Growatt 5000es - Simple protection from lost neutral?

[Mr-Sandman]

Yes I think there is. Where is the Neutral to ground bond for the circuits in your inverter panel going to come from if you don't provide that bond in the "Inverter Panel"? And since it's a common ground with the Main panel, that completes the circuit for the Autotransformer Neutral.

 

[Mr-Sandman]

I might be missing something here, I will be honest I don't have one of these 240v none split phase inverters. Mine is totally different, but I'm trying to think thru this also.

 

[Mr-Sandman]

I guess for grid pass thru to even work "with the Neutral not being passed thru the inverter", it's up to the autotransformer to provide 120v split phase even during pass thru.

 

[Mr-Sandman]

The issue with the AutoTransformer will be the bonded ground in this setup. It will try to balance the phases thru the common bonded ground. Not having a Neutral to Ground bond in the inverter panel I think would not be good. That's THE only bond all the circuits in that panel will have and is required I believe.

 

[justinjja]

My understanding is in the USA you only have 1 panel in a house with a ground - neutral bond.
All other panels must keep gnd and neutral separate for the ground to work.

This is done for the sake of the gnd, not the neutral.

 

[Mr-Sandman]

My understanding is in the USA you only have 1 panel in a house with a ground - neutral bond.
All other panels must keep gnd and neutral separate for the ground to work.

This is done for the sake of the gnd, not the neutral.

Well the issue is you aren't passing the Neutral to your inverter panel from your main panel because you don't have a "US" split phase inverter. It needs its on bond to ground since Neutral doesn't make it back to the main panel where there is a bond to ground.

 

[Mr-Sandman]

Again, I don't have a Growatt, mine is WAY different. But from my Schneider Installer manual on the subject of bonding.

System bonding for on-grid systems
The XW Pro does not switch or disconnect the AC neutral in any mode of operation, so even in invert (back-up) mode, the inverter load sub-panel neutral is bonded to ground by the utility grid system. It must not be grounded again in the inverter load sub-panel.

System bonding for off-grid systems
You must make the connection from neutral to ground in the inverter load subpanel or main distribution panel, as applicable.

The ISSUE for the Growatt and other 240v non-split phase inverters is, they do NOT pass Neutral from the main panel to the sub panel. You must treat them like an off grid system and provide the neutral to ground bond in the subpanel. Then that creates the issue with the Autotransformer having a path back to utility Neutral thru the common ground and circulating current from it balancing loads on the utility side of the inverter when in AC pass thru mode.

Simple answer you really shouldn't do AC utility pass thru on these inverters. They are OK off grid, other than the other issues already mentioned with using an autotransformer.

 

[Zwy]

Right I'm suggesting you don't bond the transformer neutral to ground.
Is there something wrong with that?

Yes

 

[FilterGuy]

My understanding is in the USA you only have 1 panel in a house with a ground - neutral bond.
All other panels must keep gnd and neutral separate for the ground to work.

This is done for the sake of the gnd, not the neutral.

Right I'm suggesting you don't bond the transformer neutral to ground.
Is there something wrong with that?

That results in a floating system. A floating system is reasonably safe in normal conditions but can cause odd equipment behaviors or failures. In addition, in the event of storms, the floating voltage can get high enough to be dangerous.




In addition, Bonding neutral to ground ensures the circuit does not float in relation to the earth. Way back in the days of Edison and Tesla, they found that letting systems float would create weird failures on equipment. Things like pitting on motor bearings would happen and in lightning storms, they would see large enough differentials to be very dangerous.....so they started grounding all systems. However, that created the problem of getting electrocuted due to connection to ground and a hot circuit. The first step to reduce this problem was to tie all non-conducting metals to ground. This ensured the breaker would blow as soon as a hot wire touched the non-conducting metal. However, if you touch hot and ground, you can still get electrocuted. Much more recently, the advent of RCDs or GFCIs were developed that can detect very low current faults and clear them before they can cause harm.

 

[Mr-Sandman]

Here's the best solution I've seen for these cheap Chinese 240V Non-Split phase inverters "Growatt 5000ES and others".

I personally would just replace them and get a good split phase inverter designed for US grid, but if you are heavily invested and want to even invest more in them, there maybe an option for you. Victron makes a "smart" autotransformer that solves most of the safety concerns if installed right.

Here's another thread with a good description of it and how it works: https://diysolarforum.com/threads/safe-grid-use-of-the-5000es-and-transformer.34121/post-429934