Pete C. wrote:
bud-- wrote:
Pete C. wrote:
bud-- wrote:
Pete C. wrote:
bud-- wrote:
Pete C. wrote:
bud-- wrote:
Larry The Snake Guy wrote:
On Aug 14, 2:51 pm, David Nebenzahl wrote:

First of all, it is an approved, UL/CSA tested, and, most importantly,
code-approved (US building code) wiring method. If it was as all-fired
bad as folks here claim, why would it still be allowed? After all, the
building codes tend to err on the side of caution.
However, all kinds of unreliable crap is UL listed. A UL listing is a
pretty good indication that something probably won't kill you or burn
down your house, but says nothing at all about whether it will
function properly.

By coincidence I have the UL standard [15 years old] for "Snap Switches".
For AC-only switches (which is what are commonly used) the switch must
pass all the following at rated voltage:
- 10,000 operations at rated current
- 10,000 operations at rated current and power factor around 0.8
- 10,000 operations at rated current controlling incandescent loads
[high inrush current]
- 100 operations at 4.8x rated current and power factor around 0.5

IMHO this is testing for whether the switch will "function properly".

My recollection is receptacle tests are similarly rigorous and include
plugging and unplugging and operating for a periods at significantly
above rated current.

I think most of us would be very unhappy if fuses or circuit breakers
that are UL listed did not "function properly".

For devices like TVs, it is not possible (or desirable) for UL to
determine if the device is actually useful. The test is whether the
device will "kill you or burn down your house".

Standards may not be perfect. They weren't for #12 backstabs, old
technology #12 and #10 aluminum wire, or devices originally used with
that wire. And standards for GFCIs have changed quite a bit.

IMHO standards are not adequate for #14 backstabs - maybe if they were
limited to #20 wire or smaller....

Building codes put a little more emphasis on
function, but are also updated fairly regularly because things that
were once required are finally proven to be bad ideas.
The NEC has very few equipment construction requirements and I can't
think of any performance requirements.

The 'prime directive' is that "equipment required or permitted by this
Code shall be acceptable only if approved".

"Approved" is "acceptable to the authority having jurisdiction."

The NEC generally has only a few rather general guidelines on what
should be acceptable. "Authorities" generally accept equipment that is
"listed" or "labeled", but it is up to the "authorities".

The NEC did not eliminate #12 backstabs or change requirements for #12
and #10 aluminum wiring.

--
bud--
The standard you quote may or may not test whether the device will
"function properly" as you did not include the pass / fail standards. If
the fail standard is "fire" and the pass standard is "no fire", then the
switch could well stop functioning "properly" well under the cycle count
limit and still pass the test.
The "pass standard", _as I stated_, is that "the switch must pass all
the following". The switch must still work after over 30,000 operations.
And that is only part of the standard.
What you stated, did not include pass criteria as *I stated*.
My original post said "the switch must pass all the following at rated
voltage". I quoted a portion of that in my last post. With minimal
reading ability anyone should be able to determine the UL test requires
a switch to survive over 30,000 operations at rated voltage and at least
rated current.
Again, that is incomplete criteria as it does not clearly specify the
pass / fail criteria. It is entirely possible for a device to be cycled
that many times, with the rated voltage and current applied and fail in
a way that presents no fire or shock hazard. and pass a safety test.
The pass criteria, as I have said several times, is the switch survives
over 30,000 specified operations at rated voltage and at least rated
current and is functional at the end of the tests. The switch is not
allowed to fail during the 30,000 tests. A switch must "function
properly" to survive over 30,000 operations.

UL standards, as they apply to wiring components (switches, receptacles,
fuses, circuit breakers, panels, wire, motor starters, wire nuts, ...),
is that those products will "function properly", not just that they will
fail safely.
You say that, but you did not post the actual UL test pass criteria.
With minimal reading ability anyone should be able to determine switches
need to pass all of the following:

- 10,000 operations at rated current
- 10,000 operations at rated current and power factor around 0.8
- 10,000 operations at rated current controlling incandescent loads
[high inrush current]
- 100 operations at 4.8x rated current and power factor around 0.5

That is what my original post said and the requirements were taken from
the UL standard.
And again, anyone with minimal reading ability can see that what you
quoted is not a complete test specification
What more do you want? From the information given I could construct
tests for the 30,000 operations. You want the exact language from UL?
Maybe you could look at your copy of UL30. The switch is not allowed to
fail during the 30,000 tests. There are other additional specs, but a
switch must "function properly" to survive over 30,000 operations. The
test is not just about "failing safely".

and does not include the
pass / fail criteria.
THE PASS CRITERIA, AS I HAVE SAID SEVERAL TIMES ALREADY, IS THE SWITCH
SURVIVES OVER 30,000 SPECIFIED OPERATIONS AT RATED VOLTAGE AND AT LEAST
RATED CURRENT AND IS FUNCTIONAL AT THE END OF THE TESTS.

Did it come through that time?

For some other equipment, like TVs and industrial control panels, it is
not practical or desirable to test if the device functions as intended,
and the test is that it fails safely. That may involve using "listed" or
"recognized" component parts that are tested to "function properly" as
above.
All UL tests that I'm aware of test only for safety, not durability,
reliability, or functionality. If the device does not cause a hazardous
condition that might result in an insurance claim (note it is
*Underwriters* Laboratories, not *Consumers* Laboratories), it passes.
Then you are apparently not aware of a lot of UL tests.
I've seen a number of them and none had anything to do with non safety
durability. A product could be a piece of crap and fail, as long as the
failure mode did not create a hazard that could lead to an insurance
claim.
As have said several times, a switch must survive all 30,000 specified
operations and be functional at the end to be UL listed. A piece of crap
is not likely to survive 30,000 operations and remain functional.

Or do you think a piece of crap can survive 30,000 operations and remain
functional?

What UL standards have you read?

Do you really think the electrical industry would allow, for example,
fuses and circuit breakers to open at random current levels, and only be
required to "fail safely"? That would be ridiculous. I have not read the
standard but I have seen references to required clearing times at 120%
and 200% of rated current rating. They certainly are tested at their
rated available fault current. I expect a lot more from fuses and
circuit breakers than that they just "fail safely".


You really have a reading comprehension issue. Again, what you have
quotes is not a complete test specification as would be used by any
reputable testing laboratory as it does not contain clearly defined pass
/ fail criteria.

You have not explained how surviving 30,000 specified operations and
remaining functional is not a pass criteria.


Your diversion into circuit breakers doesn't help your case at all since
a circuit breakers are allowed to "soft fail" and trip at lower than
their rated current.

Every manufacturer current-time trip curve shows an acceptable band. I
have no doubt UL specifies a similar band (ie max and min acceptable
clearing time at 200% of rated current). Tripping at too low a current
is also not permitted. You really think the electrical industry would
allow fuses/breakers to open at too low a current?

What UL standards have you read?

--
bud--