SpamFree wrote:
In none of the above do you make reference to anything we can check or
to anything which explains the apparent anomaly of a perfectly good
steel strip connecting the source of the fault with the building
ground not working properly if wound in the form of a spiral but being
OK if a ridiculously small gauge wire follows along the spiral. The
proffered explanation of inductive resistance seems to be definitively
crushed by Chris Lewis who in the earlier discussions was supported by
other posters who had presumably done the same calculations. In any
event no one pointed to errors in his reasoning.

You (or UL) seem to think that the EGC depends on the contact between
each of the spirals. Why? AC is a continuous length of steel that just
happens to be in a spiral form. If one were to pull apart the spirals
thereby extending the steel to its full length and properly connect
both ends wouldn't that form an adequate EGC? Corrosion between the
spirals is really immaterial. The only questions would seem to be: Is
the steel armor of sufficient gauge to carry the current and are the
ends properly connected? In the latter case you can badly connect the
NM ground too and connections can work loose over time so how does
that differ?

And please spare us the drama. "Carrying out the dead" indeed!

I would not think it that hard to ask UL about the research I have
attributed to them. My problem is that they pay their bills by getting
paid for their research efforts. Even if I bought a copy of their
report the copyright would still prevent me from posting it on line. Is
it your position that if I can't spoon feed you the supporting research
that I should not make reference to it?

I didn't see the calculations you referred to would you help me out and
point me to the postings that contain those calculations that I missed.
Did I miss someones posting that indicated a source for some research
that invalidates my willingness to depend on the testing done by UL?

Is it somehow illogical to assert that the length of the spiral armor
measured along the spiral coupled with the lower conductivity of steel
makes it a poor Equipment Grounding Conductor (EGC) unless the turns are
shorted to each other so that the larger cross sectional area of the
sheath can then make up for those factors? Why does corrugated armored
cable not have a bonding strip while the spiral tape armored cable does
have one? I've installed thousands of feet of the spiral armor type and
several hundred feet of the corrugated armor type. The post
installation testing of each type yields very similar results in terms
of the Equipment Grounding Conductor loop voltage drop.

UL's tests of armored cable that is armored with spiral wound
interlocking metal tape show that the armor alone is an inadequate EGC.
I may indeed have misunderstood why that is true but that does not
mean it is not true. Your position would appear to be that the spiral
tape must be an adequate EGC. On what are you basing that assertion?
What testing have you done or can you point the rest of us to that
supports your conclusion? If the spiral tape armor is adequate as an
EGC then why do the manufacturers install the bonding strip? The
addition of the bonding strip to the sheath is not without cost. Do you
believe that the manufacturers install it for some other purpose than
bonding the turns of spiral interlocking metal tape armor to each
other? If so what purpose do you allege the bonding strip serves.

What I do believe in this matter is that UL is acting in good faith. I
cannot see what UL would have to gain by declining listing to a simpler
cable construction that passes the listing standard. They are not the
only laboratory that conducts electrical product testing so if they
decline listing to a product that does meet the examination standard
they would simply loose that manufacturers listing fees to another
laboratory such as Southwest Research or ETL. I depend on the results
of laboratory testing. I am willing to depend on the laboratory listing
mark to determine whether an electrical component of a buildings wiring
system is suitable for it's intended use. You and a few others here
keep insisting that the reliance of myself and others here on the
laboratory listing make us somehow wrong. Fact is I've offered more
evidence than you have for our respective positions.
--
Tom H