Thread: 2 ground conductors to 2 grounding rods

Is there anything improper about 2 separate grounding conductors (of appropriate size) at the main panel connecting to 2 separate grounding rods at the exterior of the home? (As opposed to one grounding conductor connected to 2 grounding rods in series) Both are connected to the ground/neutral terminal at the panel.
Thanks.

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Case in photo.

From the 2008 NEC

(2) Grounding electrode conductor(s) shall be permitted to be

run to one or more grounding electrode(s) individually

2 separate ones will provide a better grounding solution than 2 connected in series. this is a case where one might have not been doing the job so a second one was installed to further provide a good ground or the first one was thought undersized so a second one was installed to further complement it. if in series and there is a problem in the one wire there is no back up.

Its the code here in the detroit area two grounding rod s ten feet apart

Thanks for the input. It does make sense that 2 would be an improvement. Double the capacity with double the material volume in the conductors. The electricity probably doesn't care much if it's path is split into 2 different locations if they are both significantly less resistive than anywhere else.

Problem yes.

The grounding electrode system as you describe and photograph is not correct.

See also Art. 550 IIRC regarding manufactured homes.

Originally Posted by H.G. Watson, Sr.

Problem yes.

The grounding electrode system as you describe and photograph is not correct.

See also Art. 550 IIRC regarding manufactured homes.

550 say the following. There is nothing wrong with the connection shown in the picture.

(4) Bonding and grounding of the service shall be in accordance

with Part I through Part V of Article 250.

You may not have a non-parallel or multiple GEC at or in service equipment. One unbroken GEC path to a properly constructed grounding electrode system.

Be that as it may, J.D. seems to have missed the point as to WHERE the service must be for a manufactured home/ has required and still requires methods other than what has been described and photographed.

Originally Posted by H.G. Watson, Sr.

You may not have a non-parallel or multiple GEC at or in service equipment. One unbroken GEC path to a properly constructed grounding electrode system.

Watson,

If I am reading what you wrote correctly, it is not what you meant to write.

You said: "You may not have a non-parallel or multiple GEC at or in service equipment.", I think you meant to write 'You may not have a parallel or multiple GEC at or in service equipment.' as a single GEC from the service is what is needed to the grounding electrode system.

You then said "One unbroken GEC path to a properly constructed grounding electrode system.", which fits with this 'You may not have a parallel or multiple GEC'.

What is needed is one GEC from the service equipment to the first grounding electrode (which is the grounding electrode "system"), then, from there, all other grounding electrodes are bonded together creating a more complex "system".

All the GEC and grounding electrode system is there for is to take that one rare lightning strike 'poof' down to earth as quickly as possible and causing the least damage as possible.

Multiple (parallel) GEC going to multiple grounding electrodes, creating a parallel grounding electrode system, is just going to divide the lightning strike "poof" into two or more paths, and you want one unhindered path to ground (earth).

Bonding all the grounding electrodes which are present together creates a system which will allow that lightning "poof" to get to ground (earth) quicker and easier.

To be truely parallel conductors they woul be originating and terminating at the same location, be of the same material, and exactly the same length.

The extra length outside is also unsafe.

One route for GEC, the other electrodes are connected via bonding jumpers.

Seems irrelevant as appears to be a manufactured home. "service" in home misnomer or grave error.

Thanks Jerry that description was highly comprehendible. The home was in fact a 2 story 1998 stick built on poured concrete though the picture does look double-widey.

Originally Posted by H.G. Watson, Sr.

To be truely parallel conductors they woul be originating and terminating at the same location, be of the same material, and exactly the same length.

Not quite.

They can be parallel conductors of any lengths, of different material, and of different sizes.

You are referring to what the NEC "requires" of parallel conductors, but conductors in parallel which do not meet what the NEC "requires" are still parallel conductors.

The extra length outside is also unsafe.

One route for GEC, the other electrodes are connected via bonding jumpers.

Seems irrelevant as appears to be a manufactured home. "service" in home misnomer or grave error.

Agreed on the first two parts above, and on the last part if was a manufactured home - I have the benefit of knowing it was not for my post.

Originally Posted by Jerry Peck

Watson,



What is needed is one GEC from the service equipment to the first grounding electrode (which is the grounding electrode "system"), then, from there, all other grounding electrodes are bonded together creating a more complex "system".

All the GEC and grounding electrode system is there for is to take that one rare lightning strike 'poof' down to earth as quickly as possible and causing the least damage as possible.

Multiple (parallel) GEC going to multiple grounding electrodes, creating a parallel grounding electrode system, is just going to divide the lightning strike "poof" into two or more paths, and you want one unhindered path to ground (earth).

Bonding all the grounding electrodes which are present together creates a system which will allow that lightning "poof" to get to ground (earth) quicker and easier.

What code are you basing the above ? I have a similar situation on a simple 120 volt meter base with 60 amp disconnect. I have two ground rods with one GEC from meter base. The inspector wants me to install a GEC to each ground rod separately.

Originally Posted by Bobby Barrick

What code are you basing the above ? I have a similar situation on a simple 120 volt meter base with 60 amp disconnect. I have two ground rods with one GEC from meter base. The inspector wants me to install a GEC to each ground rod separately.

Bobby,

Not exactly sure what it is you are asking, but here are some attempts at answering what I think you are asking.

(bold and underlining are mine)
- 250.50 Grounding Electrode System.
- - All grounding electrodes as described in 250.52(A)(1) through (A)(7) that are present at each building or structure served shall be bonded together to form the grounding electrode system. Where none of these grounding electrodes exist, one or more of the grounding electrodes specified in 250.52(A)(4) through (A)(8) shall be installed and used.
- - - Exception: Concrete-encased electrodes of existing buildings or structures shall not be required to be part of the grounding electrode system where the steel reinforcing bars or rods are not accessible for use without disturbing the concrete.

- 250.62 Grounding Electrode Conductor Material.
- - (C) Continuous. Grounding electrode conductor(s) shall be installed in one continuous length without a splice or joint except as permitted in (1) and (2):
- - - (1) Splicing shall be permitted only by irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process.
- - - (2) Sections of busbars shall be permitted to be connected together to form a grounding electrode conductor.
- - (D) Service with Multiple Disconnecting Means Enclosures.
- - - (2) Individual Grounding Electrode Conductors. A grounding electrode conductor shall be connected between the grounded conductor in each service equipment disconnecting means enclosure and the grounding electrode system. Each grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance conductor(s) supplying the individual service disconnecting means.

Originally Posted by Jerry Peck

Watson,


Multiple (parallel) GEC going to multiple grounding electrodes, creating a parallel grounding electrode system, is just going to divide the lightning strike "poof" into two or more paths, and you want one unhindered path to ground
(earth).

I agree with your above statement. I want to make your statement above as factually supported as possible with documentation . Is there a specific NEC code or reference you would include to support your statement as being fact,

I think 250.62 D2 is best I can find agree ????

Thanks again

Originally Posted by Bobby Barrick

I agree with your above statement. I want to make your statement above as factually supported as possible with documentation . Is there a specific NEC code or reference you would include to support your statement as being fact,

I think 250.62 D2 is best I can find agree ????

Thanks again

"I think 250.62 D2 is best I can find agree ????"

Correct for the question regarding having one path to the grounding electrode system.

Originally Posted by Jerry Peck

250.62 Grounding Electrode Conductor Material.
- - (C) Continuous. Grounding electrode conductor(s) shall be installed in one continuous length without a splice or joint except as permitted in (1) and (2):
- - - (1) Splicing shall be permitted only by irreversible compression-type connectors listed as grounding and bonding equipment or by the exothermic welding process.
- - - (2) Sections of busbars shall be permitted to be connected together to form a grounding electrode conductor.
- - (D) Service with Multiple Disconnecting Means Enclosures.
- - - (2) Individual Grounding Electrode Conductors. A grounding electrode conductor shall be connected between the grounded conductor in each service equipment disconnecting means enclosure and the grounding electrode system. Each grounding electrode conductor shall be sized in accordance with 250.66 based on the service-entrance conductor(s) supplying the individual service disconnecting means.

I'm not sure if I'm reading this correct but doesn't 250.62 c-2 (in bold red)
mean that you can have two separate ground rods with two separate GEC as long as they both terminate together at the same busbar??

Originally Posted by Ken Amelin

I'm not sure if I'm reading this correct but doesn't 250.62 c-2 (in bold red)
mean that you can have two separate ground rods with two separate GEC as long as they both terminate together at the same busbar??

Ken,

This is the type of installation that is referencing:
- http://www.schneider-electric.com.hk...s_cat_0207.pdf

Thanks Jerry!
That's very different than what I thought.

Originally Posted by Jerry Peck

Ken,

This is the type of installation that is referencing:
- http://www.schneider-electric.com.hk...s_cat_0207.pdf

I am so happy I found and joined this site. If I may ask while it is a little off the subject do you see a problem with multiple GEC to separate earth grounds rods connecting at various points along grounding conductor of a FEEDER other than at the service disconnect location ?

My concern is if at some point other than at service disconnect but along a feeder by way of the grounding conductor to other gec connnections than lighting is going to try and disapate to best earth ground source subjecting cabinets and other equipment to possible lightning damage.

In your opinion would it be better to continue a multi grounded conductor (neutral)only to each cabinet and equipment if one is installing a gec and ground rod at that equipment location and the equipment feeder (now a service) have it's own disconnect be at this location ?

For example I seen state parks with electric hookups be on feeders with only a grounding conductor and there was no way the grounding conductor size with feeder length going to interrupt breaker in case of a fault. This is an extreme example exisiting but I would much rather have the "service" with multi grounded neutral conductor extend to each individual hookup with individual disconnects at each location.

If I made my question too confusing just forget it and have a nice day anyway

I'm curious, there are a lot of words in 250.50, 250.62, and 250.64 (Jerry P. referred to 250.62(C) and (D) but those are for 250.64) that are plural or refer to multiple conductors. I can't locate anything that says the bonding jumper between multiple electrodes needs to be at those electrodes and there can't be individual conductors from individual electrodes to the main bonding jumper.

250.50 states that all electrodes present need to be bonded together (i.e. grounding rod/pipe electrodes, metal water pipes, metal frame of structure, UFER, plate electrode) as listed in 250.52 (A)(1) through 250.52(A)(6).

250.52(B) excludes gas piping and aluminum electrodes.

250.53(B) covers spacing of the electrodes.

250.53(C) specifies that the bonding jumper between electrodes shall conform to 250.64

250.58 specifies that two or more grounding electrodes bonded together form one grounding electrode system.

250.62 specifies the material of the electrode conductor.

250.64(C) simply states that the conductor(s) can't be spliced unless of a non-reversable type (welded or crimped).

250.64(F) specifies that a grounding electrode conductor can run to any convenient electrode OR to one or more electrodes individually and must be sized according to the largest required.

(For the language parsers among us, if only one grounding electrode conductor is permissible, it would read "the" conductor rather than "a" conductor.)

I think 250.64(F) doesn't make any sense if only one un-spliced conductor is allowed. Nothing in any of the articles listed says there can be only one electrode conductor. Indeed, it doesn't make sense practically since ALL electrodes present need to be bonded, and they're going to need conductors to them from some location. You can say that one conductor to one electrode is the grounding electrode conductor, and the others (to the water pipe system, for example) are jumpers, but why wouldn't the same be true for the second permissible grounding rod electrode that is required to be bonded if present?

That is, if there are two or more grounding rod electrodes I don't see any language that says they need to be bonded together outside of the structure rather than inside, nor that the main bonding jumper (which can be a busbar) can't be located in the service equipment enclosure.

There are many issues that I have read in this thread that need addressing, however, to cut to the chase and save me some time.... please refer to IAEI 'SOARES' book on grounding.

One specific note (of many) I would like to make is that only the main grounding electrode conductor is required to be unspliced (unless prem/irreversible), GEC taps are not required to be such.
Also, no mention of the lack of mechanical protection and securing for the GEC's in the pic.
Also, mention was made to "here in the Detroit area"... The State of MI has eliminated such codes as local. There are only State-wide codes as follows; MRC, NEC, and MI Code Part 8, relative to electrical installations.
Also, mention was made to "the only reason... lightning..". Some other reasons are; To assure zero (0) ground potential in and around the structure served, and to stabilize voltage.

Sorry, I'm getting carried away... Please refer to Soares.

As previously pointed out by many contributors, ALL ELECTRODES SHALL BE MADE AS ONE. 2008 NEC 250.50.

You SHALL bond the two ground rods together.