Grounding wire size

[Doctor Electric]

A co worker of mine ran number 6 bare solid to a water main as the primary ground however i just got done running a number 4 bare solid to 2 5/8ths ground rods for a secondary ground per code for a 200 amp single phase residential home service i brought this to his attention and he had mentioned that it is allowed to run a number 6 instead to the water main. I've searched section 250 and i cant find any reference or exception that states undersizing a ground for a service. Any one know or heard of this or is this just b.s. any thoughts would be appreciated

 

[infinity]

Let's start with some terminology to make this easier to understand, the conductor run to each grounding electrode is a grounding electrode conductor or GEC. GEC's are sized according to 250.66. A GEC to a ground rod electrode is not required to be larger than #6. The correct size for a GEC to a water pipe is typically a #4 copper or #2 aluminum from T250.66.

 

[tom baker]

For Grounding and Bonding "We have met the enemy and he is us" Pogo - I used this in my grounding classes.
The definition of ground is "the earth"
Definitions are important, thats why they are in Article 100.
For grounding, Mike Holt once said
"What color is it and what does it do?"

Also Primary and Secondary grounds are not code terms.

The GEC goes to a grounding electrode and then it stops, the conductor to other electrodes are bonding jumpers.
If your water pipe primary ground does not meet the requirement for grounding electrode, you still need to bond it, and if you have a ufer ground then no ground rods are required.

 

[Doctor Electric]

What is T250.66.? In other words the gec to the water main should be #4 based on the 250.66 chart for 1/0 and 2/0 thus being primary and the gec to the grounding electrodes is to be no larger than #6 no matter the size of the current carrying conductors being used thus being secondary

 

[LarryFine]

A co worker of mine ran number 6 bare solid to a water main as the primary ground however i just got done running a number 4 bare solid to 2 5/8ths ground rods for a secondary ground per code for a 200 amp single phase residential home service

The bottom line is that each of you used the wire the other should have used.

 

[electrofelon]

I like to point out for completeness that the GEC to the rods may have to be #4 depending on how it is routed and secured. Basically #4 can float freely without being secured. #6 needs to closely follow the surface and be secured. #8 needs to be in a raceway. This is from memory, don't have book in front of me....someone tell me how I did :angel:

 

[ptonsparky]

What is T250.66.? In other words the gec to the water main should be #4 based on the 250.66 chart for 1/0 and 2/0 thus being primary and the gec to the grounding electrodes is to be no larger than #6 no matter the size of the current carrying conductors being used thus being secondary

The wire to the ground rod(s)may be larger than #6, but are not required to be.

In other words if all you have in the truck is #4 and you are 60 miles from any #6, use the 4.

 

[jaggedben]

Boil it down to specifics guys.

What are the size of the service conductors?
What is the complete list of electrodes that exist on the premises? (Is there a UFER? Does the water pipe actually qualify as an electrode or is it plastic where it goes underground?)
How is the grounding electrode conductor installed, precisely? (see electrofelon's post)

The actual requirements all vary depending on the answers.

 

[infinity]

What is T250.66.? In other words the gec to the water main should be #4 based on the 250.66 chart for 1/0 and 2/0 thus being primary and the gec to the grounding electrodes is to be no larger than #6 no matter the size of the current carrying conductors being used thus being secondary

T is for Table 250.66, the second part is for ground rod electrodes. Although we tend to think of them as primary and secondary the NEC does not use those terms, for the water pipe electrode you are required to have a supplemental electrode which is typically two ground rods or a CEE. {250.53(D)(2)}

 

[electrofelon]

Ok here are the routing/physical damage requirements:

250.64(B) Securing and Protection Against Physical Damage.
Where exposed, a grounding electrode conductor or its enclosure
shall be securely fastened to the surface on which it is
carried. Grounding electrode conductors shall be permitted to
be installed on or through framing members. A 4 AWG or
larger copper or aluminum grounding electrode conductor
shall be protected if exposed to physical damage. A 6 AWG
grounding electrode conductor that is free from exposure to
physical damage shall be permitted to be run along the surface
of the building construction without metal covering or protection
if it is securely fastened to the construction; otherwise, it
shall be protected in rigid metal conduit RMC, intermediate
metal conduit (IMC), rigid polyvinyl chloride conduit (PVC),
reinforced thermosetting resin conduit (RTRC), electrical metallic
tubing EMT, or cable armor. Grounding electrode conductors
smaller than 6 AWG shall be protected in (RMC),
IMC, PVC, RTRC, (EMT), or cable armor. Grounding electrode
conductors and grounding electrode bonding jumpers
shall not be required to comply with 300.5.

 

[tom baker]

What is T250.66.? In other words the gec to the water main should be #4 based on the 250.66 chart for 1/0 and 2/0 thus being primary and the gec to the grounding electrodes is to be no larger than #6 no matter the size of the current carrying conductors being used thus being secondary

There is a difference between section 250.66 and table 250.66. The table sizes are larger than what is allowed in 250.66 for specific electrodes

 

[tom baker]

Boil it down to specifics guys.

What are the size of the service conductors?
What is the complete list of electrodes that exist on the premises? (Is there a UFER? Does the water pipe actually qualify as an electrode or is it plastic where it goes underground?)
How is the grounding electrode conductor installed, precisely? (see electrofelon's post)

The actual requirements all vary depending on the answers.

Yes and that reminds me of a question I used in my classes
What size ground for a 200 Amp Service?
While you make think you know its a #4....

 

[Doctor Electric]

So all this being said T250.122 is telling me i only need #6 copper for 200 amp or number 4 aluminum so i guess I'm confused on what this table tells me it should be vs. T250.66

 

[Dennis Alwon]

So all this being said T250.122 is telling me i only need #6 copper for 200 amp or number 4 aluminum so i guess I'm confused on what this table tells me it should be vs. T250.66

T250.122 is for the equipment grounding conductor which is the ground wire that is in every cable that ties all metal parts together. Table 250.66 is for the grounding electrode conductor which is the conductor to the ground rod, water pipe or other electrodes.

 

[infinity]

So all this being said T250.122 is telling me i only need #6 copper for 200 amp or number 4 aluminum so i guess I'm confused on what this table tells me it should be vs. T250.66

The GEC is sized based on the conductors ahead of the service disconnect not the rating of the disconnect/main. If you tried to use T250.122 you will not see any conductor sizes which would be one indication that you're looking at the wrong table.

 

[Doctor Electric]

It says " and equipment" at the end of the title for this uglys book one final clarification on this please

i have read and fully understand the previous posts thanks guys see the attachment

 

[Dennis Alwon]

It says " and equipment" at the end of the title for this uglys book one final clarification on this please

i have read and fully understand the previous posts thanks guys see the attachment

The equipment grounding conductor is the conductor that ties all metal parts of the electrical system, including any equipment wired to the system, together.

 

[kwired]

Yes and that reminds me of a question I used in my classes
What size ground for a 200 Amp Service?
While you make think you know its a #4....

Not necessarily, most the time yes, but if you oversized service conductors you may need a larger GEC. Still only need #4 max to a CEE and #6 to a ground rod.

So all this being said T250.122 is telling me i only need #6 copper for 200 amp or number 4 aluminum so i guess I'm confused on what this table tells me it should be vs. T250.66

250.122 is for "Equipment grounding conductors".

250.66 is for "grounding electrode conductors"

then there is a table in 250.102 that is very similar to 250.66 that is for "supply side bonding jumpers"

 

[roger]

View attachment 23337

It says " and equipment" at the end of the title for this uglys book one final clarification on this please

i have read and fully understand the previous posts thanks guys see the attachment

As the others have pointed out you are talking about two different items. In your opening post you're talking about the GEC and then you are looking at the EGC in 250.122. They do different things and are sized differently.

Roger