UPB UMC-DB9 Crash and burn

[pete_c]

Thank you Mike.
 
Yup checked the voltage to be fine. 
 
A while back did lose one phase of electric (underground).  1/2 of the electric went out in the house.  Electric company came right away (7 AM on a Sunday morning) and replaced meter with some device which put my electric to one phase.  About a week later a crew came over to dig (in the snow) for about 2 days (dug under a tree) and found that the tree roots had separated / broke one of the three electrical wires.  I kept the ends as a souvenir.  They fixed it and I was good to go.
 
I did find one issue this time.  (which I had nothing to do with).  The electric for two 15 AMP circuits (lights and wall power plates) used one common neutral (white) which I had never seen before. The two neutrals (light and outlet) were twisted together in one box to the one neutral coming from the panel.   I pulled a new white neutral wire back to the fuse panel (well fished it) such that the two circuits had two black (hot) and two white (neutral).  While doing this separated two 2 duplex outlets to two circuits and ran another hot and neutral wire to the panel.  (6 wires in the conduit were no issues to run). 
 
I am desoldering the MOV.  While grabbing it with tweezers it fell apart.   There is also a diode or resistor next to it that looks totally fried and is open right now.  Can't tell what it is.  Shorted where the MOV was and powered it up.  No LED lights yet...thinking though have to replace the diode next to it.

 

[mikefamig]

I did find one issue this time.  (which I had nothing to do with).  The electric for two 15 AMP circuits (lights and wall power plates) used one common neutral (white) which I had never seen before

This condition is called a shared neutral and is or at least once was allowed by national code. Two circuits can share a common neutral conductor as long as they are on opposite phases of the service. That way when one line is +120v the other is -120v so the total never exceeds the ampacity of the wire (min awg14 in this case of 15amp). The two 15amp breakers must also be physically connected to each other in a way that they move on and off together. You don't want an electrician to turn one breaker off thinking that the circuit is safe to work on when current can still get to the neutral from the second phase.
 
Mike.
 
The only reason that I can think of to do this is to save money on the cost of wire (cheap builder)
 
EDIT - did I get that right?? I'm not sure about the phase shift being +120 -120 part but I'm sure that the phase shift causes the neutral to never go over the rated ampacity of the wire.

 

[pete_c]

Understood Mike. 
 
Yup; the two hot legs went to adjacent breakers (one on each phase) but the breakers were separate (not joined.). 

 

[RAL]

Understood Mike. 
 
Yup; the two hot legs went to adjacent breakers (one on each phase) but the breakers were separate (not joined.). 

 
That's something you need to fix.  Replace the two single breakers with a double pole breaker.  As Mike pointed out, separate breakers create a safety hazard.

 

[pete_c]

Added a new neutral wire and another circuit such that there are now three breakers for the area.   The lighting and wall outlets were using the same neutral.  Now the lighting, wall outlets are using separate breakers.  Wall outlet was used for a server rack.  Now its two on two separate circuits.  Lights went from 1 to 6 boxes (6 lights).
 
Neutral + new circuit (2 wires) cable pull was some 25 feet to first box and two more wires another 8 feet to first of two outlets.  Easy peasey using conduit here.