Engineered Comfort - Quality Fan Coil Units | Vertical Hi-Rise | Underfloor




	Frequently Asked Questions Fan Coil Units What is Nailor’s typical sequence of operation for fan coils? COOLING OPERATION –– On a call for cooling, the chilled water valve will begin to modulate open. As the cooling demand increases, the valve will continue to open until the discharge air temperature reaches 52°F. When the discharge air reaches 52°F. the fan will begin to modulate toward the maximum cooling fan airflow as the chilled water valve continues to modulate open. This process will continue until the fan reaches the cooling maximum airflow and the chilled water valve reaches the maximum allowed water flow. DEAD BAND OPERATION –– With no demand in the space, there will be no call for heating or cooling. The fan will be at dead band airflow. The chilled water valve will be off. The hot water valve or the electric heater relay will be off. HEATING OPERATION –– On a call for heating, the heating valve shall open or the heating relay shall close to activate the heater. The fan shall begin to modulate from the dead band airflow toward the maximum heating airflow. As the demand for heat increases, the fan shall continue to modulate upward until it reaches the maximum heating airflow. For 2 stage heating, there will be 2 defined heating airflows, first stage heating airflow and maximum heating airflow. When the demand exceeds the first stage heating condition, the second stage heating will be activated and the fan will continue to modulate toward the maximum heating airflow. What is the maximum water coil face velocity? Chilled Water Coil: 400 - 500 fpm –– higher velocities will result in water blow-off. Hot Water Coil: 400 - 800 fpm –– higher velocities are permissible, but air pressure drop will probably be excessive. What is the recommended water velocity through water coil? Chilled Water Coil –– 2 - 4 fps –– Velocity above 8 fps will lead to premature coil failure. Hot Water Coil –– 0.8 - 2 fps –– Velocity above 8 fps will lead to premature coil failure, velocity below 0.8 will greatly reduce performance. What is the recommended water pressure drop through a coil? Chilled Water Coil –– Water Pressure Drop: 3 - 10 ft w.c. –– Max allowable depends on pump. Hot Water Coil –– Water Pressure Drop: .01 - 10 ft w.c. –– Max allowable depends on pump. What is the recommended water temperature drop or rise? Chilled Water Coil –– 8 - 15°F water temperature rise or as specified by customer. Chilled water coils generally require higher water velocities than hot water coils to achieve optimum performance. This is especially true when using glycol mixtures. Hot Water Coil –– 20 - 30°F water temperature drop or as specified by customer. WTD's less than 20°F indicate more flow than necessary. Why would we use a dual point connection instead of a single point connection? Single point connections are required on the vast majority of terminal units and fan coils in the United States. This is because the power provided to the buildings has typical connections available for use on motors (120, 208, 230, 277) that are common in our industry. However, in Canada, this is frequently not the case. Power supplies of 600 VAC with single phase 347 VAC using the neutral and one power leg do not provide voltages that typical motors can use. Therefore, they require dual power supplies, one for the heater and another for the motor. Electrical codes require that the power supplies be separated and that they both have disconnect switches that will not allow power to be present from either source if the control box is open.

Frequently Asked Questions

Fan Coil Units