Make Grainger your first choice for hydronic controls compatible with your hydronic heating and cooling systems. Air and steam vents automatically purge extraneous air and other gases from your heating system and allow it to run more efficiently. Our assortment of aquastat relays include immersion controllers, universal electronic, multi-zone and dual aquastat controllers with a variety of temperature ranges. Select a heat exchanger that can transfer heat water to water, oil to water, and R22 to water. We have float and thermostatic steam traps that help maximize the removal of latent heat for more efficient system operation. Zone valves help you control the flow of hot water from your boiler system and allow you to control the heat in different areas of the building.