Marketing InformationTaco variable speed delta-T circulator's all-in-one design combines a microprocessor based variable speed differential controller with the reliability and convenience of our 00 cartridge circulators. Simply dial in the design delta-T of the system or zone (from 5 - 50 deg F) and then sit back and watch the circulator automatically adjust its performance to match the systems ideal Btu/hr output, while conserving energy and eliminating velocity noise.