Connecting Generator Neutral to Ground Conductor

[Frankly]

Does anybody ever wonder why a world wide, world class generator mfg like Honda has purposefully decided to not connect the neutral and ground together. Even on their newly issued EU 2200 they have continued the same practice. They make these generators and turn them loose on the public with little control on where and how. For all we know there may be one on the International Space Sation for backup power.

There are valid reasons why the "powers that be" decided on making a grounded electrical systems the norm for everyday electrical distribution, but they may not be applicable in all cases. There are lots of ungrounded and resistance grounded electrical systems in operation all over.


If you feel more comfortable operating a Honda generator with the neutral and ground tied together, then a plug is easily fabricated to make that connection. IMHO it ain't no big deal.


Frankly

[a64pilot]

I am not an electrical Engineer.
However unless I’m mistaken one or two that are have posted that not having them connected is actually safer, something having to do with how most power tools you buy now are not grounded, if you look most don’t have that third ground leg anymore.

However of course ABYC requires them to be connected and I believe only once and at the source, so to be within regulations we should connect the ground and neutral together, but only at the source, which in my opinion a plug would be.

Same for inverters, they are an AC power source to, and I believe Marine inverters have a relay so that when they are inverting then can connect the neutral and ground together in the inverter, but when they are not, they are not connected.

You have to have a relay so that you don’t have the neutral and ground bonded when on generator or shore power, as that is unsafe.

So one would assume that if you bonded the neutral and ground together, you should unplug the bonded plug when using an inverter to prevent two sources of a neutral / ground bond?

[Frankly]

Keep in mind my comments were on small portable inverter/generators not larger built in generators. The latter should have the neutral and ground connected and the best (and legal) place is at the unit, but them electrons don't know no ABYC or NEC.


The marine inverters/ chargers (built in transfer switches) that I have installed on my boats all have relays that lift the ground to neutral connection when in the charge mode and establish the connection in the inverter mode. Probably got more to do with lawyers than anything electrical.

Multiple ground to neutral connections are more of a book keeping issue. Usually not a safety issue, again them electrons will take the path or paths as necessary. Can be an issue with the ELCI shore power systems that are soon coming to a marina near you.

When using my EU 2000 to power the house (I have a dedicated 20 breaker standby panel), the transfer switch does not switch the neutral so my neutral to ground connection in the main service panel is still electrically in play. But it would work just fine if it was not there.

Been a while since I mucked around in the ABYC, but is there anything in there that really speaks to portable generators.


Frankly

[s/v Jedi]

The Honda design is 100% okay as it is...

I know people tend to point at ABYC but while those rules do create a safe system, that doesn’t mean it is the only way to a safe system... better and safer systems may exist.

When you are out at anchor and use the Honda, you can not be electrocuted when you grab ground with one hand and either the hot or the neutral from the Honda.

Remember that you need to complete a circuit and when a power source is galvanic isolated from ground, the ground can never complete a circuit

[YANDINA]

Originally Posted by s/v Jedi

The Honda design is 100% okay as it is...

<SNIP>

Remember that you need to complete a circuit and when a power source is galvanic isolated from ground, the ground can never complete a circuit

That is not correct, ABYC specifications require that the galvanic isolator be capable of carrying 130% of rated current continuously. Rather than just type testing in a lab, EVERY isolator that Yandina makes is put through the ABYC electrical tests until the temperature stabilizes, including the new 2.5 volt isolator.

[Frankly]

Think we have a little terminology issue here.

The term "galvanically isolated " describes a condition of electrical isolation (think insulated).

A "galvanic isolator" is the device to reduce corrosion from electrical current. Originally installed in the AC ground to 12VDC negative/ engine connection, but now installed in series with the shore power AC ground connection.


Frankly

[YANDINA]

Sorry, I can't agree. "Electrical isolation" is the equivalent of insulated = no connection between them.
When you modify the level of isolation with the word "galvanic" it now refers to an insulator limited to "galvanic" voltages.
If you want to "think insulated" you should say insulated.

[Frankly]

I reckon we will have to agree to disagree although most current references tend to apply to ground circuit isolation but not exclusively.


Frankly

[s/v Jedi]

Originally Posted by YANDINA

Sorry, I can't agree. "Electrical isolation" is the equivalent of insulated = no connection between them.
When you modify the level of isolation with the word "galvanic" it now refers to an insulator limited to "galvanic" voltages.
If you want to "think insulated" you should say insulated.

Okay, “insulated” then. I used the term that engineers tend to use for this, not related to your product “galvanic isolator”. I agree that it may even be wrong and “electrically isolated” is better.

That said, it still means that the Honda is perfectly fine as it is. When it is used at anchor instead of shore power, by using the shore power inlet, crew can not be electrocuted by touching any grounded or bonded surface with one hand and either hot or neutral with the other hand.

Also, boats have no ground unless connected to shore power. Even when they use an underwater ground plate, it is at a different potential than land based ground or even an anchor in the seabed. I once measured 1.7V difference between anchor chain and ground plate.

[GordMay]

Isolation simply refers to keeping two things apart. It is not a “thing”, but a concept.
It is desirable to isolate human beings from high voltages. This doesn't say how you do it, just that you must keep them apart.
On the other hand, insulation refers to some physical “thing”, that is used to keep two things apart.
So, insulation is a type of physical thing, that provides isolation.
Insulation can be plastic around a wire, or a sheet of paper/cardboard, between two windings of a transformer.

[jhulmer]

okay! for the dumbass country boy mechanical engineer. Should I do anything more to connect my Honda besides plugging it into the shore power receptacle that has the grounded twist-lock plug (cord cap)?

There is a ground lug on the outside of the Honda that nags at my sense of security. "should you be connected to something" I ask?

[Frankly]

In the most general definition/ usage you are correct about "isolation". In the normal electrical usage "electrical isolation" is used as in isolation transformer, opto coupler isolation, isolation by insulation, and physical isolation where air is the insulating medium.


Insulation is also used for that stuff in walls to reduce heat transfer.


Electronics and electricity are advancing faster than the language can keep up, so we do the best we can.


Frankly

[Frankly]

Forget about the external ground lug. Plug in your shore power cable, if you want to connect the neutral and ground make a dummy plug for the extra space in the receptacle. Will work and be equally safe either way.


If your really want to improve on electrical safety make a short pigtail with a plug on one end and a gfci receptacle on the other end (installed in a box). Then plug the shore power cable into the gfi receptacle and the plug into the generator. About as safe as you are going to get without getting into some complicated and expensive stuff.


Frankly

[jhulmer]

Originally Posted by Frankly

Forget about the external ground lug. Plug in your shore power cable, if you want to connect the neutral and ground make a dummy plug for the extra space in the receptacle. Will work and be equally safe either way.


If your really want to improve on electrical safety make a short pigtail with a plug on one end and a gfci receptacle on the other end (installed in a box). Then plug the shore power cable into the gfi receptacle and the plug into the generator. About as safe as you are going to get without getting into some complicated and expensive stuff.


Frankly

I understand the dummy plug would have the neutral prong and the middle ground prong connected with a jumper? What would this accomplish on a closed system of the generator besides protection inside the generator case?

My 120v AC system is not grounded to my DC ground (except through the Galvanic isolator) nor is it grounded to the Sea as this is, as I understand, the ABYC standard. So with the GFI in the Generator circuit, I would have total protection from accidental electrocution of myself, close friends, family, pets, etc?

[Frankly]

Don't think there is any requirement to directly connect the AC ground to the seawater. There is a requirement to connect the AC ground to the engine block/ 12 Volt negative and as such will typically electrically connect the AC ground to seawater (via prop shaft/ propeller). Connecting these two grounds together electrically safer but can cause corrosion issues. This is where galvanic isolators come into the picture. Earlier times the GI was installed in this connection between the AC ground and 12 Volt ground (typically called zinc savers), more recently the GI is installed in series with the shore power AC ground on the boat (typically called galvanic isolators).


GFCI (receptacle or breaker) technology will protect you and family from shock produced by contact between the hot leg (typically black color ) and ground (the more typical electrical failure scenario ). Contact the hot leg and the neutral conductor (white or grey color) simultaneously you will receive a significant shock. Body resistance and prayer is all you got going for you then.


Generator neutral to ground connection is typically made at only one location and the special plug will fill this obligation if you feel so inclined.


Frankly