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240v on one leg of range outlet

30K views 46 replies 19 participants last post by  CoolWill 
#1 ·
ok here is what is happening. got a new oven and the display will not work, the burners do. called a tech out, and he says there is a voltage issue with the house, bad neatral. I check voltage at the plug, 120v phase to neutral both legs, 240 between phases. plug in the oven and I get 240v phase to phase, 240v from one phase to neutral, the other leg appears dead. took the whip off the range/oven and hooked a incadesent lamp between one phase and neutral to test neutral. the phase the light is hooked to drops out and shows 240v on the other phase, and phase to phase. is this a bad neutral or breaker?
 
#13 ·
Are you sure there isn't a problem at the pole or at the service? or is this problem just about the range-- if so then you have a bad cable or some connection in the range etc.
 
#20 ·
Are you sure there isn't a problem at the pole or at the service? or is this problem just about the range-- if so then you have a bad cable or some connection in the range etc.

Great Call! Had a hand hole in customers yard that constantly got flooded. Connections oxidized to three times the size till it failed.
 
#24 ·
1 word
megger!
check the whip first,(completely disconnected from the stove) then the house wiring.
if the wiring in the house is visible anywhere look for damage from rodents or nails/screws
and finally check the breaker carefully (remove it from the panel and check the resistance)
you may see a small difference in the readings here but if the reading is large then the breaker is failing.
 
#27 ·
explanation

why does the unloaded leg go to 240v and the loaded leg go to 0 when a load is applied. I would think the breaker would trip if there is some kind of short between phases or to ground shouldn't the breaker trip? I am a younger electrician and this is the first time i have seen this.
 
#31 ·
why does the unloaded leg go to 240v and the loaded leg go to 0 when a load is applied. I would think the breaker would trip if there is some kind of short between phases or to ground shouldn't the breaker trip? I am a younger electrician and this is the first time i have seen this.
You're reading 240 because one lead of your tester is on A phase and the other is on B phase thru the element. Put your ohm meter between a known good ground or neutral such as a nearby receptacle and the other on your range receptacle neutral. If you read high or infinite resistance that will tell you the neutral in the range wire is bad
 
#33 ·
the loop back voltage is when you have voltage in one leg of the supply but not the other.
while the one circuit works they share a common neutral and feeds back through the dead leg
you can read a voltage at the breaker even if its bad.
i had this same situation during my 1st year as an apprentice while working on a gould jet pump
my journeyman got quite a chuckle but explained it clearly by drawing a loop on a sheet of paper and showing test points.

i still use this method for teaching apprentices on 3 phase motors:laughing:
 
#34 ·
That is true if you have circuits that are 240v that are on. The voltage will go through an element to feed the other phase. But this is not a situation of a bad phase as he has 240 to neutral on one phase.

There are only a few things it can be -- this is not rocket science esp. if it is only on that circuit.

Assuming in electrical will get you nowhere fast
 
#35 ·
that why i said megger the circuits earlier
without being there to see it i would suspect neutral issues.
but its a matter of elimination of all possible causes.
pain in the arse i know but good learning experience
 
#36 ·
To the Op>>>>>>>>>>>

Take the wire/cable loose from both the stove receptacle and the panel

Tie one of the hots to the neutral, either with a large wire nut or strong alligator clip, splice of some sort etc.

Go to the other end and check continuity between the hot you used and the neutral.

Do the same with the other leg

Do the same with the two hots

If you don't get continuity with any combination of the hots to neutral, but do with just the hots, you have a bad neutral.
You might have some reading but it should be fairly low, say close to 0-5 ohms if it is good and you have a good connection during the test.
 
#38 ·
the picture isnt very good but clear enough to see
using continuity testing with main shut off.
you will have continuity L1- T2, L1-T3, L2-T3 but not on L1- L3,or L2-L3

powered : voltage reading
across T1-ground=240 volt
across T2-ground =240 volt
across T3 - ground =240 volt (because voltage will loop back through the windings to T3)

reading across fuses
if fuse is good!
L1 to T1 0 volts
L2 to T2 0 volts
L3 to T3 480 volts (showing open fuse) (again looped circuit)

although if using a star wound device the voltage on the legs would be different but same principle.

contiuity testing the leads on a 3 phase motor will show some resistance but a shorted winding as well as an open one would give you a drastically different reading
 

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#41 ·
You have a broken neutral prior to your panel, check meter pan and utility drop . The 120 volts on the neutral is open currents from other loads in the house looking for somewhere to go. You very well might end up releasing the magic smoke from electronic items while this current finds passage to the otherside.
 
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