Feed Through Panels

[bennie]

Re: Feed Through Panels

Bob: There's more to this topic than this grumpy old man complaining.

The requirement for redundant ground connections was not created by electricians. Manufacturers and miners were the main lobbyists and submitters. They say it is for safety, not money, believe me it is about money.

I started in the 50's when the push to run an additional conductor for ground purposes was started. We in the field were assured that no one would be electrocuted when all this good stuff happened.

We were told that all electrical appliances would have a ground wire. Grounded receptacles were installed. I am still waiting to see the grounded appliances. 50 years should be enough time for the plan to be put into effect.

Now there is more ungrounded dryers and ranges than ever before. Is this up?

I am not against grounding, I am more in favor of isolation and insulation for safety purposes.

Manufacturers are resorting to insulation in preference to grounding. That should give everyone a message. Grounding is not advancing technology, it is special interest marketing like the AFCI.

Had all the fuss about grounding not occurred, there would be more focus on insulation and isolation.

I am not living in the past, I lived in the past and know the mistakes made. The mistakes should be known to prevent repeating them in the future.

 

[tonyi]

Re: Feed Through Panels

Originally posted by iwire:
...seperate grounds and neutrals are the way it is done and to use the neutral as a ground is IMO a step backwards.

...and what's the impact of this notion on high resistance ground systems? You sure don't want a high resistance neutral .

 

[tonyi]

Re: Feed Through Panels

Originally posted by bennie:
I am more in favor of isolation and insulation for safety purposes.

Manufacturers are resorting to insulation in preference to grounding. That should give everyone a message.

The message being that plastic is cheaper than copper I suspect. All one needs do is read the CPSC recall bulletins on cord/plug appliance/lighting/etc junk and it becomes apparent that safety is NOT a high priority for many manufacturers of this garbage. Cheap rules the day.

 

[bennie]

Re: Feed Through Panels

As a matter of fact; there are many miles of neutral conductors, serving as equipment ground conductors, for safety reasons. The entire system will not function if there is a separate ground conductor.

The original plan for grounding electrical systems was to ground the neutral and to use the neutral for a ground. Review the MGN distribution system.

The NESC deals with the same electrons as the NEC.

[ October 11, 2003, 12:51 PM: Message edited by: bennie ]

 

[hornetd]

Re: Feed Through Panels

Compare the open neutral situations with a feeder that includes a separate EGC and one were the neutral is the only fault clearing path. I was called to a church summer camp because a camper had gotten knocked down by an electric shock in a bath house. The bath house having been built in the fifties it had a three wire feeder. The voltage drop on the feeder left all the electrical boxes in the bath house dangerously hot. Are you telling me that the four wire feeder and neutral isolation we installed was a waste of effort. Nobody is getting shocked off of those new four wire feeder supplied panels. How would a three wire feeder be superior.
--
Tom

 

[bennie]

Re: Feed Through Panels

The feeder with that much voltage drop is the problem. The ground conductor is a band aid, and cover up, it is not a correction of an inferior installation.

 

[hurk27]

Re: Feed Through Panels

I with Bennie on this one and yes a grounded system is needed for power lines as if one hit the ground (earth) for whatever reason there would be no fault to open the circuit to remove the power. but in a dwelling this is not the problem if we had the isolation across the pole transformer and the main breaker was a GFCI type breaker or even a GFP. this would provide far more protection against shock hazard than any grounding but we would still need the ground electrode at the service for lightning but in this way there would never be any stray current on it as the service is isolated from other systems. But as many had said the cost of changing every thing over would be to costly.

 

[hornetd]

Re: Feed Through Panels

Originally posted by bennie:
The feeder with that much voltage drop is the problem. The ground conductor is a band aid, and cover up, it is not a correction of an inferior installation.

The voltage drop was caused by failure of corroded underground splices that were made with fifties technology. With a four wire feeder such a connection failure would lead to a lack of function. With a three wire feeder it leads to a shock hazard. It is a basic tenet of safety theory that it should take two or more failures to introduce an imediate hazard. A feeder with the neutral used for equipment grounding violates that tenet.
--
Tom

 

[tom baker]

Re: Feed Through Panels

Washington State (in WAC 296-46B)if you are from Washington you will know what that is) no longer allows a 3 wire feeder to a remote building or structure, this was effective Aug 1 2003.

 

[charlie]

Re: Feed Through Panels

Originally posted by Tom Baker:
Washington State (in WAC 296-46B)if you are from Washington you will know what that is) no longer allows a 3 wire feeder to a remote building or structure, this was effective Aug 1 2003.

For what it is worth and IMO, the 2002 NEC just about requires a grounding conductor to be taken now. It is difficult to prove that a grounding path from the first building will not be taken to the second building. I feel like the NEC should be match Washington State's Code now.

 

[bennie]

Re: Feed Through Panels

I don't understand why 4 wires from the load side is any safer than 3 wires from the supply side. Both procedures are permitted.

 

[charlie]

Re: Feed Through Panels

Bennie, if you use a three wire instead of a four wire single phase to an outbuilding and a metallic path to the first exists, the metallic path will be in parallel with the grounded conductor.

Where the same wires & cables are on poles, the NESC requires that they be bonded together. That means the grounded sheath of a communications cable will be in parallel with the MGN. Is this a problem? Yes, if the communications companies do not realize the trouble they are in if they cut a cable without jumpering the sheath. That is why training is so necessary for all linemen, not just power linemen.

Imagine what would happen on a single phase primary distribution tap if a MGN were broken and a communications cable were on the same tap. The transformers would continue to operate since the earth return and the cable sheath would carry the return current. If a cable repair person were to cut the cable, the full voltage of the circuit (usually around 7 kV) would be across the open sheath and would only be attenuated by the earth grounding.

Now going back to the NEC, the sheath, pipe, or other metallic path would have the full voltage of the voltage to ground across the open metallic path if it were opened up. Assuming a pipe, you would light up a plumber if he were fixing a leak and you had a bad neutral that you didn't know about since you had a pipe to return the unbalanced current.

Sorry Bennie but IMO, the MGN has no place inside buildings.

 

[bennie]

Re: Feed Through Panels

Charlie: I look at my service conductors that are connected at the pole. The neutral to my service is connected to the MGN, and runs throughout every ground and neutral conductor in my premises wiring system.

A feeder from the load side of the service will carry the ground/neutral to a second building. The ground conductor will be (earthed)grounded again.

A feeder neutral from the supply side of the service, to a second building, will also be earthed again at the building. This is the multi-ground neutral system.

An equipment ground conductor from the service neutral/ground bus to the X-O of a transformer and then earthed at a point other than the building ground is multi point grounding of the neutral (MGN).

 

[charlie]

Re: Feed Through Panels

I agree with your comments about how the second building is served. However, if it is served from inside, it will should not be (IMO) a MGN. If it is served from an electric utility, it will be in most cases a MGN. The difference is inside electricians and outside electricians (I assume you remember those terms).

 

[bennie]

Re: Feed Through Panels

Charlie: You are correct, however stumpjumpers and narrowbacks use the same electrons.

 

[tom baker]

Re: Feed Through Panels

All: This issue deals with objectionable current, or current in parallel with the neutral on other metallic paths. Mike Holts office has a video and VDV called City of Miami Open Neutrals, that can be ordered. Fires were starting in duplexes where the meter had been pulled to one unit. The unit next door had a open netral, the unbalanced neutral current went next door and into the metal lath and nails. Over a long period of time, the low current and voltage caused pyro-phoric carbonization, and started fires. the video shows the metal lath glowing red hot with only 10 volts measured.
The fire dept had heard of pyro-phoric carbonization but had never seen it.
The same thing can happen in a bulding when a downstream panelboard neutral is rebonded in violation of 250.142

 

[Guest]

Re: Feed Through Panels

I found a very interesting article about pyro-phoric carbonization:

http://www.donpearman.com/article.php?articleId=22&sectionId=1

I have observed the carbonization of wood before from low-temperature coking but I never have witnessed any resulting pyrotechnics. I worried about it when I moved in to my house as there were inadequate clearances from flues to combustibles, but no coking. Thank you for putting a name & face to the phenomena. It reminds me of hearing about oily rags spontaneously combusting in garages when I was a kid.

It would be frightening to have your metal lathed plaster walls ignite!

 

[gwz2]

Re: Feed Through Panels

Jumping in here late.

The NEC seems to be slowly eliminating Bennies MGN in the few places that permitted the re-grounding of the Grounded Conductor ( sometimes Neutral ).

250.24(A)(5) FPN refers to 250.30(A), 250.32, 250.142.

250.32(B)(2) limits the conditions that the Grounded conductor can be re-grounded.

250.142(B) again limits the permitting of re-Grounding the Grounded conductor.

Since the NEC permitted the re-grounding of the neutral years ago, it can not demand changing existing permitted re-grounding installations to non-permitted.

I am for Single Point Grounding of the grounded conductor (Neutral) ie. Single Point Grounding of Neutral (SPGN) on the load side of the Poco transformer. But the NEC cannot put demands on the NESC for joint (NEC/NESC) installation considerations.


Yes, Bennie, I remember telling you that I started grunting in Nov 46 and stumpjumping in Apr 47.

gwz2

 

[gwz2]

Re: Feed Through Panels

Guess I'm a slow typist.
Two posts jumped in while I typed.