Is balanced power safe? I'd love to get set straight on this- I don't think so

Atmasphere

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I've seen balanced power used to reduce noise in audio systems. There is an argument for this, as it does work (although if your equipment employs proper grounding practice, there will be very little advantage). But I also think there are risks involved.

The reason for the risk is that normally the fuse for any audio equipment is on the hot side of the line and is the first thing the AC power encounters on its way into the unit. This BTW is required to get UL approval, the CE mark and generally, certification for import into nearly any country in the world. The fuse is in series with the AC power switch. In this way, if the switch is shorted to the chassis (damaged in shipment for example) it can blow the power fuse.

If for some reason the other side of the AC line (neutral) gets shorted to the chassis, nothing happens, as the neutral is connected to ground (which should be where the chassis is connected). In this situation nothing will happen.

But if you are running 'balanced' power (the correct term BTW is 'symmetrical' power), what was the neutral side of the AC line is now hot with half of the line voltage on it. So if it gets shorted to chassis, potentially (pardon the pun :)) the chassis will be live and could be quite dangerous.

I don't see any protection fuses (of which the values would have to be chosen by the user, there being a fuse for each outlet) on any of the symmetrical power products I have seen. But I've not seen all of them. Has anyone else seen this? I do not see a GFI being enough protection in this case...

So- what am I missing, or am I seeing something that others are not??
 

dmnc02

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I am in no way an expert, but it seems that the key to your concern is that a GFCI (as required on every balanced line by NEC) is not enough protection. Can you elaborate why?
 

JackD201

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Our home is 3 phase but the audio circuits are single phase. I always felt that 3 phase would be worth it for the stuff with motors, HVAC, Washer Dryers, Fridges, Freezers but did little for audio gear except reduce vibration in my amps' transformers. I had no idea there were potential dangers to 3 phase for consumer electronics. Are there really?
 

Orb

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Only used 3 phase myself in special computer-mainframe-carrier level comms related rooms/labs and definitely need a fair bit of respect when using diverse range of equipment with specific requirements, in these instances usually two of us involved; one a qualified and critically experienced electrician and then the person who has engineering understanding and knowledge of the product/system to be connected in the room.

In a domestic setup I can imagine there are many ways this all can go wrong, just quickly nice blog example:
http://nickmarkowitz.blogspot.co.uk/2011/02/be-careful-around-3-phase.html
http://nickmarkowitz.blogspot.co.uk/2012/08/grounded-3-phase-power-legs-dangerous.html

Cheers
Orb
 

Bruce B

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There are warnings that come with these units telling you not to use them with light bulbs and small household appliances.
I don't heed that warning and plug in my lava lamp when I want to.
 

dmnc02

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The blog example is relating to incorrect wiring by electricians unfamiliar with 3-phase industrial service. Balanced transformers for audio systems (such as the one in my Equitech subpanel) only require standard single-phase residential service. But of course, improperly trained electricians are dangerous whether they are wiring single-phase or 3-phase service.
 
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Orb

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The blog example is relating to incorrect wiring by electricians unfamiliar with 3-phase service. Balanced transformers for audio systems (such as the one in my Equitech subpanel) only require standard single-phase service. But of course, improperly trained electricians are dangerous whether they are wiring single-phase or 3-phase service.

Yeah that is my point, in a domestic environment probably more likely to hit that confusion and risk, especially when considering the potential requirements/design of equipment around 3-phase.
Unless I am misunderstanding where everyone is coming from; reading it as domestic products such as fridges/etc being 3-phase design and all that entails, including amps if 3-phase was a standard for domestic use..

Edit:
NVM late here and notice subtle different context between Jack and Atmasphere; I ended up focusing on the 3-phase aspect applied to "is it safe for a domestic environment with equipment standardised around it" doh :D

Cheers
Orb
 

Ronm1

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Only used 3 phase myself in special computer-mainframe-carrier level comms related rooms/labs and definitely need a fair bit of respect when using diverse range of equipment with specific requirements, in these instances usually two of us involved; one a qualified and critically experienced electrician and then the person who has engineering understanding and knowledge
Cheers
Orb
Same here, 3phase on mainframe installs, raised floor rooms back in my h/w days. Going by the book is certainly a good thing as on one install a phase was shorted to the case for one of the plugs from the breaker panel. Could have been an ugly situation. Respect power.
 

Atmasphere

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Just to be clear here, I am not talking about 3-phase power.

I am talking about something often called 'balanced' power, although it really should be called 'symmetrical' power. This involves an isolation power transformer that has a center tap, which is tied to ground and the ground connections of all the outlets it serves.

Apparently though the GFCI outlets don't even have to be grounded to work correctly, so I probably have been over-thinking this.
 

Mike Lavigne

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Just to be clear here, I am not talking about 3-phase power.

I am talking about something often called 'balanced' power, although it really should be called 'symmetrical' power. This involves an isolation power transformer that has a center tap, which is tied to ground and the ground connections of all the outlets it serves.

Apparently though the GFCI outlets don't even have to be grounded to work correctly, so I probably have been over-thinking this.

first thing I had my commercial electrician do on my balanced Equi=tech Wall Panel isolation transformer was to remove the GFI's on each of the 10 circuits and install straight jumpers. the GFI's add noise. those GFI's come standard on the Equi=tech.

the commercial electrician was concerned and cautious but observed the room where all the outlets were, noticed that it's not a bathroom, no sink, no food preparation, no children messing around as it's a dedicated listening room.....and said ok. if it was typical rec room with a bar or such things he would not have removed the GFI's. I told him only dedicated audio gear would be plugged into those outlets.

every outlet still has the 20 amp breaker.

he viewed the room as a purpose built single use facility. it's in a separate building from the main house.

there is a whole separate fully protected conventional power grid in the same building. all my balanced power outlets in the room are clearly designated as different.

if I ever sell the house I can easily re-install the GFI's.....assuming i left the Equi=tech behind.
 
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JonFo

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I built up my own Equi=Tech based power subsystem, and to prevent the problems the OP raises of equipment not designed for symmetrical power being 'off' yet with an energized neutral, I solved the problem with some automation.

In my setup, the balanced power comes out on multiple circuits, each circuit has a DPST 20amp relay between the transformer and the load.. The 30amp input from the electrical service has it's own 30amp-rated DPST relay (it's one huge sucker). These relays are controlled by my automation system so that I can sequentially turn on and off the various circuits or the whole unit.

This allows me to sequentially turn the five amps on or off, and be guaranteed that when off, they get no current on either leg.

For sources, I do leave one circuit on most of the time as all that gear is microprocessor-driven and consuming power at all times, even in 'standby'.

So for the OP, I'd say that the safest way of dealing with this would be to procure a sequential power manager with DPST relays in it and front your amps with that. Several pro-audio and specialized power conditioner companies sell those. Can't recall one off the top of my head, but IIRC, Furman had some.
 

Occam

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Atmasphere,

Indeed, you've answered your own questions quite well. A minor point, NEC refers to 120vac split phase, balanced power as 'Technical Power'. 'Symmetrical Power', depending on background, describes 3 phase as easily as balanced power. As you mentioned, the proper operation of a GFCI does not require the presence of a safety ground. Per NEC, the proper way to provide 120vac on standard 3 blade receptacles on non-safety grounded circuits is via a GFCI, with clear labeling - 'No Equipment Ground'
http://www.mikeholt.com/technical.p...FCI - Receptacles Without A Ground (12-30-99)

Fuses/Breakers protect equipment; GFCIs protect people.
 

GGA

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Aug 23, 2011
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I've seen balanced power used to reduce noise in audio systems. There is an argument for this, as it does work (although if your equipment employs proper grounding practice, there will be very little advantage). But I also think there are risks involved.

The reason for the risk is that normally the fuse for any audio equipment is on the hot side of the line and is the first thing the AC power encounters on its way into the unit. This BTW is required to get UL approval, the CE mark and generally, certification for import into nearly any country in the world. The fuse is in series with the AC power switch. In this way, if the switch is shorted to the chassis (damaged in shipment for example) it can blow the power fuse.

If for some reason the other side of the AC line (neutral) gets shorted to the chassis, nothing happens, as the neutral is connected to ground (which should be where the chassis is connected). In this situation nothing will happen.

But if you are running 'balanced' power (the correct term BTW is 'symmetrical' power), what was the neutral side of the AC line is now hot with half of the line voltage on it. So if it gets shorted to chassis, potentially (pardon the pun :)) the chassis will be live and could be quite dangerous.

I don't see any protection fuses (of which the values would have to be chosen by the user, there being a fuse for each outlet) on any of the symmetrical power products I have seen. But I've not seen all of them. Has anyone else seen this? I do not see a GFI being enough protection in this case...

So- what am I missing, or am I seeing something that others are not??

The other thing to remember is that even if you turn your component off using its own power switch or a power strip the neutral side will most likely still be energized with 60V. This is because on/off switches, from my experience, only lift the connection to the hot line. This is also true at fuse panel where with balanced power you must you double-pole breakers that lift connections to both the hot and neutral. The normally found single-pole breakers only lift the hot side.

I wonder if the incoming 60V serves to keep the electrical circuit of the component "warm," a lot like a standby switch which allows a trickle of incoming power.
 

FrantzM

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The other thing to remember is that even if you turn your component off using its own power switch or a power strip the neutral side will most likely still be energized with 60V. This is because on/off switches, from my experience, only lift the connection to the hot line. This is also true at fuse panel where with balanced power you must you double-pole breakers that lift connections to both the hot and neutral. The normally found single-pole breakers only lift the hot side.

I wonder if the incoming 60V serves to keep the electrical circuit of the component "warm," a lot like a standby switch which allows a trickle of incoming power.

Interesting post and so is the train of thoughts from atmasphere. I wonder if other approaches are not warranted in lieu of the equi=tech. Isolation transformers for one have had a bad press in the audiophile world but properly sized will offer similar , even superior benefits IMO. I am personally a fan (Unique fan ?:)) of the double conversion UPS method and think it is safer and provide a much better alternative in term of performance. You are basically providing your own power and can control almost all the power parameters amongst them Voltage, frequency stability noise since the power path is much shorter, Harmonic distortion from the power source and even EMI .... To me the favored audiophile method that of the "dedicated"circuit is flawed. Professional UPS are relatively inexpensive, especially compared to the audiophile fares of power conditioners so it represents to me the absolute best in term of system power quality.

In my hierarchy of audiophile power quality:

Double conversion Data or Telco-grade UPS. Even a 15 KW (would power almost anything audiophile including Boulder monster amps driving .5 ohm Apogee Scintilla) system would be well below $30K including installation in the US.
Isolation Transformers. Properly sized (at least 200% of the system maximum draw) of course with appropriate grounding and circuitry, although the same applies for any of the listed methods.
And finally Equi=Tech and similar. No experience with those but ...
 

JackD201

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Double conversion Data or Telco-grade UPS. Even a 15 KW (would power almost anything audiophile including Boulder monster amps driving .5 ohm Apogee Scintilla) system would be well below $30K including installation in the US.

Hi Frantz,

What kind of physical space including proper ventilation would a set up like this take up?
 

FrantzM

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Hi Jack

An 18 KVa (about 15 KW usable) dissipate about 10,000 BTU an hour.They usually don't require Air Conditioning, the better units such as the Toshiba 1600 XP series will function reliably for years under 40 deg Celsius temperature but you need to evacuate the heat.Think about the size of a small office refrigerator. The weight is substantial for such units here are the dimensions for the Toshiba 18 Kva (15 KW) 1600 XP.

39.1 in. H x 17.5 in. W x 36.1 in. D 784 lbs


15 KW is much more than most 2-ch systems would ever need. 15 KW would easily power a pair of the Boulder 3050 monos driving 2 Ohms speakers full tilt continuously without braking a sweat with over 3 KW left to power an additional more sane serious audiophile system with a pair of 500 w/ch amplifiers! ..
 

GGA

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Isolation Transformers. Properly sized (at least 200% of the system maximum draw) of course with appropriate grounding and circuitry, although the same applies for any of the listed methods.
And finally Equi=Tech and similar. No experience with those but ...

I believe an Equi=Tech is an Isolation Transformer.

There are three ways that Equi=Tech offers balanced technical power isolation transformers:

http://www.equitech.com/products/xfmrs/xfmrs.html

I think you are right about sizing. I would love to try the double conversion method but easier said than done.
 

Brucemck2

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FrantzM

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Richard Gray is no sttranger to the High End Audio scene.I do wonder however what this unit brings to the table that is different and what they would cost compared to those professional/industrial units such as the Toshiba, APC, Eaton, Marconi, etc?

Are the Equi=Tech UL Listed? BTW?
 

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