# Single Phase 120 Neutral to Ground reads 52 volts?



## comicbookmechanic (Dec 14, 2016)

I have an issue with the 120 volt outlets in our production facility. I'm reading 67 volts on phase to ground, 120 volts on phase to neutral, and 52 volts when I check neutral to ground. This circuit is being fed from a stepdown transformer. Any ideas on what would cause these abnormal readings?


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## oliquir (Jan 13, 2011)

floating neutral


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## comicbookmechanic (Dec 14, 2016)

It appears that we have a dual phase transformer, so is this floating neutral condition normal, is there any risk of damage to the load?


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## just the cowboy (Sep 4, 2013)

*Centertap not grounded*

Check the nameplate it should show a bonding jumper from the center tap neutral to ground, it sound like it is missing.

Yes for safety reasons it should be grounded, BUT sometimes a systen is not for other rare reasons.


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## PlugsAndLights (Jan 19, 2016)

Sounds like hot and neutral are ok. Problem is with gnd. Likely 
floating gnd. If so, everything will work fine but it's a hazardous 
situation as energized accessible parts won't result in tripping 
of the breaker. 
P&L


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## Fishbulb (Jun 9, 2016)

Ungrounded systems are permitted in some circumstances, but "We don't know how to properly install a transformer" isn't one of them. You've got receptacles installed, the derived system can be made less than 150 Volts to ground, it's not a health care facility - this system requires grounding.



> It appears that we have a dual phase transformer, so is this floating neutral condition normal, is there any risk of damage to the load?


No ground fault can possibly trip the OCPD, leaving all conductive materials connected to the EGC electrified. I'd call that a risk even if it isn't to the load. I'm guessing you also don't have any sort of grounding electrode or system installed for the transformer?

Call someone who knows how to do this.


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## DesignerMan (Jun 13, 2008)

oliquir said:


> floating neutral


What he said...


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## Signal1 (Feb 10, 2016)

Fishbulb said:


> Ungrounded systems are permitted in some circumstances, but "We don't know how to properly install a transformer" isn't one of them. You've got receptacles installed, the derived system can be made less than 150 Volts to ground, it's not a health care facility - this system requires grounding.
> 
> 
> 
> ...


What he said too


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## brian john (Mar 11, 2007)

If the posters is not familiar with what is happening it is doubtful he would know the term FLOATING. 

Appears as noted this is an UNGROUNDED system, either intentionally or accidentally.


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## Wiresmith (Feb 9, 2013)

what kind of step-down transformer, buck boost or isolation?


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## Flyingsod (Jul 11, 2013)

brian john said:


> If the posters is not familiar with what is happening it is doubtful he would know the term FLOATING.
> 
> Appears as noted this is an UNGROUNDED system, either intentionally or accidentally.


That kinda of helps me even. Thanks. I never could wrap my head around what a "floating" neutral was. Especially given that a lot of systems where people would use this term don't even really have a neutral conductor. 

Sent from my C6725 using Tapatalk


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## Bird dog (Oct 27, 2015)

A floating neutral is similar to a floating delta-no ground reference.


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## brian john (Mar 11, 2007)

Bird dog said:


> A floating neutral is similar to a floating delta-no ground reference.


"Floating" is a name given by tradesmen, it is in my opinion that we should utilize the correct terms when dealing with those that are trying to understand a system they are not familar with. 


Often these terms are local slang and not widely accepted, though I THINK(?) floating may be country wide?


Ungrounded.


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## brian john (Mar 11, 2007)

hd13 said:


> what kind of step-down transformer, buck boost or isolation?


Unless the whole facility is ungrounded, it is very unlikely it would be a buck/boost transformer.


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