Harper taught me how to connect the following and it's working perfectly. From (related to) the post Connecting a Pseudo-Neutral to Pig Tail of GFCI where I only have 240v black and red line of the US ac power in the Philippines and the Siemens GFCI has 120v circuitry. So Harper suggested an autotransformer with neutral to power it and worked flawlessly.
Harper, etc. Can I add the following to the above?
I mean the Neutral and Ground will be connected to the autotransformer centertapped output with the 2 Hot connected to the autotransformer input? This is to avoid surges damaging the sensitive GFCI circuitry (the internal MOV may not be enough).
Note I can easily use the Siemens First Surge by simply shorting the ground/neutral leads and not connecting it to anything and just connecting the two hots. No alarm sounded and the Siemens First Surge works without error.
But this won't offer the L-N protection mode with lower VPR (600) instead of L-L of 900v VPR (related to Let-through voltage). Hence I need to use 120v protection mode too by connecting the neutral/ground of the Siemens First Surge to the autotransformer neutral lead (which powers the Siemens GFCI breaker circuitry).