Garage Subpanel Neutral Busbar Question

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  #41  
Old 11-28-13, 08:13 AM
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But Joe, Your suggesting a ground rod simply connected to the subpanels neutral bus?
I thought that was a no-no (grounds and neutrals on same bus in subpanel)?
Your installation is probably before the code change that I think was in 2005. Prior to the code change this was not a subpanel, but a new building and a new service fed from the house. Yes, under today's code this would be a no-no.

It appears that I would have metal conduit out to the garage. It looks like 1" or so pipe leaving the main panel and out of the foundation and the same coming out of the concrete in the garage.
But is it metallic conduit underground all the way to the garage or PVC. PVC conduit underground has been almost a standard for 40 years. The conduits in your picture at the garage panel are EMT (thinwall). If you have EMT underground running to the garage, it's life expectancy is only a few years.
 
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  #42  
Old 11-28-13, 08:25 AM
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It might help you to go back and read some of the previous posts. This one for example:
Would this be something needing replacement? [Re: the garage panel]
No, if you have enough circuits but you need to remove the handle tie if there are no multiwire circuits and add a ground rod. You need to add a ground bar to the panel. If the metal conduit is not continuous to the main breaker panel you need to add an EGC. If they buried the metal conduit and it is EMT I'd add an EGC because EMT corrodes easily when buried.
Note as Joe above pointed out:
If the metal conduit is not continuous to the main breaker panel you need to add an EGC. If they buried the metal conduit and it is EMT I'd add an EGC because EMT corrodes easily when buried.
 
  #43  
Old 11-28-13, 08:31 AM
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The 1/2" emt you see is newish with the subpanel circuits. The feed comes up below (you can see it in the picture) is heavy stuff galvanized? Which was probably in place since 1967 when the garage I think was built but its possible could be as old as the 50's?

So if the metal is continous between the panels then I am OK/grandfathered? Is a ground rod needed in this case?

So prior to the 2005NEC it was acceptable to have both grounds and neutrals on same buspar of subpanel?

p.s.- Ray just got your last post while this one was loading... I have re-read as suggested. And take it I dont need a ground rod as long as the conduit between the two panels is all metal.....
 
  #44  
Old 11-28-13, 08:41 AM
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is heavy stuff galvanized?
If it is threaded then it is IMC or RMC so it should be okay as an EGC but I would test it. [Edit: On further thought though I'm not sure how.]
Is a ground rod needed in this case?
You are still confusing EGC with GEC. You need the conduit for your EGC. You need the ground rod for your GEC.

So prior to the 2005NEC it was acceptable to have both grounds and neutrals on same buspar of subpanel?
Only if there were no other metallic pathway such as gas lines, water lines, or telephone lines.
 

Last edited by ray2047; 11-28-13 at 10:30 PM.
  #45  
Old 11-28-13, 10:04 AM
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Is that a significant safety hazard?
CASUAL JOE WROTE:
I wouldn't necessarily call it significant, but there is a hazard. It's always better to do it right the first time.
I think I am starting to understand this better, you can tell its the first time I have thought of this situation.

As it stands now, what is the harm in leaving it as it is?? Im sure unless its been removed, there has never been a ground rod at the garage in 40 years.

Does a lightning strike spell disaster? Would a transient strike at the garage fry the main panel? Is this hazard to loss of property?Fire?
 
  #46  
Old 11-28-13, 10:49 AM
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If it is stuck by lightning everything is toast regardless of how it is wired but the GEC reduces the chance of it being hit, but does not eliminate it.
 
  #47  
Old 11-28-13, 01:07 PM
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If the raceway between the panels are continuous metal then I am NOT allowed to simply attach a ground bar to the panel and then #8 to the electrode(s). If the raceway is my EGC and is all metal, , that means the neutral in the subpanel is bonded to the encloser (and main panel) and attaching a ground bus and rod would be useless since anything would travel back on the neutral?

So if the conduit is all metal, then how do I incorporate the electrode?

Please dont tell me I have to run a conductor back to the main panel. Driving a rod will be next to impossible too but thats another can of worms...


What consitutes a garage being 'attached' (besides the obvious)? Can I run a phone line between the garage and house and call it attached An electrode isnt needed for attached structure... what makes it any different to a detached structure in this case as long as the EGC is continuous?

Scale to 1-10 (1 being critical) how fast do I have to get this done? How serious do you feel this is? Trying to figure out how to stretch limited resources vs. other repairs.
 
  #48  
Old 11-28-13, 06:42 PM
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I was reading tonight that if the garage was served by 1 branch circuit, then I dont need a ground rod.

Would installing a double pole breaker classify this setup as 1 circuit?

Perhaps that explains the handletie I mentioned....
 
  #49  
Old 11-28-13, 07:48 PM
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If you have a panel you need a ground rod. If you didn't have a panel and the breaker supplying the garage was no more then 20 amps then you wouldn't need a ground rod. You would though need a disconnect. However you would still need an EGC. So far you have not said if you have verified the conduit is providing an adequate EGC. That need to be done first. It can not even be used as a single circuit if there is no EGC.

So if the conduit is all metal, then how do I incorporate the electrode?
The ground rod is connected by a #6 copper wire to the ground bar you need to add to the panel.
Driving a rod will be next to impossible too but thats another can of worms...
You can drive it at 45° or bury it horizontally in a trench.

that means the neutral in the subpanel is bonded to the encloser
No, the neutral bar in the subpanel is isolated from the metal case. If it is bonded with a bonding screw or strap they need to be removed.

Scale to 1-10 (1 being critical) how fast do I have to get this done? How serious do you feel this is? Trying to figure out how to stretch limited resources vs. other repairs
Not urgent but it is wrong and should be corrected.
 
  #50  
Old 11-28-13, 08:59 PM
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The feed comes up below (you can see it in the picture) is heavy stuff galvanized? Which was probably in place since 1967 when the garage I think was built but its possible could be as old as the 50's?
At that age, there is no guarantee the heavywall conduit is still continuous, have you checked it yet?
 
  #51  
Old 11-28-13, 10:27 PM
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On further though the test for EGC I gave may not be conclusive for buried conduit because you may be fooled by soil conductivity. Probably the only way is dig it up or just run a new EGC.
 
  #52  
Old 11-29-13, 06:58 AM
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At that age, there is no guarantee the heavywall conduit is still continuous, have you checked it yet?
Just to confirm, I can do this with a multimeter by measuring betweeen the screw on a breaker and the pipe itself?



that means the neutral in the subpanel is bonded to the encloser
No, the neutral bar in the subpanel is isolated from the metal case. If it is bonded with a bonding screw or strap they need to be removed.
So likely as it stands now the neutral in the sub is not bonded to the box. Everything would stay the same, but the ground bar if added would be bounded to the box and then it would be as easy as running #6 to the ground bar and an 8' ground rod that I can bury horizontally in a 2.5' trench?

I was thinking turning it into a single circuit would have been easiest but then the 40A dp breaker and wire would need to be removed and replaced with 20A and 12awg and a disconnect added..correct?

When you say "panel" does not having a main breaker in the subpanel change anything? The book I have shows the panel at the second building having a main breaker and multiple branch circuits. I am supplying 7 outlets, 4 lights... the only load is the GDO.
 
  #53  
Old 11-29-13, 07:16 AM
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Just to confirm, I can do this with a multimeter by measuring between the screw on a breaker and the pipe itself?
No because the conduit is buried and the soil may electrically bridge any gap in the pipe.

So likely as it stands now the neutral in the sub is not bonded to the box.
We can't guess and you shouldn't. With power to the garage off at the house check with a multimeter set to ohms. Scrape a bit of paint from the panel and check for infinity from neutral bar to case.

I was thinking turning it into a single circuit would have been easiest but then the 40A dp breaker and wire would need to be removed and replaced with 20A and 12awg
The breaker must be changed but not the wire. However you can't do this if you don't have an EGC.

When you say "panel" does not having a main breaker in the subpanel change anything?
No.
The book I have shows the panel at the second building having a main breaker and multiple branch circuits.
A main breaker is only required if there are spaces for more then six breakers but it is not used as a breaker. It acts only as a disconnect. Another means of disconnect could be used.
 
  #54  
Old 11-29-13, 07:26 AM
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Just to confirm, I can do this with a multimeter by measuring between the screw on a breaker and the pipe itself?
No because the conduit is buried and the soil may electrically bridge any gap in the pipe.
Your telling me I have to dig it up?! I dont think thats possible....


Im kind of doubting If I called an electrician, he would tell me to call in the backhoe.... of course I dont know to much about this, but that seems pretty extreme.
 
  #55  
Old 11-29-13, 07:57 AM
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We can only tell you how it should be done. What you do is up to you. Maybe a pro has a way but I don't know of a way.
 
  #56  
Old 11-29-13, 11:04 AM
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I think we may be over-engineering this. You have a 3-wire feed from your main panel.

I would mount a bonded ground bar, float the neutral and connect the ground bar to one or two -- whichever your jurisdiction requires -- ground rods. If the neutral can't be unbonded, I would install a new isolated bus bar, move the neutrals to it, and use the existing bar for the grounds.

It's all up to your jurisdiction anyway. Ask them or get the licensed electrician you hire tell you what their requirements are.
 
  #57  
Old 11-29-13, 11:21 AM
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In regards to the EGC.....

Im getting like 1-2 ohms from where the pipe leaves my main panel to the subpanel. All outlets in garage test for ground as well.

Or am I way off because the neutral from the feed is the ground? (But thats not the case since the neutral shouldnt be bonded to box).

I did not test from the breaker to the enclosure or the pipe directly. (Im a novice and want to clarify, If I do this I am not going to short the circuit by testing with multimeter from breaker screw to the side of the box or to the pipe directly??)
 
  #58  
Old 11-29-13, 11:30 AM
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In regards to the EGC.....Im getting like 1-2 ohms from where the pipe leaves my main panel to the subpanel. All outlets in garage test for ground as well.
So you are good. Just follow Nash's instructions.
I did not test from the breaker to the enclosure or the pipe directly. (Im a novice and want to clarify, If I do this I am not going to short the circuit by testing with multimeter from breaker screw to the side of the box or to the pipe directly??)
That is a good second test.
 
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