The trip of some circuit breakers could be defeated by holding the
operating handle in the 'ON' position. During the interval of 1970 to
the present, what make and model breakers exhibited this behavior?
Include only those one- and two-pole breakers commonly used in USA
residential load centers (e.g., Square D QO series). Include only
breakers and 'tie back' methods that a lay user would attempt (i.e.,
only external, non-invasive means like a finger, tape, string, wire,
etc). The best answer
includes data related to the anomalous performance of the named
breaker during the entire overload curve (i.e., the trip could be
defeated for a time, but would eventually open say, because a thermal
element completed the trip despite the defeated magenetic element) and
concerning the force required to hold the breaker in the 'ON' position
during the overload condition. Please specify search strategies. |
Request for Question Clarification by
sgtcory-ga
on
01 Dec 2002 06:57 PST
Hello iota,
I would be honored to tackle this question. I just need a few
clarifications :
"but would eventually open say, because a thermal element completed
the trip despite the defeated magenetic element"
This very much depends on the application. I would presume that any
angle I take on the answer would be considered a valid answer? I would
be detailing the use of these breakers in a jet engine test
cell(rotor, fixed, you name it) application. I can offer offline and
online references.
"anomalous performance of the named breaker during the entire overload
curve"
This is also very broad :-) If we talk of one brand, one model, I can
talk to the manufacturer and be very specific. If I stay more within
the general confinement of the overall 'type' of breaker - there is no
definitive standard, as the uses of them vary from application to
application.
Please let me know if I would be heading in the right direction with
your request, or offer a little more insight as to how you would the
answer to be approached.
Thanks in advance,
SgtCory
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Clarification of Question by
iota-ga
on
01 Dec 2002 12:43 PST
I am trying to find information on one or more breakers that could be
'tied back' such that their trip mechanism could be 'overridden'.
Contemporary breakers cannot be defeated in this way. An overload
always trips them - even if you're standing there holding (forcing)
the handle in the 'ON' position. Some older breaker(s) could be
defeated. I have forgotten which ones they were and when they were
fabricated. This is the information I seek.
The critical elements of the question are:
(a) Type of breaker. It shall be the type normally found in
residential load centers; that is, a consumer type breaker, say Square
D, GE, Siemens, FPE, etc. It shall not be one like a Hienenmann,
Potter & Brumfield, Allen-Bradley, etc.
(b) Application. The type of application is not critical or
important. A breaker intended for use in residential load centers
could protect many types of loads; the fact your experience involves
an engine test cell is fine.
(c) Overload. It does not matter how the breaker is overloaded, just
that it is overloaded. It does not matter whether the overload is
predominantly resistive or reactive.
(d) Trip. The overload, regardless of type, must have been sufficient
to cause the breaker to trip.
(e) Trip defeated. The interesting answer necessarily and by
definition contains this information. The operating handle must have
been held back or tied back in some manner to override the normal
trip.
The performance over the operating range is gravy. What I was trying
to get at here concerns the nature of the trip. A 15A, single-pole
breaker (the one I'm most interested in) subjected to a resitive load
of 110% rating will cause the breaker to respond differently than an
inductive load at 800% nameplate rating. Could the breaker trip be
defeated in both scenarios? If so, this is a more interesting answer,
but not a critical or 'make / break' (pun intened :) parameter of a
successful answer.
Thanks for the inquiry. I was beginning to wonder why this quesiton
would not appeal to the esteemed group of researchers. If more
clarification needed, I am most eager to better characterize the
question.
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Request for Question Clarification by
sgtcory-ga
on
02 Dec 2002 07:33 PST
Hello iota,
One more round of clarification, to ensure I have this correct.
Are you looking for a walkthrough of how a Square D Type QO thermal
magnetic circuit breaker would work in the scenario you provided, or
was this part offered simply as a reference?
I have come to the conclusion that I could not use my field related
experience to offer any part numbers, but I would rather be able to
answer your question in a manner such as this:
a) We create a sample situation with a Square D QO series breaker
b) Create a residential application for explanation sake
c) Explain the overload, up to the trip
d) Trip defeat mechanics and theory
The type of circuit breaker you are thinking of is called the
'nontrip-free', and the others are 'trip free'. To address the
workings of nontrip free circuit breakers with respect to resistive
and inductive type of loads seems to be the question.
Let me know if I am getting warmer, or if I am making this more
complicated than it needs to be :-)
Thanks again -
SgtCory
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Clarification of Question by
iota-ga
on
02 Dec 2002 08:56 PST
No, I'm not looking for how a circuit breaker would work.
However, your comment on nontrip-free breakers is well taken. Perhaps
I can ask the question:
What nontrip-free (acting) breakers have been used in residential
applications?
Of course, no one today would think of using a nontrip-free breaker in
a residential application. And, I also understand that someone could
be crazy, walk out one day and decide, "Hey, I'll go buy some
nontrip-free breakers and install them in a house". I would not be
interested in such an unsual application. However, 20-30 years ago
there were some breakers that functioned nontrip-free even if they
were not designed or designated as such and were used in residential
(stick built and mobile homes) applications. You could by them at the
hardware store or electrical distributor counter.
I need to know what mainstream manufacturer(s) made a breaker for use
in residential applications that worked (by design or inadvertently)
in a nontrip-free mode.
I hope this helps and I appreciate your efforts to clarify the
question.
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