In most residential and some commercial systems, each room will
normally have its own circuit of tubing, or possibly several circuits.
Circuits of tubing are connected to factory-made radiant distribution
manifolds, which are typically hidden within walls or under floors,
possibly inside access cabinets or behind access hatches.
Radiant distribution manifolds often include fine balancing and flow control valves for each circuit. The fine balancing valves allow installers to adjust the flow-rate of fluid to each circuit to match the heating or cooling loads for each space. Setting these customized flow-rates can improve system response time, comfort and efficiency. Radiant designers will calculate exactly which flow-rate should be used for each area.
For room-by-room zoning, low-power manifold valve actuators, also known as powerheads or telestats, electrically open and close manifold flow control valves, based on heating or cooling demand signals from local thermostats or other zone controls. Many such actuators utilize a special thermal wax inside a small cylinder, to gently and silently open the manifold valve when called on. These efficient, reliable actuators often draw less than 4 VA (Volt-Amps / Watts) of power when operating, and allow for room-by-room zoning with no additional piping or pipe connections, just some additional wiring. Room-by-room zoning is the most comfortable and efficient strategy.