kwired
Electron manager
- Location
- NE Nebraska
Those people sometimes referred to as dirt worshippers.
Inspectors often seem to have gone to the dirt worshipping classes when they obtain their inspector certifications.
Why no splicing of ground rod conductors ?
- Thread starter avm32
- Start date
- Status
Inspectors often seem to have gone to the dirt worshipping classes when they obtain their inspector certifications.
Greg1707
Senior Member
- Location
- Alexandria, VA
- Occupation
- Business owner Electrical contractor
I am restating the question. Electrical systems allow lots and lots of splices. It seems that only the GEC is not allowed to be spliced. Why?
What is the worst thing that can happen if a GEC fails? What is the worst thing that can happen if the conductor to a hospital operating room fails?
What is the worst thing that can happen if a GEC fails? What is the worst thing that can happen if the conductor to a hospital operating room fails?
LarryFine
Master Electrician Electric Contractor Richmond VA
- Location
- Henrico County, VA
- Occupation
- Electrical Contractor
I think this may be one of those rules that developed early on, and they just never had a reason to change it as electrical systems and electrical codes evolved over the years.
R777V
Member
- Location
- Chicago IL
- Occupation
- Facilities Engineer/Industrial Electrician
Happened upon an estate sale where the neutral from the service mid span in the triplex run was dangling, it was an old 60 amp service so no ground rod and people were ducking under the drop all kinds of appliances plugged in everywhere for sale. The cold water line was only source of ground other than at pole, needless to say I was only looking for old Klein vintage tools, and cane away with a lineman pliers from 1922 stamped Bell System, and another W.U. Tel Co., a good portion of the electrical appliances and Electronics were toast. Surprised anyone even thought of buying any after seeing the line dangling right over their heads. You can’t make this stuff up! Good finds for me though!
Sent from my iPhone using Tapatalk
Sent from my iPhone using Tapatalk
kwired
Electron manager
- Location
- NE Nebraska
I'd expect nearly everyone there to not know what the condition of that line means to people like you or me.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Based on being on the forum for 20+years, electrician for 40, and attending many seminars by Mike Holt, my explanation is
based on that of a constitutionalist, ie we go back to when the rules were written
Originally, electrical systems were not grounded or connected to earth, as it is safer to have an ungrounded system. But here were many fires from transformer failures and overvoltage in the electrical system wiring. I suspect the early transformers did not have robust insulation and oils
The decision was made to require electrical grounding, this may of been about 1915. Part of the grounding was to have a GEC. At that time there were no cadwelds, or compression splices, so it was important to have an unspliced GEC. And a splce in a GEC for overvoltage or lightning creates resistance and possibly a fire from high current. this is why cell sites use cad weld, or compression connectors. I seem to recall that splicing the GEC was allowed in the early 1970's
Now as to the effectiveness of a ground rod, in lightning or overvoltage line, that's a different question and subject
based on that of a constitutionalist, ie we go back to when the rules were written
Originally, electrical systems were not grounded or connected to earth, as it is safer to have an ungrounded system. But here were many fires from transformer failures and overvoltage in the electrical system wiring. I suspect the early transformers did not have robust insulation and oils
The decision was made to require electrical grounding, this may of been about 1915. Part of the grounding was to have a GEC. At that time there were no cadwelds, or compression splices, so it was important to have an unspliced GEC. And a splce in a GEC for overvoltage or lightning creates resistance and possibly a fire from high current. this is why cell sites use cad weld, or compression connectors. I seem to recall that splicing the GEC was allowed in the early 1970's
Now as to the effectiveness of a ground rod, in lightning or overvoltage line, that's a different question and subject
Another C10
Electrical Contractor 1987 - present
- Location
- Southern Cal
- Occupation
- Electrician NEC 2020
Many will disagree but I'm pretty sure its to assure a sound unbreakable path. The weakest point of any circuit or continuity is a splice.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Ok. Well IF the GEC fails, and IF the utility system is not an MGN and IF the POCO doesn't have a rod at the transformer secondary and IF the neutral conductor is not indirectly bonded to Earth by water pipe, well casing, other structure, etc.....THEN..... You would have the electrical system floating with no ground reference. So what? Well there is a small chance voltage ratings of equipment and conductors could be exceeded without a stable ground reference. There is a very small chance of the contact with higher voltage line issue I mentioned earlier would be made worse.
- Location
- New Jersey
- Occupation
- Journeyman Electrician
This splicing difficulty could be solved by manufacturing an irreversible set screw splicing connector. Tighten the set screws and head shears off at the proper torque. Don't even need a torque wrench. Done.
Protective and performance grounding has been part of my profession for 40-years in telecom as a Power Protection Engineer.
Op, you have misunderstood 250.64(C) by not referring to the exceptions listed. You can splice the GEC provided they are exothermically welded or irreversible compression. The real question is why?
The simple answer; any mechanical pressure connector will fail in a short period of time buried in the dirt. Unfortunately, many do not think the GEC is important or does anything. Let's see if we can change that.
Ground serves five functions listed in order of importance.
1. Earth Ground or GES/GEC provides the planned safe return path for lightning and utility high voltage fault currents to return to their source. We call them Sinks or Absorbers (all 8 NEC-defined ground electrodes) for outside faults in my occupation. God and Utilities are the only entities permitted to use earth (dirt) as a circuit conductor. It is the nature (physics) of high voltage. Utilities and Lightning use earth as a return conductor back to the energy source.
Utilities multi-ground the static-neutral wire on Wye distribution. The neutral is bonded to every pole butt or tower ground. The result is a very low impedance path back to the utility distribution substation transformer. The consequence is it is the source of stray voltage. If your service transformer shorts primary to secondary, or primary distribution high voltage falls on secondary distribution, earth ground is your planned safe return path back to the utility transformer. If will operate your AC service transformer fuse instantaneously clearing the fault.
Lightning does not require a direct strike to damage property or injure us. According to IEEE and NFPA, roughly 95% of transients arrive via utility, CATV, and Telco. This is why NEC 250.94 (IBT) was adopted to form a single point ground. Lightning is looking for the earth because earth is the return path to the source. Lightning behaves differently than power frequencies. Lightning flows outward on the surface in all directions, like a wave when you throw a rock in a pond. DC and power frequencies flow deep in the earth back toward the direction of the source. This makes lightning dangerous and where the term Step-Potential comes from. The distance between your feet is enough to kill.
Interesting fact and may help in understanding. Ground rods are for power frequencies, and radials (bonding jumpers) are for lightning and high frequencies. Rods are DC and Inductively couple to earth. Above 300 Hz, the impedance rises sharply. Radials are DC and capacitively couple to earth. The higher in frequency you go, the lower the impedance. Lightning discharge along the surface, and why radio towers and facilities with sensitive equipment construct their GES with very long radials going away from the protected area. You can direct where the energy discharges.
Food for thought. Think of an uninformed homeowner or ham radio operator who places an antenna mast on the opposite side of the house from the AC service. They drive a ground rod and bond the coax shield to the rod with an ADU. They do not know they placed themselves between two earth grounds. The two rods are bonded using the radio or TV as a ground wire. Classic ground loop. They learn the hard way if lightning strikes nearby.
2. Provides 0-Volt reference point or 0-volt Touch Potential as some may know it. It sounds simple enough, but there might be more to it than you first thought. Not only does it keep chassis and enclosures at 0-volt touch potential, but it also provides a 0-volt signal reference for sensitive electronic equipment. If you allow current to flow on equipment grounds, you will develop voltage potential drops along the length of the ground conductor. Result touch potential voltages are allowed to develop, and 0-volt signal reference is lost, causing errors in sensitive equipment. If all your grounds originate from a single point, no voltage differences can develop between equipment.
3. Provides the planned fault return path to operate OCPD quickly and limit touch potential fault voltages to tolerable limits. This is your EGC and bonding jumpers job. If the line conductor breaks off inside your toaster oven and falls into the enclosure, The EGC induces a high current fault, returning the current back to the utility neutral service conductor, completing the path operating the breaker within a half-cycle, clearing the fault. Additionally, the earth ground reference limits the touch potential to tolerable limits during a fault. The impedance of the Line and EGC conductors are roughly equal, forming a voltage divider limiting touch voltage to roughly half of the supply voltage. Chassis can be as high as 60-volts in a 120 VAC circuit during a fault. Note no current ever flows through earth ground, only referenced to the earth. The breaker would still operate if you lost the GES, but the full 120-volts would be on the chassis during the fault.
4. Shorts out cable capacitance resulting in a steady-state leakage current into ground conductors. Not so much of a problem in residential settings, but in large facilities are significant. The leakage flows through the cable insulation, speeding up deterioration decreasing service life. Under transient conditions, the leakage capacitance can resonate with inductance in the circuit, causing very high voltages across the loads and cable insulation.
5. ESD or pico lightning. It may not seem important, but try telling that to the dud tester at the Looney-Tunes ammunition factory. Seriously ESD is responsible for billions of dollars in property and equipment damage and countless injuries and loss of life. From grain silos to high-tech manufacturing have strict ESD controls are in place.
High tech facilities like data centers, airports, petroleum, etc go to great lengths to protect their GES. Some like the FAA and Disney parks use cathodic protection to ensure the integrity of the GES. Hopefully, no one has to learn the hard way.
OK, I will get off my soapbox now and return to the golf course.
Op, you have misunderstood 250.64(C) by not referring to the exceptions listed. You can splice the GEC provided they are exothermically welded or irreversible compression. The real question is why?
The simple answer; any mechanical pressure connector will fail in a short period of time buried in the dirt. Unfortunately, many do not think the GEC is important or does anything. Let's see if we can change that.
Ground serves five functions listed in order of importance.
1. Earth Ground or GES/GEC provides the planned safe return path for lightning and utility high voltage fault currents to return to their source. We call them Sinks or Absorbers (all 8 NEC-defined ground electrodes) for outside faults in my occupation. God and Utilities are the only entities permitted to use earth (dirt) as a circuit conductor. It is the nature (physics) of high voltage. Utilities and Lightning use earth as a return conductor back to the energy source.
Utilities multi-ground the static-neutral wire on Wye distribution. The neutral is bonded to every pole butt or tower ground. The result is a very low impedance path back to the utility distribution substation transformer. The consequence is it is the source of stray voltage. If your service transformer shorts primary to secondary, or primary distribution high voltage falls on secondary distribution, earth ground is your planned safe return path back to the utility transformer. If will operate your AC service transformer fuse instantaneously clearing the fault.
Lightning does not require a direct strike to damage property or injure us. According to IEEE and NFPA, roughly 95% of transients arrive via utility, CATV, and Telco. This is why NEC 250.94 (IBT) was adopted to form a single point ground. Lightning is looking for the earth because earth is the return path to the source. Lightning behaves differently than power frequencies. Lightning flows outward on the surface in all directions, like a wave when you throw a rock in a pond. DC and power frequencies flow deep in the earth back toward the direction of the source. This makes lightning dangerous and where the term Step-Potential comes from. The distance between your feet is enough to kill.
Interesting fact and may help in understanding. Ground rods are for power frequencies, and radials (bonding jumpers) are for lightning and high frequencies. Rods are DC and Inductively couple to earth. Above 300 Hz, the impedance rises sharply. Radials are DC and capacitively couple to earth. The higher in frequency you go, the lower the impedance. Lightning discharge along the surface, and why radio towers and facilities with sensitive equipment construct their GES with very long radials going away from the protected area. You can direct where the energy discharges.
Food for thought. Think of an uninformed homeowner or ham radio operator who places an antenna mast on the opposite side of the house from the AC service. They drive a ground rod and bond the coax shield to the rod with an ADU. They do not know they placed themselves between two earth grounds. The two rods are bonded using the radio or TV as a ground wire. Classic ground loop. They learn the hard way if lightning strikes nearby.
2. Provides 0-Volt reference point or 0-volt Touch Potential as some may know it. It sounds simple enough, but there might be more to it than you first thought. Not only does it keep chassis and enclosures at 0-volt touch potential, but it also provides a 0-volt signal reference for sensitive electronic equipment. If you allow current to flow on equipment grounds, you will develop voltage potential drops along the length of the ground conductor. Result touch potential voltages are allowed to develop, and 0-volt signal reference is lost, causing errors in sensitive equipment. If all your grounds originate from a single point, no voltage differences can develop between equipment.
3. Provides the planned fault return path to operate OCPD quickly and limit touch potential fault voltages to tolerable limits. This is your EGC and bonding jumpers job. If the line conductor breaks off inside your toaster oven and falls into the enclosure, The EGC induces a high current fault, returning the current back to the utility neutral service conductor, completing the path operating the breaker within a half-cycle, clearing the fault. Additionally, the earth ground reference limits the touch potential to tolerable limits during a fault. The impedance of the Line and EGC conductors are roughly equal, forming a voltage divider limiting touch voltage to roughly half of the supply voltage. Chassis can be as high as 60-volts in a 120 VAC circuit during a fault. Note no current ever flows through earth ground, only referenced to the earth. The breaker would still operate if you lost the GES, but the full 120-volts would be on the chassis during the fault.
4. Shorts out cable capacitance resulting in a steady-state leakage current into ground conductors. Not so much of a problem in residential settings, but in large facilities are significant. The leakage flows through the cable insulation, speeding up deterioration decreasing service life. Under transient conditions, the leakage capacitance can resonate with inductance in the circuit, causing very high voltages across the loads and cable insulation.
5. ESD or pico lightning. It may not seem important, but try telling that to the dud tester at the Looney-Tunes ammunition factory. Seriously ESD is responsible for billions of dollars in property and equipment damage and countless injuries and loss of life. From grain silos to high-tech manufacturing have strict ESD controls are in place.
High tech facilities like data centers, airports, petroleum, etc go to great lengths to protect their GES. Some like the FAA and Disney parks use cathodic protection to ensure the integrity of the GES. Hopefully, no one has to learn the hard way.
OK, I will get off my soapbox now and return to the golf course.
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- Location
- New Jersey
- Occupation
- Journeyman Electrician
Bonding jumpers do not require irreversible connections only the GEC does I'm thinking maybe that's what you meant.
Typo, my bad for not proofreading, correction made. THX.
Although not required I would take it one step further. If more than one rod is used or other underground metals are used to keep the GEC continuous without splices or used downstream as bonding jumpers to the other electrodes. A failure anywhere along the series chain path compromises the GES. You want that horizontal run to remain intact as that is what lightning really uses top discharge. Longer the better.
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hillbilly1
Senior Member
- Location
- North Georgia mountains
- Occupation
- Owner/electrical contractor
Many years ago had the same experience with a customer, except it was the cable and phone company that screwed up. Power came in on the right side of the house, phone and cable to the far left. Every time a storm came up, it would take out his phones, or tv’s or both. He would unplug everything anytime a storm was coming. Poco, phone and cable company blamed it on each other, and refused to do anything. He had countless contractors that came out and said there was nothing they could do. First thing I looked at was the grounding and bonding. One rod at the service, no bonding at the demarc at the other end of the house. Drove another rod at the demarc, buried a #4 bare copper between the two drops, no more problems. Homeowner was very happy that he did not lose any more electronics when he wasn’t home to unplug them!
Hillbilly your experience is the same repeated thousands of times. POCO's Ma Bell, CATV, and SATV have paid for a lot of electrical equipment damage and compensation to survivors of poor electrical practices. Seen a lot in older home construction before codes were put in place to put a stop to the hazards. Fortunately, today new construction requires all services to enter at the same point. Bringing all the services in the same location makes it very easy to bond them to the GEC below the meter or disconnect. Bond the IBT right next to the GEC. Any transient coming in on any one of the services goes straight to earth.
The illustrations of 810 show clearly how it is done. Mike has a really good white paper on 810.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Obviously a single point grounding system is best practice, but I am highly skeptical that a transient "goes straight to earth" In many/most cases, I imagine a transient could care less about dirt/earth.
- Location
- Bremerton, Washington
- Occupation
- Master Electrician
Thank you Derek, we can lay this one to rest.
Johnpatrick2
Member
- Location
- Windsor, CO
- Occupation
- Retired, EE
I believe that this requirement originates because the conductor is permitted to run in environments such as through a concrete wall or in the ground where it's integrity can be compromised but not easy to visually check. The methods specified for connection are reasonably stable. If I am correct this is the code writers covering reliability under a variety of installations.
kwired
Electron manager
- Location
- NE Nebraska
With a little bit of dirt worshipping worked into the mix as well.
Lioneye
Member
- Location
- Northwest USA
- Occupation
- Commercial Electrician
The primary reason for no mechanical splices is to insure (1) future continuity in case if electrical modifications, and (2) to carry the high voltage from a lighting strike or a primary to secondary short, with minimal resistance, to the grounding electrodes. Mech connections cannot be avoided at the ends of the GEC so that is allowed.
electrofelon
Senior Member
- Location
- Cherry Valley NY, Seattle, WA
Do you have any evidence that mechanical splices would be less reliable in those situations? How does the splice resistance even really matter when your ground rods have easily 25 ohms or more resistance?
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