Taco Variable Speed Delta-T Circulator’s all-in-one design combines a microprocessor based variablespeeddifferentialcontrollerwiththereliabilityandconvenienceofour00® Cartridge Circulators. Simply dial in the design Delta-T of the system or zone (from 5 – 50°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.