2 questions covered before

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bphgravity

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I have two questions I know have been covered before but would like to refresh the discussion.

1. Would you consider a sheet metal screw as an acceptable method for attaching the bonding lug to a metal pool enclosure? Does 250.8 apply to pool bonding?

2. Is it a violation (310.4 primarily) to install a 4-wire circuit between the meter enclosure and main panel? The two enclosures are metal and connected by a metal nipple. So basically there are several parallel returns. But should the 4th wire be removed?
 
Re: 2 questions covered before

1) No, I don't see it as being acceptable. 250.8 applies, as there is nothing in 680 that supplements or modifies that section. 90.3

2) Violation of 310.4, assuming that the nuetral is bonded in each enclosure.

[ September 06, 2005, 01:04 PM: Message edited by: ryan_618 ]
 
Re: 2 questions covered before

2. Is it a violation (310.4 primarily) to install a 4-wire circuit between the meter enclosure and main panel? The two enclosures are metal and connected by a metal nipple. So basically there are several parallel returns. But should the 4th wire be removed?

In the meter, what is the 4th wire (an equipment ground?) connected to?

250.142 allows the neutral to bond metal equipment on the supply side of the service disconnect.
 
Re: 2 questions covered before

Ryan,
2) Violation of 310.4, assuming that the nuetral is bonded in each enclosure.
Click to expand...
Is the metal raceway also a violation?
Don


Oops! I hit the edit button and not the quote button! :roll: --Ryan

[ September 06, 2005, 01:14 PM: Message edited by: ryan_618 ]
 
Re: 2 questions covered before

Originally posted by don_resqcapt19:
Ryan,
2) Violation of 310.4, assuming that the nuetral is bonded in each enclosure.
Click to expand...
Is the metal raceway also a violation?
Don
Click to expand...
Although the raceway will in fact be in parrallel with the neutral, I know of no code section that prohibits it, unless you beleive 250.6 applies to it. What do you think?
 
Re: 2 questions covered before

The problem with 250.8 is that it uses the word "grounding" and not "bonding" as well. One might argue that the code says nothing about securing bonding connections with sheet metal screws.

I happen to feel that the even though the metal nipple between the two metal enclosures acts as a parallel return, it also serves another purpose by providing a raceway to attach the two enclosures. The additonal grounding conductor serves no additonal purpose therefore should be removed. Then again, it;s really not hurting anything being there? :confused:
 
Re: 2 questions covered before

Ryan,
What do you think?
Click to expand...
I think that if the parallel wire is a real problem, than the raceway is a bigger problem. It reality, I don't think either one is an acutal safety problem. Take a look at a 5' length of #4 in parallel with 5' or 2/0 and a 200 amp load. 48.8 amps will flow in the #4 and 152.2 in the 2/0.
Don
 
Re: 2 questions covered before

Problem or not I do not believe 310.4 applies to raceways, even considering 250.118 says a raceway is a EGC.

310.4 Conductors in Parallel.
Aluminum, copper-clad aluminum, or copper conductors....
Click to expand...
Genrally the raceways are steel. :D
 
Re: 2 questions covered before

310.4 ... comprising each phase, neutral, or grounded circuit conductor ...
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Does 310.4 even apply? We have a bonding conductor in parallel with a grounded circuit conductor. We do not have two grounded circuit conductors in parallel.
Don
 
Re: 2 questions covered before

Well once they are electrically connected at both ends all bets are off. :)

I say we have two grounded conductors. :)

We are required to run the grounded conductor we are not required to run a bonding conductor. That being the case if we call them both bonding conductors we have other violations.

If 310.4 does apply to raceways than every 'wire' EGC installed in EMT is also a violation.

I doubt we will ever get to the bottom of this.

Thats it shut, the grid down we have millions of homes in imminent danger. :D
 
Re: 2 questions covered before

If both the grounded and bonding conductors are the same size and over 1/0 we're good to go. :D

Roger
 
Re: 2 questions covered before

I was refering to the last sentence. "Sheet metal screws shall not be used to connect grounding conductors or connection devices to enclosures." No mention of "bonding" here yet it mentions it in the first sentence and in the title?
 
Re: 2 questions covered before

This is my toughest subject to understand. A lot a good questions to be anwsered. Correct me if I'm wrong but most meters neutrals are bonded to the meter box. If so from the meter to your first disconnect the nipple must have at less 1 bond jumper from that nipple to the service grounded conductor. That service grounded conductor(neutral) must have a screw or strap bonded to the disconnect panel. Now the GEC is connected to the disconnect neutral. Now if the nipple was pvc from the meter to the first disconnect, how would the meter box be grounded properly. Now if the meter had the EGC in it first and the neutral and the EGC were tied together on the meter then from the meter run a 4 wire circuit. Separate your grounded connector at the first disconnect from your grounding connector. I know that this does satisfy code intent but if you were to do it this way then your steel nipple that is bonded to only the grounding terminal at the first disconnect wouldn't have a parallel path back with the neutral. Again I'm just thinking.
Thanks!
Jim
 
Re: 2 questions covered before

By Don: Take a look at a 5' length of #4 in parallel with 5' or 2/0 and a 200 amp load. 48.8 amps will flow in the #4 and 152.2 in the 2/0.
Click to expand...
While the #4 will be ok if the connection of the 2/0 is good, but what about if the 2/0 lost connection?
Could be a possible fire waiting to happen if in PVC.? :eek:
 
Re: 2 questions covered before

While the #4 will be ok if the connection of the 2/0 is good, but what about if the 2/0 lost connection?
Could be a possible fire waiting to happen if in PVC.?
Click to expand...
Sure, but the same possibility exists when we use metallic pipe in this application (without the bonding conductor).
Don
 
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