Neutral and grounding wires

[Chris]

I have just reconfigured my Lima MAC from 120 volts only (Delta) to 240/120. (Zig zag). The Lima unit is a twelve wire unit.
The generator is now producing 120/240.
I have a 10 amp breaker between the neutral and ground on my main panel in the main house. (I wanted to be able to issolate the ground should I need to use my cheapo backup inverter that reqiures an issolated ground or it will be smoked and kaput).
My problem is that now the breaker trips. I am getting 120 volts between neutral and ground. When I try to ground the neutral via the breaker then gen bogs down and the breaker trips.
I am now running with a floating ground.

I did not have this problem when wired delta and 120 volts only.
Any ideas as to what is happening?

[Ronmar]

Something sounds backwards.  Neutral and ground must always be at the same potential.  Somewhere in your wiring you are applying energy where it should not be.  Most likly you have a set of the 12 wires backwards so one of the AC inputs are out of phase causing this issue. Got a link to a schematic?

Separating ground and neutral is a bad idea on most any planet.  I would highly reccomend a different inverter, or at the very least put it on a isolation transformer so you can maintain standard house wiring.

My .02

[Henry W]

The neutral and ground should never be fused.
It sounds like it is wired wrong.
Never run a generator without proper grounding.
In order for me to get proper grounding I had to drive two 8 foot grounding rods in the ground. I spaced them six feet apart from each other. I used 8 gauge copper grounging wire that ties to both grounding rods on one end and the other gets bonded directly to the generator housing.

I would get in touch with Marathon since they own Lima-Mac and find out where the ground should be connected to the generator head before you do anything else. Then find out electircal codes in your area.

Henry

[Chris]

Thanks for your comments on this.
Here in the Bahamas, and our electrical code follows the Canadian code The neutral and ground is supposed to be connected in one and only one place. It is usually at the main disconnet at the meter box. This is also a US code requirement.

Many European codes do not ground the neutral and leave it floating.
Inverters for RV units normally would not have neutral and ground interconneted and have a floating neutral.
Most low cost inverters keep ground and neutral issolated. This one of the reasons that they recommend NOT hooking up to a house panel.
All that being said, I will double check that I made the proper wiring connections when I reconfiured for 120/240 and keep you all posted.

Again thanks for your input.

Regards

[BruceM]

In most of the US, the Wye power distribution system grounding practice as implemented by the power companies is a violation of good engineering practice. The neutral is jumped around every single phase transformer, and I suspect all up/down transformers in the distribution system. It is then connected to earth hundreds of thousands of times, at many poles, every transformer, junction box, water well pump, and finally at every meter panel.  Most EE's not familiar with power engineering practice would find this unbelievable since it is such a violation of basic good engineering practice.  The result is regional level ground/neutral loops, with typically 25% of the neutral return current overall flowing back through the earth/aquifers (according to a power engineering text).  99% of the magnetic fields in the suburbs are caused by this grounding practice, as evidenced by measurement in Delta wired 'burbs, and towns where "background" readings are about 1/100th of those found in Wye served areas. Rural home sites are no better, and are often worse as wells provide such a low resistance path for neutral current.

This is a pet peeve of mine. EE's have understood about single point grounding (per isolating transformer) for over 70 years now. We have surge protection hardware and better insulation on motor wiring that makes the original perceived need for hard grounding of neutrals severely outdated.  Unigrounded Wye (as it should be done everywhere) does exist in some areas in California, for situations where Wye and Delta grids connect. Yet the madness continues, even for new development.  Then we add "smart" meters to this abortion?!

Back on topic, +1 for Ron's comment. Your 120/240 wiring of the generator head is clearly screwed up.  Without hooking it to anything, do you really see 120V to each of the two hot leads from the neutral, and 240V between the hots?  If so, then check each (L1,L2, N) resistance to your safety ground, as one hot leg must still be connected to ground.  If L1  is grounded, for example, from your previous 120V setup, then everything would work, but Neutral is now 120V relative to ground, and L2 is 240V relative to ground.

[Chris]

Brucem,

Thanks for your thoughts. L1 to L2 240v, L1 to N 120v, L2 to N 120v, N to G 120v,  not sure about L1 to G and L2 to G Will check in the morning.

I will then check my gen wiring and see if/where I screwed up.
Thanks

[BruceM]

Chris, Nice troubleshooting.  It's clear that your L1 or L2 is connected to ground.  You can confirm this with just a resistance test between safety ground and L1, then L2, with the generator off.  Likely a ground connection from the former neutral still left in place from your prior 120V hookup. Might  be a built in "ground strap" to the case that needs to be removed for your new configuration.
Best Wishes,
Bruce

[Chris]

OK problem solved, BUT I don't know why.
The generator was wired correctly. I checked my leads to my disconnect breaker. Looked for some sort of short and could not find any thing. I have made sure that all connection IE L1, L2, L0 and the wires that are tied together but not connected to any outside wire are good a separated. It is possible/probable that something was shorting before I unwound all my electrical tape to check the leads. I will get some of that rubber tape when I go to town tomorrow and really insulate the leads.

The Lima Mac (280 frame) does not have a terminal block in the dog house. It does not have much of a dog house.
Right now the wires are hanging outside the dog house.

Brucem.

Thanks for your help on this

Regards

[Randybee1]

T
In order for me to get proper grounding I had to drive two 8 foot grounding rods in the ground. I spaced them six feet apart from each other. I used 8 gauge copper grounging wire that ties to both grounding rods on one end and the other gets bonded directly to the generator housing.


Henry

Yup... Resurrecting and old thread but.... how do you determine if you have proper grounding? I thought just pounding a rod into the ground was good enough.

Randy

[sailawayrb]

I would suggest carefully re-reading what Bruce initially wrote, especially his last paragraph.

If a generator is wired properly and is working properly (i.e., there are no wiring faults) and is connected to building electrical circuits via a proper transfer switch so as to use the building ground system, adding another earth grounding rod for the generator is redundant.  If the generator is not connected to the building ground system, the generator needs to be grounded in some other way.  While redundancy is normally a good thing, when it comes to grounding it can get complicated and confusing and adding this redundancy may not be appropriate.  The primary issue is the potential of creating undesirable grounding loops that conflict with the building grounding system.  And not all buildings use grounding rods.  Some buildings (e.g., like our home), use the building's concrete encased footing rebar to create a capacitive approach (i.e., "Ufer" ground system) that provides a better AC ground where dry soil conditions exist than would be possible by using grounding rods.  And to make things even more confusing, much of the information on the Internet is wrong.

[Randybee1]

I did read it carefully. My question was not about "if" grounding is needed it was about the statement Henry made about using two 8 foot rods six feet apart. How did he determine that was needed for "proper" grounding?

[sailawayrb]

Well, only Henry can answer that...  But I would suspect by measuring the impedance to see if it complies with code...typically less than 25 ohms.  I rented one of these:

https://www.amazon.com/Fluke-1623-Ground-Tester-Kit/dp/B000VRCSDE/ref=sr_1_6?dchild=1&keywords=Fluke+1623-2+GEO+Earth+Ground+Resistance+Meter&qid=1610048883&sr=8-6

Our Ufer ground was about 3 ohms in late Summer with bone dry soil.

[Randybee1]

That's probably what I need.... where would one rent one of those?
Randy

[sailawayrb]

I would suggest Googling "Rent Ground ResistanceTester" with your locality also in the search field.  You can typically rent these for about $50/day.  

Most electrical code inspectors also have these testers and can perform the test if they are coming out your way for some reason.  

Some localities also expressely specify the grounding requirements (e.g., type and depth of ground rods, etc.) based on the average soil conductivity of the locality which may allow you to avoid testing altogether.  

Acceptable grounding tends to become more challenging as the soil becomes more sandy and more drier.  And this is the situation I would personally be more concerned about achieving adequate grounding.  But one could argue that a person is also safer from being electrocuted under these conditions too...unless they also happen to be touching water or something else that provides  better grounding...

[Randybee1]

Thanks, I will look in to renting one sometime in the near future.
Randy