What component controls the flow rate of water passing through a heating coil in an air handler?

The balancing valve on the heating loop is the component responsible for controlling the flow rate of water passing through a heating coil in an air handler. Its primary function is to ensure that the water flow is adjusted to achieve the desired temperature and uniform distribution of heating throughout the system. By regulating the flow, the balancing valve helps maintain efficiency and comfort within the system, preventing issues like overheating or insufficient heating in different areas.

In a hydronic heating system, the balancing valve allows technicians to fine-tune the flow of water based on the specific needs of the heating coil and the overall system. This adjustment can be especially important in larger or more complex systems where flow rates might vary due to resistance in various components or long pipe runs.

Other components, such as aquastats and mixing valves, serve different functions. An aquastat is designed to monitor and control the temperature of the water in the heating system rather than the flow rate. Mixing valves can adjust temperatures before water enters the heating coil or for domestic hot water systems, yet they do not specifically control flow rates within the heating loop as the balancing valve does.