CSI NUMBERS:
168 170 9500
DEFINITION:
A programmable thermostat senses the room temperature and controls the HVAC system according to a schedule established by the homeowner. This type of thermostat allows different temperature settings to automatically regulate the HVAC system at different preset times.
CONSIDERATIONS:
A thermostat is usually the least costly component of a HVAC system. It can play a major role in the energy efficiency of the HVAC system. The goal of a setback thermostat is to regulate the HVAC system to maintain a desired comfort level when the home is occupied and then enter an economizing mode when the house is unoccupied. A double adjustment, during work hours and sleep hours, will result in the greatest energy savings in the summer and winter. A single adjustment to an economizing mode each day also contributes significant savings.
Other conserving thermostats include electromechanical thermostats with setbacks and occupancy thermostats. The electromechanical types are lower cost and use bimetallic strips associated with a vial of mercury to make or break an electric current to operate the HVAC equipment. An occupancy thermostat maintains an energy conserving temperature until someone enters a room and presses a button to increase the temperature for a short period of time.
Programmable thermostats can require some effort to learn and master them. Several programmable units can accommodate different settings for every day of the week.
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| Satisfactory |
| Satisfactory in most conditions |
 | Satisfactory in Limited Conditions |
 | Unsatisfactory or Difficult |
COMMERCIAL STATUS
TECHNOLOGY
Well developed.
SUPPLIERS
Plentiful.
COST:
Range from $30 to $200.
IMPLEMENTATION ISSUES
FINANCING:
Available.
PUBLIC ACCEPTANCE
People may be intimidated by programmable thermostats and hesitate to use them to their advantage. The buyer should choose one that’s easy to operate and ask for a demonstration from the supplier, instead of relying solely on an instruction manual.
REGULATORY:
Thermostats must be wired according to electrical code requirements. Most thermostats are low voltage devices. However, electric heat systems generally require “line voltage” thermostats.
GUIDELINES
1.0 Performance Characteristics
1.1 Cooling Features
In the Austin climate, adjusting the cooling temperature from 75 degrees to 80 degrees for eight hours per day can result in a 7% to 9% savings in cooling energy.
Adjusting the temperature at night as well as during the daytime (up during the cooling season) can result in a 11% to 15% savings.
1.2 Heating season
During the winter, a single temperature setback during the day can result in a 16% to 18% savings.
A double setback (at night as well as during the day) can result in up to 30% savings.
2.0 Location
The thermostat should be located away from exceptionally warm or cool locations so that it can sense the normal temperature in the house. For example, a thermostat in a warm area (kitchen or sunny room)will sense warmer temperatures and over-cool the rest of the house.
3.0 Features For Optimum Energy Savings and Comfort
An automatic changeover between cooling and heating modes.
Sensing of outdoor conditions so that recovery from a setback setting can occur in a timely manner.
Manual program override.
Operation on electricity with a battery backup to retain the programming during a power outage.
Different scheduling ability for weekends and weekdays.
A low-battery indicator.
