Heating, Ventilation, and Air Conditioning (HVAC) systems are essential in maintaining comfort inside homes no matter the season. They help you stay warm during cooler weather and keep you cool and comfortable during the hot summer months.
But while all components in these systems work together to help you maintain the right temperature inside your home, one part that directly impacts your HVAC’s performance and efficiency is the actuator.
In this blog, we explore what an actuator is, how it works in an HVAC system and how to tell when your actuator needs replacement.
What Is an Actuator?
Actuators are generally devices converting energy into motion to control a mechanism or system. In an HVAC system, they play the essential role of opening or closing its dampers to direct hot and cold air to the places they should go, depending on the settings on the thermostat.
A Quick Look into How HVAC Systems Work
HVAC systems consist of a thermostat, furnace and blower motor, a heat exchanger, an evaporator coil, a condensing unit, refrigerant lines, ductwork, and dampers.
The furnace and blower motor are responsible for heating and distributing household air to the intended zones. Meanwhile, the evaporator coil, condensing unit and refrigerant lines work together to absorb heat from the indoor air and pump the chilled air back into the home.
The thermostat is the component that lets you regulate the temperature you want circulating inside your home. Meanwhile, dampers help you direct airflow to specific rooms.
With that said, dampers and vents are not the same. Vents also control the airflow within your house, but they simply keep the air from entering a specific room. They can’t keep warm or chilled air from moving into the ducts. On the other hand, dampers are movable plates that prevent air from entering the ductwork in the first place, as they are typically installed near the air distribution pipe openings.
But what role does an actuator have in all this? Actuators use a low-voltage signal to open and close the dampers, adjusting the flow or warm or chilled air and regulating the temperature throughout your home.
The Importance of Actuators
Actuators are an essential component in any HVAC system as they direct the airflow and temperature coming out of it. They serve as the interface between your thermostat and the mechanical parts. More importantly, they help maintain proper ventilation and comfort within your home and even improve your system’s efficiency by optimizing air movement from the unit.
A faulty actuator then keeps your dampers from functioning correctly, if at all. When the dampers don’t work as they should, faulty, weak or inconsistent airflow occurs. You may also see an increase in your energy consumption despite receiving poor performance from your HVAC system.
How to design electronic heating, ventilation and air conditioning (HVAC) valve and actuator controls that can maximize heating and cooling cycle efficiency in commercial chillers and geothermal HVAC systems?
As shown in the figure below, HVAC valve & actuator control consists of 11 parts, each part is Non-isolated DC/DC power supply, Isolated AC/DC power supply, Pump motor drive, Position sensing, Current sense, Output user interface, Digital processing, Wired interface, Self-diagnostics/monitoring, Wireless interface, Signal input/output protection. Each part has its corresponding products and product models. I will introduce them to you one by one.
Non-isolated DC/DC power supply
Multiple voltage rails are generated from the input power source to support all the devices used in the system. Buck converters may be used to step down the input voltage. Linear regulators (LDOs) are a good option for simple designs. LDOs also enable added functionalities including EMI filtering. Non-isolated DC/DC power supply includes Buck converters (integrated switch)、Boost converters (integrated switch)、Linear & low-dropout (LDO) regulators、Multi-channel ICs (PMICs)、SR & load share controllers、Buck controllers (external switch)、Boost controllers (external switch)、Charge pumps (inductorless), the corresponding product models are LMR36502、LM2700、TPS7A24、TPS65219、LM5141、LM5156H、LM27761
Isolated AC/DC power supply
HVAC valve and actuator controllers generally powered from an AC power source. An offline converter can be used to create a DC voltage from an AC power source. Isolated AC/DC power supply includes Buck converters (integrated switch)、Flyback controllers、Isolated DC/DC converters & modules、Shunt voltage references、Series voltage references、Power factor correction (PFC) controllers, the corresponding product models are TPS563203、UCC28881、LM5017、LM4040、REF4132、UCC28056
Pump motor drive
The system microcontroller operates the motor (or motors) in the system. Gate drivers can be used to control the MOSFETs that drive the motor. Pump motor drive includes Half-bridge drivers、Low-side switches、SR & load share controllers、Isolated DC/DC converters & modules、N-channel MOSFETs、PWM controllers、P-channel MOSFETs, the corresponding product models are UCC27710、TPL7407L、UCC24630、LM5160A、CSD18541F5、UCC28C52
Position sensing
A control loop is used to measure the motor current, position, speed, and direction. Operational amplifiers and analog-to-digital converters (ADC) can be used to measure the current through a current shunt resistor. Position can be measured using a rotary encoder, resolver, or Hall effect sensor. An ADC can be used to interface to the encoder or resolver. Isolation amplifiers can be used with shunt current sense resistors to provide isolation between the inverter bridge and the low-voltage circuitry. Position sensing includes General-purpose op amps、Precision op amps (Vos<1mV)、Audio op amps、Linear Hall-effect sensors、Hall-effect latches & switches、Precision ADCs、Isolated amplifiers, the corresponding product models are LM2904B、OPA2188、LME49721、TMAG5253、DRV5013、ADS8866、AMC1311
Current sense
A control loop is used to measure the motor current, position, speed, and direction. Operational amplifiers and analog-to-digital converters (ADC) can be used to measure the current through a current shunt resistor. Position can be measured using a rotary encoder, resolver, or Hall effect sensor. An ADC can be used to interface to the encoder or resolver. Isolation amplifiers can be used with shunt current sense resistors to provide isolation between the inverter bridge and the low-voltage circuitry. Current sense includes General-purpose op amps、Precision op amps (Vos<1mV)、Analog current-sense amplifiers、Audio op amps、Precision ADCs, the corresponding product models are TLV9302、OPA2188、INA199、LME49721、ADS131E08S
Output user interface
The output user interface may consist of a simple LED to indicate system status. An LED driver may be an option for flashing a single color LED. Output user interface includes RGB LED drivers, the corresponding product models are LP5030、TLC59116、LP5813
Digital processing
A microcontroller communicates with the system controller, operates the motors in the system and monitors the motor sensors. Digital processing includes C2000 real-time microcontrollers、Arm Cortex-M0+ MCUs、Arm Cortex-R MCUs、Arm Cortex-M4 MCUs、MSP430 microcontrollers、Shunt voltage references、AND gates、Noninverting buffers & drivers、Inverting buffers & drivers、I2C general-purpose I/Os (GPIOs), the corresponding product models are TMS320F2800155、MSPM0G1506、RM46L852、TM4C1231H6PM、MSP430F5529、LM4040、SN74LVC1G08、CD74ACT541、SN74LVC1G04
Wired interface
A wired interface can be used for servo-motor controls through the DAC, or for critical communication protocols where wireless interfaces are not desired. The wired interface also can be used as a current or voltage loop for other controls or sensors. Wired interface includes RS-485 & RS-422 transceivers、Digital isolators、Isolated RS-485 transceivers, the corresponding product models are THVD1449、THVD2412V、ISO6741、ISO1500
Self-diagnostics/monitoring
On-board sensors and other devices are used for self-diagnostics and system monitoring. A core temperature monitor is used to track the temperature of the PCB near the main processor. This function can be implemented using an external temperature monitor device. A voltage supervisor can keep the system in reset until the system voltage reaches valid levels. Self-diagnostics/monitoring includes Analog temperature sensors、Digital temperature sensors、Humidity sensors、Supervisor & reset ICs, the corresponding product models are LMT84、LMT01、HDC3022、TLV809
Wireless interface
The wireless interface consists of a variety of different protocols based on the end-use case. Wireless communication is suitable for locations where wired interfaces are not practical. Wireless interface includes Sub-1 GHz wireless MCUs、Low-power 2.4-GHz products, the corresponding product models are CC1354P10、CC2651R3
Hope our designs can help you a lot, and hope it is useful for lower system power consumption significantly through precision flow control.
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