The Archergas® Heating Standard produces a maximum head of just over 6 meters with a standard 1 1/2" threaded connection. As with all Archergas® circulators, it is fully ERP compliant with an impressive energy efficiency index rating of less than 0.20. The ST15 is a standalone heating circulator with 4 modes of control and a 130mm port to port size as well as a 5 year guarantee.