HVACR Temperature Control Basics

Summary

The video script discusses time control systems and their evolution from mechanical to electronic, offering greater functionality and ease of use. It explains how these systems can be programmed for specific schedules, optimizing energy use in buildings. The script further delves into the use of sensors, both digital and analog, for accurate temperature and pressure readings. It highlights the importance of modulating thermal output for maintaining desired temperatures within a deadband, using examples of thermostatic radiator valves and motorized valves. The video also touches on the challenges of controlling multiple units with a single pump and the solution of using a pressure sensor and variable speed pump to maintain consistent pressure and flow rate.

Takeaways

• 🕒 Time control systems regulate the operation of devices at specific times and durations.
• 🔧 Traditional mechanical timers have been largely replaced by electronic controllers with more functions and flexibility.
• 🏢 Advanced systems use an optimizer and programmable logic controllers (PLCs) to efficiently manage heating in large buildings based on occupancy schedules and outdoor temperatures.
• 🌡️ Modulation of thermal output is more effective than simple on/off control for maintaining desired room temperatures.
• 📊 A thermostat compares room temperature to the set point and adjusts the heating system accordingly.
• 🔄 Digital sensors provide binary on/off information, while analog sensors offer a range of values for precise measurements.
• 🔧 Deadband conditions are set to prevent unnecessary fluctuations in temperature, maintaining a stable environment.
• 💧 Special valves, like motorized valves and thermostatic radiator valves, can modulate the thermal output of heating systems.
• 🔄 Variable speed pumps maintain constant pressure and flow rate in heating systems with multiple radiators or fan coil units.
• 📚 Understanding HVAC engineering involves learning about the operation and integration of various components like sensors, valves, and controllers.

Q & A

What is the primary function of time control in systems and components?

The primary function of time control is to manage the operation of systems and components by turning them on and off at specific times and for certain durations, which can be useful for maintaining comfort and efficiency in various settings.

How has the technology of timers evolved from the past to the present?

Timers have evolved from being mechanical devices that used cams to control the opening and closing of contacts, to modern electronic controllers that are compact, easier to use, and offer more functions, such as seven-day schedules and multiple on-off times per day.

What is the role of a relay in electronic timers?

Relays are used in electronic timers to open and close circuits, allowing for the control of electrical devices and systems according to the set schedule.

How does a programmable logic controller (PLC) optimize heating systems in large buildings?

A PLC checks the clock to determine if heating should be turned on, considers the scheduled occupancy time, current room temperature, desired temperature, and outdoor temperature to calculate the necessary start time and heat output for efficient and comfortable heating.

What is the purpose of modulating the thermal output in a heating system?

Modulating the thermal output allows for better temperature regulation by increasing or decreasing the temperature to match the actual load, ensuring energy efficiency and maintaining a comfortable environment.

What are the two main types of sensors used in heating systems, and how do they differ?

The two main types of sensors are digital and analog. Digital sensors can only detect on/off states, while analog sensors provide a range of values, allowing for more precise measurements such as exact temperature or pressure.

How does a thermostatic radiator valve work in a heating system?

A thermostatic radiator valve uses a chamber filled with a wax-like substance that expands and contracts with room temperature changes, controlling the valve position and adjusting the heat output of the radiator to match the room's demand.

What is the significance of a deadband condition in temperature control?

A deadband condition, typically set at plus or minus one degree Celsius from the required temperature, helps to alleviate temperature swings by turning the heating on and off within a small range around the desired temperature, maintaining comfort and efficiency.

What issue arises when using a fixed speed pump with multiple radiators or fan coil units?

When using a fixed speed pump, closing one valve can cause a pressure increase in the pipework, leading to increased flow rate through other valves. This can disrupt the system's control and cause the valves to constantly adjust, potentially leading to faster breakdowns.

How can a variable speed pump help in maintaining a constant flow rate through radiators?

A variable speed pump adjusts its speed in response to changes in valve positions, working to maintain a constant pressure and flow rate through the radiators, regardless of when other valves open or close.

What additional features do modern electronic controllers offer for temperature regulation?

Modern electronic controllers offer features such as programmable schedules, the ability to set different on-off times per day, and integration with other systems like PLCs for more sophisticated temperature and energy management in buildings.