Thanks for the note.

[Ken Rowe]

Number 11, 15 amp labelled lights. Other two, 15 amps labelled bedrooms. Can you think of any legitimate reason for these to be connected together?

http://i295.photobucket.com/albums/mm152/nunrleft/Mobile%20Uploads/20140410_162346_zpso1scqwai.jpg

[Jerry Peck]

Depends on how the breakers are connected together (what 'connected together' actually means).

The high wattage tankless water heaters have three circuits and all three breakers need to be turned off to remove all power to all of the elements.

However, not okay if a large high amperage device is fed with large conductors and the large conductors are split (strands unwound and run to different breakers) - that is a definite no-no).

When you looked inside the panel, what did you see as to how they were connected together?

[Ken Rowe]

They weren't connected together inside the panel. As I stated, all three breakers were 15 amp, one labelled for a lighting circuit and two labelled for bedroom circuits. Apparently the three circuits are somehow spliced together somewhere in the home.

[Jerry Peck]

Ken,

My guess as to what the cause was is this: two of those were on a multiwire branch-circuit, someone not aware of what a multiwire branch circuit (MWBC) is, does, or how it is wired, connected one leg of the MWBC to another leg of some other circuit, resulting in shared and possibly crossed neutrals somewhere which now keeps power on until all three breakers are turned off.

The worst (excepting electrical shock to the unsuspecting) thing is that one or both of the neutrals may now be carrying twice the current it was intended to carry.

[Mbrooke]

Someone wire nutted all the hots or neutrals in a box somewhere would be my guess.

[Rich Goeken]

Number 11, 15 amp labelled lights. Other two, 15 amps labelled bedrooms. Can you think of any legitimate reason for these to be connected together?


Can't, especially since there are three, not two circuits involved. Two I could see if they did not understand basic wiring practices. Weird.

Definitely time for the phrase (or equivalent) "have an electrician evaluate the service panel and the house wiring"

[Mike Clarke]

could be different circuit wired into same box/enclousure somewhere ?
light switch, outlet ect on different circuits in same box/junction, other ?