On Tuesday, November 19, 2013 8:32:46 AM UTC-5, Stormin Mormon wrote:
Perhaps. I just thought of another way to make krw's day.
It's a little complicated and clearly over his pay grade.
His position is that with split-phase service, there is only
one phase present, that you can't say the two hot legs are
180 deg out of phase, etc, because it originates from only one
phase of the primary distribution. Well, then what about
open delta? Open delta allows a utility to provide 3 phase
service for lighter loads using just TWO transformers, instead of
3. It saves the cost of an additional transformer. One transformer
is connected to each of TWO primary high voltage lines.
So, they have connections to only 2 primary phases, yet
they deliver 3 phase power. According to krw's standards,
that should be called 2 phase, because it only uses two of
the transmission's 3 phases. Yet it's called 3 phase, there
are 3 phases that you can see on a scope and just like
the 240V/120V service it's done with transformers.
On 11/19/13 8:53 AM, firstname.lastname@example.org wrote:
Another thing a bit odd is the corner ground delta used by some of
the local utilities for irrigation well hookups. 3ø, 480 vac, 100 hp or
less in my area. The meter sockets look like single phase meter
sockets. The utilities usually bring four wires into the sockets. Two
of them go to the grounded center pole. One of those two will have the
green/white stripe on it.
On Monday, November 18, 2013 9:50:53 PM UTC-5, Doug Miller wrote:
Good luck explaining that to krw. According to him, the only
proper term apparently is "opposite". What a precise engineering
term...... I've even given him references to an IEEE paper
delivered at a conference of power engineers that specifically
addresses the point. But he just ignores it all.
Probably. Not sure what your question is, but 2-phase, where the two
are 90 degrees apart is interesting in that any phase relationship and
any number of phases can be generated with simple transformers and a
(very small) bit of trigonometry. It's quite useful but exceedingly
Two phases generated 180 degrees from each other make no sense at all.
It's no more efficient (less, actually) than single-phase and much
less efficient than three-phase. There are all sorts of other
alternatives, as well. Six-phase is somewhat interesting at times but
it's not as efficient as three phase. There's a reason the world uses
On Saturday, November 16, 2013 6:12:14 PM UTC-5, email@example.com wrote:
I believe his question is the same one I have, which is why
you insist on referring to a 180 deg phase difference between two AC waveforms only as "opposite" and deny that it is also correct that they differ by 180 degrees in phase. 180 deg is just one possible relationship between two
waveforms, where one is the opposite of the other. And that is what
you have at the dryer connection.
but 2-phase, where the two
Except of course to run the dryer, because regardless of
whatever you want to call it, there are two hots going to that
dryer that differ in phase by 180 deg. If you were in an EE
physics, or math course and they presented you with a voltage vs time
graph of two waveforms that you would get from an oscilloscope
hooked up to:
Hot 1 to neutral and
Hot 2 to neutral
And they asked, what is the phase relationship of these
two voltage waveforms, what would your answer be?
On 11/16/2013 10:38 AM, firstname.lastname@example.org wrote:
The NEC previously allowed the *neutral* for ranges and dryers to also
be used as the ground. It is not allowed now for new circuits, but is
explicitly grandfathered for old circuits that were compliant when
There are a number of limitations on using the neutral as both neutral
and ground. One of them is the circuit has to originate in the service
panel. The neutral and ground are bonded at the service. It has to
originate on the neutral bus. In many panels the neutral and ground bus
are the same. If there is a separate ground bus that only connected to
the enclosure the wire can not be connected there.
Another limitation is uninsulated wires in romex can not be used.
From gfretwell in a recent post:
"During WWII they jammed through an exception allowing the neutral to
also be used as the ground to save copper.
In the 1996 code cycle CMP 5 finally accepted Phil Simmon's assertion
that the war was over and they should dump this exemption for new
circuits. (existing can stay)"
Not always. Older, or cheap, load centers used to do this, but the
newer panels give a dedicated ground bus with a tapping screw to the
panel case and an isolated grounded conductor bus.
In some instances, in meter-main/load center combos, the tapping
screw may be allowed as the point at which the grounded conductor
obtains its bond to ground, but it is preferred to do this in the
meter section of all installations so that there is no messing things
up via some moron coming in at a later time and thinking that it
is all the same...
Why I hated residential work...
It is common practice to use the same bus for both neutral and ground in
a service panel. The bus is bonded to the enclosure (N-G bond), and the
earthing electrode system connects to it.
Can also be done with a separate ground bar connected to the enclosure.
(Neutrals can't connect to such a ground bar.)
The neutral bar in a service panel must be bonded to the
Not obvious what you are saying.
The system N-G bond is at the service disconnect.
It is common for the neutral in a meter can to be connected to the can.
That is done to "ground" the can.
Your post would be more clearer to most people if you used "neutral"
instead of "grounded conductor".
In a 3 wire dryer circuit it is acting as a neutral and as a ground.
It is more of just what you want to call it. As most dryers use the 120
volts from one leg to power the control circuits and light , the third wire
is acting as a neutral. At the same time it is connected to the frame of
the dryer and is acting as a neutral. I am sure if you search the
electrical code there will be some name for this wire.
On the 4 wire dryer wiring , you do have a seperate ground and neutral wire,
but they both connect to the frame of the breaker box so in effect it is
just one wire but they go to two differant places on the dryer. Outside the
fact they may be differant sizes and color code differantly to meet the code
it would not really mater which wire was hooked to the neutral or ground at
the dryer as they both go to the same place in the breaker box.
Having a seperate ground wire for the dryer just gives an extra layer of
On Sat, 16 Nov 2013 12:05:12 -0500, Ralph Mowery wrote:
Well, that answers my question as to whether the neutral is carrying
Since there are 120v "things" on that dryer (e.g., the timer, the
bulbs, etc.), there *must* be some current in that neutral (unless
the loads are perfectly balanced).
So, in the case of my 3-wire dryer, the neutral is always carrying
current, whereas a ground wire shouldn't normally be carrying current
(because once you carry current, there is a chance that there will
be resistance, and if there is resistance, you get a potential,
whether you like it or not).
So, maybe, just maybe, my spark, is due to a high-resistance neutral?
Geez. How do I check for a high-resistance neutral?
On Sat, 16 Nov 2013 20:18:17 +0000 (UTC), Danny D'Amico
Yes, though it's possible to balance the two, it would be quite
expensive to perfectly do so under all conditions. The fourth wire is
It would have to be a very high resistance neutral to get a spark.
Even if there is no neutral, the voltage on the common point (the
neutral on the dryer) would be very close to ground. The imbalance is
proportional to the ratio of the current in the heater and the timer.
You would measure resistance with an ohm meter. ;-)
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