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 What is the replacement for the UH3 Wiring Centre? Can the UH8 work with 2 port valves and provide a volt free boiler enable switch? I need to put more than 8 thermostats on one manifold Can I use my Heatmiser controller for an Immersion? What thermostats will work with the UH8-RF V2 or the UH8-RF