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Where does the Growatt SPF 5000 ES get its ground?

uzernaam

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If one were to simply connect a wire to the AC OUT ground terminal, it wouldn't make the wire a ground unless the terminal itself is wired internally to the chassis which is then wired to ground... or unless the AC OUT ground terminal gets its ground from the AC IN terminal, correct?

I would open the case and look inside, but that voids my warranty.

How does one provide a ground to the unit to pass on through the AC OUT ground terminal? In my situation I will not be using the AC IN, but I suspect I might need to connect ground to the AC IN terminal anyway?

Should I run a ground wire to the AC IN terminal, the AC OUT terminal, both, or neither?

Thanks!
 
I have not looked at the SPF 5000, but every inverter I have ever been able to get data on has the case, AC-in Ground , and AC out Ground tied together.
 
Forgive me if you have already checked and not found a clear answer, but a good first place to check with specific grounding questions is your inverter documentation. I believe this manual for the "Growatt SPF 5000 ES" corresponds to the inverter you have? If so, you may find the specifics of what you are looking for there (if Filterguy hasn't already answered your question in full).
 
I will not be using the AC IN,
This inverter does not create a Neutral-Ground Bond.

  • If the AC-in is never used, there will need to be a NG bond installed on the output of the inverter. This can be a simple connection between Ground and Neutral on the output.

  • If the AC-in is used with a generator without an NG-bond, an NG bond needs to be installed on the output of the inverter. This can be a simple connection between Ground and Neutral on the output.

  • If the AC-in is used with an independently derived power source, there needs to be a dynamic NG-bond established when not on grid power. (Examples of an independently derived power source is the Grid or shore power or a generator with an NG bond.)

    A dynamic NG bond can be implemented using the Dry Contact output.

EDIT: Changed diagram for more detail and less battery usage
1636339121025.png



1636337755402.png
 
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The Growatt SPF 5000 ES has 240VAC output, no Neutral.
If you are not using the AC in terminals and the system is completely isolated from the grid, you need to drive grounding rods and connect them to a circuit breaker panel ground bus powered by the Growatt.
You need to run a ground from the panel to the Growatt.

If you are using a transformer to create 120V split phase power, you need to bond the neutral and the ground in the panel where the transformer connects.
The ground connection in the transformer is a safety ground only, it is not bonded internally to the transformer neutral.
 
Desert_AIP: I have a ground rod just outside the building driven all the way into the ground. It has a 2 gauge cable attached coming inside to the ground bus on the breaker panel.

The inverter has AC IN and AC OUT. I saw a video online which shows the internals; the ground on the AC IN/OUT are both wired straight to chassis. I went ahead and ran 6 gauge to both of these terminals and connected it to the ground bus in the panel.

I powered up the inverter with only the battery (no solar or AC connected) and waited for the output to turn on. I set at 240V and 60Hz, then measured voltages on the two hot buses: referenced to neutral I get 120 volts on each. Referenced to ground, I get 100V and 140V.

My fear is that if there is any kind of DC offset on the output, it would appear as a dead short to ground, although I also recognize the possibility that this offset will vanish harmlessly once I drive in the bonding screw connecting ground to neutral.

Filterguy: There is no "neutral" on the output. Just two hot legs that make 240V relative to each other. I am concerned that if I ground the center tap on the autotransformer, the inverter might "see" a ground at low-frequency/DC on an output terminal and go into a fault condition or cause damage?


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There's a robust discussion about neutral bonding and how to deal with loss of neutral here.

 
Pictures:
Observations
You aren't supposed to run sheathed cable (Romex) through conduit. It can't properly dissipate heat.

You should not run the PV wires in the same conduit as the AC output.

Also, you have the AC input to the panel running through a CB, but you hardwired the transformer to the bus bars.
The transformer has no protection of its own.

 
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I have less than 10 feet of romex inside the conduit. Above the ceiling, it goes through grommets and runs across the attic. As far as heat, I'm really not worried about it in this situation. If it's required that I use THHN wiring, then I would have to splice into my underground-burial cable (which runs to the shed) to convert it to THHN for running inside conduit. The romex supplies 25 watts of LED lights on one circuit, 2 garage receptacles on another, and a shed receptacle on the 3rd. I'm using yellow 12 gauage on both receptacle circuits.

What problems can running the DC wires in the same tube with an AC circuit cause? Will it cause inductance across circuits?

Why does the transformer need "protection?" If I put the trans on its own breaker, when it breaks it causes a flying neutral potentially delivering 240V to my 120V circuits because of load/phase imbalance. If the transformer itself becomes a fault (short circuit) then the breaker which feeds power to the panel will go off and protect everything. Even if this puts my transformer at risk, I'd rather fry it than half of the equipment plugged in to the system.

I want to be sure everything is done right before I start turning things on and I'm just sharing my thought process. I hope no one thinks I'm trying to argue the points they make.
 
The NEC has been updated to clarify this one:
"You should not run the PV wires in the same conduit as the AC output."

If all the wires are part of the same PV system, and they all have the same temperature and voltage ratings (of the highest voltage conductor), they can be colocated in the same conduit.
You couldn't run a grid AC circuit in the same conduit with the PV.
But this looks ok.

I think the romex is still an issue.
I'd look at the insulation markings on the conductors inside the romex.
You might be able to just remove the sheathing and run the wires through the conduit.

The only way to kill power to the transformer is to kill the input breaker to the entire panel.

The "rules" aren't written for when everything goes right and works.
The safety rules are often written in blood based on stuff that went badly in the past.
 
Hi Guys,
Hopefully this thread is still active and my question is relevant to the neutral ground bond discussion. I assembled an off-grid Growatt 5000 ES/autotransformer system powered by a 3.7 kW PV array and 48V battery. The inverter/autotransformer outputs 240V/120V but when I bond the neutral to ground in my panel, the Growatt faults with error code 51 (overcurrent or surge). Removing the bond fixes the fault, however, both of my EV chargers (Juicebox and Tesla universal charger) will not operate. I suspect this is because of the missing N-G bond.

I've attached a schematic and photo. Any help is greatly appreciated!Off grid EV charger wiring.png
 

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