Grounding Metal Outlet Boxes and Isolated Ground Receptacles
Just installed six really nice separate dedicated 20 amp lines (with 6 awg) for my new dedicated listening room. Decided to use heavy metal outlet boxes so that I could make my six Furutech Receptacles as strong and sturdy as possible. I also had my electrician run 4-wire 6 agw to the boxes so that we could have one ground wire to the metal receptacle box and then a separate ground wire to the isolated ground screw on the Furutech.
I sent some photos of the setup to a friend of mine (who just happens to be an electrical engineer) and he raised an the issue that since my Furutech Receptacles are metal and they will be screwed into the metal box with metal screws, then we have effectively now tied the two separate grounds together! Help! Is that a bad idea? Is having the box and receptacle setup in this way going to cause issues once my gear is in place; ground loop hums, etc?
I was asked by my local inspector or should I say forced to add Afci to all my gfci dedicated runs. Nevermind bedrooms/living areas as they are normally intended for where homes do not have smoke carbon detects ran in series..
you asked if it was maditory. It was for me but would depend on the inspector from what I've seen. What cannot be ignored unfortunately is basically the amount of labor required to complete jobs satisfactory.
A GFCI breaker cannot be used on multi wire branch circuits. ( The neutral is shared on multi wire branch circuits) The GFCI breaker will just trip open the second any load is connected to the other hot circuit wire of the multi wire branch circuit. The hot and neutral connected load to the GFCI must be balanced. If an imbalance is detected on either line the breaker will trip open.
In the case of a 120V circuit where a GFCI breaker is used each 120V circuit has to have its’ own neutral conductor. Both the Hot, ungrounded conductor, and the neutral, the grounded conductor, of the branch circuit connects to the single pole GFCI breaker. (Depending on the electrical panel, the GFCI breaker used may have an insulated white neutral pigtail wire that connects to the neutral bus in the panel, or the breaker may be the type that connects directly to special neutral bar, rail.) I personally prefer using a GFCI duplex receptacle over a GFCI breaker.
In the case of a multi wire branch circuit where GFCI protection is needed, or required per code, example in a kitchen above counter tops, A GFCI duplex receptacle is used.
In my previous post I asked you about if Chicago requires AFCI (Arc Fault Circuit Interrupter) protection in dwelling units.
2014 NEC requires the use of CAFI (Combination Arc Fault Interrupters) on all 120V 15 amp and 20 amp lighting and receptacle outlet branch circuits in dwelling units for new construction, as well as a newly installed branch circuit/s in existing dwelling units.
The CAFI device can be a CAFI breaker or a CAFI duplex receptacle device. The CAFI will trip open, breaking the circuit, if it detects series or parallel arcing.
A GFCI’s purpose, function, is to protect life from electrocution. If the sensing unit in the device detects more than 5 to 6 ma of ground fault current from the hot to an earth grounded object the unit will trip open. (The earth grounded object could be the safety equipment grounding conductor, or any other earth grounded object the person, or pet, may come into contact with while in contact at the same time with the HOT conductor.) (NOTE: The actual ground fault circuit is from the HOT conductor >> through the person’s body >> out to the earth grounded contacted object >> to the electrical service’s earth grounded service neutral conductor. A complete closed circuit.)
A CAFI’s purpose, function, first priority is to protect property from an electrical fire caused from an electrical arcing event. By doing so ultimately the CAFI may protect life if a person or pet is in the home at the time of the electrical arcing event.
Like the GFCI breaker a CAFI breaker cannot be used on a multi wire branch circuit. Like the GFCI breaker both the Hot and neutral conductors of the branch circuit connects directly to the breaker.
Has there been problems with AFCI/CAFI breakers nuisance tripping? yes... Not so much now though. Most of the problems were because of improper installation of the branch circuit wiring and improper connections in electrical outlet boxes. Some problems with nuisance tripping with the early AFCI breakers was because of interactions with some lighting dimmers. Lutron being one such dimmer.
Manditory with the conjunction of any gfci outlet. Your talking in newer builds money adding each of those to a panel. All must have dedicated neutral and cannot be shared. I've seen debate there but it's my understanding the faults won't work correctly unless dedicated.
any remodel on older work must also incoperate same or your grandfathered in.
all interior raceways must be emt or rigid. Why run rigid when yiu can use emt.
You can can whip up to 5 feet only for lighting. Some inspectors will require a ground with that use.
As as far as I know all exterior work must be rigid only.
also depends on the inspector and what that one thing they look for... you know how it is.
The city Electrical Department is still following some of the electrical standards of the 1993 NEC, (National Electrical Code). I find that incredible they have not kept up with NEC since 1993. LOL, NEC is updated every 3 years.
That may not be accurate.
From the supplied Link,
In general, rules and regulations included in the 1993 Edition and later editions of the National Electrical Code are herein implied.
bimmer528,
Is AFCI protection required in new homes built in Chicago today?
Are they required if new branch circuits are added in an existing home? For the rewire of an older home?
i am in Chicago, very strict here on what can and can’t be acccepted.
That’s an understatement.
I assume this is current electrical code for Chicago.
Chicago IL Residential Electrical Code.
RESIDENTIAL WIRING:
A.
All wiring changes or additions to electrical systems in residences previously constructed should be rigid or electrical metallic tubing where possible and all basements should be in conduit.
1.
Where necessary to fish through existing partition, BX or flexible conduit may be used and must terminate within twenty-four inches (24") of its entrance into any basement or crawl space area.
2.
Where a question exists as to methods or materials used, the ruling of the Electrical Inspector shall govern.
3.
All conduit on or below grade, shall be galvanized rigid conduit PVC (Minimum Schedule 40 Poly Vinyl Chloride), rigid conduit to be used in concrete only.
(No. I.M.C. Steel) burial depth a minimum of twenty-four inches (24").
B.
All wiring systems installed in new residences shall be in rigid conduit or electrical metallic tubing.
1.
Junction boxes may not be installed in inaccessible or concealed locations. This does not exclude use of said boxes in basements, crawl spaces or attics. Junction boxes may not be installed under overhang or decorator or soffits.
2.
Said conduits shall be installed on what is known as the "loop system" and shall be completed between the approved outlets, having not more than four (4) right angle or equivalent bends including those at the outlets.
C.
All service entrance conductors shall be installed in one and one-fourth inch (1¼") conduit or larger if required. All new services must be in rigid metal conduit, meter sockets and panels are to be installed with butterfly bolt or anchors and have a branch circuit panel with a minimum capacity of sixteen (16) poles.
1.
Underground services shall be installed as approved by the local public utility rules, as filed with the Illinois Commerce Commissioner and must be at least two (2) No. 2 gauge wire and one No. 4 wire for neutral conductor. For direct burial, wire approved for that use must be installed.
2.
There shall be no splices in any wire approved for direct burial.
3.
Connections between outside meter fittings and inside service connecting device must be run in outside of building as much as possible and be installed in conduit without the use of concealed fittings.
4.
For a single-family dwelling, the service disconnecting means shall have a rating of not less than one hundred (100) amps. Service entrance conductors shall be not less than two (2) No. 2 gauge copper or approved 4 gauge copper wire, approved for use.
5.
Two-family houses shall have a one hundred (100) amp disconnecting means for each family unit. Service entrance conductors for two-family houses shall not be less than 3/0 gauge copper wire and one No. 1/0 gauge copper for neutral wire. For three (3) to six (6) more meters the service riser will have to carry a one hundred (100) amp for each meter.
D.
In all cases service entrance conductors must be adequate for the connected load.
E.
Grounding for combination systems and equipment, grounding to be done with No. 4-B & S gauge, copper or equivalent current-carrying capacity; wire run directly from neutral in service disconnecting or distribution box to the street side of the water shut-off valve, where said valve is inside of the building.
1.
In all homes without basements, of slab or other construction, entry of water service or shut-off valve shall be the location of ground locations.
2.
On approved two-jaw type, one ground clamp of metal similar to that attached shall be used.
3.
Said ground wire must be installed under basement concrete floor.
4.
Ground wire may be solid, stranded bare, insulated or of weather-proof type No. 4.
5.
Electrical ranges may be grounded to the neutral conductor. No other cabinet or appliance can be grounded to the neutral conductor.
6.
Bare neutral can be used only on service entrance as far as supply disconnect device.
F.
Rooms not now wired or additions to homes now built, shall be done by the rules covered herein and also shall have at least one circuit for each five hundred (500) square feet of area for general lighting purposes.
G.
Each single-family home or separate apartment shall have its own disconnecting device located as determined by the 1993 edition and later editions of the National Electrical Code and the Electrical Inspector.
H.
Each single-family home or separate apartment of multiple dwelling occupancies shall have at least two-appliance circuit, wired with No. 12 B & S gauge wire and may be fused at twenty (20) amperes, to supply the receptacles located in kitchens, dining rooms, dinettes, breakfast room, pantry, utility rooms and laundry. No lighting shall be installed on this circuit.
1.
Outlets for electrical clocks cannot be on this circuit.
2.
Receptacles shall be installed on the wall, two feet (2’) from the laundry tray in the laundry room and shall be a three-pole type suitable for grounding purposes. Recommended use of one of the types now available and suitable to receive present two-prong type of attachment plug now in general use. Receptacles or switch installations in garage areas must be mounted not less than fifty inches (50") from finished floor.
3.
Combination light and receptacle outlets may not be used in place of laundry outlets required.
4.
Certain other laundry equipment, such as dryers, may be required to be on separate circuits according to the loads used and judgment of the Electrical Inspector.
I.
Heating or air conditioning systems are to be on separate circuits and to a switch installed on or near the equipment disconnecting ungrounded conductors.
If
No. 12 size conductors are used and less than twenty-five feet (25’) in length, then the sub-main terminals may be used, provided a fuse-type switch is used at the equipment.
J.
No circuit wired with No. 12 B & S gauge wire should have more than thirteen (13) outlets or receptacles for general lighting purposes connected thereto.
K.
No circuit wired with No. 14 B & S gauge wire should have more than ten (10) outlets or receptacles for general lighting purposes connected thereto.
L.
In any case a circuit shall be able to carry any load connected thereto.
M.
All outdoor or entrance outlets should have an outlet box suitably installed and waterproofed, must be on ground fault.
N.
Ceiling joists may not be notched for installation of conduit without written permission of the Electrical Inspector. Ceiling joists or studding may be drilled for conduit installation.
O.
All conduit run on top of the ceiling joist shall be run straight and at right angles to the joist and strapped thereto. Conduit run parallel to the ceiling joist shall be set down beneath the top edge of same.
P.
All exposed runs in basements or other locations should be installed in a neat and workmanlike manner.
Q.
Ceiling joist shall be notched one-eighth inch ( 1/8 ") for bar hanger installation.
R.
All outlets for general lighting purposes shall be one and one-half inches (1½") in depth and three and three-fourths inches (3¾") in diameter of 1900 type of box.
S.
Switch and receptacle box shall be 1900 or four inch (4") square by one and one-half inch (1½") type of box set flush with studding.
T.
On dry wall construction a flat type of outlet cover box shall be used. Otherwise all covers for outlet boxes shall be at least one-half inch (½") in depth.
U.
Where three and three-fourths inch (3¾") octagon box is used for ceiling outlets, the shallow offset type of box shall be used to bring the outlet box to the edge of the rock-lath or other material.
V.
The box should be installed to come within one-fourth inch (¼") of the finished surface.
W.
Wires not to be drawn into conduit until wall finishes are applied or all mechanical work is completed without written consent of the Electrical Inspector.
X.
Hot travelers for three-way switches are not allowed.
Y.
All fuses shall be of the approved time delay type "S" or breakers.
Z.
Metal fixtures installed over kitchen sinks or in bathrooms shall be mounted so as to be grounded and controlled by wall switch.
AA.
Outlets in closets shall be installed in the ceiling close to the door. Brackets can be used only over doorways.
BB.
All circuit splices shall be made with approved connectors.
CC.
At least one wall receptacle for each twelve feet (12’) of lineal wall space as measured horizontally around the room at the baseline, including all door or window openings in all living rooms, bedrooms, dining rooms, library rooms and kitchens. Receptacles not to be installed in floor unless of the approved type and must be within two feet (2’) of the wall to be counted as one required above.
DD.
All boxes mounted back to back to be firmly bolted together or nippled between, to insure continuity of ground. All connections, couplings, locknuts or bushings to be set up tight.
EE.
All recessed lighting outlets to be connected with approved wire suitable for the purpose and have temperature rating of one hundred fifty degree centigrade (150°C). Not more than one conduit may be run to any direct or recessed lighting fixture unless run to a junction box outside of fixture in the manner approved by the Electrical Inspector.
FF.
Installation of household electric ranges of not more than twelve and three-fourths (12¾) K.W. capacity may be installed in three-fourths inch (¾") conduits using two (2) No. 8 gauge and one No. 10 gauge wire.
GG.
Porcelain pull-chain type of fixtures must have insulator between pull-chain and attached chain. No grass shell type of sockets allowed in basement or other damp areas. All drop cords shall be of the type approved for locations used.
HH.
Three-wire branch circuits are approved, providing the conductors are of different colors and other than white and providing they are so connected as to apply two hundred thirty (230) volts across the phase wires. Otherwise two-wire circuits must be run. If more than one three-wire circuit is run in the same conduit, then all underground conductors should be of different colors.
II.
In general, rules and regulations included in the 1993 Edition and later editions of the National Electrical Code are herein implied.
The city Electrical Department is still following some of the electrical standards of the 1993 NEC, (National Electrical Code). I find that incredible they have not kept up with NEC since 1993. LOL, NEC is updated every 3 years.
The mandated requirement that rigid conduit, EMT, must be used in single family dwellings, houses, in 2016 is just plain nuts.
As an outsider of Chicago looking in it appears to me the central governing body, power, of Chicago is/has been for years, bought off by the Electrical Contractor Lobby. As I read some of the code requirements I seen unnecessary $$$$$ in added material and labor costs that drives up the building cost of a new home, built in Chicago.
No mention what so ever of AFCI (Arc Fault Circuit Interrupter) protection any where in the code. Of course in 1993 they did not exist. Not until 1999 did NEC first speak of branch circuit arc fault protection. In 2001 NEC required AFCI protection on all branch circuits feeding receptacles in bed rooms. By NEC 2008 their use was expanded followed in other areas of the home. NEC 2011 even more expansion, and even more in NEC 2014. Electrical acing is one of the biggest causes of electrical fires in homes.
My guess is the governing body of Chicago is aware of the NEC requirement for AFCI protection in residential units. They just don’t want the general public to know. Why? How could they then justify the mandated requirement for rigid conduit in homes for all branch circuit wiring? $$$$$$
Always follow code first. The use of plastic boxes are not legal in many areas. Nor is armored cable and romex Given what you posted I’m assuming 1900 4 by 4 deep boxes were used and emt is the conduit. Running a separate ground is pointless. The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box
#6 is overkill. Amplifiers draw between 2 and 4 amps max
depending on what your running I would have ran two dedicated 20 amp on min #10 wire on a shared neutral.
the outlets you bought are good but so is just about any hospital grade. I’d be surprised if a furutech accepts #6 wire.
verify the panel is grounded correct. Tap after your main water shut off and jump to before the shut off valve
cheers
//
Always follow code first. The use of plastic boxes are not legal in many areas. Nor is armored cable and romex
Actually, I would be willing to bet they are approved for use in most single and multi family residential dwelling units in the US.
Yes, there are a few exceptions. AHJ (Authority Having Jurisdiction) has the final say.
Given what you posted I’m assuming 1900 4 by 4 deep boxes were used and emt is the conduit. Running a separate ground is pointless. The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box
You? I guess you are addressing me.
Yes, a 1900 box is a 4" X 4" square box.
As for running a separate equipment grounding conductor in an EMT conduit technically per NEC code it is not required. The metal conduit is an accepted approved equipment grounding conductor, with some exceptions. 2014 NEC 250.118 Types of Equipment Grounding Conductors. Of course the AHJ has the final say. They may require a conduit/box ground wire.
The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box
How about where the branch circuit wiring is NM and the outlet box is metal? How about if the Yoke, supporting back strap, does not come into solid contact with the box, and or raised device cover, for a flush installation and the receptacle used is not an approved auto ground type? How about if a surface mount 4" X 4" square box is used and the receptacle is mounted to the back of a steel raised receptacle cover. Lots of how abouts. The ground terminal is there because NEMA, NEC, UL, ect, says it shall be there. //
depending on what your running I would have ran two dedicated 20 amp on min #10 wire on a shared neutral.
That meets bare minimum NEC Code. Sucks for audio equipment though. Especially for audio equipment that is connected together by wire interconnects.
For the layman reading this post multi wire branch circuits, (in this instance 2 separate hot conductors, breakers fed from L1 and L2, and 1 shared neutral conductor. Per NEC the 2 separate circuits shall be fed from a 2 pole breaker.)
Note: Two 120V separate circuits..... NOT two 120V dedicated circuits...
(A) Practical Safeguarding. The purpose of this Code is the practical safeguarding of persons and property from hazards arising from the use of electricity.
B) Adequacy. This Code contains provisions considered necessary for safety. Compliance therewith and proper maintenance results in an installation that is essentially free from hazard but not necessarily efficient, convenient, or adequate for good service or future expansion of electrical use.
FPN: Hazards often occur because of overloading of wiring systems by methods or usage not in conformity with this Code. This occurs because initial wiring did not provide for increases in the use of electricity. An initial adequate installation and reasonable provisions for system changes provide for increase in the use of electricity.
(C) Intention. This Code is not intended as a design specification or instruction manual for untrained persons.
(D) Relation to Other International Standards. The requirements in this Code address the fundamental principles of protection for safety contained in Section 131 of International Electrotechnical Commission Standard 60364-1, Electrical Installation of Buildings.
FPN: IEC 60364-, Section 131, contains fundamental principles of protection for safety that encompass protection against electric shock, protection against thermal effects, protection against overcurrent, protection against fault currents, and protection against overvoltage. All of these potential hazards are addressed by the requirements in this Code.
Always follow code first. The use of plastic boxes are not legal in many areas. Nor is armored cable and romex Given what you posted I’m assuming 1900 4 by 4 deep boxes were used and emt is the conduit. Running a separate ground is pointless. The screws and or outlet mount fins is what grounds it. The reason there is a seperate ground screw on the outlet is because there has to be. Grounding screw on all outlets. It’s there for when metal is not used as the transmission. I.e... using a plastic box
#6 is overkill. Amplifiers draw between 2 and 4 amps max
depending on what your running I would have ran two dedicated 20 amp on min #10 wire on a shared neutral.
the outlets you bought are good but so is just about any hospital grade. I’d be surprised if a furutech accepts #6 wire.
verify the panel is grounded correct. Tap after your main water shut off and jump to before the shut off valve
* For 120V audio equipment that is connected together by wire interconnects all audio equipment should be fed from the same Line, leg, in the electrical panel. ALL from L1 or all from L2. NOT from both.
This may not be practical, electrically a good practice, in all cases. Especially where big 120V fed mono amps are used in an audio system. A good example might be a pair of Krell 600 mono amps.
Putting both power hungry mono amps on the same Hot Line, leg, to neutral without trying to balance the load across the two Lines, legs, in the main electrical service panel could stress the electrical service panel bus and main breaker as well placing a large unbalanced load on the service neutral conductor and the power company’s utility power transformer.
It would be less of an issue if the electrical service is 200 amp or even less an issue if 400 amp. If the electrical service is 100 amp then the unbalanced 120V load could/would be a problem. If the house is old and the service might still be a 60 amp that would definitely put a strain on the electrical service.
Technically when fairly large 120V loads are know they should be balanced across the two Lines, legs, in the electrical panel. Only the imbalanced 120V load returns on the service neutral conductor to the utility power transformer. Example: IF all the 120V loads on L1, leg, equal 40 amps, and all the 120V loads on L2, leg, equal 40 amps then zero amps will return on the service neutral to the source. In this case the power company’s utility power transformer. In the case of a sub panel the same thing holds true. Only the imbalanced load returns on the feeder neutral to the main service electrical service neutral conductor.
The balanced 120V loads on L1 and L2 are in series with one another.
First, I assume cdrc’s comments are directed at stickman451.
Second I believe the electrician stickman451 hired is a licensed electrician. I determined that to be the case by the posts of the OP when describing the wiring methods and materials used for the installation. From this side of the monitor reading the OP’s posts I do not know the quality of workmanship of the install. I assume it is fine.
cdrc said:
I don’t know if it is a bad idea but I do not think it is good. I also would doubt what you outlined is within code not knowing which state you live in.
The wiring method and materials used in stickman451 posts, for the installation, meets NEC.
What amperage breakers are you using?
I believe stickman said the branch circuit breakers are 20 amp. NEC code, for a NEMA 20 amp rated receptacle says a 20 amp branch circuit breaker must be used. Minimum size branch circuit wire used is #12awg. NEC code is bare minimum. NEC code is not intended to be used as a design manual.
I would DEFINATELY run a separate wire to bond your metal boxes and emt raceway.
At the time of his posting of this thread he has a box ground. He actually at the time of his posting had 2 equipment ground wires at each metal outlet box. One for the box ground and the other for, what stickman451 thought at the time, the IG (Isolated Ground) terminal of his duplex receptacles. Go back and read my responses to him on the subject.
For your Furutech receptacle ground wires I would braid them as you see in my sub panel pic. This will firthur reduce your noise floor a great amount from this simple trick.
That is not a braid. The green equipment grounding conductors are twisted together in a spiral. They are not braided, weaved together with one another.
To braid, simply install one end of your ground wires in a drill chuck, tighten the chuck and run the drill. Get a nice tight braid, the difference will be magical.
You might get that pass an electrical inspector beings they are equipment grounding conductors, but I would be willing to bet he would red flag the job if you used that method twisting the HOT and Neutral conductors together that way.
//
Here are a few things I found looking at your pictures where I believe you could improve the SQ, sound quality, of your audio system.
* Get rid of the steel ferrous EMT conduit and steel boxes.
* For exposed work use MC cable with an outer aluminum armor instead, if possible. Solid core wire only! Stranded wire will smear the sound. Boxes could be malleable aluminum boxes.
(In your case, from looking at your pictures, you could have built a box out below the surface mount electrical panel. The box out could have a removable cover if you thought you needed access for future installs or changes. With this method you could of used NM-B sheathed cable, (Romex is a Trade Name). Plastic boxes, for your branch circuit outlets receptacles. Providing NM cable is approved by the AHJ in your area.) The installation would meet NEC.
* Avoid STEEL ferrous receptacle cover plates! Even low grade stainless steel cover plates will have ferrous impurities in the stainless steel. Use a strong magnet to check for ferrous materials. A steel receptacle cover plate kills the SQ of an audio system. See my post above on the subject. By the way the late Al Sekela was an EE.
In your case you could pull the raised 1900 duplex receptacle cover plates and replace them with a 1900 raised device cover plate. Fasten the cover to the 1900 box. Support the back strap of the duplex receptacle to the device cover. Install a P&S non-breakable nylon cover on the duplex receptacle.
* Technically a true dedicated branch circuit never shares the same conduit with other branch circuits. Not only can a voltage be induced from the current carrying hot and neutral conductors to other circuits sharing the same conduit but also the AC noise of the current carrying conductors.
* At least for audio equipment if conduit is used, twist the hot and neutral conductors together in a slightly to moderate spiral twist the entire length of the branch circuit wiring. Just install the equipment grounding conductor straight along side the hot and neutral twisted pair.
* For 120V audio equipment that is connected together by wire interconnects all audio equipment should be fed from the same Line, leg, in the electrical panel. ALL from L1 or all from L2. NOT from both.
Jim, thanks for calling this thread thread to my attention, via your post in the directional interconnects thread. My response there on 12-6-2016, near the bottom of page 3 if posts are sorted most recent last, may be of interest to some here.
Stickman’s wiring may already have been finalized, but FWIW re:
Jea48 11-14-2016
I would wonder if the floating insulated wire might act as an antenna and pick up air born RFI. I would probably connect the end at the panel to the ground bar. Nothing wrong with that as far as a code issue. Ask your electrician if he has a problem with it.
It would be nice to hear from Al, (almarg), what he thinks. Would he connect the end of the spare insulated wire at the electrical panel to the ground bar, or leave it floating above ground?
I agree. Antenna and RFI effects are always hard to predict, of course, and it might not matter either way. But grounding the wire at the panel, in addition to perhaps reducing RFI pickup, would add a bit of capacitance between the AC conductors and ground that I suppose might provide at least a slight benefit in terms of filtering RF noise that may be present on the incoming AC.
Regarding Bflowers issue, the only thoughts that occur to me beyond what Jim has said are:
1)It would probably be a good idea to measure the AC voltages (120 volts on each leg, relative to neutral, and the 240 volt difference between the legs), during typical listening hours. If practical it would be preferable to do that while the system is powered up and playing music at normal volumes.
2)Regarding:
Bflowers 12-1-2016 BTW, had serious ground loops in the old room, but the Boulder gear was fairly impervious to it. I demoed a single ended Lamm amp and it buzzed like a fiend!
Not sure which Lamm model you tried, but I see that the currently produced models that are described as single-ended provide unbalanced inputs on their XLR connectors. Which if connected to the balanced outputs of your Boulder preamp via an XLR cable would short the inverted signal on XLR pin 3 to the circuit grounds of both the amp and the preamp. Given the relatively low output impedance of the Boulder preamp (spec’d at 100 ohms, which probably corresponds to 50 ohms per leg), that could conceivably have resulted in the buzzing you heard. See this thread for an example of a situation in which exactly that occurred, although very different equipment was involved.
Also, while very unlikely it is conceivable that the output stage of the preamp which drives XLR pin 3 on each channel might have suffered some damage as a result of having that signal shorted to ground. So to be sure, subsequent to the Lamm audition did you put the older Boulder amp back in place, and find the system to perform the same as previously?
bflowers said, In metal conduits. Single run of 12G braided wire in each conduit. Run
from subpanel is <8 ft in all cases. Probably 20 or so lines coming
of the subpanel. Don't know about the interconnects. There are 2
legs, but all my equipment fits on one leg.
There are 2 legs, but all my equipment fits on one leg
I just learned from almarg the amp is 240V. Hopefully almarg will read your posts on this thread. He may have some thoughts. Jim
IF the dedicated branch circuit wiring for the power amp is braided (hot, neutral, an IG ground conductors braided) together that might be the problem. Think of it as an 8ft shielded power cord. ( 3 braided conductors inside a steel outer shield) With the braid basically you have 1 hot ungrounded conductor, (120V above ground potential), and 2 conductors at ground potential. (The neutral, the grounded conductor, and the equipment ground, the grounding conductor.) Most power amps do not like shielded power cords. My experience it sucks the air from the sound of the amp.
For a couple hundred dollars labor plus material you could find out for sure if my theory is correct.
Have your electrician pull out the braided wire from the conduit that feeds the Boulder 3060 power amp.
For the new wire that will be pulled back in the conduit use solid core, not stranded, THHN/THWN. (Stranded wire can smear the sound)
Ask the electrician to slightly, to moderately, twist the hot and neutral conductors together the entire length of the conduit run. The IG equipment ground conductor will be pulled straight along side the hot and neutral twisted pair.
In metal conduits. Single run of 12G braided wire in each conduit. Run from subpanel is <8 ft in all cases. Probably 20 or so lines coming of the subpanel. Don't know about the interconnects. There are 2 legs, but all my equipment fits on one leg. Old room had lines slowly added over time. Amp was running 240 in there as well. I believe it was wired with 10G solid core cable. There was a mix of metal and "plastic" conduits and boxes in the old room. ( BTW, had serious ground loops in the old room, but the Boulder gear was fairly impervious to it. I demoed a single ended Lamm amp and it buzzed like a fiend!) Using a mix of hubbell and voodoo (cryoed hubbell outlets) in new room. Plastic plates.
System incorporates isolated grounds and IG outlets.
Is the branch circuit wiring installed in metal conduit? Steel or aluminum?
IF yes, does each dedicated branch circuit have its’ own dedicated conduit? A true dedicated branch circuit should never occupy the same raceway, conduit, with other branch circuit wiring.
What is the type of branch circuit wiring the electrician installed?
Example:
Metal conduit with wires installed inside the conduit/s after the conduit was installed?
Aluminum or steel armor? Solid or stranded conductors?
>
NM-B sheathed cable? (Romex is a trade name)
>
What size of conductors, wires?
Approximate length of the dedicated branch circuit runs from the electrical panel to the wall outlets?
Number of dedicated branch circuits?
Are all the branch circuits, that feed audio equipment connected together by wire interconnects, fed from the same line, leg, in the electrical panel? All from Line 1 or all from Line 2? Not from both L1 and L2.
The advantage I have is that I know how my system should should because I only changed one piece of equipment from my old to new room.
How about the branch circuit wiring in the old room? Was the same type wiring used in the new room? How about the wall rough-in outlet boxes used in the new room compared to the old room. Same? Steel or plastic/fiber boxes?
How about the duplex receptacles. Same as the old room? Duplex cover plates. Same as the old room?
What manufacture, series, style, IG (Isolated Ground) type duplex receptacles did the electrician install? Duplex cover plates installed?
I am in a near identical situation and would love your (or anyone else who knows) feedback. Don't want to hijack the thread, but I don't see a way to send a direct message on AGon anymore (haven't been on the site for some years now).
In short, I had a custom room built and spared no expense. Hired a power consultant who designed a system with a 15KVa isolation transformer and a custom breaker panel that feeds only the audio room. System incorporates isolated grounds and IG outlets. The advantage I have is that I know how my system should should because I only changed one piece of equipment from my old to new room. System is Wilson Alexandria, Boulder 2110 pre, 3060 amp (had 2060 before and they sound very similar) and full vivaldi stack. System had incredible detail and thunderous bass. Now has decent detail and soggy bass (hyperbole). After a year, I had the electrician take the isolation transformer out of the system and run a new line from the street to the breaker panel. Everything is much better now, but still has a layer of syrup over the presentation that shouldn't be there and loose bass. Room acoustics are a bit different, but the power is the biggest difference. What gives? Again happy to take offline if appropriate.
LOL, believe it or not tests have been done using non breakable nylon duplex cover plates. I for one tried the nylon plate after Albert Porter posted he was using the P&S plates. Of course Albert’s post was back around 2005. I think the important thing about the P&S nylon plate, and the Leviton plate as well, is the backside construction bracing. Also the nylon plate does not ring like a plain hard plastic plate does. The nylon plate basically is just covering the wall duplex outlet while adding some dampening.
Stay away from any duplex cover that has ferrous materials in it. Steel is the worst. Low grade stainless steel will have ferrous materials in the plate. Always check the plate using a magnet. Steel can/will suck the air out of the music.
Brass plates are not as bad as steel but can still can have an impact on the SQ of the audio equipment.
Posted by Al Sekela (A) on February 10, 2006 at 09:53:28
I just finished a five-way comparison of outlet cover plates (on 2-gang metal box):
1. no outlet plate (old standard); 2. magnetic SS outlet plate with Nylon screws (verified not grounded with ohmmeter); 3. same, but with one steel screw to ground it; 4. same as 3. with magnets stuck to outside of plate; 5. High-abuse Nylon plate with Nylon screws. Also tested with both 2-gang boxes covered with Nylon plates.
Test CD was Shirley Horn, _You Won’t Forget Me_, Verve 847 482-2.
Numbers 1 and 5 were so close I decided to leave the Nylon plates in place.
Number 2 gave an added sense of air and resonance, which led me to test the SS plate for acoustic ringing.
It rings like a bell with a pure, sweet, high sustained tone, and a lot of atonal immediate crash like a cymbal. With this thing vibrating near the outlet and not grounded, it is acting like a dynamo and converting acoustic vibration into electrical noise within the power circuit and/or safety earth.
Numbers 3 and 4 dulled the sound compared to number 1: not in the sense of lost treble, but in a lack of midrange presence. With my system tuned up, I can hear Shirley smile as she sings, "...should there be eyes like [:)]yours..." near the beginning of track 12, "You Stepped Out of a Dream." This sense of a smile was diminished with treatments 3 and 4. The piano tone was also less appealing in general.
Her voice seemed less cohesive over her range.Thus, my results are similar to yours with respect to grounded versus floating plates, but I believe the apparent improvement with the ungrounded plate is due to euphonic coloration rather than increased detail retrieval. You can confirm this by listening carefully with the ungrounded plate in place, and then with it removed. Other inmates have observed improved performance with no plate at all on the outlet, but clearly this is not safe for most people and violates code. In my case, anyone who approached the uncovered outlets would probably have died from tripping over the equipment and cables before reaching the outlets, so I was not concerned about the safety aspect. The Nylon plates’ appearance matches the other outlets in the room, so I will leave them on.
Posted by rcrump ( M ) on March 21, 2003 at 01:28:05 In Reply to: Genuine insanity: What kind of cover plate do I need? posted by rhizomatic on March 20, 2003 at 09:10:15:
I made some power strips probably fifteen years ago using some black plastic boxes and ordered some really beautiful cast brass plates for the fourplex boxes only to find that the solid brass made the sound just bright as the devil....A couple of nylon screws and some tape on the backside of the plate took care of the problem....Aluminum doesn’t have that sort of problem BTW....
One option we are looking at is to pull out the metal boxes, put in a high quality plastic or fiberglass box and elimintate any ground to the box.
I don’t think the electrician will find a plastic or fiber receptacle outlet rough-in box big enough for 6-3 with ground that will meet NEC for the conductor fill requirements. (2014 NEC 314.16) That’s why, I believe, the electrician used a steel square box with a single gang raised device cover. I personally would leave what you have now. If the receptacle supporting back strap was made of steel then you might hear a difference in sound. The supporting back strap on the Furutech is not made of ferrous steel. What type of duplex cover plate are you going to use? THAT can change the sound of your audio system!
i appreciate you giving me your thoughs on this! Thanks! I'd also be curious on almarg thoughts on this; he know's his stuff!
I will run the options that you suggested by my electrician and see what he says. One option we are looking at is to pull out the metal boxes, put in a high quality plastic or fiberglass box and elimintate any ground to the box. The extra insultated ground wire would just be left unused.
Main issue is I do not want to create an electric hazard (pretty sure my electrician is very capable) and I do not want to create a bunch of ground loop issues!
From the description of the wiring materials and wiring methods used in your posts everything meets or exceeds electrical safety code. At least NEC. I would imagine your electrician followed any local electrical codes that differed from NEC.
As for any ground loop problems, just my opinion, your branch circuits runs are too short to cause any ground loops. If they were long, say 60ft to a 100ft, the 6-3 with ground may have been a problem as I described in an earlier post. Especially paralleling the bare equipment ground wire with one of 3 insulated conductors of the cable.
I wouldn’t be surprised though if the electrician doesn’t rework the equipment ground wiring in the six wall rough-in outlet boxes after you tell him the 6 duplex receptacles are not IG grounding type duplex receptacles. He has to hang his name and reputation on the job when he’s done.
As far as the way I would do it now, knowing the duplex receptacles are not IG, I would cap off the insulated wire in the box and just leave it as a spare unused wire. I would pigtail the bare equipment ground with two pigtails. One to bond the metal box and the other to connect to the ground terminal on the duplex receptacle.
(Just going from memory the construction of 6-3 with ground NM-B cable (Romex), the bare ground wire is in the middle of the three twisted insulated wires. For me anyway, that lessens any chance of an induced voltage transfer from the hot and neutral current carrying conductors onto the equipment ground wire.)
As for what to do with the spare capped off wire of the 6-3 with ground Romex at the electrical panel end? Normally it would be capped off and left laying in the bottom of the panel for future....... But in this instance it is part of a cable assembly that will be feeding an audio system. An audio system where the user has spent big bucks in hopes of getting the lowest noise floor possible. I would wonder if the floating insulated wire might act as an antenna and pick up air born RFI. I would probably connect the end at the panel to the ground bar. Nothing wrong with that as far as a code issue. Ask your electrician if he has a problem with it.
It would be nice to hear from Al, (almarg), what he thinks. Would he connect the end of the spare insulated wire at the electrical panel to the ground bar, or leave it floating above ground?
The average length of the six dedicated runs is approx 30 feet. The room is 29' L x 21'-10" W. The longest two runs are about 36 ft from the front wall back to the sub panel in the room. The shortest run is about 25' from the sub panel.
The sub panel is a GE PowerMark Gold.
All of the six 6awg dedicated lines will be on the same phase in the sub panel. Lighting and standard wall outlets will be on the opposite phase.
The sub panel in my room is approx 60 ft from the main panel (which is in the car garage).
Not sure on your other questions but should get those answers tomorrow when i speak with the electrician.
The Furutech outlets are Not Isolated Ground for sure. I checked the continuity with a Radio Shack tester and the ground screw is connected to the outlets metal mounting brackets.
Main issue is I do not want to create an electric hazard (pretty sure my electrician is very capable) and I do not want to create a bunch of ground loop issues!
Yes, both ground wires from the outlet/metal box are attached to the ground bar in the sub panel.
Glad to hear that. That’s the way it should be done.
You would be surprised how many posted messages I have read over the years on audio forums where the IG safety equipment grounding conductor was connected directly to the earth connection (Grounding Electrode) for the main electrical service. Or the IG ground was connected to an isolated earth driven ground rod that is not tied, bonded, to the main grounding system of the electrical service, which is quite dangerous. Neither of the two methods meet NEC code.
The purpose of the equipment grounding conductor is to provide a low resistive path for ground fault current to return to the source, the electrical service grounded neutral conductor.
The 2 ought from the sub panel runs back to the main panel. The main panel is grounded to the steel rebar in the house foundation
Just curious, did the electrician wire the new sub panel 120/240V?
2 hot wires, 1 neutral wire, and 1 equipment ground wire.
Did he use 1/0 - 3 with ground romex?
Metal conduit and install three 1/0 conductors plus an insulated equipment ground conductor?
1/0 - 3 with ground MC (Metal Clad) armor cable?
How far (distance) is the sub panel from the main electrical service panel?
If the sub panel is 120/240V did you tell the electrician to feed all 6 dedicated 120V branch circuits from the same Line, leg, from the panel? All from Line 1 (L1) or all from Line 2 (L2)? Audio equipment that is connected together by wire ICs should be fed from circuit breakers fed from the same hot Line, leg, and neutral.
What manufacture brand electrical panel did he install? Style/model? Copper bus? Example, Square D QO.
.
What is the average length of the 6 dedicated 20 amp branch circuits? Longest? Shortest?
How did the electrician terminate, connect, the #6 wire to the 20 amp circuit breakers?
//
Are the six 20 amp circuit breakers CAFCI ( Combination Arc Fault Circuit Interrupter) type?
How did the electrician terminate the #6 neutral wire to the breaker?
IF the sub panel is a Load Center panel it must look pretty busy, full, inside. (A Load Center electrical panel is the type of panel used typically in a residential dwelling unit.)
Or did the electrician install an actual electrical panelboard that is physically much bigger than a Load Center. Lots more wiring space inside. About twice the price of a Load Center.
Second question is does it really matter if the outlets are isolated ground or not?
An IG receptacle is used in commercial and industrial buildings where the branch circuit wiring is installed in metallic conduit. The idea, theory, for using an IG is to isolate the equipment ground of the receptacle from the metallic conduit supposedly to prevent electrical noise that may be traveling on the conduit. Believe it or not National Cash Register was the main reason for the use of IG receptacle years ago. Their specs called for an IG receptacle and if they came out and the receptacle for the cash register was not an IG they would not install their equipment until IG receptacles were installed.
In a residential dwelling unit, house, even if the branch circuit wiring is installed in metallic conduit what AC noise could possibly be traveling on the conduit?
When using Romex an IG receptacle would not serve any purpose or added isolation.
As for what you have now I can’t see where it would violate NEC code. Odd yes...
Also I wouldn’t worry about the branch circuit outlet steel boxes. They are fine.
In your last post you mentioned a sub panel..... I assume the electrician terminated both the box ground wire and the receptacle ground wire on the same ground bar in the sub panel. Is that correct? OR do the IG insulated equipment ground wires, that were intended for IG receptacles, pass through the Sub Panel and connect to the equipment ground bar in the main electrical service panel? (Which meets NEC code for an IG receptacle.)
//
But, evently all the ground wires end up at the grounding pole ( which by code in our area is the steel rebar in the house foundation).
But, evently all the ground wires end up at the grounding pole
Please explain in detail what you mean......
.
Mother Earth does absolutely nothing for the sound quality of an audio system.
Thinking that the Furutech GTX-D G was an isoloated receptacle, we decided to use four-wire Romex. So, one ground wire went directly to the outlet, one to the metal outlet box. The metal boxes are larger and made it easier to jump from 6 awg down to a short piece of 10 awg that would all fit in the one box. And the metal boxes are stronger and make it easier to tightly secure the outlet to the box.
The first question is whether or not the Furutech outlets are actually 'isolated' ground. I am re-checking that now. Second question is does it really matter if the outlets are isolated ground or not? In either case, we have two grounds in the same box, one on the outlet and one tied directly to the metal box. There are six of these dedicated 20 Amp lines in the room. Two boxes are for the mono block amps, two are for subs, and the remaining two are for the front-end components. A two ought line runs from the subpanel to the main panel for the house.
Since the outlet is metal and the box is metal, we have effectively tied the grounds togther right at the box. But, evently all the ground wires end up at the grounding pole ( which by code in our area is the steel rebar in the house foundation).
Same same here as stereo5. New room, 4 dedicated 20 amp lines with the normal plastic boxes. No ground issues or noise. Probably overkill here with potential issues in the future.
What concern did the engineer express? The way you describe is legal except for patient care areas where the two ground paths must be separate. (Maybe that's his thinking).
Your chances for a ground loop are not from the two ground paths but from plugging in separates into different outlets. If you have an amp on one outlet, a preamp in another, a DAC in another and a transport in another still, each component has four separate ground paths when the interconnects are installed. Any unbalance in the neutrals may induce a ground loop hum, especially if the grounding conductors back to the panel are of different lengths.
At the time the electrician looked at the job with you, you must not have had the duplexes to show him. You must have just told him they were IG receptacles. That is the only reason the electrician should have installed 4 wire branch circuit wiring for a 120V dedicated circuit. By code he needed a second equipment ground wire for the metal box. (Unless the branch circuit raceway is hard metallic metal conduit like EMT (thin wall) for example, then the box ground can be the conduit per NEC providing it is a continuous run from the box to the electrical panel. The conduit can connect to other electrical metal boxes along its’ way to the electrical panel.)
Is the wire 6-3 with ground NM-B cable, Romex? If so, there is no reason to ever use an IG receptacle when NM-B cable is used.
Just a guess the electrician used steel boxes because of the #6 wire you wanted him to install. Just a guess he installed a deep 1900, 4" x 4" X 2 1/8" deep box, with a 1 gang raised device cover, for a single duplex receptacle. He may have needed the bigger box to meet the percentage of fill required by NEC for the #6 wire.
In my quest to really do it 'right' I may have screwed-up! No, sheet rock is not up yet!
I will contact Furutech distributor to confirm whether not the outlets are truly 'isolated' ground and go from there. If they are isolated ground, should I leave them as is or pull out metal boxes?
Please explain. I didn’t know Furutech made an isolated ground (IG) type receptacle.
A true isolated grounding type receptacle has the metal supporting back strap of the receptacle insulated from the "U" shaped ground contact of the receptacle. The green equipment ground screw on the receptacle is connected only to the "U" shaped ground contact. An insulated green equipment grounding conductor, wire, connects to the green equipment ground screw and is ran with the branch circuit wiring, and connects to the ground bus in the electrical panel.
If the receptacle is truly an IG receptacle NEC requires the receptacle to have an orange triangle on the front face plate. Or the face plate might be entirely orange with a triangle.
If the Furutech is not an IG duplex receptacle then you wasted your money installing a 3 wire with ground, I assume NM-B cable. (Romex is a trade name of NM-B)
Not only did you waste your money you may find the hot and neutral current carrying conductors of the branch circuits will induce a small voltage onto the equipment ground wires. The induced voltage can cause ground loop hum.
You should have used 2 wire with ground NM-B cable.
Notice the bare equipment grounding conductor, wire, is in the middle between the Hot and neutral wires? The magnetic fields of the hot and neutral wires cancel each other out. With 6-4 wire because of the geometry, lay, of the wires inside the outer sheath, jacket, the 2 equipment ground wires you have are more likely to pick up an induced voltage by the hot or neutral or both. You may find the 6-2 with ground NM-B is 3 wires ran in a slight tight spiral twist as well.
Addendum to Power Distribution White Paper (87 KB)
//
As for the metal box. Many guys have experimented using metal and plastic boxes. There have been mixed opinions on the subject. There was an EE on Audio Asylum that ran some kind of tests and from his results he recommended plastic over steel.
I believe Albert Porter, an Agon member, did some tests as well, just going from memory, and he went with plastic boxes for his dedicated circuits as well.
I would expect that if you used a licensed electrician that all is well. Personally, when I had my electrician install 3 dedicated 20 amp lines in my home, I had him use the plastic boxes and the worked fine with the Shunyata recpticles that were installed in them. I had him use 8 gauge wire as that will handle a lot more than 20 amps.
No, you won't have ground loops... it's just a little um, pointless. :)
So by NEC you must run a dedicated ground from your panel all the way to the box where your outlets are, and ground the outlet AND The box there. This is to ensure if a short occurs inside the box it is grounded and trips the appropriate breaker.
You ran a separate ground wire to the receptacle... which is kind of pointless. :)
Your friend is right, they will be bonded at the box, but they would be anyway. The problem is you wanted a separate ground but you won't have it. Probalby the easiest solution at the beginning would have been to use plastic outlet boxes.
You only have to worry about ground loops when you have different potentials. Like if you hooked up some equipment to one outlet, and other equipment to a second outlet that had significant resistance between the two grounds.
You must have a verified phone number and physical address in order to post in the Audiogon Forums. Please return to Audiogon.com and complete this step. If you have any questions please contact Support.
