In a hydronic heating system, what does a 3-way valve do?

In a hydronic heating system, what does a 3-way valve do?

• A. Directs air flow in the duct system
• B. Directs flow of hot water between the boiler, domestic hot water coil, and load as required
• C. Mixes cold water with hot water to temper hot water
• D. Keeps boiler pressure constant

Answer: (B)

A three‑way valve in a hydronic heating system is used to route hot water among multiple circuits depending on demand. With three ports, it can direct boiler water to the space heating load, to a domestic hot water coil, or switch between these paths as needed. This lets the system serve space heating and domestic hot water efficiently without separate pumps for each circuit, and it can also provide a bypass or mixing path to maintain proper temperatures. It’s not responsible for directing air in the duct system, nor is its primary job to keep boiler pressure constant, and while some three‑way valves can temper water, the typical function described here is directing flow between the boiler, the load, and the domestic hot water coil.

A three‑way valve in a hydronic heating system is used to route hot water among multiple circuits depending on demand. With three ports, it can direct boiler water to the space heating load, to a domestic hot water coil, or switch between these paths as needed. This lets the system serve space heating and domestic hot water efficiently without separate pumps for each circuit, and it can also provide a bypass or mixing path to maintain proper temperatures. It’s not responsible for directing air in the duct system, nor is its primary job to keep boiler pressure constant, and while some three‑way valves can temper water, the typical function described here is directing flow between the boiler, the load, and the domestic hot water coil.