3 prongs dryers

[iwire]

Well luckily it's all a moot point.


I maintain my view and when doing condos in the 80s that was how it was enforced around here. Also how it was taught in trade school.

Again it makes no sense to be concerned about the differance of potential in a conductor hidden in a wall but not worried about exposing the appliance user to this exact same potential.

Either the potential is an issue or it is not.

To each their own.

 

[mbrooke]

Well luckily it's all a moot point.


I maintain my view and when doing condos in the 80s that was how it was enforced around here. Also how it was taught in trade school.

Again it makes no sense to be concerned about the differance of potential in a conductor hidden in a wall but not worried about exposing the appliance user to this exact same potential.

Either the potential is an issue or it is not.

To each their own.

What do you mean by this?

 

[iwire]

What do you mean by this?

In this thread I am being told the reason only SE must originate at the service panel is due to the bare neutral making incidental contact with grounded items.

Here it is from the handbook

In the bottom diagram the service-entrance cable installed from the feeder panelboard to the range or clothes dryer outlet contains an insulated grounded conductor to prevent incidental contact between the conductor and metal enclosures. Such contact could result in current being introduced onto circuit paths other than on the intended path, which is the grounded (neutral) conductor.

OK if I accept that incidental contact is a problem for a conductor buried in a wall or enclosure surely that is also a problem if the frame of the dryer or range is touching a grounded object. Say the grounded washing machine beside it.

 

[mbrooke]

In this thread I am being told the reason only SE must originate at the service panel is due to the bare neutral making incidental contact with grounded items.

Here it is from the handbook



OK if I accept that incidental contact is a problem for a conductor buried in a wall or enclosure surely that is also a problem if the frame of the dryer or range is touching a grounded object. Say the grounded washing machine beside it.

The incidental contact of concern takes place in the subpanel, not the wall. The bare concentric neutral in a sub panel connecting to the neutral bar and then touching the walls of the sub panel breaking the neutral to ground isolation is the concern.

But I think I might be getting at what your trying to say

 

[mbrooke]

Ok you do bring up a good point. Cant say you don't. A 3 wire dryer in contact with a washer is in theory breaking the neutral bond in a sub panel. Current would flow from the neutral bar in the sub panel through the 3 wire dryer cord through the washer EGC and thus current will flow on the grounding system, even with the dryer off. Valid issue.


In theory it is practically a neutral to ground bond in a sub panel.


However, from the way the code is written, the semi colon and sentence structure allowed you to have a 3 wire come from a sub panel be the neut insulated. Would it have been better to require all 3 wires from the main? Objectionable current wise, Yes! But, for what ever reason CMP decided to word it that way. IMO I think the NEC had already started something they knew would be hard to change.

 

[kwired]

Well luckily it's all a moot point.


I maintain my view and when doing condos in the 80s that was how it was enforced around here. Also how it was taught in trade school.

Again it makes no sense to be concerned about the differance of potential in a conductor hidden in a wall but not worried about exposing the appliance user to this exact same potential.

Either the potential is an issue or it is not.

To each their own.

In this thread I am being told the reason only SE must originate at the service panel is due to the bare neutral making incidental contact with grounded items.

Here it is from the handbook



OK if I accept that incidental contact is a problem for a conductor buried in a wall or enclosure surely that is also a problem if the frame of the dryer or range is touching a grounded object. Say the grounded washing machine beside it.

Probably all good reasons why the changes were made in 1996 that no longer allowed using the grounded conductor for equipment grounding also. For some reason at some time it was deemed safe enough or it would have never been the standard practice that it was. Of course the only reasons for any language of how to do this since the 1996 was involving exceptions for existing installs that were code compliant at one time, that is part of why I earlier said you need to put yourself back in time when reading and trying to interpret what was intended in those older codes, as they did not have the changes that were made later to add confusion to any intrepretation of what was written at that time. They did do a better job of clarifying what they wanted to see run to service panels vs non service panels in later codes.

 

[Little Bill]

In this thread I am being told the reason only SE must originate at the service panel is due to the bare neutral making incidental contact with grounded items.

Here it is from the handbook



OK if I accept that incidental contact is a problem for a conductor buried in a wall or enclosure surely that is also a problem if the frame of the dryer or range is touching a grounded object. Say the grounded washing machine beside it.

I posted this before. It is from the 2011 handbook.

In many instances, the wiring method was
service-entrance cable with an uninsulated neutral conductor
covered by the cable jacket. Where Type SE cable was used
to supply ranges and dryers, the branch circuit was required
to originate at the service equipment to avoid neutral current
from downstream panelboards being imposed on metal objects,
such as pipes or ducts.

Also, I nor anyone else has said this was best practice or necessarily safe. I (and others) was only trying to point out to you what the code says as written.

I can only guess as to why it was written that way. My guess is since the SE cable was easiest and most commonly used wire in residential, for ranges and dryers, that the code making panels allowed it but with stipulations. Stipulation/exception being if it was used with the bare neutral that it had to originate from the service panel.

 

[iwire]

I posted this before. It is from the 2011 handbook.

I posted that as well, I see what it says and it makes no sense. It would not be the first time I disagree with the handbook.

Also, I nor anyone else has said this was best practice or necessarily safe. I (and others) was only trying to point out to you what the code says as written.

I was not trying to put words in your mouth but you and others have been pointing to the handbook reason which is not the code.

It may be what you and some others feel the code says but it is not what I feel the code says. Neither did the inspectors in Boston during the 80s when I did literally 100s of range and dryer outlets.

I can only guess as to why it was written that way. My guess is since the SE cable was easiest and most commonly used wire in residential, for ranges and dryers, that the code making panels allowed it but with stipulations. Stipulation/exception being if it was used with the bare neutral that it had to originate from the service panel.

That is as much pure speculation as I have been posting, the only difference is that I feel my way makes much more sense electrically even if not grammatically correct in your view.

I do not think of the CMPs as linguists so I have no problem accepting a possibly misplaced comma.


Again much ado about nothing, its been a done deal since 1996.

 

[kwired]

I posted this before. It is from the 2011 handbook.



Also, I nor anyone else has said this was best practice or necessarily safe. I (and others) was only trying to point out to you what the code says as written.

I can only guess as to why it was written that way. My guess is since the SE cable was easiest and most commonly used wire in residential, for ranges and dryers, that the code making panels allowed it but with stipulations. Stipulation/exception being if it was used with the bare neutral that it had to originate from the service panel.

NEC handbook commentary is not any official NFPA interpretation of the actual code content, it is the opinion of those that wrote the commentary. Though I do mostly agree with what you have said for this particular issue.

SE cable - I have seen a lot of it for three wire range circuits, dryer circuits see to see mostly NM cable (with insulated neutral most of the time) in these parts for those older circuits. Occasionally will see where someone used 10-2 with bare ground (NM) for a dryer, but not just too often.

 

[Little Bill]

I do not think of the CMPs as linguists so I have no problem accepting a possibly misplaced comma.

It wasn't misplaced, it wasn't there (the second one you want)

I would think after many code cycles and re-writing the book that if there was an error it would have been corrected by now!

NEC handbook commentary is not any official NFPA interpretation of the actual code content, it is the opinion of those that wrote the commentary. Though I do mostly agree with what you have said for this particular issue.

I know and I said as much when I posted this earlier in this thread.
But I have heard that some of the commentary was either written by members of a CMP or have been contacted by authors of the handbook. I can't confirm this though.

 

[mbrooke]

I posted that as well, I see what it says and it makes no sense. It would not be the first time I disagree with the handbook.

I was not trying to put words in your mouth but you and others have been pointing to the handbook reason which is not the code.

It may be what you and some others feel the code says but it is not what I feel the code says. Neither did the inspectors in Boston during the 80s when I did literally 100s of range and dryer outlets.





That is as much pure speculation as I have been posting, the only difference is that I feel my way makes much more sense electrically even if not grammatically correct in your view.

I do not think of the CMPs as linguists so I have no problem accepting a possibly misplaced comma.


Again much ado about nothing, its been a done deal since 1996.

So wait the inspectors made you use NEMA 14-30 and 14-50 outlets? Where did you/they also find the appliance cords? Yes I know mobile homes had it this way, but Ive never seen a 4 wire setup in a home or business built prior to 1996. Inspector here always allowed it. Although, to be fair, you do find the occasional 100 unit condo complex where every dryer is on 10-2 with barge ground:happyno:



IMO I think the wording is deliberately left vague. I see that often with controversial rules in the NEC. Its difficult for the CMP to bluntly admit 3 wire shouldn't have been allowed for so long or that it was frequently mis applied. Kind of their way of skirting direct liability I guess.

 

[kwired]

I posted that as well, I see what it says and it makes no sense. It would not be the first time I disagree with the handbook.




So wait the inspectors made you use NEMA 14-30 and 14-50 outlets? Where did you/they also find the appliance cords? Yes I know mobile homes had it this way, but Ive never seen a 4 wire setup in a home or business built prior to 1996. Inspector here always allowed it. Although, to be fair, you do find the occasional 100 unit condo complex where every dryer is on 10-2 with barge ground:happyno:



IMO I think the wording is deliberately left vague. I see that often with controversial rules in the NEC. Its difficult for the CMP to bluntly admit 3 wire shouldn't have been allowed for so long or that it was frequently mis applied. Kind of their way of skirting direct liability I guess.

14-30 and 14-50 outlets and cords were maybe harder to find but not impossible to find back then.

 

[iwire]

I would think after many code cycles and re-writing the book that if there was an error it would have been corrected by now!

They only recently changed the wording for using reduced conductor sizes for residential services and feeders. It turns out many areas had been misinterpreting it for many many code cycles.

 

[iwire]

So wait the inspectors made you use NEMA 14-30 and 14-50 outlets? Where did you/they also find the appliance cords?

They where / are all standard supply house items here as we have been using four wire outlets for a long time up here.

 

[mbrooke]

They only recently changed the wording for using reduced conductor sizes for residential services and feeders. It turns out many areas had been misinterpreting it for many many code cycles.

I bet the appliance installers not accustomed to that area were surprised

They where / are all standard supply house items here as we have been using four wire outlets for a long time up here.

I think I know what your referencing. Every sub panel around here used to get 2AL protected at 100amps which was though to be good for 100amps. Even HD still lists it as good for 100amps:happyno:

 

[kwired]

They only recently changed the wording for using reduced conductor sizes for residential services and feeders. It turns out many areas had been misinterpreting it for many many code cycles.

Don't expect anybody that was confused before to understand the change that was made. The main thing they did was get rid of the table and give a multiplier instead. You still can only apply it to conductors that feed an entire dwelling unit, and not just any dwelling feeder.

If you use the old tables from previous codes, you likely come up with just about the same minimum size conductor nearly every time as you did before. Though the way things were before there was no way to determine any ampacity adjustments if you run into those situations where the way it is now it is not really any different then adjusting ampacity of another conductor.