In a gravity return system, circulation depends upon the

In a gravity return system, circulation depends upon the

• A. Temperature difference
• B. Difference between the weight of the hot and cold water
• C. Pump pressure
• D. Pipe diameters

Answer: (B)

Circulation in a gravity return system is driven by buoyancy from the density difference between hot and cold water. Hot water is less dense and tends to rise, while cold water is denser and tends to sink, creating a natural loop without a pump. The key factor is how much the hot and cold water weights differ, which directly sets the driving force for the circulation. A larger density (weight) difference strengthens the circulation, while a smaller difference weakens it. Temperature difference causes the density change, but the actual mover of the flow is that weight difference between the two streams. Pipe size and friction affect how freely the water can move, and a pump would override gravity, so they aren’t the primary cause of the circulation in this setup.

Circulation in a gravity return system is driven by buoyancy from the density difference between hot and cold water. Hot water is less dense and tends to rise, while cold water is denser and tends to sink, creating a natural loop without a pump. The key factor is how much the hot and cold water weights differ, which directly sets the driving force for the circulation. A larger density (weight) difference strengthens the circulation, while a smaller difference weakens it. Temperature difference causes the density change, but the actual mover of the flow is that weight difference between the two streams. Pipe size and friction affect how freely the water can move, and a pump would override gravity, so they aren’t the primary cause of the circulation in this setup.