Actuators for Chilled Water Valve - These chilled water actuators control the flow rate for a chilled water system in a data center. There are various sequences of operations for chilled water systems and the sequence of operations is usually always different from one chiller plant to another chiller plant.

Actuators for Chilled Water Valve | DDC Commercial Systems

It depends on the components in the loop, the application the chilled water system is supplying cold water for, and what the demand of the system requires for the chiller plant. Some chilled water valves control two-way valves while others control three-way valves. A three-way valve can either be a mixing valve or a diverting valve but the actuators control the flow in either type of application. Other actuators modulate a valve based on demand. The actuator usually receives its command for the position for control from the DDC system or another type of control system.

The actuator usually receives its command for the position for control from the DDC system or another type of control system. In this case, these actuators are controlled by DDC. In the sequence of operation, the chiller plant will have a valve line-up usually in a valve matrix that was compiled by the original design engineer and this valve matrix shows the default position of the valves which are controlled by the actuators. Some applications in the piping that are controlled by the actuators include:

Actuators for Chilled Water Valve - Applications

• Primary – Secondary system where a primary loop is attached to a secondary loop via a decoupling loop. The primary loop is constant volume while the secondary loop is variable capacity.
• Variable Flow Primary loop only has one loop and the flow varies according to demand and pressure set point. For better flow control a variable flow primary loop system will have a bypass loop for better control of loop pressures. In the bypass and on the loads you will find actuators that control chilled water flow.
• Other applications where the control actuators can be found are in a free cooling sequence of operation where the chillers are shut down and bypassed completely to take advantage of free cooling when the temperatures are optimal for a free cooling application.

The actuators control the amount of chilled water going to the evaporator coil by automatically moving a valve. Chilled water systems provide air conditioning typically too large buildings. These air conditioning systems, or cooling systems, use cold water which is piped through a coil in a large air handler. The control actuator can modulate allowing only a certain amount of cold water to reach the evaporator coil.

Actuators for Chilled Water Valve - Economics

Depending on the cooling supply air setpoint will depend on where the control actuator will modulate the valve in the piping. Chilled water systems offer an economical way of cooling large commercial buildings. These air conditioning systems are a great alternative to direct expansion constant volume air conditioning systems. There are constant volume air conditioning systems that use chilled water but most constant volume air conditioning systems use direct expansion. Many chilled water systems are used for VAV systems where there are many zones on a large air handling unit. Both constant volume air conditioning systems and VAV zoning air conditioning systems can be either direct expansion or chilled water systems.

Actuators for Chilled Water Valve

Control actuators, in chilled water systems, offer control of the flow of chilled water which is routed to the evaporator coil. This photo shows a new installation of a control actuator and piping. The control actuator is modulating and on a three-way valve. The valve will modulate depending on the supply air temperature of the air handling unit which provides air-conditioned air to the space. The piping was installed with several unions so that if the valve malfunctioned it could easily be replaced.

The air handler being served by this control actuator and piping serves a large commercial kitchen. In the summer it is critical for the air conditioning system to remove the heat produced by the ovens and grills so that workers remain safe and comfortable. The air conditioning increases the worker’s productivity and morale. The piping feeds chilled water to an evaporator coil inside the air handler. The blower in the air handler moves the air from the kitchen across the coil where the heat in the air is absorbed into the coil and the water. The conditioned air is then ducted back into the kitchen at a cooler temperature than when it left the kitchen through the return duct.

Conclusion

Chilled water actuators give chilled water systems the ability to precisely control chilled water systems and precision control results in an added efficiency of the chilled water system. The chilled water actuators are typically controlled by the building automation or DDC system that gives the chilled water actuators added control and precision control.

Actuators for Chilled Water Valve

Resource: The Fundamentals of HVAC Direct Digital Control