The expandable UPZC Series of zone controls from Grundfos Pumps is designed to manage circulator and boiler control in residential hydronic heating systems. The non-networked devices control up to six heating zones, and can be coupled together in various configurations to accommodate any application. The zone relay control connects to standard thermostats using either two or three wires. The optional third wire provides 24-volts AC to thermostats that require external power. The UPZC operates in a cold-start configuration with a call for heat from a thermostat. 800/921-7867; us.grundfos.com.