Arg, for the THIRD TIME... lol... My date was estimated, originally, to be (Mid Fed to Late Feb)... Which was before the chip-MFG, (Bitmine) announced they had delayed shipping chips to everyone. (Which included AMT's order of chips.)
The 1.0THs miners run at 1065W at the wall, running at 1.0THs, at
chip-voltage... That would only be about 1278W for a 1.2THs, which a 1200W PSU can deliver. 1200W @ 80% efficiency will draw 1440W at the wall. It still delivers 1200W, but it consumes 20% additional power, to provide that 1200W. (Eg, my 750W PSU pulls up to 900W continuous power at the wall. Though, that is right at the PSU's maximum ability. Borderline operation at that point.)
However, that being said...
The 1.0THs miner from Bitmine.ch pulled 1065W at the wall, but the PSU was only delivering 852W to the boards, even less to the chips themselves. So, I would assume they were using a 1000W PSU or 1200W PSU. Are you still confusing chip-consumption with unit-consumption?
The 1500W PSU should be able to handle the 1.5THs worth of boards. Just not in high turbo mode. It should be able to handle 1.5THs in normal power, whatever they set as the default normal power for the unit. Running the 1.5THs unit at 1.2THs would be getting into the low-power mode, and the PSU should handle that without stress. Might be able to do 1.2THs under 900W at the wall, with the 1.5THs unit.
1500w psu 100a on 12v rail will blow 6 modules reaching 1.2t+ Just save this hassle in your "trial and error development process" and to your customers later . And tell them to change their fuses in their homes 
The 1.0THs miners run at 1065W at the wall, running at 1.0THs, at
chip-voltage... That would only be about 1278W for a 1.2THs, which a 1200W PSU can deliver. 1200W @ 80% efficiency will draw 1440W at the wall. It still delivers 1200W, but it consumes 20% additional power, to provide that 1200W. (Eg, my 750W PSU pulls up to 900W continuous power at the wall. Though, that is right at the PSU's maximum ability. Borderline operation at that point.)However, that being said...
The 1.0THs miner from Bitmine.ch pulled 1065W at the wall, but the PSU was only delivering 852W to the boards, even less to the chips themselves. So, I would assume they were using a 1000W PSU or 1200W PSU. Are you still confusing chip-consumption with unit-consumption?
The 1500W PSU should be able to handle the 1.5THs worth of boards. Just not in high turbo mode. It should be able to handle 1.5THs in normal power, whatever they set as the default normal power for the unit. Running the 1.5THs unit at 1.2THs would be getting into the low-power mode, and the PSU should handle that without stress. Might be able to do 1.2THs under 900W at the wall, with the 1.5THs unit.