No water pipe to ground to

[mike1061]

In Chicago, in a residential detached garage I want to install a 100 a, 240 v, service. There is no water service. So am I correct, that I could drive a rod 6' feet away from the driven rod by the meter? That rod would be connected the same as if it were conneted to the water service?
Thanks
Mike

 

[infinity]

Yes two rods a minimum of 6' apart will be sufficient. The building has no CEE?

 

[Dennis Alwon]

I am not sure I understand what you are asking. Are you installing a new meter on the detached garage or are you running a feeder from the existing service?

 

[ritelec]

Yes two rods a minimum of 6' apart will be sufficient. The building has no CEE?

From the other discussion Rob......please let me confirm that it is a "service", with no water or cee, only 1 rod would be compliant (although 2 is better), and the GEC would only have to be a #6, correct?


Mike.....as far as Dennis's post........looks like a service is going in. Again..only 1 rod would be needed. Seams the only difference (besides having a meter and observing clearances) would be bonding of the neutral/ground at the panel vs floating the neutral.

QUESTION....Would the provisions for 310.15(B)(7) also apply to a "residential" detached garage for a service? I think not. It's not a Dwelling.

 

[Dennis Alwon]

No water then just drive two rods a minimum of 6' away. That is all that is needed. I was thinking this may be a feeder from the existing building but I am guessing it probably is a new service.

 

[ritelec]

But Dennis.......just to be clear, only 1 is required correct? No supplemental electrode is required........right or wrong?



http://forums.mikeholt.com/showthread.php?t=143843&page=3


What's your take on sizing the service entrance conductors?

 

[infinity]

But Dennis.......just to be clear, only 1 is required correct? No supplemental electrode is required........right or wrong?

There is no water pipe so a supplemental electrode is not required. You still need two rods unless you want to take on the arduous task of proving a single rod has a resistance of 25 ohms or less.

 

[Dennis Alwon]

But Dennis.......just to be clear, only 1 is required correct? No supplemental electrode is required........right or wrong?



http://forums.mikeholt.com/showthread.php?t=143843&page=3


What's your take on sizing the service entrance conductors?

This is why I was confused. I thought the op was using one rod from the existing building and another at the detached garage. As Trevor stated 2- rods unless you can show 25 ohms. Read 250.66

 

[iwire]

As Trevor stated 2- rods unless you can show 25 ohms. Read 250.66

I bet you mean .56

2008 NEC

250.56 Resistance of Rod, Pipe, and Plate Electrodes. A
single electrode consisting of a rod, pipe, or plate that does
not have a resistance to ground of 25 ohms or less shall be
augmented by one additional electrode of any of the types
specified by 250.52(A)(4) through (A)(8). Where multiple
rod, pipe, or plate electrodes are installed to meet the requirements
of this section, they shall not be less than 1.8 m
(6 ft) apart

But for 2011 that is gone from there and now in 250.53(A)

250.53 Grounding Electrode System Installation.
Informational Note: See 547.9 and 547.10 for special
grounding and bonding requirements for agricultural
buildings.

(A) Rod, Pipe, and Plate Electrodes. Rod, pipe, and plate
electrodes shall meet the requirements of 250.53(A)(1)
through (A)(3).

(1) Below Permanent Moisture Level. If practicable, rod,
pipe, and plate electrodes shall be embedded below permanent
moisture level. Rod, pipe, and plate electrodes shall be
free from nonconductive coatings such as paint or enamel.

(2) Supplemental Electrode Required. A single rod, pipe,
or plate electrode shall be supplemented by an additional
electrode of a type specified in 250.52(A)(2) through
(A)(8). The supplemental electrode shall be permitted to be
bonded to one of the following:

(1) Rod, pipe, or plate electrode

(2) Grounding electrode conductor

(3) Grounded service-entrance conductor

(4) Nonflexible grounded service raceway

(5) Any grounded service enclosure

Exception: If a single rod, pipe, or plate grounding electrode
has a resistance to earth of 25 ohms or less, the
supplemental electrode shall not be required.

(3) Supplemental Electrode. If multiple rod, pipe, or plate
electrodes are installed to meet the requirements of this
section, they shall not be less than 1.8 m (6 ft) apart.
Informational Note: The paralleling efficiency of rods is
increased by spacing them twice the length of the longest rod.


It goes on .....

 

[ritelec]

There is no water pipe so a supplemental electrode is not required. You still need two rods unless you want to take on the arduous task of proving a single rod has a resistance of 25 ohms or less.

I'm all for driving 2. But just questioning here, who are you proving to, and, whoever who is, how could they prove the resistance. Just doing some reading around here and measuring is Very difficult.

Now, before I bow on this, just two questions.

What gives the just drive 2 rods argument weight? Is it not feasible that even 2 rods would still have a resistance of 25.1 ohms or more? Or is it because you took the extra effort, 25 ohms more or less no one enforcers it?

And secondly...............just to confirm, if you have a resistance of 25 ohms or less to one ground rod, one ground rod with no supplemental electrode would only be needed, correct?

Thanks ,
Rich.......or maybe Jack

 

[ritelec]

I bet you mean .56

2008 NEC



But for 2011 that is gone from there and now in 250.53(A)

what happened to iwires' quote?

I found this part interesting......

(3) Supplemental Electrode. If multiple rod, pipe, or plate
electrodes are installed to meet the requirements of this
section, they shall not be less than 1.8 m (6 ft) apart.
Informational Note: The paralleling efficiency of rods is
increased by spacing them twice the length of the longest rod.

so using 8' rods, spacing 16 feet is better.......I like that............what would 3 or 5 times the length do...??

amazing.



Yeah I know. Put 2 rods in six feet away from each other and walk away from it.



Thank you,

Rich.....or was that Jack

 

[infinity]

I'm all for driving 2. But just questioning here, who are you proving to, and, whoever who is, how could they prove the resistance. Just doing some reading around here and measuring is Very difficult.

Now, before I bow on this, just two questions.

What gives the just drive 2 rods argument weight? Is it not feasible that even 2 rods would still have a resistance of 25.1 ohms or more? Or is it because you took the extra effort, 25 ohms more or less no one enforcers it?

And secondly...............just to confirm, if you have a resistance of 25 ohms or less to one ground rod, one ground rod with no supplemental electrode would only be needed, correct?

Thanks ,
Rich.......or maybe Jack

The NEC requires two rods for it to qualify as an electrode. There is an exception that permits one rod when the resistance is 25 ohms or less. If you install the two rods no one cares if the resistance is 5 ohms or 500 ohms.

Again you've used the term supplemental electrode. The only electrode that requires a supplemental electrode is a metallic water pipe.

 

[mike1061]

Sorry I didn't get back sooner.
Yes it is a new service to a detached garage. There is a service for the house it self, but it's tough to dig up the yard to bring more circuits to the garage.
Thanks for all the replies.
Mike

 

[ritelec]

Again you've used the term supplemental electrode. The only electrode that requires a supplemental electrode is a metallic water pipe.

May I ask you?

First I'd like to thank you all for sharing all of this with me. I started frequenting here a couple a months ago after just going out and wiring and letting the "tech" aspect of this fall by the wayside.

Let me ask you.............. What if this detached garage had no water, but it did have a gas pipe run to it?

From what I see the code says it must be bonded.......yet with the ceu I went to, it was mentioned that it is grounded thru the electric cord from the oven, or dryer, or thru a boiler, and the instructor said
in his opinion the gas pipe should not be grounded/bonded.........and if the inspector wanted it to be (which I guess he should cause it's in the good book), you should have him sign off on it.


Now.........this detached garage........lets say it has no water but it does have a gas line...............if there's nothing hooked up to it should it be bonded? If it's going to have an appliance that requires electricity,
I guess the same thought as above would apply and maybe you would not or should not bond it. I'm not sure of gas devices out there that wouldn't need electricity, but what if it used a thermopile, or you lit it by hand?



Again, just wondering, and thank you for getting my gray matter working.



By the way, what is your take on the conductors feeding the detached garage? Treated as part of a service for dwelling or not.


Thanks again!
Rich




snubber

 

[ritelec]

Sorry I didn't get back sooner.
Yes it is a new service to a detached garage. There is a service for the house it self, but it's tough to dig up the yard to bring more circuits to the garage.
Thanks for all the replies.
Mike

Ha ha ha ha...........OH.

You coming off a utility pole for a "NEW SERVICE" or gonna come off the house for a sub panel? ...ha ha ha



I'm starting to like this place.


Jack

 

[kwired]

I'm all for driving 2. But just questioning here, who are you proving to, and, whoever who is, how could they prove the resistance. Just doing some reading around here and measuring is Very difficult.

Now, before I bow on this, just two questions.

What gives the just drive 2 rods argument weight? Is it not feasible that even 2 rods would still have a resistance of 25.1 ohms or more? Or is it because you took the extra effort, 25 ohms more or less no one enforcers it?

And secondly...............just to confirm, if you have a resistance of 25 ohms or less to one ground rod, one ground rod with no supplemental electrode would only be needed, correct?

Thanks ,
Rich.......or maybe Jack

There was a change from 2008 to 2011. Requirements were not really changed but the way things are worded was. In 2008, 250.56 said "..that does not have a resistance to ground of 25 ohms or less shall be augmented by one additional electrode..". 2011 changed it (and moved it to 250.54) and says you must have the second rod, with an exception that says "If a single rod, pipe, or plate grounding electrode has a resistance to earth of 25 ohms or less, the supplemental electrode shall not be required." By changing this wording to the way it is pretty much means you must prove there is less than 25 ohms or else you must use two rods. Before that you could (sort of) require the AHJ to prove there is 25 ohms or less or tell AHJ that is just too bad if he can't prove it.

Even before this change I think it has been determined that if you can't get less than 25 ohms after driving two rods each additional rod is not going to change the net resistance by very much.

what happened to iwires' quote?

I found this part interesting......

(3) Supplemental Electrode. If multiple rod, pipe, or plate
electrodes are installed to meet the requirements of this
section, they shall not be less than 1.8 m (6 ft) apart.
Informational Note: The paralleling efficiency of rods is
increased by spacing them twice the length of the longest rod.

so using 8' rods, spacing 16 feet is better.......I like that............what would 3 or 5 times the length do...??

amazing.



Yeah I know. Put 2 rods in six feet away from each other and walk away from it.



Thank you,

Rich.....or was that Jack

Funny I was just at a CEU class tonight and the instructor used pretty much the exact same words. "Minumim of 6 feet apart, 16 feet is even better". Then he proceeded to say that a ground rod typically has about an 8 foot zone around it that is effective for doing the job needed , 6 feet apart makes them more effective, and 16 feet apart gets theeach rod outside that 8 foot zone of the other rod maximizing effectiveness of both.

 

[iwire]

Then he proceeded to say that a ground rod typically has about an 8 foot zone around it that is effective for doing the job needed , 6 feet apart makes them more effective, and 16 feet apart gets theeach rod outside that 8 foot zone of the other rod maximizing effectiveness of both.

You may know this but he is talking about the 'sphere of influence'.


http://www.esgroundingsolutions.com...g/grounding-electrode-sphere-of-influence.php

 

[jmellc]

May I ask you?

First I'd like to thank you all for sharing all of this with me. I started frequenting here a couple a months ago after just going out and wiring and letting the "tech" aspect of this fall by the wayside.

Let me ask you.............. What if this detached garage had no water, but it did have a gas pipe run to it?

From what I see the code says it must be bonded.......yet with the ceu I went to, it was mentioned that it is grounded thru the electric cord from the oven, or dryer, or thru a boiler, and the instructor said
in his opinion the gas pipe should not be grounded/bonded.........and if the inspector wanted it to be (which I guess he should cause it's in the good book), you should have him sign off on it.


Now.........this detached garage........lets say it has no water but it does have a gas line...............if there's nothing hooked up to it should it be bonded? If it's going to have an appliance that requires electricity,
I guess the same thought as above would apply and maybe you would not or should not bond it. I'm not sure of gas devices out there that wouldn't need electricity, but what if it used a thermopile, or you lit it by hand?



Again, just wondering, and thank you for getting my gray matter working.



By the way, what is your take on the conductors feeding the detached garage? Treated as part of a service for dwelling or not.


Thanks again!
Rich


Bonding to a gas line scares me to death with no water line present. Without the water line, seems the gas line might become the ground path for a fault current. I worked on a service with old splices overhead, tape long since weathered off & many bare spots. Wind blew a hot into the neutral. Popped a bit and a literal "ring of fire" traveled down the ground wire to the ground rod and set fire to the grass around it. If the gas line became the ground path, would such an arc not ignite the gas within?

 

[kwired]

May I ask you?

First I'd like to thank you all for sharing all of this with me. I started frequenting here a couple a months ago after just going out and wiring and letting the "tech" aspect of this fall by the wayside.

Let me ask you.............. What if this detached garage had no water, but it did have a gas pipe run to it?

From what I see the code says it must be bonded.......yet with the ceu I went to, it was mentioned that it is grounded thru the electric cord from the oven, or dryer, or thru a boiler, and the instructor said
in his opinion the gas pipe should not be grounded/bonded.........and if the inspector wanted it to be (which I guess he should cause it's in the good book), you should have him sign off on it.


Now.........this detached garage........lets say it has no water but it does have a gas line...............if there's nothing hooked up to it should it be bonded? If it's going to have an appliance that requires electricity,
I guess the same thought as above would apply and maybe you would not or should not bond it. I'm not sure of gas devices out there that wouldn't need electricity, but what if it used a thermopile, or you lit it by hand?



Again, just wondering, and thank you for getting my gray matter working.



By the way, what is your take on the conductors feeding the detached garage? Treated as part of a service for dwelling or not.


Thanks again!
Rich




snubber

250.52(B) does not permit using a gas pipe as a grounding electrode.

250.104(B) does require bonding metal piping systems including metallic gas piping.

 

[ritelec]

Thanks all.



Now this is pretty cool.

You may know this but he is talking about the 'sphere of influence'.


http://www.esgroundingsolutions.com...g/grounding-electrode-sphere-of-influence.php

"Sphere of influence"? Interesting, Any relation to the "Cone of Silence" ?

Thank you,
Max

I miss 99.