You are not understanding, the square wave is not allowing the pump to turn and it is appearing to the UPS that it is an overload. The pump is not truly overloading the UPS. It's not the size of the pump or the UPS that is the problem, it is the incompatibility between the pump and the square sine wave. It's the same problem, just different symptons between the two brands of pumps. Simply buying a larger UPS is not going to fix it.
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