120v and 160v = 277v on 230v Circuit

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PM5K

Member
Location
San antonio
The circuit is supossed to be 230 volts single phase, each leg to ground reads 120 and 160 respectively, and together 277.


Whats's going on here? Some electrical work was recently done and I'm assuming there's a neutral wiring problem.
 

PM5K

Member
Location
San antonio
This is powering a 230v single phase water pump. It worked fine Wednesday, the service was cut off by the city while a new electric panel was installed, Thursday morning the work was completed and the pump worked fine until about 5 in the afternoon.

Its a a strange setup where we share a well with our neighbor, but the service to it comes from their side.
 

gar

Senior Member
Location
Ann Arbor, Michigan
Occupation
EE
160610-1141 EST

PM5K:

It is not clear whether you are an electrician or not, and whether I should respond.

That you read 120 from one hot line to ground and thus possibly to neutral and 160 from the other hot to ground, and 277 from one hot to the other hot line implies two single phase waveforms that are 180 degrees out of phase. 120 plus 160 = 280 which is very close to 277. Your source does not appear to be a 3 phase 277/120 wye.

Normally a single phase 240/120 source is from a single center tapped secondary.

You should call the power company.

Go to your neighbor's home. Make voltage measurements there. If there is any 120 V outlet with with 160 V get the power company out immediately, and remove anything plugged into outlets with 160 V.

It would be better to make line to neutral measurements in the main panel, but your neighbors might not like you to do that.

You need to clarify your background .

Also you should go look at what the power company distribution transformer setup looks like. How many transformers, and what do the bushings and connections look like?

A 240/120 single phase system would usually (virtually always) have a single transformer with three output terminals, and for high voltage either two input insulated bushings, or one insulated bushing.

.
 
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