Defeating Circuit Breaker Trip Mechanisms

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 bysgtcory-ga

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

Clarification of Question byiota-ga

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.

Request for Question Clarification bysgtcory-ga

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

Clarification of Question byiota-ga

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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