The output is volt free what does this mean? November 30, 2018 02:49 Updated Follow This means the output is a switch, we haven't put a voltage on this switch so you can use any voltage you wish up to 230v AC Related articles Can the UH8 work with 2 port valves and provide a volt free boiler enable switch? What is the replacement for the UH3 Wiring Centre? Using the Temperature Hold Function I need to put more than 8 thermostats on one manifold Can I use my Heatmiser controller for an Immersion?