Hot answers tagged

11

Yes, this does sound like a problem. Assuming your panel is like most, the breakers are on the same phase and you have two problems: No Common Shutoff MWBC is required to have common maintenance shutoff. That means if you turn off one breaker to work on the circuit, the other is turned off too. That is important for safety. This can be done with a handle-tie ...


10

Multiwire branch circuits (MWBCs) share a neutral. There is a code rule that prohibits wiring devices, such as receptacles, in a way that the removing the device would open (i. e., disconnect) that shared neutral. If the device is pigtailed, that rule is satisfied because removing the device doesn't disconnect anything else on the circuit from the neutral. ...


7

No, you really need to fix that. Search this site for "Lost Neutral" for what happens when the neutral wire has a problem. It's bad, and it can set stuff on fire. Look at that neutral in your photo. Simply to transit this box, current must go through four splices. Two on each receptacle - supply, jumper, jumper and onward. That's 4 places for ...


5

This is fine, provided you obey a few rules While a MWBC serving a mix of 120V and 240V receptacles certainly may look strange to the uninitiated, or those who interact with electrical systems in a professional capacity yet are not trained to the full panoply of NEC requirements, this setup is Code-legal in the 2017 NEC, provided the breaker protecting it ...


4

The problem is not a fire it is a shock hazard. As far as if it is important, it has been code for decades. The issue comes when the neutral may get separated then everything down from there won’t work, but there are still 2 hot legs with GFCI protection. The risk is low but it should be updated. A wirenut and pigtails to the receptacles really won’t take ...


4

This will work as long as the breakers are not GFCI. As long as the GFCIs are after the shared neutral, you are fine. BTW, this arrangement is called a multi wire branch circuit and you are required to use either a double (240 volt) breaker or two breakers with the handles tied together.


3

Cap the neutral off and you’re done. However, since your breaker is 2-pole with common trip, you’re perfectly allowed to eat your cake and have it too. You can replace one side’s receptacle with either a dual NEMA 6-15 a dual or single NEMA 6-20, or a combo NEMA 5-20 NEMA 6-20, giving one socket of each. Come off the hot of the other receptacle to the 2nd ...


3

Code requires 2 things: First that all junction boxes be accessible, and second that wire splices happen only inside junction boxes. That is why everyone is expecting this should be accessible. So there are 2 big problems. First that breaker's handle-tie is completely hork-a-dork (credit for having a handle-tie, but they should've gotten a proper one). ...


2

To add to the other answer, your two phases are 180 degrees out of phase so that it creates what is called destructive interference Now this doesn't totally fit because your electricity is all flowing in the same direction, but the same principle holds. Note that wave A and wave B are completely canceled out. Even with the two waves running in the same ...


2

is that a dangerous way of connecting everything, is it a latent defect? Absolutely it is dangerous, having unblalanced currents in a cable can cause inductive heating of the apertures the cable passes through. for this reason it is a code violation. What you have drawn looks bad, there could be other faults lurking there too that would be revealed by ...


2

Perhaps. Firstly, without a time machine you have a 240V 20A receptacle and want to add 120V 20A receptacles. You may need to replace the breaker with a dual-pole GFCI breaker as it's quite likely that the 120V circuits will need GFCI protection depending where they are and what version of code is adopted in your area at the time you do the work. Other ...


2

Yeah, I work a lot with MWBC. That looks fine to me... It should limbo under the NEC 2017 guidelines. If you don't get this permitted by the time your state adopts NEC 2020, then your entire plan falls apart. At that point you'll need a 2-pole GFCI breaker, and the GFCI recep will be superfluous. Your best defense to NEC 2020 is to get a HUGE panel. ...


2

Not a lost neutral A lost neutral in an MWBC is easy to test for. Just remove all loads and plug in two 240V-tolerant loads, one into each half of the MWBC. (watch it - the appliances may see voltages as high as 240V!) If one leg has higher voltage than 120, and the other has lower voltage than 120, and they total to 240, then you have a lost neutral. ...


2

Even with your power factor shift it is not that large over all most motors have a power factor of 80 or better. The vast majority of loads are resistive or inductive not only in residential but industrial also, yes there are some high capacitive loads but they are rare. Harmonics actually are more of a concern for multiwire branch circuits on 3 phase ...


1

Generally speaking, unless you are making changes, you don't need to add AFCI or GFCI to existing circuits. That being said, GFCI is of potentially major benefit in the kitchen. As you have found, you generally won't find AFCI + GFCI in a double-pole breaker, and you also won't find a GFCI/dual-receptacle that supports MWBC. Assuming you don't need AFCI, my ...


1

Years ago handle ties were not required. They have been for decades , if you think it’s is a multi wire turn off both breakers verify both hots in your box are dead, you can open your breaker panel and most of the time NMB or Romex is used. There will be a red on 1 breaker a black on the other going to a cable with a ground and a neutral, that would be 100% ...


1

We can't really tell from this close up of a picture, but your primary remark that they aren't handle tied isn't alarming since the requirement for handle ties is only about 20 years old. Any work older than the requirement change only needs to be brought up to current code when modified. But while you're there you need to look at the panel cover and see ...


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