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Topic starter
November 19, 2024 6:24 pm
I have a question about grounding of the Chargeverter. I am connecting the DC output to an EG4 rack system bus with six LL-S batteries. I plan to power the input with a small portable 2000 watt 120VAC generator (this scenario is only intended in case a grid outage lasts longer than my battery backup duration). The Chargeverter will be grounded to the generator through the L14-30 ground conductor. However there is no provision on the product to connect a ground conductor from the Chargeverter to the battery rack. The rack is connected to equipment ground, though an 18Kpv inverter, back to the main service entrance bonding point. But the generator has no earth ground connection. So this will essentially create a floating ground between the Chargeverter and the battery system. My question is should the Chargeverter external case be grounded to the battery rack ground lugs? Or should this remain floating?
November 19, 2024 7:13 pm
Does the generator have a neutral frame ground?
November 19, 2024 7:48 pm
Not an expert on this, but the chargeverter doesn't utilize the neutral and if the chargeverter is isolated from the rest of your system and you are only connected directly to the batteries with DC only then during a ground fault between the generator and chargeverter the voltage would seek neutral to trip the generator breaker. Most newer small generators are neutral frame grounded and if so then I think you are covered. The earth ground on the generator would only really be need for power surge protection like lightning. The battery rack seems to be covered by the neutral bond on your main panel. AC always seeks the source not the ground.
This post was modified 2 months ago 2 times by Ron
Joel Brodeur reacted
Topic starter
November 20, 2024 2:04 pm
The generator does not have have the neutral conductor bonded to ground. It has a ground connection terminal, which is connected to the ground pin of the 120V receptacle, but there is no continuity between the ground and neutral receptacle pins.
This is a small generator that outputs 120VAC only, using a standard NEMA 5-20 outlet. The Chargeverter may not use the neutral conductor of the 4-wire L14-30 connection for 240VAC operation, but it does use the neutral of a 120V input, which is supposed to be wired to one of the L14-30 hot/line pins instead of the neutral pin. So a "standard" L14-30 to NEMA 5-20 adapter plug will not work for this application since they apparently just tie the two hot/line pins together and connect ground-ground and neutral-neutral. I'll be making my own adapter to follow the wiring for 120VAC shown in the Chargeverter manual.
The Chargeverter case is tied to the ground pin of the L14-30 connector. Neutral-ground is not bonded anywhere. A short to neutral condition should cause the breaker at the generator to trip. However, a short to ground in this system could create a hot-skin condition at the Chargeverter without tripping the breaker, which seems like a bad idea. I'm going to remove one of the Chargeverter case screws and use it to connect a bonding jumper to the battery rack equipment ground, unless someone from EG4 speaks up here and says that's a bad idea.
November 21, 2024 1:42 pm
Why wouldn't you just bond the neutral on the generator? A ground fault has to find neutral to trip the breaker. Your battery rack would be covered by your main panel bond.
November 21, 2024 1:45 pm
Even though your generator has a ground to earth terminal it may also be bonded from ground to neutral. Usually a wire inside the case.
November 21, 2024 3:02 pm
I am not a grounding expert so take all of as more of a question:
I have noticed a mixed bag in NG bonding with generators. I always double check - with the gen off, disconnected from everything, and battery disconnected (I am paranoid), check resistance between neutral and ground lug. if there is continuity the gen is NG bonded, if open then not bonded. The OP appears to have checked this -
but there is no continuity between the ground and neutral receptacle pins
So, if I am understanding the OP, the Batteries are bonded via the case to the inverter, the chargeverter is bonded to the gen via the plug. But there is no bond between the chargeverter and the batteries? Therefore, Gen and Chargeverter are ungrounded. Even if the Gen had NG bond, they would both be ungrounded.
Wouldn't a bond from Gen to house grounding system work?
Not trying to muddy the water just trying to wrap my head around is as I am thinking about a chargeverter for emergencies.
Thanks,
JB
Sometimes the easiest solution is the best solution.
Sometimes not.
November 21, 2024 4:26 pm
Joel, Bonding means neutral connected to ground. In a ground fault situation you want the current to follow through the ground wire until it finds the neutral completing the circuit and overheating and tripping the breaker. Earth grounds are really only for overloads like lightning.
The source of the power/disconnect/breaker should always be the only Neutral bond. That is the only way for a ground fault to trip the breaker. You also can never have more than 1 NGB in any circuit or you create a loop. AC flows to source not ground.
November 21, 2024 4:50 pm
That makes sense. Thank you.
To further the question, for touch potential, wouldn't you want the gen and chargverter to be at the same potential as the inverter and house?
So, wouldn't that mean that the gen or the chargeverter ground should be tied back to the house ground at some place? And would not want the gen to be NGB since that would add a NGB to the already existing NGB of the house?
I am definitely not a sparky so just trying to figure this out. 🙂
JB
Sometimes the easiest solution is the best solution.
Sometimes not.
Topic starter
November 21, 2024 4:58 pm
Thank you both for your comments. Joel is correct that what I wrote earlier means there is no NG bond at the generator - it was checked with a meter. I suppose I could add that at the generator, but that seems weird to do - I don't know if that might cause some problem with the generator design, but mostly because the Chargeverter is using one of the L14-30 line conductors to convey the 120V neutral. Also, if I later switch to a larger 240VAC generator for this application, whether or not it has an NG bond will be irrelevant. As Ron already pointed out, the Chargeverter doesn't use the L14-30 neutral conductor at all - its input cable has only 3 pins - L1, L2, and ground. So with a 240V generator I'd be back to a floating ground in the Chargeverter-generator system.
I can ground this system at either the generator or at the Chargeverter, doesn't matter. I prefer to do it at the Chargeverter only because it will be permanently mounted near my battery rack indoors, while the portable generator will only come out of storage when it might be needed. So grounding the Chargeverter case will be a permanent connection, rather than fiddling with a ground jumper every time I connect the generator outside. FWIW, the generator will be sitting very near where the 18Kpv is mounted on an outside wall, so it would be easy enough for me to drop a ground pigtail out of the 18Kpv cable box and leave it hanging for whenever it's needed. So either way, this is going to be grounded to the inverter-battery system which has an NG bond 40 feet away at the main panel.
November 21, 2024 6:08 pm
a 120v circuit needs the neutral to complete the circuit. A 240 volt does not. For the inverter to function correctly on 120v you need to bond at the generator. A ground fault at our before the inverter needs the ground to be able to return to the source neutral.
If the chargeverter is set up to connect directly to the batteries you have 2 sources of power to the batteries. The first source is the generator which needs a neutral bond and the main panel through the inverter all the way to the battery rack is the outher circuit. Both need a neutral ground as they are separate paths
