If the meter socket is factory bonded and a service panel has the main bonding jumper installed and the meter socket is joined to the panel by a metallic conduit, since current can travel over the conduit, wouldn't this be a description of objectionable current and illegal according to the code?
I'll 2nd that Scott. This has also burned up it's share of cyberspace. It should be noted that 250 is often in violation of itself, as it poses 250-6 as a fix to other 250 articles. Also note 250, once again in the 2002 cycle is the 'left-line' change hog. CMP-5, and the former ad-hoc 'fix-250' committee will forever go in circles it seems. The malady I see is that we as field electricians are not allowed to quantify much of it's requirements, only install as prescribed. The ultimate fix would be G/N isolation back to the serving X-former, which the utilities would never go for. Other systems should be studied as to thier viability ( Hats off to Paul)
Re: Objectionable current?#127746 10/29/0110:46 AM10/29/0110:46 AM
The ultimate fix would be G/N isolation back to the serving X-former, which the utilities would never go for.
I agree with you that bonding at the transformer is the right fix. My area's multi state power company has, for the past 15 years or so, been studying the magnetic field density in single family dwellings, at no cost to the occupants (all they have to do is request it). Given the 20 years duration of the dust up around the physiological effects of low level alternating magnetic and electric fields, I'm inclined to suspect that the poco is as interested as anyone.
It seems to me that a cheap (to the poco) reduction of the unbalance fields that are directly related to their side of the main disconnect might be moving the GEC / neutral bond to the transformer, and careful placement of the GEC and service entrance in the dwelling to keep it away from the sleeping areas. I suspect that they are acutely aware of the potential liability posed by an eventual scientific linking of health problems and EMR and are looking to improve their position.
That's very interesting Al. There was a poster here who would isolate and meter N to G for any 'loop' effect. I have read about the power quality people who will monitor the guass in industry, and weed out/alter the offending circuitry. There was also a poster over in Mike H's forum who apparently caused quite a flap over a children's playground built under some High-V lines.
The very way i wire daily is in question by some of these savey individuals, i always have an ear open for them.
So what would the fix be? Attach the grounds to the neutral only in the meter socket?
Require the conduit connecting meter socket to the service panel be PVC? Some type of bond is still required between the socket and the panel, so there is sort of a catch 22. Which is the worse of the two evils?
If the metersocket is outside and the service panel inside, it would be impossible to be in contact with both so any potential between them would not be hazardous. But if they are located next to one another then a potential difference could be hazardous and neutral current across the conduit may be the lesser evil.
I argue with contractors about this all the time but have no data showing any posssible hazards or that current will travel across the conduit at all because of the path of least resistance arguement. Any data as to how much current, if any, will travel across a conduit in parallel with a neutral conductor with 2 phase conductors 180 degrees out of phase in the conduit as well, would be appreciated. And if there will be current, what are the harzards? Is there a possiblity of potential besides to the phase conductors?
Re: Objectionable current?#127749 11/07/0107:43 AM11/07/0107:43 AM
Steve, I sense your frustration, so do others it would seem;
From pg 6 sep.-oct IAEI
There appears to be interest, especially in the international area, to promote the use of performance based electrical safety code rules instead of those of a prescriptive tyoe. While that concept may sound good when described by promoters of that concept, it is not a practical approach by itself. Without clear guidlines of a prescriptive code with readily definable parameters on how to achieve the objective on performance based rules, enforcement of those rules is extreemly difficult. If a roadway sign states " Drive at a Safe Speed", is it possible to enforce taht rule? While it can be agreed that the stated rule is an ideal one, it is easily recognized that drivers will not interpet that general rule as the same.
seems to hit the 'nail' on the head....
As an example, performance requirements are stated in 250.4 as to the objectives of grounding and bonding and reference is made to the remainder of art 250 for the rules needed to accomplish those goals. This combination of the two types of rules is a workable solution.
really? , it would seem debated constantly.........
Re: Objectionable current?#127750 11/07/0108:14 AM11/07/0108:14 AM
Here's a new 2002 NEC rule and FPN that covers the subject of this thread.
630.15 Grounding of Welder Secondary Circuit. The secondary circuit conductors of an arc welder, consisting of the electrode conductor and the work conductor, shall not be considered as premises wiring for the purpose of applying Article 250.
FPN: Connecting welder secondary circuits to grounded objects can create parallel paths and can cause "objectionable current" over equipment grounding conductors.
LOL! probably the pwr co's are tired of fried x-formers from mom & pop welding shops clampin' onto whatever is available with the ol' static welder. Once again, however, we have an electrical code most welders will probably pay little attention to....
so Joe, what's your view on this?
Should I as a field eletrician be let to blindly install a 250.32(B)(2) with the rigid raceway interupted only by a pvc sweep?
Should a pwr co. be let to land an x-former pad within arm's length of the meter/metal building?
Can I continue to run a 250.66 GEC to a common municipal water line,close x-former nieghbors, etc,tec... sparks included on contact?
Should we continue the practice of mettalic raceway's that, as Steve stated, serve as an obvious nuetral?
Or should 250 be arranged as to allowing the field electrician to design/build around these 'objectionable' circumstances without fear of violatins.
Maybe metersockets should not be factory bonded. Anybody see any problems with this? Does the utility require the metersocket to be bonded? I know the metersocket can be bonded but does it have to be bonded? If the metersocket is made so a bond jumper can be installed if it is needed, then it could also be not bonded to meet the requirements of Article 250 and specifically to prevent objectionable current.
Thanks for the responses, I'm glad to know my thinking isn't off track.