Elec info needed 20A circuits

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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
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Charles Bishop wrote:

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

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.
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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
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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).

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

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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.

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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
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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.
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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
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Chris Lewis wrote:

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

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
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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.)
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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
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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.
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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
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Some are coupled internally, though you are probably right.

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.
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