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gyoung
Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas
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 Posted: Sun Jan 27, 2008 2:46 am Post subject: Circuit breaker polarity |
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I am rewiring my Navion panel using busses with Potter-Brumfield W31 switch breakers and Klixon 7277 c/b's. I put the P-B buss bar on the bottom following their Load-Line labeling but put the Klixon bar on top to ease access to the load terminals. My IA neighbor (not my supervising IA) tried to tell me it was backward but I had already checked and there is no labeling on the Klixon c/b's. I see no intuitive reason it should care about polarity but then I don't have a real understanding of their inner workings. Did I miss something? Does polarity matter for the Klixons? If so, I can change my buss. If not, why does P-B label their units (it's also on their W23 c/b's?) Is it real or just a case of eliminating choice? Thanks for the education.
Regards,
Greg Young
[quote][b]
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rampil
Joined: 04 May 2007
Posts: 870
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| Posted: Sun Jan 27, 2008 5:56 am Post subject: Re: Circuit breaker polarity |
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Breakers have no polarity. Element heating occurs in either
direction!
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nuckolls.bob(at)cox.net
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| Posted: Sun Jan 27, 2008 11:06 am Post subject: Circuit breaker polarity |
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At 04:39 AM 1/27/2008 -0600, you wrote:
| Quote: | I am rewiring my Navion panel using busses with Potter-Brumfield W31
switch breakers and Klixon 7277 c/b's. I put the P-B buss bar on the
bottom following their Load-Line labeling but put the Klixon bar on top to
ease access to the load terminals. My IA neighbor (not my supervising IA)
tried to tell me it was backward but I had already checked and there is no
labeling on the Klixon c/b's. I see no intuitive reason it should care
about polarity but then I don't have a real understanding of their inner
workings. Did I miss something? Does polarity matter for the Klixons? If
so, I can change my buss. If not, why does P-B label their units (it's
also on their W23 c/b's?) Is it real or just a case of eliminating choice?
Thanks for the education.
|
Intuitively, the physics of a series-connected
heat-tripped, switch do not suggest a reason why
the breaker would care which way electrons flow
through it . . . and in particular, AC system
breakers where electrons are known to turn around
and run the other direction 120 times a second!
You've already had some good responses but I'll
take this opportunity to elaborate. Not all
breakers are rudimentary . . . i.e. a simple
spring-loaded, heater-tripped latch holding a
set of single or double-break contacts closed.
Breakers can be had with auxiliary switches,
indicator lights, voltage sense coils, and
all manner of enhancements where proper function
of the enhancement depends on a connection to
power being available even when the breaker is
open. Obviously, some third terminal is necessary
for an enhancement to function, this is sometimes
an obvious connection, or perhaps it gets hooked
up through the mounting.
In any case, it's not uncommon for a manufacturer
to use common tooling to mold a breaker housing
for all versions, hence you often see the word
"load", "line" or both formed right next to the
breaker's terminals . . .
I've asked several tech reps for breakers and
except for enhanced breakers, orientation in
the system doesn't matter. Interestingly enough,
if an electrician encounters "line" and/or "load"
labels on a breaker, he'll wire it up that way
whether it matters or not. And I suspect many
aviation techs do too . . . not because the
physics matters but because some inspector who
doesn't know any better can be counted on to
insist that the protocols be followed.
The only time I've encountered this as a
"problem" is when a builder finds it convenient
to fabricate a two-row bus-bar and take load
feeders off opposite ends of the breaker. When
they come stamped with a breaker rating,
they look pretty funky with one row upside-down
in their holes!
Bob . . .
----------------------------------------)
( . . . a long habit of not thinking )
( a thing wrong, gives it a superficial )
( appearance of being right . . . )
( )
( -Thomas Paine 1776- )
----------------------------------------
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gyoung
Joined: 09 Jan 2006
Posts: 211
Location: Republic of Texas
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| Posted: Sun Jan 27, 2008 8:08 pm Post subject: Circuit breaker polarity |
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| Quote: |
In any case, it's not uncommon for a manufacturer
to use common tooling to mold a breaker housing
for all versions, hence you often see the word
"load", "line" or both formed right next to the
breaker's terminals . . .
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That's likely. There are a bunch of P-B series that use the same case.
| Quote: |
I've asked several tech reps for breakers and
except for enhanced breakers, orientation in
the system doesn't matter. Interestingly enough,
if an electrician encounters "line" and/or "load"
labels on a breaker, he'll wire it up that way
whether it matters or not. And I suspect many
aviation techs do too . . . not because the
physics matters but because some inspector who
doesn't know any better can be counted on to
insist that the protocols be followed.
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It just happened that the labeling on the P-B's matched my preferred bus bar
mounting. The Klixon row below it has the bar on the opposite terminals
which then looked wrong to the "do it the standard way and don't ask why"
crowd.
| Quote: | The only time I've encountered this as a
"problem" is when a builder finds it convenient
to fabricate a two-row bus-bar and take load
feeders off opposite ends of the breaker. When
they come stamped with a breaker rating,
they look pretty funky with one row upside-down
in their holes!
Bob . . .
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Thanks for reaffirming my choices. Insightful as always.
Regards,
Greg Young
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