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DLDGTO
Re: Socket dilemma

Thanks guys for all the info. I'm not sure I completely understand it all,but I want to be well informed when I hire an electrician to do the work -- so I'm not taken to the bank on this. Here is what I'm understanding MAY be a possible option, so please correct me if I've misunderstood: If the existing 2 prong ungrounded outlets are replaced with correctly labeled GFI outlets, a satisfactory level of safety could be achieved. Additionally, for those outlets deemed dedicated for 3 prong electronics such as computers, it might be advisable to run a copper groung from the breaker box to that outlet. I don't want to spend a fortune on this, but I also don't want to get dead. Thanks, David

JLMCDANIEL
Re: Socket dilemma
DLDGTO wrote:

Thanks guys for all the info. I'm not sure I completely understand it all,but I want to be well informed when I hire an electrician to do the work -- so I'm not taken to the bank on this. Here is what I'm understanding MAY be a possible option, so please correct me if I've misunderstood: If the existing 2 prong ungrounded outlets are replaced with correctly labeled GFI outlets, a satisfactory level of safety could be achieved. Additionally, for those outlets deemed dedicated for 3 prong electronics such as computers, it might be advisable to run a copper groung from the breaker box to that outlet. I don't want to spend a fortune on this, but I also don't want to get dead. Thanks, David

You have learned well grasshopper.

Jack

jled96
Re: Socket dilemma

If you have properly grounded boxes through bx cable , that is technicaly considered a ground in an existing installation, because the house was wired in 1960 that can be used as a groung under grandfathered use. If you need to add more outlets that would be easier to chase new runs from the panel, here in boston it is now 200-250 per opening if there is open access to everything, if not open access then it would be $300-400 if have to rill up walls through fire stops, top plate, bottom plate,exc.! Good Luck!

Re: Socket dilemma
JLMCDANIEL wrote:

A round wire does not provide personal safety. If the hot wire should be shorted to the metal case of an appliance and you touched it and ground, it would take 15 amps to trip the breaker. It takes less than a ¼ amp through your body to kill you, 15 amps would burn you to a crisp. The ground wire's purpose is to trip the breaker and prevent the in-wall cabling from overloading and causing a fire , not to provide personal safety.

If the hot wire shorted to the metal case, wouldn't it trip the breaker?

I found this at: http://www.iaei.org/magazine/2008/03/equipment-grounding-for-safety/

"The first task accomplished by the equipment grounding conductor is establishing a conductive connection to ground (the earth) for the electrically conductive parts of equipment. The process of equipment grounding by use of the equipment grounding conductor electrically connects the conductive parts of equipment to the earth and attempts to hold these conductive parts at or as close to ground potential as possible during normal operation. This helps minimize the possibilities of electrical shock for persons that come in contact with this equipment."

Fencepost
Re: Socket dilemma

The ground wire provides a measure of personal safety by grounding the metal case of an appliance. In the event of a failure of the electrical insulation in the appliance where the cabinet would become energized, in most cases this permits enough current to flow to ground to trip the circuit breaker. In addition, by grounding the frame of the appliance, you ensure that it is at nearly the same electrical potential as the floor the user is standing on, so that there isn't enough voltage difference to flow through the user's body and cause electrocution.

The GFI provides an additional measure of safety for appliance that do not have metal frames (commonly called "double insulated") and therefore are not required to have a ground prong, but which could come in contact with water. In the event these appliances come in contact with water (hairdryer in the sink scenario), the electrification of the water does not provide enough current to trip the breaker, but it does provide enough voltage to cause electrocution. The GFI compares current flowing out with the current flowing in, and if there is a difference it assumes a fault so the GFI trips, preventing the voltage of the water from becoming high enough to cause electrocution.

In the case where there is no ground wire available, a GFI may be used to provide electric shock protection, even for appliances which normally would have a grounded metal case. Should the case become electrified, there may be enough stray current to trip the GFI (since there is no ground conductor). If not, a person touching the case (and completing a circuit to ground) would cause enough current to trip, but it should trip before electrocution occurs.

As has been noted before, a GFI only provides for personal safety. If ungrounded, your appliances will NOT be protected from power surges or electromagnetic fields, even if a surge suppressor is used on a GFI. Surge suppressors require a ground in order to function properly.

As a side note that really has nothing to do with the original poster's question, an older tube-type amplifier (such as is used with guitars) will often emit stray current through radiation, which can sometimes cause a GFI to trip even if the amplifier is in proper working order. Sometimes, turning on an amplifier will trip a GFI because the charging of capacitors can cause an imbalance in the current. Nevertheless, it is now recommended that stages and sound equipment be GFI equipped, because sometimes sound equipment does fail, and a microphone or other instrument could become energized causing electrocution of the performers. Such has happened.

Re: Socket dilemma

Well said. Admittedly, I am not an expert in this area, but I have been learning about grounds and BX lately because of my own home.

I'm not well versed in electrical code, but I also don't think installing a new outlet and using the metal sheath for ground on BX is considered grandfathered. I think if that was installed before the new code it would be.

The problem with using BX armor as the ground is that it can be a high resistance path back to the panel. They manufactured quite a bit of the armor by galvanizing the sheet metal first and then cutting the strips. This left the edge of the metal armor prone to oxidation and increases the resistance of the ground path. Should there be a short to ground on a cable like that, the breaker may not trip and will heat the armor to the point it glows red. If you can see a thin metal strip on the inside of the armor, you don't have BX and it is ok to use the sheath as a ground.

jled96
Re: Socket dilemma

Yes I agree that old bx cable sheath is not an ideal ground under todays code, but any ground back to panel/earth is better that just using the hot/neutral which is not completly safe under any standards, I always recommend to the customer to add properly grounded runs/ gfci's in kitchen,bath,basements,and any outdoor areas. New codes also stipulate the use of arc fault breakers in many applications. Grandfathered use is not a way of cheating the system, it simply allows customers to use there existing wiring with modern devices, I have had a few cases latley where the wiring was simply antiquated and had to be completly rewired. Good Luck!

JLMCDANIEL
Re: Socket dilemma
jled96 wrote:

Yes I agree that old bx cable sheath is not an ideal ground under todays code, but any ground back to panel/earth is better that just using the hot/neutral which is not completly safe under any standards, I always recommend to the customer to add properly grounded runs/ gfci's in kitchen,bath,basements,and any outdoor areas. New codes also stipulate the use of arc fault breakers in many applications. Grandfathered use is not a way of cheating the system, it simply allows customers to use there existing wiring with modern devices, I have had a few cases latley where the wiring was simply antiquated and had to be completly rewired. Good Luck!

90% of all home appliances and fixtures only use a 2 pronged plug. The only saftey measure possible is the hot/neutral current flow provided by a GFCI or AFCI. The presence of a ground at the outlet provides no pesonal safety.

Jack

Fencepost
Re: Socket dilemma
JLMCDANIEL wrote:

The presence of a ground at the outlet provides no pesonal safety.

Except when the ground is connect to the metal case of an appliance with faulty electrical insulation.

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