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Thermostat Basics: Types and Applications
- 1. Learning Center THERMOSTATS Types and Applications Intellectual rights apply © Jackson Systems, LLC 2011
- 2. Learning Center THERMOSTATS PRODUCT DEFINITION A THERMOSTAT is a key component of any HVAC system. It maintains the space temperature by cycling the heating or cooling equipment on and off to maintain a desired temperature which is referred to as the thermostat setpoint. Intellectual rights apply © Jackson Systems, LLC 2011
- 3. Learning Center THERMOSTATS PRODUCT DESCRIPTION Thermostats sense the change in space temperature and turn the heating equipment on when the temperature drops below the setpoint and off when the temperature reaches setpoint. They also turn the cooling equipment on when the temperature rises above the setpoint and off when the temperature reaches setpoint. The majority of thermostats operate on low voltage (24VAC) control circuits. The source of the 24 VAC is a transformer located in the heating/cooling equipment. Intellectual rights apply © Jackson Systems, LLC 2011
- 4. Learning Center THERMOSTATS PRODUCT DESCRIPTION Line voltage 120VAC or 277VAC thermostats are also available. Modern thermostats are almost exclusively digital. A digital thermostat uses a simple device called a thermistor to measure temperature. A thermistor is a resistor which changes its resistance value as the temperature changes. The microprocessor in a digital thermostat can measure the resistance change and converts the resistance value to an actual temperature reading. Intellectual rights apply © Jackson Systems, LLC 2011
- 5. Learning Center THERMOSTATS PRODUCT DESCRIPTION Thermostats are categorized by their function and the type of equipment being controlled. Thermostats can have two (2) functions: Programmable Non-Programmable Intellectual rights apply © Jackson Systems, LLC 2011
- 6. Learning Center THERMOSTATS PRODUCT DESCRIPTION Thermostats can control different types of HVAC equipment. Single stage (1 heat / 1 cool) Multi-stage (2 heat / 2 cool) Heat pump ( 2 heat / 1 cool) Heat pump ( 3 heat / 2 cool) Dual fuel ( 2 heat / 1 cool) Dual fuel (3 heat / 2 cool) A “universal thermostat” means that it can be configured to work with any of the above systems. Intellectual rights apply © Jackson Systems, LLC 2011
- 7. Learning Center THERMOSTATS PRODUCT DESCRIPTION One of the most useful features of a digital thermostat is programmable settings. In the winter you can program the thermostat to automatically turn up the heat for an hour in the morning while you get ready for work, turn down the heat while away from home, turn up the heat in the evening and then turn down the heat while you sleep. The same is true for cooling. Programmable thermostats save energy by automatically adjusting the temperature based on a user program. Intellectual rights apply © Jackson Systems, LLC 2011
- 8. Learning Center THERMOSTATS PRODUCT DESCRIPTION Residential thermostats typically have 4 schedules per day Wake or Morning Leave or Day Return or Evening Sleep or Night Commercial thermostats typically have 2 schedules per day Occupied or Day Unoccupied or Night Intellectual rights apply © Jackson Systems, LLC 2011
- 9. Learning Center THERMOSTATS PRODUCT DESCRIPTION Thermostats can be hardwired or wireless A hardwired thermostat requires 18 gauge thermostat wire running from the thermostat to the HVAC equipment. A wireless thermostat does not wire directly to the equipment but rather wirelessly communicates via radio waves to an equipment interface module (EIM) mounted near the HVAC equipment. The EIM is then hardwired to the equipment. A wireless thermostat can be used when it is difficult or impossible to run wires from the equipment to the thermostat. Wireless thermostats are almost always powered by batteries. Intellectual rights apply © Jackson Systems, LLC 2011
- 10. Learning Center THERMOSTATS PRODUCT DESCRIPTION Powering thermostats The three most common types of thermostats are 24VAC hardwired, battery powered, and dual powered. 24VAC hardwired stats require constant 24 Volts AC from the equipment transformer. Battery powered stats do not require 24VAC to power the thermostat. Dual powered stats can be powered by the equipment transformer or by batteries. Intellectual rights apply © Jackson Systems, LLC 2011
- 11. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS Most, if not all, digital thermostats today contain “Advanced Installer Settings”. Advanced installer settings are typically accessed only by the contractor during installation. Advanced installer settings allow for equipment configuration and selected user preferences. Depending on the thermostat manufacturer and model, there can be dozens of advanced installer setting options. Advanced installer settings are either set by configurable dip switches or programmed through the key pad or touchscreen. Intellectual rights apply © Jackson Systems, LLC 2011
- 12. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS SYSTEM TYPE Matches the thermostat to the equipment such as single stage, multi- stage, or heat pump system. FAN CONTROL Allows the equipment to energize the fan or the thermostat to energize the fan during a call for heat. SCHEDULE FORMAT Thermostat can be set up as programmable or non- programmable. Intellectual rights apply © Jackson Systems, LLC 2011
- 13. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS CHANGOVER VALVE Selects O or B reversing valve for heat pumps. AUXILIARY HEAT Selects electric or fossil fuel auxiliary heat for heat pumps. BACKLIGHT Selects backlight always on or on after a key is pressed. MANUAL/AUTO-CHANGOVER Allows the stat to have both heating and cooling available (auto changeover) or just heat or cool available (manual). Intellectual rights apply © Jackson Systems, LLC 2011
- 14. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS TEMPERATURE DISPLAY Allows selection of Fahrenheit or Celsius to be displayed. REMOTE SENSOR Allows selection of no remote sensor, outdoor sensor, or indoor sensor. Some stats allow both an indoor and outdoor sensor. LOW BALANCE POINT Allows the heat pump to be locked out on a call for heat below a certain outside temperature (i.e. 30°F) and only allow the auxiliary heat to be used. Intellectual rights apply © Jackson Systems, LLC 2011
- 15. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS HIGH BALANCE POINT Allows the auxiliary heat to be locked out above a certain outside temperature (i.e. 60°F) and only allows the heat pump to be used. Intellectual rights apply © Jackson Systems, LLC 2011
- 16. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS ADAPTIVE RECOVERY When adaptive recovery is OFF, the thermostat will bring on the HVAC equipment at the exact time of a scheduled event. When adaptive recovery is ON, the thermostat will bring on the HVAC equipment earlier than the schedule event time. The thermostat anticipates how long it will take to reach the next scheduled setpoint based on the temperature in the space and the rate of recovery of the equipment. PROGRAM PERIODS Allows 4 or 2 programs per day. Intellectual rights apply © Jackson Systems, LLC 2011
- 17. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS SHORT CYCLE PROTECTION Allows a time delay (typically 5 minutes) between cooling calls for conventional equipment and both heating and cooling calls for heat pumps. Intellectual rights apply © Jackson Systems, LLC 2011
- 18. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS HEATING LIMIT Allows selection of a maximum heating setpoint adjustment. COOLING LIMIT Allows selection of a minimum cooling setpoint adjustment. KEYPAD LOCKOUT Allows the thermostat buttons or touch screen icons to unlocked or locked to limit user access to certain functions. Intellectual rights apply © Jackson Systems, LLC 2011
- 19. Learning Center THERMOSTATS ADVANCED INSTALLER SETTINGS INTERNAL SENSOR CALIBRATION Allows calibration of the thermostat temperature sensor. FAN PURGE Allows selection (0-5 minutes) of extended fan run time after a heating or cooling call ends. STAGE DIFFERENTIAL Allows selection of the temperature difference above or below the setpoint before the equipment will be allowed to run. Example: 70 degrees heating setpoint with a selected 2 degree differential will allow the heating to come on at 68 degrees. Intellectual rights apply © Jackson Systems, LLC 2011
- 20. Learning Center THERMOSTATS INSTALLATION Typical terminal designations for a thermostat controlling conventional equipment. R-Wires to the hot side 24VAC equipment transformer C-Wires to the common side 24VAC equipment transformer W1-Wires to the first stage heating relay W2-Wires to the second stage heating relay Y1-Wires to the first stage cooling relay Y2-Wires to the second stage cooling relay G-Wires to the fan relay Intellectual rights apply © Jackson Systems, LLC 2011
- 21. Learning Center THERMOSTATS INSTALLATION Typical terminal designations for a thermostat controlling heat pump equipment. R-Wires to the hot side 24VAC equipment transformer C-Wires to the common side 24VAC equipment transformer W1-Wires to the auxiliary heat O/B-Wires to the heat pump reversing valve Y1-Wires to the first stage compressor Y2-Wires to the second stage compressor G-Wires to the fan relay Intellectual rights apply © Jackson Systems, LLC 2011
- 22. Learning Center THERMOSTATS INSTALLATION An important part of thermostat operation is location. The location should represent the ambient space temperature. The stat should be mounted on an interior wall. The stat should be about five (5) feet up from the floor. The stat should be out of direct sunlight. The stat should be mounted in a room that is centrally located and frequently used. The thermostat should not be installed in an area where drafts are present, near the floor, behind doors or on an exterior wall. Intellectual rights apply © Jackson Systems, LLC 2011
- 23. Learning Center THERMOSTATS SAMPLE TEST Thermostats should be configured to match the . . . A. Color of the house B. HVAC equipment C. Location where it will be installed D. All of the above For a conventional thermostat, Y1 is for . . . A. First stage cool B. Second stage cool C. First stage heat D. Second stage heat Intellectual rights apply © Jackson Systems, LLC 2011
- 24. Learning Center THERMOSTATS SAMPLE TEST For a conventional thermostat, W2 is for . . . A. First stage cool B. Second stage cool C. First stage heat D. Second stage heat For a heat pump thermostat, Y1 is for . . . A. First stage compressor B. Second stage compressor C. Fan D. Auxiliary heat Intellectual rights apply © Jackson Systems, LLC 2011
- 25. Learning Center THERMOSTATS SAMPLE TEST Which of the following is an advanced installer option? A. Adaptive recovery B. Low balance point C. Backlight display D. All of the above Intellectual rights apply © Jackson Systems, LLC 2011
- 26. Learning Center THERMOSTATS SAMPLE TEST Residential programmable thermostats typically have how many schedules per day? A. 1 B. 2 C. 3 D. 4 Commercial programmable thermostats typically have how many schedules per day? A. 1 B. 2 C. 3 D. 4 Intellectual rights apply © Jackson Systems, LLC 2011
- 27. Learning Center THERMOSTATS THERMOSTAT BASICS Types and Applications Intellectual rights apply © Jackson Systems, LLC 2011
- 28. 888.652.9663 www.jacksonsystems.com Intellectual rights apply © Jackson Systems, LLC 2011