I'm working with Wirsbo / Uponor zone control module that has a solid state switching output "ES" stated to be totally isolated. Although I see 5 millivolts between leads. The new Weil-McLain high efficiency boiler requires "dry contact" signal , they certainly don't want 24V. what about 5 millivolts? do I need to add relay or not ? Both manufactures pass the buck to the other and are not helpful.