Let's set the record straight, the 80A 3 pole MCB breaker on the EPS Out is FACTORY INSTALLED AT GROWATT period. Growatt have the unit UL tested to UL 1741 standard and is clearly listed on the label pasted on the left side of the chassis.
I've posted links to Eaton, one of the world's larger breaker manufacturer article that explains the function and safety of a breaker. The EPS output provides both L1-L2 (120V/240V) pass through directly from the 16K Critical Load to the EPS input of the Growatt autotransformer. If the load are balanced prior at the 16K, the Neutral leg of the transformer will not used and just pass through. Any unbalanced 120V EPS load will enter the transformer and the return current carried by the generated Neutral wire back to the Transformer. The function of the breaker is to protect any ground fault, arc fault and overcurrent and trip the breaker. Bear in mind, the generated Neutral wire does not carry any Voltage but it does carry the return current. If L1/L2 is for example drawing 1.5KW/120V=12.5A, if you use a clamp meter on the neutral, it will show 12.5A, same current as the L1/L2 12.5A. If for any reason the transformer generated Neutral wire is at fault, all 3 pole will trip at the same time to prevent the connected EPS LOAD panel from being energized with 240V that will FRIED ALL 120V APPLIANCE. Growatt is the ONLY autotransformer that provide a 80A 3 pole MCB breaker for EPS output protection. The Victron Autotransformer DOES NOT, it only provide a 2 pole MCB breaker at the Input leg of the autotransformer.
The L-L leg of the Growatt transformer in it's original form uses a pair of contactors to provide the AST (Auto-Transfer-Switch) for the AC Grid input and the Inverter EPS output. For my application, the AST function are not required as I will be using it off-grid without AC Grid input. The unit is rated by Growatt to provide 11.4KW 48A passthrough. The wired install at the factory are UF-B 8 AWG wire rated for 40A at 60C and 50A at 75C. At 48A*240=11.5KW. The mod that I've completed and tested is to remove the pair of ABB Contactor and replaced with a 2 pole MB breaker rated at 80A (to match the EPS output 3 pole MCB breaker) to protect the transformer from any faulted output of the 16K EPS LOAD output and rewire between the pair of breaker with THHN 4 AWG wire that are rated 95A at 75C ~ 95A*240V=22.8KW, restricted to 80A*240V=19.2KW due to the 80A rated MCB breakers install at the factory and my mod.
I will not discuss any further about about the function of circuit breakers, it waste of everyone's bandwidth. It's a non starter.
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