Advanced valve actuation system with integral freeze protection
A valve and actuator assembly includes a valve to control a flow of liquid into a coil, and an actuator to control the valve. The assembly includes a first temperature sensor to sense the temperature of liquid flowing through the valve, a second temperature sensor to sense the temperature of air surrounding the coil, and a flow meter to measure a flow rate of liquid through the valve. The actuator includes a module that receives data from the first and second temperature sensors and from the flow meter, and determines, based on data received from the flow meter and temperature sensors, a likelihood that the liquid in the coil will freeze. The actuator operates the valve to allow a minimum flow of the liquid through the valve and coil during a potential freeze condition. The minimum flow is sufficient to prevent the liquid in the coil from freezing.
1. An HVAC valve and actuator assembly with integral freeze protection, the assembly comprising:
a valve configured to control a flow of water or a water mixture into a water coil;
a valve actuator configured to control opening and closing of the valve;
a first temperature sensor configured to sense the temperature of the water or water mixture flowing through the valve;
a second temperature sensor configured to sense the temperature of air surrounding the water coil;
a flow meter configured to measure a flow rate of the water or water mixture through the valve;
wherein the valve actuator includes a control module configured to receive data from the first and second temperature sensors and from the flow meter, and further configured to determine, based on data received from the flow meter and first and second temperature sensors, a likelihood that the water or water mixture in the water coil will freeze; and
wherein the valve actuator operates the valve to allow a minimum flow of the water or water mixture through the valve and water coil sufficient to prevent the water or water mixture in the water coil from freezing.
2. The HVAC valve and actuator assembly of claim 1 , wherein the valve includes a throttling plug disposed in a flow passage of the valve, the throttle plug moveable within the valve to control the flow of water or water mixture in the flow passage.
3. The HVAC valve and actuator assembly of claim 1 , wherein the valve actuator comprises:
a motor and geartrain coupled to the throttling plug by a linkage assembly; and
a circuit board having control circuitry to regulate operation of the motor and geartrain, and communications circuitry to enable the actuator to communicate with a building management system via a serial communications bus.
4. The HVAC valve and actuator assembly of claim 1 , wherein the valve actuator is configured to operate the valve as either a pressure-independent valve or a pressure-dependent valve.
5. The HVAC valve and actuator assembly of claim 4 , wherein the valve actuator operates the valve as a pressure-independent valve, and wherein the pressure-independent valve has a minimum flow rate to prevent a freeze condition in the water coil, and a maximum flow rate over a defined differential pressure range.
6. The HVAC valve and actuator assembly of claim 4 , wherein the valve actuator is configured to operate the valve as either a pressure-independent valve or a pressure-dependent valve by the setting of a jumper switch.
7. The HVAC valve and actuator assembly of claim 1 , wherein the flow meter comprises differential pressure sensors coupled to the valve and configured to measure a pressure drop across the valve.
8. The HVAC valve and actuator assembly of claim 7 , wherein the differential pressure sensors comprise one of venture tube sensors, orifice plate sensors, pitot tube sensors, flow tube sensors, flow nozzle sensors, target sensors, elbow tap sensors, annubar sensors, v-cone sensor, and rotameter sensors.
9. The HVAC valve and actuator assembly of claim 1 , wherein the flow meter comprises mass flow sensors coupled to the valve and configured to measure a mass flow rate of water or water mixture through the valve.
10. The HVAC valve and actuator assembly of claim 9 , wherein the mass flow sensors comprise one of coriolis sensors, thermal sensors, and calorimeter sensors.
11. The HVAC valve and actuator assembly of claim 1 , wherein the flow meter comprises at least one velocity sensor coupled to the valve and configured to measure a volumetric flow rate of water or water mixture through the valve.
12. The HVAC valve and actuator assembly of claim 11 , wherein the velocity sensors comprise one of a turbine sensor, a vortex shedding sensor, an exchange sensor, an electromagnetic sensor, an ultrasonic sensor, a swirl sensor, a transit-time sensor, a Doppler sensor, and a conada effect and momentum sensor.
13. The HVAC valve and actuator assembly of claim 1 , wherein the valve comprises one of a ball valve, a shoe valve, a butterfly valve, a gate valve, and a globe valve.
14. The HVAC valve and actuator assembly of claim 1 , wherein the valve actuator has a plurality of adjustable operating parameters, whose values control the operation of the valve actuator.
15. The HVAC valve and actuator assembly of claim 14 , wherein the plurality of adjustable operating parameters can be adjusted either locally or remotely.
16. The HVAC valve and actuator assembly of claim 1 , wherein the water mixture comprises a mixture of water and anti-freeze.
17. A method of operating a valve and actuator assembly with integral freeze protection, the method comprising the steps of:
sensing a temperature of liquid flowing through an HVAC valve into an HVAC coil used to heat or cool a space;
sensing a temperature of air surrounding the HVAC coil;
measuring a flow rate of the liquid flowing through the HVAC valve;
determining a likelihood, based on the sensed liquid and air temperatures and on the flow rate measurement, that the liquid in the HVAC coil will freeze;
controlling the flow of liquid through the HVAC valve and HVAC coil to provide a minimum flow sufficient to prevent freezing of the liquid in the HVAC coil.
18. The method of claim 17 , wherein determining a likelihood that the liquid in the HVAC coil will freeze comprises determining a likelihood that the liquid in the HVAC coil will freeze, based on whether the liquid is water or water mixed with a known concentration of anti-freeze.
19. The method of claim 17 , wherein controlling the flow of liquid through the HVAC valve and HVAC coil to provide a minimum flow sufficient to prevent freezing of the liquid in the HVAC coil comprises providing the minimum flow sufficient to prevent freezing of the liquid in the HVAC coil until the liquid temperature rises to a target temperature at some level above a freeze temperature setpoint, for a predetermined time period.
20. The method of claim 19 , further comprising the step of discontinuing the minimum flow sufficient to prevent freezing of the liquid in the HVAC coil if it is determined that there is no likelihood that the liquid in the HVAC coil will freeze.
21. The method of claim 19 , further comprising setting the freeze temperature setpoint, the target temperature, and the time period, wherein a user can set the freeze temperature setpoint, the target temperature, and the time period either locally or remotely.
22. The method of claim 19 , wherein the target temperature is at least 10 degrees above the freeze temperature setpoint, and the time period is at least five minutes.