Adding Safety Ground to Old 2 Conductor Wiring

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john12ax7

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Oct 15, 2010
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In an apartment (older building),  the outlets have been replaced with 3 prong but there is no actual ground connection  :eek:  inside is only two wires.

There is a one room addition with modern grounded outlets. So how to get ground to the others? Run long extension cords? Use some romex on the walls to just get the ground distributed?

Landlord is unwilling to fix it.  Need something safe and effective.
 
In this situation, the 3 pin receptacles need to be "GFCI" receptacles.  Small form-factor "GFCI" receptacles are available to fit in the old smaller wall outlet boxes.

It is not permitted by NEC Code or local laws to attach convention 3 pin receptacles to a 2 wire circuit.

The "GFCI" receptacles will ad a human safety factor but won't do anything about noise and leakage currents.
 
john12ax7 said:
In an apartment (older building),  the outlets have been replaced with 3 prong but there is no actual ground connection  :eek:  inside is only two wires.

There is a one room addition with modern grounded outlets. So how to get ground to the others? Run long extension cords? Use some romex on the walls to just get the ground distributed?

Landlord is unwilling to fix it.  Need something safe and effective.
My house (I guess I'm the landlord) has 2 wire mains wiring throughout. There are old two blade outlets everywhere. I have replaced a few with 3 wire outlets when they failed (one became high resistance and heated up, another became intermittent.) They don't sell two blade outlets any more.

I have installed GFCI protected outlets in the several locations near water and the obvious shock hazard from cold water ground (even though my galvanized water main pipe was replaced with PVC several years ago opening that natural earth ground path through plumbing).

The bathroom outlet is now GFCI, kitchen and laundry room are both GFCI with my own DIY added safety ground wire tied back to the fuse box panel. 

I also bonded the copper plumbing in my laundry room  to that same fuse panel ground. (I had an incident a couple years ago when my failing hot water heater energized my hot water and I felt the voltage tingle when testing my shower water temperature with a finger before stepping in).  :eek:

So A) ground bond all copper plumbing, and B) use GFCI outlets in rooms where humans can be exposed to both ground and mains voltage.

JR

PS: Two wire power is generally safe, when used with modern two wire equipment (double insulated) while old legacy three wire gear expects a safety ground bond. It is a little awkward but a suitable extension cord between a grounded outlet and a power strip in your recording area could telescope a temporary safety ground. DO NOT BOOTLEG  a safety ground to neutral, this is against electrical code and can be dangerous.
 
scott2000 said:
All of them?
I believe the convention is the 'first' receptacle must be GFCI, and it will protect all downstream outlets, provided those downstream outlets are connected to the 'load' side of the GFCI outlet.
 
Matador said:
I believe the convention is the 'first' receptacle must be GFCI, and it will protect all downstream outlets, provided those downstream outlets are connected to the 'load' side of the GFCI outlet.
Yes you can hang additional outlets off the downstream side of a GFCI outlet, but I wouldn't try to wire up an entire branch through one GFCI outlet. I think in Europe they use GFCI (called RCD over there) breakers with a higher than 6 mA trip threshold to protect entire branches.

The leakage current will be cumulative for the entire string of outlets downstream of one GFCI, so if the sum of leakage from the sundry outlets combine to >6 mA the GFCI device will trip and shut off the entire string.

As long as you have modern two wire gear (double insulated)  there is not much (safety) benefit from a safety ground (old 3 wire legacy gear is a different story it expects a robust ground bond to pop the fuse/breaker in case of a fault).

You can plug an power strip into a GFCI outlet and it will protect the entire strip (while cheap power strips are notorious for having leaky protection devices.) 

JR
 
JohnRoberts said:
As long as you have modern two wire gear (double insulated)  there is not much (safety) benefit from a safety ground (old 3 wire legacy gear is a different story it expects a robust ground bond to pop the fuse/breaker in case of a fault).

Why do you consider 3 wire to be legacy? Almost all my expensive modern equipment is 3 wire.  The only 2 wire stuff  tends to cheap consumer electronics.

Side question.  Is it safe to run 3 wire appliances on ungrounded GFCI?
 
john12ax7 said:
Why do you consider 3 wire to be legacy? Almost all my expensive modern equipment is 3 wire.  The only 2 wire stuff  tends to cheap consumer electronics.
perhaps a personal problem...

Last century I put 3 wire line cords on some products because it was perceived as more professional. The customer is always right.  ::)
Side question.  Is it safe to run 3 wire appliances on ungrounded GFCI?
It is safe to use anything in ungrounded GFCI, that is why they developed them.

JR
 
john12ax7 said:
Is it safe to run 3 wire appliances on ungrounded GFCI?
It's safe, but very likely to be humming. Generally, audio equipment begs to be grounded, although there are examples of ungrounded (unearthed?) HiFi set-ups that work remarkably noiselessly. For more or less professional use, I consider grounding as necessary.
In terms of noise performance, an ideal set-up would have only one piece of equipment earthed, all the rest being grounded via the cable shields. That's the case when the console is earthed, and the mics are not (that would be the case with dynamics and passive ribbons), but as soon as you connect tube mics (with their own PSU), CD players and keyboards, all sorts of ground loops can happen.
In that case, an unearthed source is preferrable.
I have strong memories of pulling hair over cassette players that ruined an otherwise perfect studio set-up.
That's an area where safety and performance integrity collide.
Caveat: don't take this as a recommandation to use a cheat plug!
 
abbey road d enfer said:
It's safe, but very likely to be humming. Generally, audio equipment begs to be grounded, although there are examples of ungrounded (unearthed?) HiFi set-ups that work remarkably noiselessly. For more or less professional use, I consider grounding as necessary.
In terms of noise performance, an ideal set-up would have only one piece of equipment earthed, all the rest being grounded via the cable shields. That's the case when the console is earthed, and the mics are not (that would be the case with dynamics and passive ribbons), but as soon as you connect tube mics (with their own PSU), CD players and keyboards, all sorts of ground loops can happen.
In that case, an unearthed source is preferrable.
I have strong memories of pulling hair over cassette players that ruined an otherwise perfect studio set-up.
Been there done that... My evil villain last century was dealing with consumer VCRs synced up to my 4T cassette deck (that was 3 wire grounded) using SMPTE time code tracks on both machines.

Yes, consumer gear can work reasonably well in a consumer environment but unbalanced I/O can reveal flaws in ground quality.

One not very obvious technique used inside some consumer VCRs was a cap coupled pseudo ground shield connection between chassis (unbalanced audio low) and mains neutral. This generally worked OK (neutral is nominally 0V), but the occasional mis-wired outlet with line and neutral swapped directly injects mains frequency hum current into audio grounds. These caps were small enough to not create a human safety hazard.
That's an area where safety and performance integrity collide.
Caveat: don't take this as a recommandation to use a cheat plug!
Especially not on 3 wire gear that needs the safety ground bond to protect us from mains faults.

I can imagine mostly safe alternatives to floating grounds with 3 wire gear, but none that UL would ever approve, so never mind.

JR
 
JohnRoberts said:
One not very obvious technique used inside some consumer VCRs was a cap coupled pseudo ground shield connection between chassis (unbalanced audio low) and mains neutral.
In essence, that's the same scheme as the meat-puppet killer cap in guitar amps.

This generally worked OK (neutral is nominally 0V), but the occasional mis-wired outlet with line and neutral swapped directly injects mains frequency hum current into audio grounds.
Loud hum (and a serious tinge) was the clear sign of this reversal; actually, most gtr amps had a polarity switch that allowed choosing the less noisy (and less lethal).

These caps were small enough to not create a human safety hazard.
In guitar amps, they were large enough to be a threat to cardiac people.

I can imagine mostly safe alternatives to floating grounds with 3 wire gear, but none that UL would ever approve, so never mind.
That's a paradox IMO. UL is finicky about these things, and quite restrictive to its accepted methods, but OTOH whoever is in charge of electricity distribution seems to be lax about the private side.
The generalization of 220/240V in Europe has prompted the ruling organisms to impose drastic rules. The electricity distributor will not open the tap if the rules are not obeyed, checked and verified.
One may think it's an unacceptable deprivation of liberty, but I feel safer for that.
 
abbey road d enfer said:
In essence, that's the same scheme as the meat-puppet killer cap in guitar amps.
aka "stinger cap"...
Loud hum (and a serious tinge) was the clear sign of this reversal; actually, most gtr amps had a polarity switch that allowed choosing the less noisy (and less lethal).
In guitar amps, they were large enough to be a threat to cardiac people.
That's a paradox IMO. UL is finicky about these things, and quite restrictive to its accepted methods, but OTOH whoever is in charge of electricity distribution seems to be lax about the private side.
I wasted time and my own money talking with UL (those UL specs are not free).  They are heavily invested in a strategy of robust ground bonding so mains voltage faults will draw lots of current and trip fuses/breakers.  I spent some time thinking about protecting meat puppets while performing. All too often the voltage hazard and ground path is not from the same branch circuit so simple GFCI (RCD) will not protect against inter-branch faults***  where the solid ground bond contributes to the human hazard.

I designed one safety device (for use on stage) that included its own GFCI to interrupt local power if it was causing the fault, and also sensed for fault current flowing into the ground from elsewhere.  I used a 3 pole relay so disconnected all three; line, neutral, and safety ground if external safety ground current exceeded a threshold similar to GFCI thresholds. I built a working prototype as proof of concept, but didn't even bother to throw more time and money at UL...  The market for this is very narrow , and musicians are not big on spending money for safety.  Further I had insurmountable odds against persuading UL to let me open the safety ground.

Now we can purchase off the shelf GFCI power strips that will provide 90% of the protection my device did. The rare incident that would be protected by also lifting the safety ground, is not worth the costly argument with UL (even if the strategy had merit). 

The generalization of 220/240V in Europe has prompted the ruling organisms to impose drastic rules. The electricity distributor will not open the tap if the rules are not obeyed, checked and verified.
One may think it's an unacceptable deprivation of liberty, but I feel safer for that.

JR

**** inter branch faults are protected if all branches have their own GFCI/RCD but I was operating under the assumption that GFCI protected power was rare so one GFCI does not protect against another branch that is not GFCI protected.
 
john12ax7 said:
In an apartment (older building),  the outlets have been replaced with 3 prong but there is no actual ground connection  :eek:  inside is only two wires.

There is a one room addition with modern grounded outlets. So how to get ground to the others? Run long extension cords? Use some romex on the walls to just get the ground distributed?

Landlord is unwilling to fix it.  Need something safe and effective.

I sympathize mate.  I miss lots of things about California but dealing with apartment renting and landlords aren't on the list.
Kicking up a fuss about things that need updating generally doesn't go over well and gets you a 'trouble tennant' label and it's sometimes just better to fork out a bit if cash yourself.  But not too much.


What I would do is:
If you have access to the fuse panel for your apartment, an RCD breaker for the ungrounded outlets might be an option if you're concerned about safety with using them.  If not, just buy a couple of protected outlets and install them.
Run all your pro audio stuff from the real grounded outlets in the room that has them.  Make a long extension plug strip if you have to.

Anything you buy can be taken with you and used elsewhere.  Stapling ground wires to the skirting board most probably can't and might lose you your security deposit.

My $0.01 worth of opinion.

P.S.  don't rely on copper pipes for grounding, you have no idea if part of it has been replaced with plastic somewhere down the line.
 
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