Report Supplemental Information
Grounding and Bonding
Grounding and Bonding
In my reports comments are made about ground wires, bonding of gas pipes, water pipe grounding and their deficiencies in regards to grounding or bonding. While it is very difficult to explain and for EVERY CIRCUMSTANCE to be covered in a report please note that when the report calls out for 'further review by an electrician' this is exactly what you should be doing.
What is the difference between grounding and bonding?
Bonding is the connection of non-current-carrying conductive elements like enclosures and structures.
Grounding is the attachment of bonded systems to the earth, like with a ground rod, rebar, metal pipes.
Both are necessary to safeguard people and property from electric hazards. All home electrical systems must be bonded and grounded according to code standards. This entails two tasks: First, the metal water and gas pipes must be connected electrically to create a continuous low resistance path back to the main electrical panel. Second, the main electrical panel must be grounded to a grounding electrode such as a ground rod or rods driven into the earth near the foundation of your house.
Bonding and grounding explained
All home electrical systems must be bonded and grounded according to code standards. This entails two tasks: First, the metal water and gas pipes must be connected electrically to create a continuous low resistance path back to the main electrical panel. Second, the main electrical panel must be grounded to a grounding electrode such as a ground rod or rods driven into the earth near the foundation of your house.
Although the piping system is bonded to the ground through your main electrical service panel, the panel grounding and the piping bonding are unrelated when it comes to function. The grounding wire that runs from your electrical panel to the grounding electrode helps even out voltage increases that often occur because of lightning and other causes
Bonding is the connection of non-current-carrying conductive elements like enclosures and structures.
Grounding is the attachment of bonded systems to the earth, like with a ground rod, rebar, metal pipes.
Both are necessary to safeguard people and property from electric hazards. All home electrical systems must be bonded and grounded according to code standards. This entails two tasks: First, the metal water and gas pipes must be connected electrically to create a continuous low resistance path back to the main electrical panel. Second, the main electrical panel must be grounded to a grounding electrode such as a ground rod or rods driven into the earth near the foundation of your house.
Bonding and grounding explained
All home electrical systems must be bonded and grounded according to code standards. This entails two tasks: First, the metal water and gas pipes must be connected electrically to create a continuous low resistance path back to the main electrical panel. Second, the main electrical panel must be grounded to a grounding electrode such as a ground rod or rods driven into the earth near the foundation of your house.
Although the piping system is bonded to the ground through your main electrical service panel, the panel grounding and the piping bonding are unrelated when it comes to function. The grounding wire that runs from your electrical panel to the grounding electrode helps even out voltage increases that often occur because of lightning and other causes
What is pipe bonding?
The main purpose of this bond is to ensure that the metal water pipe is at the same zero voltage to ground as the service grounded conductor. A secondary purpose is to ensure that there is a path back to the service for electrical current flow if the metal water pipe becomes energized.
The main purpose of this bond is to ensure that the metal water pipe is at the same zero voltage to ground as the service grounded conductor. A secondary purpose is to ensure that there is a path back to the service for electrical current flow if the metal water pipe becomes energized.
Below are examples of building grounding and bonding
What is the electrical code for bonding gas pipe?
G2411. 2 (310.2) Gas Pipe Bonding—Systems That Contain CSST
A gas piping system that contains any corrugated stainless steel tubing (CSST) shall be electrically continuous and shall be directly bonded to the electrical service grounding electrode system. Building Codes requiring bonding of CSST flexible gas lines came into practice no earlier than 2007. This code came in as a response to damage to flexible gas lines and fires in homes struck by lightning. However, if this pipe was installed prior to that new code requirement any pipe that is not currently bonding in existing homes is STRONGLY recommended to by bonded.
G2411. 2 (310.2) Gas Pipe Bonding—Systems That Contain CSST
A gas piping system that contains any corrugated stainless steel tubing (CSST) shall be electrically continuous and shall be directly bonded to the electrical service grounding electrode system. Building Codes requiring bonding of CSST flexible gas lines came into practice no earlier than 2007. This code came in as a response to damage to flexible gas lines and fires in homes struck by lightning. However, if this pipe was installed prior to that new code requirement any pipe that is not currently bonding in existing homes is STRONGLY recommended to by bonded.
Do propane lines need to be bonded?
Bonding directly connects the propane tubing to your home's grounding electrode. In the event of a lighting strike, bonding reduces the risk of an arc forming between your propane tubing and other metal objects. Such an arc could cause a gas leak by creating a pinhole in the CSST.
Bonding directly connects the propane tubing to your home's grounding electrode. In the event of a lighting strike, bonding reduces the risk of an arc forming between your propane tubing and other metal objects. Such an arc could cause a gas leak by creating a pinhole in the CSST.
Do water lines have to be grounded?
The NEC requires that water pipes be bonded to ground, even if these metal pipes are not used as part of the grounding system.
Can a water pipe be used as a grounding electrode?
For a metal underground water pipe to qualify as an electrode, we need to have at least 10 feet in direct contact with Earth. This also needs to be electrically continuous or made electrically continuous to the point of attachment for the grounding electrode conductor or bonding jumper. The NEC requires that water pipes be bonded to ground, even if these metal pipes are not used as part of the grounding system.
Should house plumbing be grounded?
Answer: Most electrical codes require a home's electrical system to be grounded through the copper or galvanized-iron water supply pipes that lead from the water main to your faucets. This is done by clamping the ground wire from the panel to a pipe.
Why is there a ground wire on my water pipe?
The wire is a bonding wire. Even though no metal water pipes come into the house, whatever metal pipes there are have to be grounded. For example, if a live wire happens to touch a copper pipe, then the electricity will travel through the pipe, to the wire, and trip the breaker.
Where do you ground water pipes?
Interior metal water piping located 10 feet from the point of entrance to the building may be used as a grounding electrode conductor. The GEC connection must be within the first 5 feet and the metal water pipe must be electrically continuous with a metal underground water pipe electrode.
Does PEX pipe need to be grounded?
PEX is a plastic, and therefore an insulator. A residential electrical panel needs to be grounded according to the NEC ( National Electrical Code ) or whatever local electrical codes are being enforced.
Do branch water supply pipes need bonding?
If the pipes are made of plastic, they do not need to be main bonded. If the incoming pipes are made of plastic, but the pipes within the electrical installation are made of metal, the main bonding must be carried out.
The NEC requires that water pipes be bonded to ground, even if these metal pipes are not used as part of the grounding system.
Can a water pipe be used as a grounding electrode?
For a metal underground water pipe to qualify as an electrode, we need to have at least 10 feet in direct contact with Earth. This also needs to be electrically continuous or made electrically continuous to the point of attachment for the grounding electrode conductor or bonding jumper. The NEC requires that water pipes be bonded to ground, even if these metal pipes are not used as part of the grounding system.
Should house plumbing be grounded?
Answer: Most electrical codes require a home's electrical system to be grounded through the copper or galvanized-iron water supply pipes that lead from the water main to your faucets. This is done by clamping the ground wire from the panel to a pipe.
Why is there a ground wire on my water pipe?
The wire is a bonding wire. Even though no metal water pipes come into the house, whatever metal pipes there are have to be grounded. For example, if a live wire happens to touch a copper pipe, then the electricity will travel through the pipe, to the wire, and trip the breaker.
Where do you ground water pipes?
Interior metal water piping located 10 feet from the point of entrance to the building may be used as a grounding electrode conductor. The GEC connection must be within the first 5 feet and the metal water pipe must be electrically continuous with a metal underground water pipe electrode.
Does PEX pipe need to be grounded?
PEX is a plastic, and therefore an insulator. A residential electrical panel needs to be grounded according to the NEC ( National Electrical Code ) or whatever local electrical codes are being enforced.
Do branch water supply pipes need bonding?
If the pipes are made of plastic, they do not need to be main bonded. If the incoming pipes are made of plastic, but the pipes within the electrical installation are made of metal, the main bonding must be carried out.
EXPLAINATION
Here is an article from Electrical Construction & Maintenance (EC&M)
The Shocking Truth About Grounding Electrode Conductors Nov. 1, 2006
by: Edward J. Osoliniec Osoliniec is a private consulting engineer located in Warren, N.J. He is a licensed professional engineer and electrical contractor in the state of New Jersey
Have you done any service work lately, and noticed a spark as you connect or reconnect the grounding electrode conductor to the ground rod of what appeared to be a perfectly normal electric service? Have you ever disconnected the grounding electrode conductor at a water pipe and received a shock? Have you ever noticed any arcing or sparking at a loose grounding electrode conductor at an outbuilding
Almost every electrical system in a new home or home with an recently updated electrical service has multiple grounding electrodes; ground rods, water pipes, building steel, etc., with a grounding electrode conductor to each. A service with multiple grounding electrode conductors that has a higher resistance on one of the conductors, and little or no measurable current in it, may still have significant current in the other grounding electrode conductors. Therefore, measuring the current in the conductor going to the ground rod and proving it safe does not mean there is a safe current level in the conductor going to the water pipe.
Your neighbor's problem is now your problem. Let's take a look at another example. This time you're working in a building or a house, and you're sure there is a continuous neutral. You look at the service entrance conductors, and don't see any breaks. Everything appears to be in good condition, including the neutral conductor and all neutral connections. You are convinced that since there have been no complaints about fluctuating voltages, or any other indications of an open neutral, that a neutral problem at this building doesn't exist. You even go as far as measuring current in the neutral, and convince yourself that since there is current in the neutral conductor, there can't be an open neutral. This leads you to have no fear of opening up any grounding electrode conductors. Is this a safe assumption?
Even though the building you're working on may have a completely continuous neutral back to the transformer, the house next door or a building somewhere in the general vicinity may have an open neutral. If the building you're working in and the building with an open neutral have some type of conductive path between them, current may return via that path. A metal water pipe is a good example of such a connection. Current can come “up” through a ground rod or a water pipe into the building you're working on, due to an open neutral in a neighboring building. Figure 3 on page C16 illustrates this condition. The metal water pipe common to the buildings has such a low resistance, that it may not be apparent at the building with the open neutral that there is a problem. The current exits the building with the open neutral through the metallic pipes and finds its way back up through the
grounding electrode conductors in your building. Any grounded electrically conductive path between buildings can serve as a return path for current for a building with an open neutral.
The grounded coaxial braid in the jacket of cable television drops can also serve as return paths for the neutral imbalance current from a building with an open neutral (Fig. 4). Cable television systems should be grounded as they enter the premises as per Art. 680 of the NEC. Since the cable television connection blocks typically get grounded directly to the same grounding electrodes that the electric service uses (or they have their own separate grounding electrode, and that electrode gets bonded to the electrical system grounding electrode), this can become a return path. However, this situation is quite rare, since the ampacity of the return current tends to burn out the coaxial cable). Nonetheless, it can still exist and create a hazard.
Is the current coming or going? So now you're convinced that there can be current flowing in a grounding electrode conductor. Next time you're on-the-job, use your ammeter to measure the current in the grounding electric conductor before you open up that connection. If you measure a current, how do you know if it's due to current going “down” into the ground at this building or current coming up through the grounding electrode conductor in your building and returning back to the source via your neutral?
Unfortunately, putting an ammeter on the conductor will only prove that there is current flowing in the conductor. It does not tell you the direction of that current. You must use Kirchoff's Law to determine the direction of the current flow. Kirchoff's Law states that all currents entering a connection are equal to the currents leaving a connection. Simply put, all currents must balance. Let's look at a couple of examples for clarification.
Example No. 1. You're working on a single-phase, 120/240V service. You measure 11A in the black conductor at the main service panel. You measure 5A in the red conductor at the main service panel. On a single-phase service, the neutral current is the difference between the two legs of the transformer, which in this case is 6A. Therefore, if you measure 6A in the grounding electrode conductor and 0A in the neutral service entrance conductor, you can be relatively certain that the neutral is open, and your building is dumping current into an alternate return path (i.e. the grounding electrode).
Example No. 2. You're working on a single-phase, 120/240V service. You measure 11A in the black conductor at the main service panel. You measure 5A in the red conductor at the main service panel. As in the first example, the neutral current will be the difference between the two legs of the transformer, which is 6A. However, this time you measure 8A in the grounding electrode conductor. How can this be? Can there possibly be more current being dumped into the ground by the system you're working on than the system imbalance current? Are there 2A of extra phantom current? When you measure the current in the neutral, you find 14A. Now you're really confused. Applying Kirchoff's Law to the circuit, you quickly realize that the 6A of current imbalance from the system you're working on is being joined with 8A coming into this system from somewhere else.
Final thoughts. Neutral current will return to its source via any means possible. That return path could be through a conductor or connection that may seem unlikely to you, such as a grounding electrode conductor.
As electrical services in some neighborhoods around the country age — and the likelihood of an open neutral is more probable as well as in areas with high population density where at least one open neutral may exist — neutral currents seeking return paths through what may be considered unconventional means become more likely. In any and all cases, shock hazards can exist with all electrical conductors, including grounding electrode conductors.
Things to Consider
Here is an article from Electrical Construction & Maintenance (EC&M)
The Shocking Truth About Grounding Electrode Conductors Nov. 1, 2006
by: Edward J. Osoliniec Osoliniec is a private consulting engineer located in Warren, N.J. He is a licensed professional engineer and electrical contractor in the state of New Jersey
Have you done any service work lately, and noticed a spark as you connect or reconnect the grounding electrode conductor to the ground rod of what appeared to be a perfectly normal electric service? Have you ever disconnected the grounding electrode conductor at a water pipe and received a shock? Have you ever noticed any arcing or sparking at a loose grounding electrode conductor at an outbuilding
Almost every electrical system in a new home or home with an recently updated electrical service has multiple grounding electrodes; ground rods, water pipes, building steel, etc., with a grounding electrode conductor to each. A service with multiple grounding electrode conductors that has a higher resistance on one of the conductors, and little or no measurable current in it, may still have significant current in the other grounding electrode conductors. Therefore, measuring the current in the conductor going to the ground rod and proving it safe does not mean there is a safe current level in the conductor going to the water pipe.
Your neighbor's problem is now your problem. Let's take a look at another example. This time you're working in a building or a house, and you're sure there is a continuous neutral. You look at the service entrance conductors, and don't see any breaks. Everything appears to be in good condition, including the neutral conductor and all neutral connections. You are convinced that since there have been no complaints about fluctuating voltages, or any other indications of an open neutral, that a neutral problem at this building doesn't exist. You even go as far as measuring current in the neutral, and convince yourself that since there is current in the neutral conductor, there can't be an open neutral. This leads you to have no fear of opening up any grounding electrode conductors. Is this a safe assumption?
Even though the building you're working on may have a completely continuous neutral back to the transformer, the house next door or a building somewhere in the general vicinity may have an open neutral. If the building you're working in and the building with an open neutral have some type of conductive path between them, current may return via that path. A metal water pipe is a good example of such a connection. Current can come “up” through a ground rod or a water pipe into the building you're working on, due to an open neutral in a neighboring building. Figure 3 on page C16 illustrates this condition. The metal water pipe common to the buildings has such a low resistance, that it may not be apparent at the building with the open neutral that there is a problem. The current exits the building with the open neutral through the metallic pipes and finds its way back up through the
grounding electrode conductors in your building. Any grounded electrically conductive path between buildings can serve as a return path for current for a building with an open neutral.
The grounded coaxial braid in the jacket of cable television drops can also serve as return paths for the neutral imbalance current from a building with an open neutral (Fig. 4). Cable television systems should be grounded as they enter the premises as per Art. 680 of the NEC. Since the cable television connection blocks typically get grounded directly to the same grounding electrodes that the electric service uses (or they have their own separate grounding electrode, and that electrode gets bonded to the electrical system grounding electrode), this can become a return path. However, this situation is quite rare, since the ampacity of the return current tends to burn out the coaxial cable). Nonetheless, it can still exist and create a hazard.
Is the current coming or going? So now you're convinced that there can be current flowing in a grounding electrode conductor. Next time you're on-the-job, use your ammeter to measure the current in the grounding electric conductor before you open up that connection. If you measure a current, how do you know if it's due to current going “down” into the ground at this building or current coming up through the grounding electrode conductor in your building and returning back to the source via your neutral?
Unfortunately, putting an ammeter on the conductor will only prove that there is current flowing in the conductor. It does not tell you the direction of that current. You must use Kirchoff's Law to determine the direction of the current flow. Kirchoff's Law states that all currents entering a connection are equal to the currents leaving a connection. Simply put, all currents must balance. Let's look at a couple of examples for clarification.
Example No. 1. You're working on a single-phase, 120/240V service. You measure 11A in the black conductor at the main service panel. You measure 5A in the red conductor at the main service panel. On a single-phase service, the neutral current is the difference between the two legs of the transformer, which in this case is 6A. Therefore, if you measure 6A in the grounding electrode conductor and 0A in the neutral service entrance conductor, you can be relatively certain that the neutral is open, and your building is dumping current into an alternate return path (i.e. the grounding electrode).
Example No. 2. You're working on a single-phase, 120/240V service. You measure 11A in the black conductor at the main service panel. You measure 5A in the red conductor at the main service panel. As in the first example, the neutral current will be the difference between the two legs of the transformer, which is 6A. However, this time you measure 8A in the grounding electrode conductor. How can this be? Can there possibly be more current being dumped into the ground by the system you're working on than the system imbalance current? Are there 2A of extra phantom current? When you measure the current in the neutral, you find 14A. Now you're really confused. Applying Kirchoff's Law to the circuit, you quickly realize that the 6A of current imbalance from the system you're working on is being joined with 8A coming into this system from somewhere else.
Final thoughts. Neutral current will return to its source via any means possible. That return path could be through a conductor or connection that may seem unlikely to you, such as a grounding electrode conductor.
As electrical services in some neighborhoods around the country age — and the likelihood of an open neutral is more probable as well as in areas with high population density where at least one open neutral may exist — neutral currents seeking return paths through what may be considered unconventional means become more likely. In any and all cases, shock hazards can exist with all electrical conductors, including grounding electrode conductors.
Things to Consider
- Never assume that a grounding electrode conductor is “dead,” or you may be.
- If there is no current in one of the grounding electrode conductors, this doesn't mean there is no grounding electrode current flowing somewhere in the system. Treat all grounding electrode connection points individually.
- Always assume the grounding electrode conductor is “hot,” and treat it as such, until proven otherwise.
- Even though the system you're working on may be functioning correctly, and have a good neutral, a dangerous condition may still exist if there is an open neutral in a neighboring building.
- Even if the main circuit breaker in the building you're working in is open, as long as the neutral provides a path for that imbalanced current, current can be flowing up through your grounding electrodes, and back through your neutral.
- Current can come into the system you're working on from a local faulty system.
- The neutral in the building you're working on was sized for its own service, not for additional current from another service. If a neighboring building has an open or faulty neutral, it may affect the system you're working on.
More Information: This is not an all encompassing explanation of the subject. You are strongly encouraged to have a licensed electrician review your electrical system, especially if it is an older home. Code has changed and improved safety over the years. You are encourage to make improvements to your home especially in the electrical area. Trust me, the building community has learned a lot over the years and the code is finally catching up and REQUIRING those things in new construction. Many improvements to grounding and bonding are not that expensive and can really make a difference in the electrical safety of your home.