Low volt programmable master thermostat for floor heating over 15 A. This system is specially designed for large floor heating applications exceeding 15 A. A floor heating area exceeding 15 A is separated into zones with a linked unit responsible for heating each zone. All linked units are controlled by a master thermostat responsible for settings/programming of the entire floor. No settings dial. Settings controlled by master means units can be installed anywhere. ON/STANBY switch enables unit's heating area to be shut down independently of other heating areas. Built-in GFCI/EGFPD with test light. No need to buy separate safety cutoff.