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This Grounding Thing
- Thread starter speakerman1
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The mention of a dedicated ground rod is a concern as it most likely violates the electric code and creates a safety hazard. Never lift the ground wire at the outlet or breaker panel in favor of an isolated/dedicated ground wire. There is a document provided by our government that addresses these issues for computer power systems. It's free.
http://www.everyspec.com/NIST/NIST-FIPS/FIPS_PUB_94_3307/
http://www.everyspec.com/NIST/NIST-FIPS/FIPS_PUB_94_3307/
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When I was an Electrician. This was our Bible. I do not know the code that refers to grd.s that was many years ago. http://www.nfpa.org/codes-and-standards NFPA is accepted in most localities. If I'm running a different CB pnl or dedicated wouldn't you run a different rod? I'm just asking. If you want to be safer you could go GFI way.
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Larrt, most home panels are either grounded thru the water pipe(old standard) or the ground wire running from the pole. Not many ground rods in home use today.
In the 3 phase field stuff Iuse a 10 foot ground rod at each motor and each pump panel......no one fried yet..as both of those are also tied to the bare copper ground coming from the pole.
In the 3 phase field stuff Iuse a 10 foot ground rod at each motor and each pump panel......no one fried yet..as both of those are also tied to the bare copper ground coming from the pole.
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Unless you live in a cave, this should apply to you.
Most residential, single or multi-family homes, apartments, or condos have either in-ground, overhead to in-ground, or overhead service lines. The wires to your home carry split-phase (also called three-wire, single-phase, midpoint neutral) 120/240 or 120/208 Volts on a three wire system. The three wires are 1) a bare ground wire and every power pole on the planet has a ground wire running back down 8-10 feet into the ground, 2) one insulated power wire, which is 120 Volts, and 3) another insulated power wire is also 120 Volts but 180 degrees out of phase with the other insulated wire.
If you have a distribution transformer “can†on your power pole it is simply a transformer, which typically has 7,200 (or dual power 4.8/16 kVolts) on the primary (the power wire and the ground or two power wires; some localities have 3-phase overheads) and a center-tapped 240 Volt secondary. This allows you to run 120 Volt products and 240 Volt appliances over the same distribution system. The center tap of the transformer is grounded at the pole and should be grounded in your “Service Entry†power box (bare copper or aluminum), this is called Protected Earth (PE). The reason for this is to protect every home from an accidental loss of ground at the power pole (car accident?). The grounding of this wire is accomplished as Lee said, by a clamp to a cold water pipe (which runs through the ground), or a driven ground rod. We are on a water well with a plastic water pipe to the house, so we must use a driven ½†ground rod at the service entry for our PE.
In your power panel all of the ground wires from the distribution throughout your house must connect to the PE ground wire in the panel. In the power panel all of the white “Neutral†wires, or the other half of the 120 Volt side, are connected together and also connected to the PE ground wire. For the 240 Volt distribution (red and black), neutral is not used because the appliance requires both legs of the 120 Volt power and a ground for safety. So each appliance is fed the 120 Volts (black wire) from a circuit breaker and the neutral (white wire) that is electrically connected to the center tap ground wire on the nearest power pole distribution transformer and ground/PE. This is what allows the “return†of the voltage to the source, without this difference of potential (120 Volts and 0 Volts) there is no current flow.
Now, how does this affect my stereo? The power lines are noisy; there is electrical leakage in some of the appliances in your home (if you could disconnect the neutral and the PE wires) add up to probably a few millivolts of 60 HZ AC; and there are many (potentially poor) connections between the chassis of your equipment to the actual earth. How to fix this? Remove the ground (ground loop) from the equipment through a two prong to three prong plug adapter or by cutting the ground wire inside the cabinet? Not so fast, my friend.
This could be dangerous because the circuit breaker detects current flow to ground. If you remove the low-resistance path to ground, you may defeat the breaker. Never remove the green ground wire. An isolation transformer may help but know what you are buying - safety regulations including IEC 950 and UL 1950 require that an isolation transformer is only allowed to isolate the hot and neutral wires; the grounding wire must be passed straight through.
What to do? Do you have hum? Here are some suggestions from various sources:
Good Luck!
Mark
Most residential, single or multi-family homes, apartments, or condos have either in-ground, overhead to in-ground, or overhead service lines. The wires to your home carry split-phase (also called three-wire, single-phase, midpoint neutral) 120/240 or 120/208 Volts on a three wire system. The three wires are 1) a bare ground wire and every power pole on the planet has a ground wire running back down 8-10 feet into the ground, 2) one insulated power wire, which is 120 Volts, and 3) another insulated power wire is also 120 Volts but 180 degrees out of phase with the other insulated wire.
If you have a distribution transformer “can†on your power pole it is simply a transformer, which typically has 7,200 (or dual power 4.8/16 kVolts) on the primary (the power wire and the ground or two power wires; some localities have 3-phase overheads) and a center-tapped 240 Volt secondary. This allows you to run 120 Volt products and 240 Volt appliances over the same distribution system. The center tap of the transformer is grounded at the pole and should be grounded in your “Service Entry†power box (bare copper or aluminum), this is called Protected Earth (PE). The reason for this is to protect every home from an accidental loss of ground at the power pole (car accident?). The grounding of this wire is accomplished as Lee said, by a clamp to a cold water pipe (which runs through the ground), or a driven ground rod. We are on a water well with a plastic water pipe to the house, so we must use a driven ½†ground rod at the service entry for our PE.
In your power panel all of the ground wires from the distribution throughout your house must connect to the PE ground wire in the panel. In the power panel all of the white “Neutral†wires, or the other half of the 120 Volt side, are connected together and also connected to the PE ground wire. For the 240 Volt distribution (red and black), neutral is not used because the appliance requires both legs of the 120 Volt power and a ground for safety. So each appliance is fed the 120 Volts (black wire) from a circuit breaker and the neutral (white wire) that is electrically connected to the center tap ground wire on the nearest power pole distribution transformer and ground/PE. This is what allows the “return†of the voltage to the source, without this difference of potential (120 Volts and 0 Volts) there is no current flow.
Now, how does this affect my stereo? The power lines are noisy; there is electrical leakage in some of the appliances in your home (if you could disconnect the neutral and the PE wires) add up to probably a few millivolts of 60 HZ AC; and there are many (potentially poor) connections between the chassis of your equipment to the actual earth. How to fix this? Remove the ground (ground loop) from the equipment through a two prong to three prong plug adapter or by cutting the ground wire inside the cabinet? Not so fast, my friend.
This could be dangerous because the circuit breaker detects current flow to ground. If you remove the low-resistance path to ground, you may defeat the breaker. Never remove the green ground wire. An isolation transformer may help but know what you are buying - safety regulations including IEC 950 and UL 1950 require that an isolation transformer is only allowed to isolate the hot and neutral wires; the grounding wire must be passed straight through.
What to do? Do you have hum? Here are some suggestions from various sources:
- Plug all of the audio equipment into the same circuit (use a power strip).
- Flip the two-wire plug on one piece of equipment to see if that reduces hum.
- Connect all of the equipment chassis cases to each other using a dedicated wire. (Avoid using the “Ground†connection on turntables, which is just for the RCA cables).
- Remove the power ground to the audio interconnects.
- Use “Star†grounding in the audio components (all audio signal grounds connected to a single point in the chassis).
- Use short audio interconnects and never coil any wires because that sets up a magnetic field.
- Drive a ground rod and make a dedicated connection to the chassis of your amplifier.
- Ensure your system is not connected to the shield of a Cable TV (CATV) system.
- Three wire ground the amplifier and then use two-wire plugs on all other components as long as the interconnects ground the next chassis down the line from the amplifier.
- Install “technical power†which is an isolation transformer with a center tap, used to create a separate supply with conductors at a balanced 60 Volts with respect to ground.
- Use balanced audio connectors which carry a dedicated ground as a shield to the next piece of equipment.
Good Luck!
Mark
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