclosure or the equipment ground bar. The feeder neutral bar must be left isolated/insulated from the metal sub panel enclosure. (Green bonding screw or neutral bonding strap that came with the panel discarded.) If the the feeder neutral conductor/neutral bar is bonded to the enclosure/equipment grounding conductor/equipment ground bar then the equipment grounding conductor will be connected in parallel with the feeder neutral conductor. What happens then is the equipment grounding conductor will carry neutral current back to the main electrical panel, or where the service neutral is bonded, connected to the enclose, equipment ground, and earth. Not good for the equipment grounding conductor to carry neutral current. @ lowrider57 IF you feel confident with yourself looking inside the sub panel I can guide you through things to look for. Something that may be wrong with the way the sub panel is wired. 1) Do you have a multi meter? 2) Is the sub panel wired for straight 120V or 120/240V? What is the approx distance the sub panel is from the main panel, it is fed from? Any idea what size the feeder wires are? What size is the breaker, in the main panel, that feeds the sub panel? 3) Turn off the breaker at the main electrical panel that feeds the sub panel. 4) Verify the sub panel is dead. You can check for voltage at the dedicated circuits outlets first. Use the meter, audio equipment, or a table lamp. 5) Remove the panel cover from the sub panel. 6) Verify 100% the sub panel is dead, de-energized. Use your meter set to auto AC volts or an AC voltage scale above the known voltage feeding the panel. Locate the feeder wires, conductors, and with the meter verify they are dead. 7) What you should see. Feeder wires that enter the sub panel. If 120V only, 1 Hot conductor 1 White color neutral conductor 1 equipment grounding conductor If 120/240V, 2 Hot conductors 1 white neutral conductor 1 equipment grounding conductor. *One of the two above must exist. If Not post back. Do not go any further. Hot feeder wire/s, conductor/s connected to the bus/s of the sub panel, or connected to a main breaker installed in the sub panel. Single pole for 120V, 2 pole for 240V. You will see a neutral bar, with white color insulated wires that connect to it. You should see the feeder neutral conductor, white in color, connected to the bar. You should also see the dedicated branch circuit white color neutral wires also connected to the bar. The bar should be mounted to a factory installed insulating material. Usually the insulator is black in color. Look closely at the neutral bar, (or possibly 2 neutral bars that may be mounted on each side of the 2 Hot bus and circuit breakers), for a green colored screw head that is made to bond, connect, the neutral bar to the metal panel enclosure. If you see one IT MUST BE REMOVED. Remove the bonding screw and discard. Next look for any other wire or metal strap that may be bonding the neutral bar to the metal panel enclosure. If you see one REMOVE IT and discard. No bare wires or green color equipment ground wires should be connected to the neutral bar. Only neutral wires can be connected to the neutral bar of a sub panel. Next thing to look for is the equipment ground bar. It should be mounted/secured directly to the metal panel enclosure. You should see the feeder equipment grounding conductor connected to the bar. The wire may be bare, green in color, or have green marking tape wrapped around the insulation of the wire. You also should see the bare equipment grounding conductor, wires, of your Romex dedicated branch circuits connected to the ground bar. If the electrician installed an Aux earth driven ground rod you will see the ground wire, from the ground rod, connected to the equipment ground bar as well. (Again an Aux ground rod serves no real purpose and may do more harm than good. Especially in the event of a lightning storm.) Any questions? |
@ lowrider57,On second thought, if you see the green bonding screw on the neutral bar or a bonding strap connected to the neutral bar that is connected to the metal enclosure, do not remove it. Post back what you find. Do not change anything in the panel. Just post back what you see. |
@jea48 , Thank you so much for taking the time to share what I consider expert advise and knowledge.
I'm going to email your information to the electrician and we'll find out what is really going on. (I'm hoping that I'm wrong about how the subpanel is wired).
And @almarg , you're always a key resource for any audio issues I have.
What do you fellas think is the issue with the Atma-Sphere preamp (single ended)? It has always caused hum in my system.
It is designed with star-grounding and I confirmed that the safety ground is tied to the chassis. (also confirmed the grounding on the amp). This hum (which sounds like a ground-loop) has been constant even during the time I had the original dedicated line. Before that, I had a Rogue pre with no issues.
Your thoughts?
|
did you get construction permits for this project? Was the work inspected by your town's electrical inspector? @cleeds , I just noticed your post. In Philadelphia, a permit is not required for an electrical addition or upgrade in a residence. The law states that an inspection is required at the time a house is being sold. |
Thanks for the nice words, Lowrider.
Given that when only the preamp and power amp are connected there is a loud hum when a cheater plug is not used and a lower but still significant hum when a cheater plug is used, it sounds like two problems are present. One being a ground loop between preamp and power amp, and the other probably being due to something internal to the preamp, such as some of the possibilities Davehrab mentioned.
I say "probably" because it is also conceivable that what you are hearing when only the preamp and power amp are connected is the result of having the preamp’s high impedance inputs left unconnected and essentially "floating." Unconnected high impedance inputs often tend to be susceptible to pickup of hum and noise, that may even be coupled into them from elsewhere within the same component. Which would have no relevance to what would occur when a powered up source component having reasonably low output impedance is connected. And if you also hear a low level hum when a powered up source component is connected, perhaps that is due to a ground loop between source component and preamp. (Although if I recall correctly you may have sorted out that possibility some time ago with a Jensen transformer and/or a cheater plug).
But to assure that assessments that are performed with unconnected inputs are meaningful it would be desirable to purchase some RCA shorting plugs. A search for "RCA shorting plugs" at eBay will return many sellers offering those at low prices.
Finally, regarding the possibility of an internal problem in the preamp, the next time you are in contact with Ralph (I recall that you’ve discussed this issue with him) you might ask if the UV-1 uses AC or DC on its tube filaments. While I suspect the answer will be DC, if perchance AC is being used I would speculate that a tube problem may be contributing, unless you've eliminated that possibility via tube substitutions.
Good luck. Best regards,
-- Al
|
@almarg ... Thanks, Al. Can always count on you. I thought about using shorting plugs a while back, but now I can't remember if they can be used on the UV-1. I'll reach out to Ralph next. What if Lowrider57 has lost a power supply cap or has a cracked solder joint in one of his component's Yes, it's possible that there is an internal problem. I did use a Jensen, following your recommendation, on the preamp output and the sonics were so terrible I quickly removed it. Ralph has stated many times how adding a transformer inline with an OTL component can have a negative effect, and wow, he was not kidding. So I can't remember if it corrected the ground loop. The Jensen did perform well on the source which was involved in the ground-loop in my system. If you recall, my Sunfire amp was designed with the signal and the safety ground tied together, which threw a wrench into the entire system. I now have a tube amp, properly grounded, so there should be no ground-loop. I can't confirm that, of course, until the electrician verifies that his wiring is correct. Many thanks to you and Jea48, Jim |
lowrider57 ... In Philadelphia, a permit is not required for an electrical addition or upgrade in a residence.
The law states that an inspection is required at the time a house is being sold. Sorry, but you’re mistaken. " Electrical permits are required for the installation, alteration, replacement or repair of electrical and communications wiring and equipment within or on any structure and for the alteration of an existing installation. " see: https://business.phila.gov/electrical-permit/That your contractor didn't know this - and didn't insist on applying for the required electrical construction permit - raises questions about his competency, and whether he's even licensed to perform this work. |
I agree, almarg and jea48 are a wealth of knowledge and willing to share.
Thanks guys...
|
Cleeds, that's interesting. The company that I use has about 20 electricians on staff. They come to the house to give a free estimate, then return about a week later to do the work. Perhaps they get the necessary permit before starting the job. Maybe someone in their office does this.
This the third time they have done work for me; an upgrade with new breakers, lines and receptacles, then my first dedicated line after I entered this hobby, and the latest work 2 weeks ago. |
lowrider57 The company that I use has about 20 electricians on staff. They come to the house to give a free estimate, then return about a week later to do the work. Perhaps they get the necessary permit before starting the job. The permit is held by the property owner or occupant, not the contractor. When the work is complete, the project should be inspected in accordance with the permit, and an approval sticker affixed at the site. If you don’t have these permits and stickers, the work was not done in compliance with your local code: Code requires the permit and inspection. Please don’t take my word for this - contact your city’s construction department for details. And while we're at it, please share the name of the electrician you've been using. |
lak,
Thanks for the kind words.
Jim
|
cleeds said:
That your contractor didn't know this - and didn't insist on applying
for the required electrical construction permit - raises questions about
his competency, and whether he's even licensed to perform this work.
I would be willing to bet, in most States electrical permits are not pulled for the limited type of electrical work lowrider57 had done in his home. Just because an electrical permit was not pulled, may not have been pulled, does not mean the electrician did not install his work and use the proper materials to meet NEC, state, county, and or city, electrical codes. |
jea48I would be willing to bet, in most States electrical
permits are not pulled for the limited type of electrical work
lowrider57 had done in his home. We have different definitions of "limited electrical work." the OP had " 2 dedicated lines installed ... They originate at a sub-panel off the main circuit box. The sub-panel is
connected by the hot lead and has it’s own ground including a second
grounding rod." My electrician would insist on a permit for this.
Just because an electrical permit was
not pulled, may not have been pulled, does not mean the electrician did
not install his work and use the proper materials to meet NEC, state,
county, and or city, electrical codes.
That depends on the jurisdiction.
Where I live, code requires a permit and inspection; licensed contractors can face substantial fines for failing to obtain a permit first. And the details about the OP's installation suggest that the work itself - because of the grounding - does not meet code. Safety aside, I'll tell you why this matters. Where I live, when an offer is made to buy a property, closing attorneys routinely file under the state's open public records rules for copies of the property's construction permits. The attorney then gives copies of those permits to a construction expert - often a licensed sub-code official - who performs an inspection of the property on behalf of the buyer. If the inspector determines that work was done without proper permits and inspections, it's a huge red flag that can not only delay a sale, but require that permits and inspections be done after the fact. Was electrical work done behind Sheetrock that's now been sealed and painted? The electrical inspector can insist that the wall be cut open to reveal the work and prove that it was done in compliance with code. There's simply no good reason to not file for the permit. I'd never use a contractor that would seek to avoid a permit and a proper inspection of his work. It's cheap insurance for the homeowner. |
who performs an inspection of the property on behalf of the buyer. If the inspector determines that work was done without proper permits and inspections, it's a huge red flag that can not only delay a sale, but require that permits and inspections be done after the fact. Was electrical work done behind Sheetrock that's now been sealed and painted? The electrical inspector can insist that the wall be cut open to reveal the work and prove that it was done in compliance with code.
This part is true in my city. The difference is that the inspector is hired by the buyer and his real estate agent. As I stated earlier, I hope I'm wrong about how the subpanel was wired. I asked him at the end of the job, maybe I misunderstood. One thing I do remember is that he said new code requires 2 grounding rods. The name of the company is Generation 3 aka GEN 3 in Philly. Started out as a son, father, grandfather business with very affordable rates. Not so anymore. I will report back with my findings. |
@lowrider57
Don't let it get to you. Your electrician probably did everything to code.
B |
gdnrbobYour electrician probably did everything to code. We already know that he didn't follow code. The electrician didn't get the required construction permit and the project wasn't inspected by a city official before it was put into use. |
I heard from my electrician and all is good. I copied the instructions posted by @jea48 and @almarg and sent an email. He said that the additional wiring of the new panel matches jea48's information. One exception is that he believes the 2nd grounding rod should come from the subpanel, rather than 2 rods from the main circuit box. (new code requires 2 ground rods per residence). So, Jea and Al, thank you again for the time you spent dealing with this issue. @cleeds , the project wasn't inspected by a city official before it was put into use. Inspection is done at the time a house is being sold during the closing process; Title search, Home Inspection, and Pest Inspection are required. The buyer may use an attorney or a realtor for the closing process and must hire the certified building inspector. As far as permits, I saw the law that you posted, and I know it applies to construction or an addition to a residence, but my neighbor and I both have had electrical and plumbing work performed without a permit from a licensed contractor. |
Oh, and @jea48 , I have a 2 phase panel with 60A service (small row home and still meets code). Electrician installed a 60A Double-pole breaker in the main panel, then ran wire in a conduit to the subpanel.
It's about 5" to the side of the main.
|
Not that it will help, but gotta say, @jea48 is just so generous with his knowledge- he helped me with some questions I had about an isolation transformer install, and I had a big electrical contractor do the work, open a permit, etc. There is a gap in knowledge, I think, between the electrician community and audio-- and jea48 gets "it"- no code shortcuts, but getting to the issues.
I’ll watch this thread with interest. I always learn something on these electrical/code/wiring threads.
What’s scary in Texas (unlike NY) is that it is caveat emptor for buyers. When we were looking at houses here, I’d say, hmmm, I wonder what the file says, and my broker would pull it, go to the city or county as applicable. Outbuidlings that were never permitted, additions, ditto. So, when you buy, it’s on you, the buyer. You may be ok until you want some work done, and then a city official comes by and says, "sir, that outbuilding there- we have no record of it." And you are in backwards compliance land.
I lived in PA many years ago, but have zero knowledge of practices there.
Good luck with this low-- you’ll get it sorted.
bill hart |
Many thanks, @whart . I agree that @jea48 has the knowledge that crosses that boundary between electrician and electronics. All that and I bet he can cook.
|
Thanks Bill (whart), and lowrider57, for the kind words.
Jim
|
Question for @jea48 or @almarg ... The sub panel feeder Hot/s, neutral, and safety equipment ground conductor are all fed from the same main panel.
The sub panel feeder neutral conductor/neutral bar can not be bonded, connected to the sub panel metal enclosure or the equipment ground bar. The feeder neutral bar must be left isolated/insulated from the metal sub panel enclosure. (Green bonding screw or neutral bonding strap that came with the panel discarded.)
If the the feeder neutral conductor/neutral bar is bonded to the enclosure/equipment grounding conductor/equipment ground bar then the equipment grounding conductor will be connected in parallel with the feeder neutral conductor. What happens then is the equipment grounding conductor will carry neutral current back to the main electrical panel, or where the service neutral is bonded, connected to the enclose, equipment ground, and earth.
Not good for the equipment grounding conductor to carry neutral current. If the subpanel (containing breakers for 2 lines) takes a feed of hot, neutral, and safety ground from the main panel, are these 2 new lines truly dedicated? IOW, by tying in to the main panel (which may have shared neutrals and grounds), is there a chance of causing a ground-loop in the new lines originating from the subpanel? |
lowrider57
If the subpanel (containing breakers for 2 lines) takes a feed of hot,
neutral, and safety ground from the main panel, are these 2 new lines
truly dedicated?
IOW, by tying in to the main panel (which may
have shared neutrals and grounds), is there a chance of causing a
ground-loop in the new lines originating from the subpanel?
Yes, that is how a subpanel should be wired. Provided that the lines go directly from the subpanel to the receptacle used by the components, those are considered dedicated lines. Tying the neutral and grounds together at the main panel is required by code and helps prevent ground loops. |
@lowrider57 - @cleeds has it right- all "dedicated" means for our purposes is that the circuit isn’t being shared by other appliances, switches, lighting, etc. It reduces, but does not in my experience, eliminate, noise from other parts of the electrical system. My set up in NY (which was "permitted," but didn’t follow best practices I later learned), picked up noise from a low voltage light two floors away, and from various plug-in appliances, like a humidifier or hair dryer being used in another part of a large house. I also suffered from a nasty zap over the lines every time my tonearm air compressor motor kicked in- this could have been eliminated by properly separating the lines rather than bundling them.
I guess the other reason why one would install a dedicated line is to be sure that you have no competition for current drawn from the same line.
I believe that the job done in TX in my new place is far better than the one in NY, based in part on the level of knowledge of the electricians, and my prodding with questions (some of which were helpfully answered by @jea48 along the way).
|
Tying the neutral and grounds together at the main panel is required by code and helps prevent ground loops. Thanks, fellas. Good to know that this helps prevent ground-loops. Also relieved that my electrician confirmed his work conforms to code and matches Jea's instructions. BTW, each dedicated line travels separately to a receptacle with the ground wire attached to the outlet...not self-grounded. |
I didn't read this entire thread but I would look at a balanced power unit from Furman, Equi=Tech or other manufacturer. feed it with your dedicated line then plug everything into the balanced power unit. That should eliminate any line noise. Read more here... http://www.equitech.com/lifting-the-grounding-enigma/ |
@falconquest , I've been following the balanced power threads and it seems like the way to go. I don't have the funds to do it now, but I see it in my future. Would be much better than using filters and grounding blocks.
Thanks.
|
After much troubleshooting I can confirm that both dedicated lines are extremely quiet. My preamp is emitting a low-level hum (even through a power transformer). Swapping preamps proved that the mains had no noise to speak of.
So I will address this issue with the manufacturer, then hopefully move on to some "black-background" listening sessions.
Thanks again to all.
|
|
