Can these tango?

Status
Not open for further replies.
defears said:
Two services on the same building must be tied to a common grounding electrode.
Click to expand...

I believe they are but they are using the ground bar in the panel. 250.64(C)(1) in the 2011 allow this connection for connectors that are listed for grounding and bonding equipment.

Now is a ground bar or neutral bar considered a connector-- IMO, yes. Is it listed for grounding and bonding-- I would think so-- thus the install should be legal, at least in 2011-- the rest is a guess.
 
Here I'm going to 'think' and 'feel,' though I have no doubt that others will happily find my errors and correct them! :D

The ground rod/ Ufer/ whatever has nothing to do with clearing faults, only for 'natural' electricity such as static and lightning. Thus our rule 'every structure gets a ground rod.' Note that it says nothing about every SERVICE getting a ground rod.

Now, let's look at your typical duplex or apartment building with independent metering of each unit. As I see it, one building, one ground rod, one GEC to one point anywhere in the stack. If there's a main disconnect, that's where I think the GEC needs to go. (Big opening here for differing opinions).

What if there's no main disconnect? Well, I say terminate the one GEC to any of the panels. Treat them all -whether the GEC is in the box or not - as a 'main' service and bond the cases to the neutral bar.

For example ... imagine a service mast to a sealed gutter, and that gutter feeding two 'all-in-ones.' I'd run the GEC to either of them, and leave it at that.

I'd do that for two reasons. The first is that both meter sockets likely also have the neutral bonded to the case, and I consider it enough to 'bond' the second panel via the PoCo neutral to the GEC in the second panel. (Second invitation to be corrected).

The second problem is: how do you get the GEC to both panels? The metering sections are deliberately arranged to make it difficult to feed it past the meters, through the gutter, and into the other panel. Indeed, I think there's even an NEC rule against ANY wires 'returning' to the metered side. Connect the two panels with pipe? I think there's a rule against that as well- and if not, you're certainly setting the stage for mixing services later on. Two GECs, one from each, to the same ground rod? I don't see what that would accomplish.

Now, I did see one duplex which had the respective panels on opposite sides of the building, and separate service drops. There's one instance I would want to see a GEC from each service to the same ground rod. I certainly would NOT want there to be two unconnected rods.

I'm very welcoming of different opinions on this one.
 
I can't speak for circa 1975 or even Dennis 2011 Code section, but the way I read 2005 and 2008 it would not be permissible.
From handbook commentary it appears it is not permissible to route the GEC in a manner that removal of one panel/switch will interrupt the path of another,
 
augie47 said:
I can't speak for circa 1975 or even Dennis 2011 Code section, but the way I read 2005 and 2008 it would not be permissible.
From handbook commentary it appears it is not permissible to route the GEC in a manner that removal of one panel/switch will interrupt the path of another,
Click to expand...

Well I just spoke to NFPA and they were confused as well. They got back to me and said if the ground bar was listed for grounding and bonding then it would be compliant-- I can't imagine the bar is not listed for grounding and bonding but who knows. They were talking 2008 NEC
 
I don't have my book with me, it's in a snow covered van right now.

I thought a common grounding electrode conductor of 3/0 could be tapped with whatever size was needed for the individual discos if a gutter was used. That way, this would be met.

From handbook commentary it appears it is not permissible to route the GEC in a manner that removal of one panel/switch will interrupt the path of another

Honestly, the fact that there was bonding at all, is good.
 
Dennis,
I think "location" may be the key here. The fact that the bar is listed for grounding but is inside a panel I think makes a difference based on the wording in 250.64(D)(1) {08} "A tap conductor shall extend to the inside of each service disconnecting means enclosure."
In 250.64 it discusses the taps to each enclosure. That and the handbook pictorial lead me to believe that the connections must be made independent of the service disconnect/switch. I can not, however, find specific wording to support that beyond what I quoted.
 
Status
Not open for further replies.
Top