removed the equipment ground from my converter

[John Frum]

I have a very weird usage model.

mains->converter->inverter->load

Both the converter and inverter equipment grounds were tied to the dc negative busbar
I noticed that the ground pin on the converter plug and the ground pin on the inverter receptacle had continuity
This would be a problem for my planned usage model which is so kludge-ugly I won't describe it here.
That converter equipment ground wire was quite stylish and I will miss it but it had to go.
I guess the majority of diy installs leave the EG disconnected.

afaict an ac fault to chassis should trip the ac supply breaker.
A dc short to chassis would not automatically clear.

Are there any ramifications that I should be aware of?

 

[SolarBro]

Thats a good question. Are the DC grounds and the AC grounds supposed to be isolated from each other?

I have everything bonded together on a common ground bar, AC and DC side. Current always go back to its originator, So i figured an AC ground fault would travel on the EGC to the neutral-ground bond and trip the breaker that way. I don't know if this would damage DC equipment on the shared Ground bar, which if there was a DC fault, it would travel to the origin source and trip the either GFDI or source breaker.

There is not a whole lot I could find to read on the subject.

 

[John Frum]

Thats a good question. Are the DC grounds and the AC grounds supposed to be isolated from each other?

Probably not but I didn't think of it until during the design phase.
Occurred to me after I had mounted all the pieces.

 

[Zil]

I can't see how it would matter as the AC hot and AC neutral must be separated. The DC negative has no reference to ground. It is a return circuit. Connecting AC ground and DC negative would be fine. In your "kludge-ugly" could you just isolate one device? I chose inverter. That 120V AC is already self contained and doesn't need the chassis. I could trust not converter tied into external power with out chassis and devices and what ever tied to the green earth ground.

 

[John Frum]

In your "kludge-ugly" could you just isolate one device?

That is what I did.
I chose the converter because its was a ~.33 the price of the inverter.

 

[Zil]

As long as you are not part of the ground path.

 

[John Frum]

As long as you are not part of the ground path.

24 volts isn't dangerous.

 

[HRTKD]

My inverter and converter share the same ground bus bar on my trailer.

 

[John Frum]

My inverter and converter share the same ground bus bar on my trailer.

How does that impact your neutral/ground bond strategy?

 

[HRTKD]

How does that impact your neutral/ground bond strategy?

Beats the heck out of me. Downstream, the main distribution (handles both 12v DC and 110v AC) also has a ground. It's hard to tell with the rats nest of wiring I have to look at.

 

[John Frum]

Beats the heck out of me. Downstream, the main distribution (handles both 12v DC and 110v AC) also has a ground. It's hard to tell with the rats nest of wiring I have to look at.

This is a saftey issue.
There is supposed to be one and only one neutral/ground bond.
This is so fault current will trip an over-current device to clear a fault condition among other things.
If you have both your converter's and inverter's equipement grounds connected together that means you potentially have 2 neutral/ground bonds.
The one upstream of the pedestal and the one that may/or may not be in the distribution panel.

If there is a bond in the panel then you have 2 when connected to shore power.
If there is no bond in the panel the you have 0 when disconnected from shore power.

This is usually solved by getting an ul-458 listed inverter/charger and disabling the converter.

 

[Zil]

24 volts is not as dangerous as 120 volts AC. A converter connects to line voltage. Or do you refer to something that is not a converter?

 

[John Frum]

24 volts is not as dangerous as 120 volts AC. A converter connects to line voltage. Or do you refer to something that is not a converter?

I'm referring to this https://powermaxconverters.com/wp-content/uploads/2018/07/PM3-24V-LK_Spec-Sheet.pdf
and I already basically the same thing https://diysolarforum.com/threads/removed-the-equipment-ground-from-my-converter.11735/post-130158

UPDATE: not really an issue as described.
Its 2 different power domains.
Just because the grounds are bonded doesn't matter.
In this case you need 2 different neutral/ground bonds because its 2 different power domains.
Power returns to its origin.

 

[HRTKD]

So, false alarm?

 

[Zil]

So, false alarm?

Sometimes I get the impression Joey likes to throw controversy into the air just to get us all excited. He means no harm.

 

[John Frum]

So, false alarm?

Yes.
But there is a ground loop issue... for my setup.

 

[HRTKD]

Sometimes I get the impression Joey likes to throw controversy into the air just to get us all excited. He means no harm.

Kind of like Crazy Uncle Louie?

It spurs some interesting conversation.

 

[GXMnow]

I have not wired a complete mobile system on my own, I only helped on a large trailer and a motor home and that was many years ago. So I don't know the legality of what is needed, but from a safety standpoint, I think the ground system should always be tied together. Multiple grounding points are very common and rarely cause any issue in an AC power system. If there is any real current flowing in the ground, then there is a problem. When my solar was added to my house, they actually required two grounding rods to be tied into my main panel. And the two rods had to be more than 6 feet apart.

On the DC side of a vehicle, it is a bit different as there could be a fairly large amount of DC current in the ground as many mobile systems just use the chassis as the current return. I never liked doing that, and I do run a negative power lead and an isolated negative power bar when I have built high power sound systems. Using the chassis for the negative power side always puts noise in the audio. I like to treat it more like an AC power system with a hot +12 volt, Neutral 0 volt, and safety ground = Chassis. With the negative power and the chassis bonded at the alternator/engine block/frame ground strap. What is the "Ground Loop Issue" that you are tring to fix by lifting a ground connection?

With an AC system on a vehicle, I always thought the neutral bond was switched by the transfer switch that selects the shore power connection. If you are off the grid, the neutral must be grounded at the main panel ONLY. When the transfer switch selects shore power, it lifts that ground so the neutral is grounded by the incoming service panel. The trailer I helped wire was an autocross race timing and announcing "tower" with a few computers and a PA system in it. When we ran on generator, we had a ground cable we would clamp onto a sign post to ground the chassis. We even carried a 4 foot ground rod if were were near dirt, we could drive it in and clamp to that. Without the ground connected, the PC's all worked fine, but we would sometimes hear "data" in the PA system. We also had several 200 foot cables run out to the timing lights, and speakers up on towers. We rarely ran in rain, but if lightning came in quick, the grounding could save lives. Would have been nice to have a battery bank and solar panels instead of that noise generator running for 12 hours straight.