What is the correct way to wire a midpoint transformer (Solar Edge) and connect sub panel to main

[hipringles]

I will be setting up 2x Growatt 5k's for a backup system. I plan to basically have a setup similar to David Poz does here, then connecting this subpanel to a lockout switch protected breaker on my main panel.

However both on David's video and a few others, people say the way this transformer is wired is dangerous in the case of a fault. What are the alternatives?

Additionally, using the transfer, what is the correct way to connect to the main? Is it just as obvious as connecting L1/L2 to the breaker, then the neutrals/ground like a normal generator hookup?

thanks!

 

[automatikdonn]

The issue is switching the neutral and hot wires separately. All current conductors should be on the same breaker, so if the load is too high everything is switched at the same time. You could bond breakers together, or ideally use something like a 3 phase breaker.

As for genset hookup it depends on how you are connected. Full off grid or grid tie. The most important thing is to remember that any electrical system can only have one neutral bond to ground.

I am not an electrician, so please research the topics, talk to an electrician and read your local code.

 

[tntneave]

I would like to bump this thread. I am a newbie and have been considering three 5000 ES Growatts to power the offgrid system I am working on designing. I like the Solaredge midpoint transformers as they allow the ability to adjust the legs based on the demand per leg. I was thinking two of the Solaredge Midpoint transformers would provide some redundancy as well as capacity cushion in the off chance I exceed 5kw of 120 power demands. I have heard David Poz and others mention a problem with how he wired his to the panel. The post above makes sense that the double pole breaker connection (like David Poz used) to connect the auto transformer to the panel does not include the neutral in the breaker protection. Is that a critical problem? Can anyone help explain what the safe way to wire two of these Solaredge auto transformers would be?

 

[tntneave]

I am no electrician and am just learning about how all of these offgrid solution work, but would it be possible to have the output lines from the midpoint transformer terminate to a second load center that distributes only 120 loads? It seems like that way if the transformer circuit powering the transformer faults or trips that 120 load center would lose all power while allowing the inverter to still provide power to the 240v load center powered by the inverter? Would this work, or does the midpoint transformer require L1, L2 and N return to the same load center it receives its L1, L2 from?

 

[Struc]

This thread deals with your questions in detail:

Design Review - Growatt SPF 5000 ES Grid Backup & Neutral Bonding

This seems to be a very popular setup, but thus far, nobody seems to have cracked the DaVinci code of safely using a Growatt SPF 5000 ES with a SEAUTO-TX-5000 Auto-Transformer and using the AC input of the Growatt in a 'utility first' configuration. Signature Solar has posted a schematic that...

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