Thermostat Basics: Types and Applications From Jackson Systems Information on the components of thermostats and their uses. Review quiz included at end of presentation

1. Learning Center
THERMOSTATS
Types and Applications
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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.
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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.
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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.
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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
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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.
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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.
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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
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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.
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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.
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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.
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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.
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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).
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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.
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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.
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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.
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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.
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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.
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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
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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
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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
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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.
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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
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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
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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
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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
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27. Learning Center
THERMOSTATS
THERMOSTAT BASICS
Types and Applications
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