Voltage across neutral to ground on AC circuits

Anything electric, AC or DC

Voltage across neutral to ground on AC circuits

Postby mcubberley » Fri May 19, 2017 1:28 pm

Testing outlets I discovered voltage across the neutral to ground. Seems to be about 10v. I installed a PD4045 and grounded the ground buss to the trailer. All GFCI outlets are grounded to this bus bar. Otherwise, the everything is wired according to the instructions and based on all the information I have seen here. I do not have the battery connected yet so what I have read tells me I shouldn't see any power on the DC circuits. But the voltage on the neutral seems to be associated with the DC converter circuit. If I remove power to the converter (leaving the converter breaker off) there is no voltage across the neutral to ground.

So somehow the dc circuit is feeding voltage back onto the neutral it seems. Is this because the battery is not connected? Where should the DCcircuits have the black wires terminated?

I guess thats where I am at right now. Figured I would ask here since I won't see an electrician for a little while and this converter is adding a layer of complexity that seems to be confusing me a bit.
Some day I will figure out something to put here. But for now....
Image
_____________________________________________________________
I made my own image hosting, feel free to create a free account: http://shoppics.org
I made my own blog, feel free to browse: http://themodernshopteacher.com
User avatar
mcubberley
Teardrop Master
 
Posts: 117
Joined: Thu Mar 16, 2017 5:08 pm
Location: Roanoke, VA

Re: Voltage across neutral to ground on AC circuits

Postby low277 » Sun May 21, 2017 11:21 am

Is the 10 volts you see measuring AC or DC?
NW Minnesota
low277
Teardrop Master
 
Posts: 142
Images: 5
Joined: Fri Jan 06, 2012 2:11 pm
Location: NW Minnesota

Re: Voltage across neutral to ground on AC circuits

Postby H.A. » Sun May 21, 2017 2:18 pm

Itsse.
Last edited by H.A. on Thu Jul 06, 2017 4:11 am, edited 1 time in total.
H.A.
The 300 Club
 
Posts: 429
Images: 0
Joined: Tue Nov 15, 2011 8:16 pm
Top

Re: Voltage across neutral to ground on AC circuits

Postby low277 » Sun May 21, 2017 9:45 pm

Is there any load on the circuit that you are measuring the voltage on?
NW Minnesota
low277
Teardrop Master
 
Posts: 142
Images: 5
Joined: Fri Jan 06, 2012 2:11 pm
Location: NW Minnesota
Top

Re: Voltage across neutral to ground on AC circuits

Postby mcubberley » Mon May 22, 2017 5:52 pm

Thanks for the replies. No there is no load on the circuit. I believe the current was ac because when I discovered it I was double checking to make sure the outlet was wired correctly. Testing hot to neutral, hot to ground, and neutral to ground. I will need to go back and double check though to make sure.

I guess what is throwing me is that if the pd4045' is receiving power (the dedicated breaker is on) the voltage is there. If I disconnect the converter (turn off that breaker) the voltage goes away.

Could it be that the D.C. Circuits share the ground with the ac curcuits since everything is ground to the trailer?

I will take some pictures here soon but I am pretty sure my install is ok. Just haven't connected a battery yet.


www.themodernshopteacher.com
Some day I will figure out something to put here. But for now....
Image
_____________________________________________________________
I made my own image hosting, feel free to create a free account: http://shoppics.org
I made my own blog, feel free to browse: http://themodernshopteacher.com
User avatar
mcubberley
Teardrop Master
 
Posts: 117
Joined: Thu Mar 16, 2017 5:08 pm
Location: Roanoke, VA
Top

Re: Voltage across neutral to ground on AC circuits

Postby GuitarPhotog » Mon May 22, 2017 10:55 pm

Is the trailer grounded to the 120V AC supply ground (green wire)?

<Chas>
:beer:
GuitarPhotog
Silver Donating Member
 
Posts: 1668
Images: 55
Joined: Tue Feb 08, 2011 12:52 pm
Location: Grants Pass Oregon
Top

Re: Voltage across neutral to ground on AC circuits

Postby mcubberley » Tue May 23, 2017 3:14 pm

Yes the ground bus bar from the pd4045 panel is grounded to the frame. So the shore power comes in and hot to 30amp main breaker. Neutral to neutral buss bar and ground to ground bus bar. The ground bus bar is then grounded to the frame. The D.C. Negatives are in a buss bar that are grounded to the ground bus bar and thus the frame as well.


www.themodernshopteacher.com
Some day I will figure out something to put here. But for now....
Image
_____________________________________________________________
I made my own image hosting, feel free to create a free account: http://shoppics.org
I made my own blog, feel free to browse: http://themodernshopteacher.com
User avatar
mcubberley
Teardrop Master
 
Posts: 117
Joined: Thu Mar 16, 2017 5:08 pm
Location: Roanoke, VA
Top

Re: Voltage across neutral to ground on AC circuits

Postby H.A. » Tue May 23, 2017 5:10 pm

[quoad.
Last edited by H.A. on Thu Jul 06, 2017 4:12 am, edited 1 time in total.
H.A.
The 300 Club
 
Posts: 429
Images: 0
Joined: Tue Nov 15, 2011 8:16 pm
Top

Re: Voltage across neutral to ground on AC circuits

Postby Aguyfromohio » Wed May 24, 2017 10:35 am

This is very interesting, let us know when you get this solved.

While I've never used these panel/converters, I do have some experience with solid state switches.
We used lots of solid state relays like below to control little industrial heaters.
In my experience they leak.
More precisely, they can allow a fraction of a milliamp current when switched off.
So I would not be surprised if a solid state converter panel leaked a bit when it should be shut off.

The specifications for the relay shown are below. Notice the off state leakage current.
Of course, Progressive Dynamics knows all this and certainly must have designed around it to produce no leak panel. Otherwise they would be out of business.
I only raise it as a plausible failure mode for a solid state current control device.
If some other component has failed in the leak control circuit for some sort of power transistor, the unit might work fine when ON but leak when OFF.

Output
Switching Voltage: 0 - 50 Vdc
Current Range: 0.02 - 80 A
Surge Current: 200 A
On-state Voltage Drop: 0.64 V
Off-state Leakage Current: 0.1 mA
Turn-on Time: 0.5 ms
Turn-off Time: 0.5 ms
Image
Aguyfromohio
Silver Donating Member
 
Posts: 97
Joined: Sun Jan 29, 2017 5:02 am
Top

Re: Voltage across neutral to ground on AC circuits

Postby H.A. » Wed May 24, 2017 3:00 pm

Tion.
Last edited by H.A. on Thu Jul 06, 2017 4:12 am, edited 1 time in total.
H.A.
The 300 Club
 
Posts: 429
Images: 0
Joined: Tue Nov 15, 2011 8:16 pm
Top

Re: Voltage across neutral to ground on AC circuits

Postby Aguyfromohio » Wed May 24, 2017 3:21 pm

H.A. wrote:The "leakage" on SSRs is thru the load terminals. If a load appliance exists to complete the "leakage" circuit is what allows the electronic brains of a SSR to switch on or off. That leakage in its self will have nothing to do with the prior described scenario.
Any form of applying load to a grounded neutral can create a measurable voltage potential to another grounded or grounding conductor.
Btw,
The tiny voltage drop of a SSR is the powersource for its internal electronics to function.


Thanks H.A.
Once again I have proven that when it comes to electrical engineering, I'm a pretty good mechanical engineer.
:? :shock: :oops:
Aguyfromohio
Silver Donating Member
 
Posts: 97
Joined: Sun Jan 29, 2017 5:02 am
Top

Re: Voltage across neutral to ground on AC circuits

Postby mcubberley » Wed May 24, 2017 4:08 pm

H.A. wrote:
No there is no load on the circuit.I believe the current was ac because when I discovered it I was double checking to make sure the outlet was wired correctly. Testing hot to neutral, hot to ground, and neutral to ground. I will need to go back and double check though to make sure.

I guess what is throwing me is that if the pd4045' is receiving power (the dedicated breaker is on) the voltage is there.If I disconnect the converter (turn off that breaker) the voltage goes away.

Sounds like a contradiction ??
If the PD4045 is switched on, There is a load.


Sorry I assumed you meant something drawing on that branch circuit where I am taking the readings. The panel has power and all breakers on when I get the reading. There is nothing plugged into the outlets and only led lights on the D.C. Side but those don't work without a battery installed.


www.themodernshopteacher.com
Some day I will figure out something to put here. But for now....
Image
_____________________________________________________________
I made my own image hosting, feel free to create a free account: http://shoppics.org
I made my own blog, feel free to browse: http://themodernshopteacher.com
User avatar
mcubberley
Teardrop Master
 
Posts: 117
Joined: Thu Mar 16, 2017 5:08 pm
Location: Roanoke, VA
Top

Re: Voltage across neutral to ground on AC circuits

Postby low277 » Wed May 24, 2017 6:16 pm

The only true neutral to earth currents I have any experience with was a new dairy barn in the early 1990s. I was contracted to wire a new small parlor style dairy barn on a site that had never had electricity. Power company brought in a new overhead supply line, transformer and disconnect. I wired the barn to the current NEC code. Equal potential plane on rebar in the floor, etc. We discovered about 5 volts of potential between neutral and ground and it was affecting the cows severely. After we had the the local power company on site, the regional power generating provider, a competing power companies "stray voltage" experts and a team from the Public Ultilities Commision on site for 4 days the problem was determined to be ineffective utility grounding on the power utilities wood poles on a 7 mile stretch feed the area. It was tough on the cows, the farmer who almost lost the farm because of no milk production and myself, as I was under a microscope until the cause was identified.

2 things I learned from that experience. 5 volts potential from neutral to earth is very bad and I will never wire anything in a dairy barn again!
NW Minnesota
low277
Teardrop Master
 
Posts: 142
Images: 5
Joined: Fri Jan 06, 2012 2:11 pm
Location: NW Minnesota
Top


Return to Electrical Secrets

Who is online

Users browsing this forum: No registered users and 2 guests