Home Repair (alt.home.repair) For all homeowners and DIYers with many experienced tradesmen. Solve your toughest home fix-it problems.

Reply
 
LinkBack Thread Tools Search this Thread Display Modes
  #1   Report Post  
Charles Bishop
 
Posts: n/a
Default Elec info needed 20A circuits

I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

charles
  #2   Report Post  
zxcvbob
 
Posts: n/a
Default

Charles Bishop wrote:
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

charles



The circuit uses a 2-pole breaker instead of 2 individual breakers
because the left and right outlets share a common neutral wire. It's
called an "Edison circuit".

Bob
  #3   Report Post  
RBM
 
Posts: n/a
Default

It is code when both circuits are fed from a three wire cable, sharing the
neutral
"Charles Bishop" wrote in message
...
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

charles



  #4   Report Post  
HaHaHa
 
Posts: n/a
Default

From: "RBM"


It is code when both circuits are fed from a three wire cable, sharing the
neutral


It's not against the code, but it wasn't necessary unless somewhere in that
circuit, before the neutral splits off to feed 2 different circuits, there is a
device where both circuits are connected to the same yoke.

Such would be the case if those 2 circuits went around the dining room and fed
split receptacles, with one circuit for the upper 1/2 of the outlets and the
other circuit for the lower 1/2 of the outlets.


"Charles Bishop" wrote in message
...
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

charles












  #5   Report Post  
frank-in-toronto
 
Posts: n/a
Default

"Charles Bishop" wrote in message
...
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

On Mon, 17 Jan 2005 20:44:09 -0500, "RBM" rmottola1(remove
wrote:

It is code when both circuits are fed from a three wire cable, sharing the
neutral

it sounds to me as if code is broken here. in ontario the fridge
needs to be on it's own circuit. and outlets beside the kitchen sink
have a separate breaker for top and bottom. these breakers ONLY
control/feed that outlet. maybe this is different elsewhere.
....thehick


  #6   Report Post  
toller
 
Posts: n/a
Default

It is called a multiwire circuit.
It saves a little wire and can be a bit more efficient on big loads. The
breakers are tied together because they share a neutral, and it is best that
you turn both off it you turn either off. Also, tying them together
prevents you from putting both on the same leg; which is what someone did to
one of mine. (Like 240v circuits, a multiwire uses opposite legs.)


  #7   Report Post  
John Hines
 
Posts: n/a
Default

frank-in-toronto wrote:

"Charles Bishop" wrote in message
...
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

On Mon, 17 Jan 2005 20:44:09 -0500, "RBM" rmottola1(remove
wrote:

It is code when both circuits are fed from a three wire cable, sharing the
neutral

it sounds to me as if code is broken here. in ontario the fridge
needs to be on it's own circuit. and outlets beside the kitchen sink
have a separate breaker for top and bottom. these breakers ONLY
control/feed that outlet. maybe this is different elsewhere.


Canadian code is different in this area than the USA. In the US, 20 amp
circuits in the kitchen, on GFCI, is preferred, in Canada two 15 amp
circuits per outlet is preferred. That is because electrical appliances
are more common up north, than in the US of A.
  #8   Report Post  
Charles Bishop
 
Posts: n/a
Default

In article , "toller" wrote:

It is called a multiwire circuit.
It saves a little wire and can be a bit more efficient on big loads. The
breakers are tied together because they share a neutral, and it is best that
you turn both off it you turn either off. Also, tying them together
prevents you from putting both on the same leg; which is what someone did to
one of mine. (Like 240v circuits, a multiwire uses opposite legs.)


Given that the house is wired with romex (12-2) is there a benefit to
doing it like this? I can see where there might be using 12-3, but if it's
just black/white/ground it seems like the same amount of wire needs to be
run. Maybe 12-3 comes into one of the j-boxes and they use 12-2 from
there?

charles
  #9   Report Post  
TURTLE
 
Posts: n/a
Default


"zxcvbob" wrote in message
...
Charles Bishop wrote:
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?

charles



The circuit uses a 2-pole breaker instead of 2 individual breakers because the
left and right outlets share a common neutral wire. It's called an "Edison
circuit".

Bob


This is Turtle.

Hey you say it is legal but the fellow ask if the breaker set up in a set. Will
one make the both of them trip properly as if they were seperated. Not being
smart at all but it even being legal will each breaker trip properly as one side
getting over loaded and the other side not over loaded ?

TURTLE


  #10   Report Post  
toller
 
Posts: n/a
Default


"Charles Bishop" wrote in message
...
In article , "toller"
wrote:

It is called a multiwire circuit.
It saves a little wire and can be a bit more efficient on big loads. The
breakers are tied together because they share a neutral, and it is best
that
you turn both off it you turn either off. Also, tying them together
prevents you from putting both on the same leg; which is what someone did
to
one of mine. (Like 240v circuits, a multiwire uses opposite legs.)


Given that the house is wired with romex (12-2) is there a benefit to
doing it like this? I can see where there might be using 12-3, but if it's
just black/white/ground it seems like the same amount of wire needs to be
run. Maybe 12-3 comes into one of the j-boxes and they use 12-2 from
there?

Sorry, I "assumed" it was 12/3. The only reason to run two completely
separate circuits to a 240v breaker is that you have half of a outlet on
each circuit; then it is nice that they go off together.
But since you don't have that, I can only think the electrician was using
what he happened to have with him.




  #11   Report Post  
Charles Bishop
 
Posts: n/a
Default

In article , "toller" wrote:

"Charles Bishop" wrote in message
...
In article , "toller"
wrote:

It is called a multiwire circuit.
It saves a little wire and can be a bit more efficient on big loads. The
breakers are tied together because they share a neutral, and it is best
that
you turn both off it you turn either off. Also, tying them together
prevents you from putting both on the same leg; which is what someone did
to
one of mine. (Like 240v circuits, a multiwire uses opposite legs.)


Given that the house is wired with romex (12-2) is there a benefit to
doing it like this? I can see where there might be using 12-3, but if it's
just black/white/ground it seems like the same amount of wire needs to be
run. Maybe 12-3 comes into one of the j-boxes and they use 12-2 from
there?

Sorry, I "assumed" it was 12/3. The only reason to run two completely
separate circuits to a 240v breaker is that you have half of a outlet on
each circuit; then it is nice that they go off together.
But since you don't have that, I can only think the electrician was using
what he happened to have with him.


Perhaps, but the two breakers can be decoupled (separated electrically)
easily by taking off the plastic connector that ties them together.

Does my suggestion that it's 12/3 from the breaker box to a j-box, then
from there using 12/2 make any sense? It seems like a lot of trouble to
save a little on wiring. I can look into the breaker box next time. The
house is oldish, but was remodeled within the last 20 years I'd think.

charles
  #12   Report Post  
toller
 
Posts: n/a
Default


Perhaps, but the two breakers can be decoupled (separated electrically)
easily by taking off the plastic connector that ties them together.


Some are coupled internally, though you are probably right.

Does my suggestion that it's 12/3 from the breaker box to a j-box, then
from there using 12/2 make any sense? It seems like a lot of trouble to
save a little on wiring. I can look into the breaker box next time. The
house is oldish, but was remodeled within the last 20 years I'd think.

Again I apolgize for reading your post too quickly; I thought you said it
was 12/2. I have to stop reading these things when I can't sleep.
Yes, you only carry 12/3 to where the two circuits split, then it is 12/2.
There are two hots and a neutral to the first box, and then the neutral
branches and the hots go their separate ways.
It saves a little wire, is less to stuff through little holes in the joints,
and gives less voltage drop. If the two circuits are reasonably balanced,
then nothing comes back over the neutral, so the resistance is lower for a
one way trip.


  #13   Report Post  
Chris Lewis
 
Posts: n/a
Default

According to TURTLE :

Hey you say it is legal but the fellow ask if the breaker set up in a set. Will
one make the both of them trip properly as if they were seperated. Not being
smart at all but it even being legal will each breaker trip properly as one side
getting over loaded and the other side not over loaded ?


tie-barred breakers (whether manufactured that way, or later add-on)
will both trip if either of the breakers overloads.

That's the whole point of tying the handles together.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #14   Report Post  
Chris Lewis
 
Posts: n/a
Default

According to frank-in-toronto :
"Charles Bishop" wrote in message
...
I was working in the kitchen, replacing the outlets near the sink with
GFCIs. When I went out to turn the breaker off, I found out that the
breaker that turned off the five outlets was two 20A breakers that had
been connected in the panel as if they were a 20A 240 V circuit. When I
disconnected the two of them, I found that one breaker controled the
outlets on the left hand side of the sink (2 outlets on the counter, one
for the refigerator and one for the microwave) while the other breaker
controlled 3 outlets on the right side of the sink.

What's the reason for connecting the two breakers together in the breaker
box? If there is a short in one of the outlets on the right hand side,
will both breakers together trip as easily as the one would by itself?


On Mon, 17 Jan 2005 20:44:09 -0500, "RBM" rmottola1(remove
wrote:


It is code when both circuits are fed from a three wire cable, sharing the
neutral


it sounds to me as if code is broken here. in ontario the fridge
needs to be on it's own circuit. and outlets beside the kitchen sink
have a separate breaker for top and bottom. these breakers ONLY
control/feed that outlet. maybe this is different elsewhere.


As mentioned elsewhere, Canadian code is different. For example, Canadian
code requires a separate circuit for the fridge (can only be shared
with a clock). US code does not. The main reason is that US code encourages
20A general purpose 120V circuits, but they were illegal in Canadian code
until recently, and sharing a 20A circuit with a fridge isn't as bad
as sharing on a 15A circuit.

Up until recently, Canadian code explicitly required 15A split-duplex (officially
"multi-wire-branch" circuits) with dual gang-trip breaker, circuit per half of
outlet for kitchen counters. These circuits could feed at most two non-adjacent
receptacles,

Split-duplex circuits _were_ common in the US, and still permissible
[subject to GFCI reqts. below] for kitchen counters but the US has
mostly switched to 20A non-split circuits. Which was fortuitous,
because the US has been gradually increasing the requirements for GFCI
on kitchen counters, and now _all_ counter outlets must be GFCI'd.

Canadian code is now "catching up" with the NEC regarding GFCI on kitchen
counters, and now explicitly permits unsplit 20A 120V circuits with GFCI as
a substitute for split duplex 15A. Further, if you still want to use split
duplex, you have to use a dual GFCI breaker.

[Candian code simply didn't permit the 15/20A dual-use 120V circuits so common
in the US _until_ the 20A GFCI'd kitchen counter outlet stuff came along a
few years ago.]

Part of the issue with split/non-split and GFCI is that a non-split receptacle
can be GFCI'd with a cheap GFCI outlet. To GFCI a split circuit, you need
a very expensive dual GFCI breaker (or use _five_ conductor cable and/or large
boxes with two GFCIs in them). So, to keep costs in check, Canadian code
is "borrowing" the US arrangement.

[I still think the split-duplex 15A solution is better than a single 20A,
but it's now very expensive to meet code on them for kitchen counter
purposes. They're still great, legal and cheap for a workshop.]

Another US/Canadian (subtle) "difference" is the gang trip requirements
for multi-wire branches. US code permits multi-wire branch circuits to _not_ be
gang-tripped if no "strap" (essentially device) is fed from both legs.

Canadian code essentially says a multi-wire branch circuit MUST be
gang-tripped period, and furthermore, you can't feed multiple circuits
into a box _unless_ there's a single disconnect or there's a physical
barrier to prevent contact with both sides. [Which explains why our
main panels are slightly different than US ones.]
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #15   Report Post  
Chris Lewis
 
Posts: n/a
Default

According to toller :

Perhaps, but the two breakers can be decoupled (separated electrically)
easily by taking off the plastic connector that ties them together.


Some are coupled internally, though you are probably right.


Does my suggestion that it's 12/3 from the breaker box to a j-box, then
from there using 12/2 make any sense? It seems like a lot of trouble to
save a little on wiring. I can look into the breaker box next time. The
house is oldish, but was remodeled within the last 20 years I'd think.


Again I apolgize for reading your post too quickly; I thought you said it
was 12/2. I have to stop reading these things when I can't sleep.
Yes, you only carry 12/3 to where the two circuits split, then it is 12/2.
There are two hots and a neutral to the first box, and then the neutral
branches and the hots go their separate ways.
It saves a little wire, is less to stuff through little holes in the joints,
and gives less voltage drop. If the two circuits are reasonably balanced,
then nothing comes back over the neutral, so the resistance is lower for a
one way trip.


Think of it this way: multi-wire branch circuits are primarily a labor-saving
technique when you need two circuits in the same place on the other side
of the house. The time saved can be quite significant in more sophisticated
wiring jobs.

It often doesn't save much money in materials, because due to the way
demand/supply/volume works out, two lengths of, say, 12/2 often cost
less than one length of 12/3, despite it needing two copper conductors
_more_.

If your electrician is on hourly rates, it's probably better to go with the
12/3 if circumstances permit.

The only real drawback is that people (and even some electricians!) aren't
very familiar with them. A secondary problem can be you might not be able
to figure out which circuit is overloading if the breaker trips. But
there are ways to diagnose that. Another issue is if the installer
is sloppy, lazy and/or doesn't know about the neutral pigtailing requirements.

I use them occasionally when it makes good sense.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.


  #16   Report Post  
TURTLE
 
Posts: n/a
Default


"Chris Lewis" wrote in message
...
According to TURTLE :

Hey you say it is legal but the fellow ask if the breaker set up in a set.
Will
one make the both of them trip properly as if they were seperated. Not being
smart at all but it even being legal will each breaker trip properly as one
side
getting over loaded and the other side not over loaded ?


tie-barred breakers (whether manufactured that way, or later add-on)
will both trip if either of the breakers overloads.

That's the whole point of tying the handles together.
--
Chris Lewis


This is Turtle.

I don't need a lesson in double breaker and them tied together at all and ask a
pin point question that you missed and did not answer.

The question again here is : Useing one side off a 220 volt double breaker
circuit for 120 volt circuit. Will the one side heat up enough to trip both side
as if I had a single breaker on it ? Will the double breaker trip as fast as the
single breaker because of the other side may have a little little bit of a hold
to keep the double in gauged a split second longer ? I know this maybe a
judgement call for I have never seen any data as to it making any difference.

TURTLE


  #17   Report Post  
Chris Lewis
 
Posts: n/a
Default

According to TURTLE :

"Chris Lewis" wrote in message
...
According to TURTLE :


Hey you say it is legal but the fellow ask if the breaker set up in a set.
Will
one make the both of them trip properly as if they were seperated. Not being
smart at all but it even being legal will each breaker trip properly as one
side
getting over loaded and the other side not over loaded ?


tie-barred breakers (whether manufactured that way, or later add-on)
will both trip if either of the breakers overloads.


That's the whole point of tying the handles together.


I don't need a lesson in double breaker and them tied together at all and ask a
pin point question that you missed and did not answer.


That's actually the question I answered but without deeper detail. I'll give
the detail.

The question again here is : Useing one side off a 220 volt double breaker
circuit for 120 volt circuit. Will the one side heat up enough to trip both side
as if I had a single breaker on it ? Will the double breaker trip as fast as the
single breaker because of the other side may have a little little bit of a hold
to keep the double in gauged a split second longer ? I know this maybe a
judgement call for I have never seen any data as to it making any difference.


Most of this you already know, but in the interests of telling the full
story for others, and so you understand how it answers your question,
I'll include it all here.

The purpose of a breaker is to trip if the current thru the hot wire exceeds
specs (given time-delay/how much it overcurrents etc). It doesn't matter where
the current goes to (whether the other side of a dual in 240V applications
or thru the neutral in 120V applications (split or dual), or split between the
two in a multi-wire branch).

The current sense is done in a bimetallic strip (and/or magnetic depending
on OC levels) whose thermal response and resulting physical deflection is
not affected (significantly) by anything else is in the circuit.

Remember that the physical force required to throw the handle (and thereby
interrupt the current) is derived from the spring you tension when you
arm the breaker, and that the overcurrent "detector" (bimetallic strip etc)
merely trips a "catch" on that spring. The force required to move the
handle and interrupt the current is _not_ generated from the overcurrent
itself - it's from the spring. The force required to trip the catch
isn't dependent on what else is tiebarred to that handle.

In a tie'd breaker, then, the worst case is that only one breaker trips
the catch, and there's slightly more mass for the spring to move during
the initial part of the trip. But once the trip progresses "far enough",
it mechanically trips the other catch, and then you have _both_ springs
moving the tie'd handles.

So, if only one breaker OCs (which is likely even in a pure 240V
situation given variations in sensitivity anyway), the worst case is a
_slight_ delay in interruption due to Newton's "F=MA" equations ;-).

Now, consider this: these breakers are tested by the standards bodies to
conform within a certain OC-level/time-to-break curve. In _both_
"one breaker OC sense" and "two breaker OC sense" modes - because that's
what they see in the real world even on pure 240V circuits. Since they
passed certification, the time delay isn't significant in the certification
process.

Remember: breaker trip times are often quite long with mild overloads (often
10s of seconds). A few micro or milliseconds of additional delay trying
to get that other handle moving don't make no real difference.

There are probably some _extreme_ situations where it might make the difference
between a breaker self-destruct and a "normal" trip. But this
is already tested for up to the max fault current rating (like, 20KA or more),
and isn't an issue. With a direct lightning strike the thing might be
_slightly_ more likely to explode because it's a dual and not a single,
but at that level, you're going to have far worse damage than a fried breaker.

As a by the by, I should point out that some jurisdictions frown (or even
outlaw) add-on tiebars, perhaps depending on the equipment, and insist
upon "manufactured duals". The concern is that the tiebar may be so
loose that one side could trip but not the other. Or, that the tiebar
jams and one side (or even both sides) don't trip. Rather than spending
MUCH more time trying to cross-certify the breaker with every possible
"permissible" add-on tiebar making allowances for worst-case workmanship,
they just say "don't do that". Of course, in industrial/commercial systems
add-on tiebars are much more common, but that equipment is spec'd for it -
that's partly why it's more expensive.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #18   Report Post  
TURTLE
 
Posts: n/a
Default


"Chris Lewis" wrote in message
...
According to TURTLE :

"Chris Lewis" wrote in message
...
According to TURTLE :


Hey you say it is legal but the fellow ask if the breaker set up in a set.
Will
one make the both of them trip properly as if they were seperated. Not
being
smart at all but it even being legal will each breaker trip properly as
one
side
getting over loaded and the other side not over loaded ?


tie-barred breakers (whether manufactured that way, or later add-on)
will both trip if either of the breakers overloads.


That's the whole point of tying the handles together.


I don't need a lesson in double breaker and them tied together at all and ask
a
pin point question that you missed and did not answer.


That's actually the question I answered but without deeper detail. I'll give
the detail.

The question again here is : Useing one side off a 220 volt double breaker
circuit for 120 volt circuit. Will the one side heat up enough to trip both
side
as if I had a single breaker on it ? Will the double breaker trip as fast as
the
single breaker because of the other side may have a little little bit of a
hold
to keep the double in gauged a split second longer ? I know this maybe a
judgement call for I have never seen any data as to it making any difference.


Most of this you already know, but in the interests of telling the full
story for others, and so you understand how it answers your question,
I'll include it all here.

The purpose of a breaker is to trip if the current thru the hot wire exceeds
specs (given time-delay/how much it overcurrents etc). It doesn't matter
where
the current goes to (whether the other side of a dual in 240V applications
or thru the neutral in 120V applications (split or dual), or split between the
two in a multi-wire branch).

The current sense is done in a bimetallic strip (and/or magnetic depending
on OC levels) whose thermal response and resulting physical deflection is
not affected (significantly) by anything else is in the circuit.

Remember that the physical force required to throw the handle (and thereby
interrupt the current) is derived from the spring you tension when you
arm the breaker, and that the overcurrent "detector" (bimetallic strip etc)
merely trips a "catch" on that spring. The force required to move the
handle and interrupt the current is _not_ generated from the overcurrent
itself - it's from the spring. The force required to trip the catch
isn't dependent on what else is tiebarred to that handle.

In a tie'd breaker, then, the worst case is that only one breaker trips
the catch, and there's slightly more mass for the spring to move during
the initial part of the trip. But once the trip progresses "far enough",
it mechanically trips the other catch, and then you have _both_ springs
moving the tie'd handles.

So, if only one breaker OCs (which is likely even in a pure 240V
situation given variations in sensitivity anyway), the worst case is a
_slight_ delay in interruption due to Newton's "F=MA" equations ;-).

Now, consider this: these breakers are tested by the standards bodies to
conform within a certain OC-level/time-to-break curve. In _both_
"one breaker OC sense" and "two breaker OC sense" modes - because that's
what they see in the real world even on pure 240V circuits. Since they
passed certification, the time delay isn't significant in the certification
process.

Remember: breaker trip times are often quite long with mild overloads (often
10s of seconds). A few micro or milliseconds of additional delay trying
to get that other handle moving don't make no real difference.

There are probably some _extreme_ situations where it might make the
difference
between a breaker self-destruct and a "normal" trip. But this
is already tested for up to the max fault current rating (like, 20KA or more),
and isn't an issue. With a direct lightning strike the thing might be
_slightly_ more likely to explode because it's a dual and not a single,
but at that level, you're going to have far worse damage than a fried breaker.

As a by the by, I should point out that some jurisdictions frown (or even
outlaw) add-on tiebars, perhaps depending on the equipment, and insist
upon "manufactured duals". The concern is that the tiebar may be so
loose that one side could trip but not the other. Or, that the tiebar
jams and one side (or even both sides) don't trip. Rather than spending
MUCH more time trying to cross-certify the breaker with every possible
"permissible" add-on tiebar making allowances for worst-case workmanship,
they just say "don't do that". Of course, in industrial/commercial systems
add-on tiebars are much more common, but that equipment is spec'd for it -
that's partly why it's more expensive.
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.


This Turtle.

So you say there could be a small Nano-second longer for a double pole breaker
to trip on one side and no amps on the other than a single pole breaker and no
other breaker attached.

I seen this on a old country bar in the middle of no where. They did not have
any singles at all but all doubles and when needing a single they just used 1
leg of the double. This place is fixing to burn soon.

TURTLE


  #19   Report Post  
Chris Lewis
 
Posts: n/a
Default

According to TURTLE :

So you say there could be a small Nano-second longer for a double pole breaker
to trip on one side and no amps on the other than a single pole breaker and no
other breaker attached.


A nano-second is a very short time for a mechanical device. I'd suggest
it might make a 1 or 2 millisecond difference in trip time. Which might
be 10% of the trip time at max fault (20,000A), but fractional percentages
of more usual trips (10s of seconds).

I seen this on a old country bar in the middle of no where. They did not have
any singles at all but all doubles and when needing a single they just used 1
leg of the double. This place is fixing to burn soon.


But not because they were using one side of duals tho. It's likely to be
a sloppy job in other MUCH more hazardous ways. Ie: did they use zip
cord in places because they ran out of building wire too...?
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.
  #20   Report Post  
Chip C
 
Posts: n/a
Default

Chris Lewis wrote:

Canadian code is now "catching up" with the NEC regarding GFCI on

kitchen
counters, and now explicitly permits unsplit 20A 120V circuits with

GFCI as
a substitute for split duplex 15A. Further, if you still want to use

split
duplex, you have to use a dual GFCI breaker.


But the GFCI's are required, in Canadian code, only on the outlets near
(1m) the sink, right?

[I still think the split-duplex 15A solution is better than a single

20A,
but it's now very expensive to meet code on them for kitchen counter
purposes. They're still great, legal and cheap for a workshop.]


Apart from the outlets near the sink, can the rest of the kitchen not
be wired with the traditional split-duplex 15A circuits? My reading of
the latest P.S. Knight book leads me to think so.

Chip C
Toronto



  #21   Report Post  
TURTLE
 
Posts: n/a
Default


"Chris Lewis" wrote in message
...
According to TURTLE :

So you say there could be a small Nano-second longer for a double pole
breaker
to trip on one side and no amps on the other than a single pole breaker and
no
other breaker attached.


A nano-second is a very short time for a mechanical device. I'd suggest
it might make a 1 or 2 millisecond difference in trip time. Which might
be 10% of the trip time at max fault (20,000A), but fractional percentages
of more usual trips (10s of seconds).

I seen this on a old country bar in the middle of no where. They did not have
any singles at all but all doubles and when needing a single they just used 1
leg of the double. This place is fixing to burn soon.


But not because they were using one side of duals tho. It's likely to be
a sloppy job in other MUCH more hazardous ways. Ie: did they use zip
cord in places because they ran out of building wire too...?
--
Chris Lewis, Una confibula non set est
It's not just anyone who gets a Starship Cruiser class named after them.


This is Turtle.

All the wires are run with # 12-no ground cloth Romex from the 15 amp breaker to
the 60 amp breaker. The owner use a 1,000 foot roll of #12-No ground cloth romex
to wire it with when he built it in 1954 and still has another 1,000 foot to use
as replacement wire when a wires burn . He only has about a 100 foot of the
1,000 ft. roll left to use up. I like the 2- 24,000 btu window units on 1 # 12
wire circuit with a 60 amp breaker. He does not understand the connection on all
the wires and plugs burning off from time to time. When both are running in the
summer the wire is hot as hell but will not burn up or off but just the plugs
and connection will burn off.

Well he has two new circuits run with new type Romex 12-2 with ground for the 2
of the beer coolers he has for my electricial would not use his cloth no ground
wire-- wire. These beer coolers only need 10 amps R.L.A. and 12 does good on 20
feet runs. I sub out electric work like this and I try to stay just HVAC/R .

TURTLE


Reply
Thread Tools Search this Thread
Search this Thread:

Advanced Search
Display Modes

Posting Rules

Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are On
Pingbacks are On
Refbacks are On


Similar Threads
Thread Thread Starter Forum Replies Last Post
Dedicated Micros help needed Cessna Electronics Repair 2 January 5th 06 04:44 PM
Tower Building Help / Info needed Jess Metalworking 19 January 17th 05 04:57 AM
one-off gear cutting info needed. [email protected] Metalworking 2 December 16th 04 06:41 PM
WTD Info on Tapmatic 700X and info on Tapmatics Marty Escarcega Metalworking 3 June 8th 04 04:00 AM
Lorch Junior lathe slide rest info? Hans van Dongen Metalworking 3 November 18th 03 04:30 PM


All times are GMT +1. The time now is 11:07 AM.

Powered by vBulletin® Copyright ©2000 - 2024, Jelsoft Enterprises Ltd.
Copyright ©2004-2024 DIYbanter.
The comments are property of their posters.
 

About Us

"It's about DIY & home improvement"