Product Description Taco Zone Valve Controls work with two-, three-, or four-wire zone valves. All are fuse protected; it also includes two isolated end switches and a built-in priority switch. The contractor friendly PC board layout eliminates incorrect wiring and the unfinished look of conventional zone valve installations. The sturdy screw connections add even more reliability, while the external indicator lights provide instant diagnostic feedback to reduce installation time and troubleshooting. For those larger jobs, the -EXP controls can be expanded up to 120 zones with priority. All Taco Zone Valve Controls are UL listed and are available in three, four, five, and six zones. External Diagnostics: The indicator lights show full functionality of the products wired to the zone valve control. The green light indicates power is connected. When the thermostat calls for heat, both the appropriate zone valve and yellow indicating light are energized. From the Manufacturer Taco Zone Valve Controls simplify the wiring nightmare. They work with 2-, 3- or 4-wire zone valves and their easy-to-follow PC board layout eliminates the problems caused by incorrect wiring and the “unfinished” look of conventional zone valve installations. External indictor lights give you instant diagnostic feedback and reduce installation time. Use them combined with Taco Zone Valves and Thermostats to maximize system performance and dependability.