garage panel

[RUWired]

It seems to me that the supplementary rod need for the house could be the rod needed at the garage.The buildings are 25' apart.

 

[DaveTap]

Just checking...

Just checking...

I'm just checking... there is a ground rod at the meter isn't there?

 

[wbalsam1]

Interestingly, it does not state that you should bond the electrodes present at each seperate structure only at the seperate structure. Read literally, it means you have to bond all the GE together from all the structures.

That would imply running the GEC from the garage ground rod back to the house GES, and not attaching it to the ground bar in the garage, which would make a lot more sense than the way it is presently done.

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(6) 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)(7) shall be installed and used.

Each means the individual building or structure. Or doesn't imply you have a choice, it means that each one is subject to the rule. In mike01's example, both locations are buildings, i.e., the house is a building and the garage is a building. They could both be structures and would still each have to comply with 250.50. JMHO.:smile:

 

[petersonra]

250.50 Grounding Electrode System. All grounding electrodes as described in 250.52(A)(1) through (A)(6) 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)(7) shall be installed and used.

Each means the individual building or structure. Or doesn't imply you have a choice, it means that each one is subject to the rule. In mike01's example, both locations are buildings, i.e., the house is a building and the garage is a building. They could both be structures and would still each have to comply with 250.50. JMHO.:smile:

You need to read my post a little closer. I do not disagree that there should be a GES at each structure, only how the GE at the separate structure gets bonded to the GE at the house. If I can bond the two GE systems together through the EGC in this particular case, why can't I do it that way in others?

 

[lpelectric]

You need to read my post a little closer. I do not disagree that there should be a GES at each structure, only how the GE at the separate structure gets bonded to the GE at the house. If I can bond the two GE systems together through the EGC in this particular case, why can't I do it that way in others?

I could understand interconnecting the GES systems if the individual GES of the garage were within 6 feet of the individual GES of the house, but I don't see the great advantage in extending a GEC more than 20' away to interconnect with another GES. :smile:

 

[cschmid]

I agree that there is no advantage to connecting the rods..But since a seperate ground wire has already been run that would bond the two together..I think this was a costly install..

 

[Lee Honeycutt]

I'm convinced the code requires the seperte GE. My question is, should the nuetral on the garage feeder be bonded at the garage panel?

 

[cschmid]

I do not think so since the service is on the house..

 

[RHytonen]

As an electronics design and facility chief engineer (retired,) in wiring my own garage after a life of renting, studying code has me wondering how driving a rod at each structure isn't creating a nightmare of ground loops.

I would also question whether the inspection-required one or two copper rods of NEC spec. would ohm out under 25 at 60Hz 240v and 60a. Most things probably would. (Do they test at expected worst-case conditions? What's the ground reference for that test anyway?) I would definitely require an inspector to perform that test on my building frame before insisting on a ground rod. I think 8x 2.5" 18" deep mild steel tube, electrically welded, through a 4'"x13'x28' slab, just might make it.

Add that my garage is essentially a (heavily grounded, deep-sunk 2.5"D.) welded steel tubing pole structure, or grounding grid, and there is an underground gas pipe bonded to the main building (house) service panel, which runs to the concrete slab-and-block garage. Add the two feed conductors, and certainly that grounding is already inadvisedly redundant.
If I used a CNC tool it would be *so* flaky from the RF in those loop currents already....

From the high VA/low frequency (electrical) aspect, if there is a shock hazard from unbalanced ground currents, certainly the practice of adding a separate but redundant path to ground would cause more problems than it solved.

It also seems lightning protection is a separate building issue even where there is no power run. The (about 5' !) 'overhead' (and not locally grounded at my garage) power line, running on the electrical right-of-way along the length of the metal roofed structure, has that covered I'm told it gets hit all the time.

A system should ground at one point. Either continuous, or (preferably) individual home runs, or a "star ground." The more geographically separated the added redundant grounds, the worse it becomes (at least until the day the earth becomes more conductive than refined copper....) Adding redundant localized "hard" grounds ALWAYS caused more and more issues, even where it seemed at first to mitigate one. Why would it not be so at higher currents and potentials?

The only balanced way (to preserve the difference intended by the different gauges in the feeder) is if the grounded conductor and grounding conductor (4-wire feed) are equal in length to the common grounding point (service panel.) That would mean carrying the feeder grounding conductor through (just like the grounded conductor 'shall' be) without sinking another rod and regrounding at the sub, or even connecting to the panel (which is unavoidably bonded to ground by mounting.)

Of course, in my case it could be argued that the grounding and neutral (a year ahead of my time buses should be isolated and carried through, and the panel itself grounded only by a local rod, or even bonding to the building frame. Wait - that's what it would be if I simply floated the ground bus (the disconnects are fuses until I get a breaker panel.)

Of course realistically I must follow code (or rather an inspector's interpretation,) but technically IMHO it's a crock. Is the copper industry hurting that badly?

also wondering,
Rod

something I have often wondered.

since grounding electrodes do not serve much of a purpose anyway, how does having one at a separate structure improve electrical safety?

the stated purpose of having a GES is to limit voltage during lightning strikes, line surges, etc. That makes sense when it is connected to neutral.

At a separate structure, it is connected to the EGC rather than neutral. How does this help anything?

 

[lpelectric]

Welcome to the forum. Are you on code-making-panel # 5? If not, you probably should be. :wink:

 

[George Stolz]

I'm convinced the code requires the seperte GE. My question is, should the nuetral on the garage feeder be bonded at the garage panel?

In the installation originally described, there are two handles on the service disconnect on the originating house. There is an EGC present with the feeder conductors to the detached garage. Therefore, the ground-fault-clearing path for the detached garage is the EGC that has been run with the feeder.

The neutral and EGC should remain seperate at the detached building, since they have been bonded together at the service of the originating building. Otherwise, neutral current will flow back to the source on the feeder's EGC.

The grounding electrode system (GES) present at the detached building is required to be used, at that building. Note I bolded "system" - it's not just a matter of driving a rod and walking away, the GES at the detached building is under the exact same requirements as the originating building.

The GES is connected to the EGC at the detached building, since the feeder contains an EGC. (250.32(B)(1))

Take a look at the FAQ on this topic, it might help. It might hurt, who knows.

 

[RHytonen]

Thanks for your kind hospitality, IP -

Since my experience is in broadcast electronics I don't feel qualified
to sit with the many here licensed and steeped in code, much less with lifetime experienced specialized power electricians.

I could only discuss considerations scaled to electronic matters, as in these posts, attempting to compare grapes and grapefruit, only valid in that they're both fruits. I've only designed power and HVAC subsystems as an adjunct to the black art of analog, and then digital, broadcast studio design - systems (equipment,) cabling and timing (NYC.) Someone had to do it and it had to work. I hear they still do.

I presume to post only hoping to pick their brains about how far to take the analogy in designing a safe and legal fed subsystem. But this is not MA, NY, CO, or CA.

Here's an amusing update:
We went to the local town hall to clarify local practice and requirements.

Unless (and until) I redo the roof, my plan for next summer, there are no permits or inspections needed for interior framing, finishing or wiring.

It was interesting when I asked about rewiring - One of the very friendly and personable female community elders (who run the tiny place, and know everything about the area and inhabitants' histories there is to know) looked back at another at her desk, and facetiously asked her if she'd like to go out and look at my wires. i.e. - There is no inspector (and incidentally no zoning.)
What they said about framing and wiring was, "Just go ahead and do it."

It looks like I'm the master of my own fate (and safety.)
I'll undoubtedly be doing more than they could ever require in that vein, and am glad to be able to do it properly as my experience and code research have indicated.

I will also be following code to whatever letter I can possibly reconcile with truly safe practice - if only to show off, and of course satisfy the insurance companies, should they ever care.... knock, knock.

I maintain the 8 steel poles constitute a ground grid, and so I might not reground. To clarify, the panel will be grounded with its own rod (or rather, the poles,) but that will probably not be used to reground the (4-wire 60a.) underground feeder, which will carry through as equipment ground, but in isolation on its own bar.

Anything else would create a loop, and ground currents,
with the Earth leg's impedance from service to fed system, providing an undesirable imbalance very similar to grounding the Neutral.

I will of course be removing the bonding of the neutral to ground which I currently find (inherited) at the panel feeder entrance, and create a second
-floated- bar for Neutral to carry it through to the outlets. This is one of many reasons I never considered seeking a local electrician. I may have done so for a stamp -should it have existed- for the insurance co. There would be nothing to stamp, LOL.

In Summary -
Out here in the mountains, they do not mess with what you do inside your own property. If they can't see it, they don't want to, and make neither provisions nor requirements for doing so.

Interestingly they do require registering a $10 permit when reroofing (but not when only repairing.) This ($10) permit lasts legally all summer - longer than, as they put it, ".. the month or so after which the ink will fade in the sun, becoming unreadable posted in your window."
There is no inspection involved. There is no inspector.

LOL, "Mountaineers Live Free."
Cheers,
Rod

Welcome to the forum. Are you on code-making-panel # 5? If not, you probably should be. :wink: