In piping a water coil, why should the supply line be connected to the bottom rather than to the top of the coil?

In piping a water coil, why should the supply line be connected to the bottom rather than to the top of the coil?

• A. To make installation of the coil easier
• B. To prevent freeze-up of the coil
• C. To prevent reverse flow
• D. To help the air to vent out the top of the coil

Answer: (D)

Air removal and proper filling are the key ideas here. Air tends to collect at the highest point in a coil, so feeding water from the bottom forces water to push upward and carry any trapped air toward the top where a vent is located. The air can then escape, allowing the coil to fill completely and water to circulate freely. If you fed from the top, air would be trapped at the bottom and hinder filling and flow. This bottom-in, top-vent setup is all about letting air escape to avoid air pockets that disrupt circulation and heat transfer.

Air removal and proper filling are the key ideas here. Air tends to collect at the highest point in a coil, so feeding water from the bottom forces water to push upward and carry any trapped air toward the top where a vent is located. The air can then escape, allowing the coil to fill completely and water to circulate freely. If you fed from the top, air would be trapped at the bottom and hinder filling and flow. This bottom-in, top-vent setup is all about letting air escape to avoid air pockets that disrupt circulation and heat transfer.