Can the UH8 work with 2 port valves and provide a volt free boiler enable switch? November 28, 2018 06:24 Updated Follow Yes. The boiler enable on the UH8 is volt free or you could use the orange and grey end switch of your valves. Related articles The output is volt free what does this mean? How do radiator zones on the Heatmiser wiring centres enable the boiler? What does Ls and Lr mean? How do I wire a manifold valve to my UH4 What cables do I need to connect my thermostats?