Hi Bogie, yu can't just run another wire, though this would seem the easiest way, it's just not legal to do. You would need to remove the 3 wire cable and run two cables of either 14/2 or 12/2 and connect each to a separate breaker. Your best alternative here would be to install a double pole breaker and connect each hot lead to the breaker. This is the normal way this is done.
I don't understand when you say you still had voltage. If both breaker are open then you should have no voltage on these wires. You may need to remove the main panel cover and verify that just one hot wire is connected to each breaker. With the breakers closed, you should read 240 volts when measureing across both hot leads. I also think if you're doing some additional remodeling that you should run a new circuit instead of trying to tap power from this multiwire circuit, that would be your safest route.
I'm gonna provide you below with alot of information about multiwire circuits. This info comes straight from an expert and should fill you in on all the details about multiwire circuits. Hope this helps, and please ask back with any questions.
MULTIWIRE BRANCH CIRCUITS 12-3G AND 14-3G
MULTIWIRE CIRCUITS USING 12-3G ETC ARE NOT A RECOMMENDED WIRING METHOD FOR DIY.
BUT "DIY" WILL COME ACROSS THESE ..VERY/VERY/VERY OFTEN..SO MUST COME TO UNDERSTAND THEM!!
300-3.b..."all conductors of the same circuit shall be contained within the same raceway or cable.."..
..if not, we risk overheating.
More on these 120volt ,three conductor 'multi-wire' ,SHARED /COMMON/NEUTRAL branch circuits ,that appear to be 240v (208v) circuits at first glance,and how they apply to residences
THEY ARE 120V CIRCUITS!...ONLY [Generally]
They are generally ran using 14-3G and 12-3G NM-B cable.
Multi-wire branch circuits are permitted by 'the' code...but DIY are usually advised to avoid them.We do not save that much time or $$$...but add to the confusion.
We do save space in the panel and on the neutral busbar!
They generally are permitted to serve only 120v line to neutral' loads,and commonly are choosen to serve 120v receptacle outlets ,permanently wired kitchen appliances ,split-wired duplex receptacle outlets ,and many other 120v loads, that occupy the same area.The kitchen receptacles may be every other one, on the opposite leg or 'split' between the upper and lower after removing the receptacle conductive tab...on the 'HOT' side only.
Many 'split-wired' 120v receptacle outlets, where one half of the duplex is on one circuit and the remaining half is on another,will many times, be supplied with a multiwired circuit.Both of these are on the same yoke.
It is my understanding that the Canadian electrical code, requires all duplex receptacles serving the kitchen counter, to be 'split ',and also are limited to 15amps.
The 3 wire service to your house is sort of like a multi wire circuit ,that also serves 240v loads,but this is not exactly the same!
Many electricians are suspicious of 3 wire , multi-wire ,shared neutral circuits ,because when it works as designed, all is well,but its tolerance for failure is usually catastrophic,when the neutral opens and places voltages in excess of 120v across certain random 120v loads…including electronic stuff.
It can also result in popping light bulbs!
For this reason….Always terminate the mutlwire white neutral, to a receptacle in a chain,via a pigtail jumper.
Don’t use the receptacle two silver screws as a tie point...unless the receptacle is the end-of-run.
The circuit MUST be supplied by the two opposing legs (lines) of the 120v/240v (120/208v)service.This is usually accomplished by feeding via a full size 2 pole breaker ,2 pole GFCI breaker,or a set of ADJACENT single pole, full size breakers ,which may be code required to be tied together,[handles secured together], so as to open both legs at once,especially if this multi-wire circuit supplys a "Split-Wired" receptacle,or device, on a single yoke.
Two adjacent half size or tandem/twin/duplex/piggyback/halfsize/wafer, breakers can not be used ,as they feed from the very same single leg,and if the multi wire circuit were fed this way, the neutral would very likely OVERHEAT and become a safety issue!!!
Remember ,by definition,the multiwire circuit is fed from two opposing legs and will have a voltage difference between them;240 volts in most residential ;208v in others.
Close attention must be exercised,as to how the circuit splits off, when it reaches any GFCI receptacle(s) ,and the neutral can no longer be 'shared'.
The neutral must never be allowed to open ,'upstream',along any part of the circuit,as it would place many of the 120v loads downstream,in series with one another and the full 240volts across these various sets ,and proceed to damage each 120v load in turn, over a short period,until none are left to destroy!
This is why the receptacle device, neutral connection, MUST always be via 'pigtails',and not the 2 silver-nickel screws on the side of the receptacle...or backstabbed.....unless of course the outlet is at the end of the run.
Multi wire branch circuits that are fed from a configuration, that by design or over-sight,does not simultaneously open and disconnect all legs of the circuit ,can really surprize an unsuspecting DIY or experienced electrician, that is working in a device or splice box,thinking that they have the circuit 'off' when in fact ,they do not!
Remember there is 240v or 208v in that box!
Two wire circuits are confusing to many,but three wire multiwire circuits,must be fully understood , and we must be absolutely aware of its advantages and also any consequences!
1999 NEC ref:....art 100 def:Branch Circuit,Multiwire
Section 210-4
Section 225-33.b Section 240-20.b.1 Section 300-13.b
FPN: Neutrals in 3Ø 4 wire 208/120v WYE systems ,etc,found in commercial and industrial supplies serving non-linear loads,like lighting ballasts,computer power supplies, etc will have high 3rd order harmonic currents and may have to be oversized,to prevent OVERHEATING
RECAP:
A MULTIWIRE branch circuit is considered a single circuit….and by the code definition...is "...A branch circuit that consists of two or more ,ungrounded..[NOT NEUTRAL]..conductors that have a voltage between them ,and a grounded [NEUTRAL] conductor that has EQUAL voltage between it and each ungrounded [HOT] conductor of the circuit and that is connected to the neutral or grounded conductor of the system.
This translates to ..120v from the shared white neutral to EITHER the red or the black...and ..also you will have 240v between the red and the black.
This all saves a wire..3 instead of 4....
this also saves $$$ and install time...and is common in kitchen circuits and some other rooms.
We will still have two breakers involved...and they MUST be on opposite phases...generally on adjacent spaces.
Generally a 2pole breaker.
But we can use two SP breakers and….
Generally handle tied .
The full sized single pole breakers ,if used instead of a 2 pole breaker… MUST be handle tied, if the multiwire circuit supplies both halves of a split duplex receptacle on the same yoke-strap.
Generally it is a 2 pole breaker ..TWIN TANDEM BREAKERS WONT WORK!
,,,and is possible, due to current cancellation... because we do not double the amps in the neutral..4 times the heat..but will approach ZERO amps.
The red and black wires will have currents flowing through them that do not ADD in the neutral ,but will cancel.
This principle is used in many circuits..especially in the service drop to our homes...3 wire!!!...
...and also all 120v/240v sub panel feeds.3 wire plus ground.
..as mentioned ,the best [common] example in our homes is in the kitchen receptacle outlets,for the required two 20amp small appliance circuits....two circuits ran in a single NM cable sheath..that share the single common neutral.
Some schemes choose to split the receptacles..upper on the red ..lower on the black...
..other schemes will alternate receptacle duplex outlets.
Every-other one on the red and black
..or even the dishwasher/disposal feed..etc
Read all the caveats ,..because they are touchy,even when installed by professionals.
When replacing split wired eceptacles...If we fail to also remove the BREAK-OFF tab on the new receptacle, we may wind up tripping the breaker,when the two opposing lines of a multi wire circuit come together..in a large 240v ZAPPP!
Many split receptacles are supplied via a 3wire cable, that is a multi wire circuit.240v between the red and black.
Not all 3 wire cables in switched receptacle boxes indicate a mutiwire circuit,as it may only involve just the switch loop...and half of the receptacle is hot, while the lower half is switched.
THE PRIMARY DIFFERENCE IN GFCI TYPE BREAKERS AND GFCI TYPE RECEPTACLES..IS SIMPLY THAT THE BREAKER IS 'LOOKING' AT THE ENTIRE CIRCUIT..AND..WIRING.....THE RECEPTACLE IS CONCERNED ,ONLY WITH THE OUTLET ITSELF AND ANY APPLIANCE THAT IS PLUGGED INTO IT...AND.. ANY DOWNSTREAM OUTLETS AND WIRING THAT EXTENDS FROM THE ‘LOAD SIDE’ OF THE PARTICULAR GFCI RECEPTACLE.
...this lower sketch in the image,where a 'normal ' breaker is feeding two gfci receptacles..look real hard ..as we can use these two gfci receptacles to feed and protect 'SLIT WIRED' generic duplexes that have the 'tab'(s) broken off...
..just be certain to NOT share the neutral ..we need a separate 2 wire + grnd extension from the load side of each gfci receptacle!
..one gfci load side can feed the top half of the split...and the other gfci load side can feed the lower half of the same split receptacle ...
Also remove the 'tab' on the neutral side....!!! or it will not set up for you.
>>>>>>>>>>>>&g t;>>>>>>>>>>>> >>>>>>>>>>>>&g t;>>>>>>>>>>>> >>>>>>>>>>>>&g t;>>>>>>>>>>>> >>>>>>
Another Multiwire circuit 120and 240 from one duplex!
STRANGE NEMA 5/6-20R COMBI RECEPTACLE
Pass and Seymour..P/N 5890..[5290 if 15amp].
Available at Home Depot.
The NEC references this as a multiwire circuit in 210-4.c ex 2..and since we are on a single same yoke... must be supplied via either a 2 pole breaker, or 2 full size single breakers with handle tie to provide a common trip.
If supplied via two fuses then we must provide a 2 pole disconnect.
NEC 225-30, when discussing second buildings and the ONE branch or feeder restriction,considers this a SINGLE circuit.
BUT OUR REQUIRED DISCONNECT NOW, MUST BE AT MINIMUM, A 2 POLE SWITCH!
AND GFCI IS ALSO AN ISSUE IF WE ARE IN AN OUTBUILDING...WE WOULD HAVE TO FEED THIS VIA GFCI BREAKER IN THE UPSTREAM PANEL.
NEC 210-4 permits multiwire branch circuits to be considered as multiple circuits.
THIS COMBINATION RECEPTACLE, AND ALSO COMBINATIONS OF MULTIPLE RECEPTACLES ON THE SAME CIRCUIT WITH THIS ARE "CODE"..BUT NOT GENERALLY RECOMMENDED...UNLESS USED IN VERY RESTRICTED SITUATIONS LIKE FOR A WINDOW AIR CONDITIONER
Have your local AHJ rule whether they consider each receptacle on this single yoke... restricted to 80% or 50 % ...!!!
See fastened in place.
This would restrict any possible applications ,even more.!!!
MULTI WIRE CIRCUITS ARE CONFOUNDING ENOUGH, BEFORE WE ALSO TOSS IN THIS HYBRID.
http://www.ecmweb.com/ar/electric_mu...anch_circuits/
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Linear Mode
