Electrical Main Breaker Flips

Exactly---this is where power surges originate when someone is working on a circuit ---

I'll let an electrician explain fully--in a nut shell---two circuits each on separate leg in the breaker box can share one neutral---without over loading that neutral because they are on a different phase.

this is called a multi wire branch circuit---ideally the breakers would be locked together like a 220 appliance breaker.

The trouble begins when working 'live'---if the circuits branch out of a box heading to different rooms ,for example, you will have three neutrals in that 'bundle'---

if you have a load on both circuits---say one to your computer room and one to your kitchen---

and you remove the neutral heading back to your breaker box---but leave the other two connected----you will have the return load 'crossing over' to the other circuit--

The lights will become super bright---and all your LED displays will fry ,along with your computer--and the sensitive electrical supplies to the appliances.

I'm not a licensed electrician----So I hope I put this in an understandable manner---Mike----

I will throw my part as well .,

Like any spilt single phase circuits which it is typical used in North Americian side.

One example is on one side of MWBC is portable heater which it is 1500 watt then on other side of MWBC is your TV or computer which they useally draw about 200 ish watts and the netural is carry the differnce between the two loads.

Now let say someone which not aware this is MWBC and loosen up the netural for some reason instead of normal parallel split phase circuit it become series due the 240 volts will work it way around without netural so it will foruce 240 volts thru the example as I posted the heater itself will surive very easy but not for the computer or tv due the voltage for computer or tv will spike up anywhere from 140 to 240 volts depending on how well it designed.

That one quick prime example is 120 volt light bulb suddenly get super bright and burn out or explode ( I have see it happend from time to time but not often ) same thing with tv or computer or any appalinces with electronic control can get fried by overvoltage.

It will be the same idea with whole house system if you see large number of bright or dimmed light that usally indecated that you have comperised netural so anything on 120 volts will either get damaged or survived depending on the layout of circuits.

Oh by the way this not only affect the single phase MWBC's but it will do the excat the same thing with three phase MWBC's as well.

Let me post one example



one of our members in here do have wonderfull diagram so therefore Merci to Stubbie.,

Here the other one this will really clear it up alot .,



Merci,
Marc