Programmable Thermostat 101

What is a Programmable Thermostat

A programmable thermostat is a thermostat which is designed to adjust the temperature according to a series of programmed settings that take effect at different times of the day. Programmable thermostats may also be called setback thermostats or clock thermostats. They come with settings that allow you set the temperature of your house based on your family’s schedule.

There are five basic types of automatic and programmable thermostats:

  1. Electromechanical:- (EM) thermostats are usually the easiest devices to operate and they work with most conventional heating and cooling systems. Most have manual controls such as movable tabs to set a rotary timer and sliding levers for night and day temperature settings. EM controls have limited flexibility and can store only the same settings for each day.


    Electromechanical (EM) Thermostats

  2. Digital:- Digital thermostats have LED or LCD readout and data entry pads or buttons. They offer the widest range of features and flexibility, and they can be used with most heating and cooling systems. Digital thermostats provides precise temperature control, and they permit custom scheduling. The downside of these thermostats is that programming some models can be difficult!

    Digital Thermostat

    Digital Thermostat

  3. Hybrid:– Hybrid Thermostats are a combination of both digital controls with manual slides and knobs to simplify use and maintain flexibility. These are Ideal for both new and existing HVAC equipment.

    Hybrid Thermostat

    Hybrid Thermostat

  4. Occupancy:- Occupancy thermostats maintain the setback temperature until someone presses a button to call for heating or cooling. They do not rely on the time of day. As part of an HVAC energy management system, occupancy sensors enable facility managers to automatically control HVAC operation based on room occupancy. Passive infrared (PIR) sensing technology and intelligent logic control enable Net/X sensors to verify the occupancy status of rooms. If the room is physically occupied, then the system will control the temperature to predetermined set points. Once a room is vacant, the NT-OSC or NT-OSW signals the HVAC controls to automatically perform a setback. In this way no energy is wasted to condition an empty room. Occupancy thermostats are best suited for spaces that remain unoccupied for long periods of time.

    Occupancy Thermostat

    Occupancy Thermostat

  5. Light sensing thermostats.:- These thermostats are activated by lighting levels that are preset by the owner. When the sensor detects light the thermostat enters the Occupied 1 time period and will heat or cool according to the Occupied 1 setpoints. If the room is dark the thermostat will follow its programmed schedule. Light will put the thermostat into Occupied 1, and darkness will ‘release’ the thermostat to follow its programmed schedule. These thermostats are dependent on a photocell inside the thermostat that senses unoccupied conditions and allows space temperatures to fall 10° below the occupied temperature setting. When lighting levels increase to normal, temperatures automatically adjust to comfort conditions. These units do not require programming or batteries. In the event of a power failure, they will reset them selves. Light sensing thermostats are designed primarily for stores and offices where occupancy determines lighting requirements, and therefore heating requirements.

    Light Sensitive Thermostat

    Light Sensitive Thermostat

Advances in technology has made it possible program your thermostat remotely. Companies such as Nest has made programming your thermostat from your computer, tablet or smart phone possible. With Remote Programming, you can make changes in real time, miles away from the device.or example, your device can:

  • Automatically sense when you’ve left the house so it will turn itself off. they adjust to your home’s needs.
  • They can sense whether your home needs to be humidified or dehumidified. 
  • They can let you know when the thermostat has found a setting that saves you energy.


    Nest – Remote programming

Heating and cooling losses from a building (or any other container) become greater as the difference in temperature increases. A programmable thermostat allows reduction of these losses by allowing the temperature difference to be reduced at times when the reduced amount of heating or cooling would not be objectionable.

For example, during cooling season, a programmable thermostat used in a home may be set to allow the temperature in the house to rise during the workday when no one will be at home. It may then be set to turn on the air conditioning before the arrival of occupants, allowing the house to be cool upon the arrival of the occupants while still having saved air conditioning energy during the peak outdoor temperatures. The reduced cooling required during the day also decreases the demands placed upon the electrical supply grid.

Conversely, during the heating season, the programmable thermostat may be set to allow the temperature in the house to drop when the house is unoccupied during the day and also at night after all occupants have gone to bed, re-heating the house prior to the occupants arriving home in the evening or waking up in the morning. Since most people sleep better when a room is cooler and the temperature differential between the interior and exterior of a building will be greatest on a cold winter night, this reduces energy losses.

How to Choose a Programmable Thermostat

When choosing a thermostat, here are some questions you should ask:

  • Does the unit’s clock draw its power from the heating systems’s low-voltage electrical control circuit instead of a battery? If so, is the clock disrupted when the furnace cycles on and off? Battery-operated, back-up thermostats are preferred by many homeowners.
  • Is the thermostat compatible with the electrical wiring found in your current unit?
  • Are you able to install it yourself, or should you hire an electrician or a heating, ventilation, and air conditioning (HVAC) contractor?
  • How precise is the thermostat?
  • Are the programming instructions easy to understand and remember? Some thermostats have the instructions printed on the cover or inside the housing box. Otherwise, will you have to consult the instruction booklet every time you want to change the setback times?

How to properly use your programmable thermostat – (as recommended by the US Environmental Protection Agency – EPA).

  • Keep the temperature set at its energy-saving set-points for at least eight hours.
  • All thermostats let you temporarily make an area warmer or cooler, without erasing the pre-set programming. This override is cancelled automatically at the next program period. Please Note: You use more energy and will pay more on energy bills if you consistently override the pre-programmed settings.
  • Thermostats typically have two types of hold features: (a) hold/permanent/vacation; (b) temporary. Avoid using the hold/permanent/vacation feature to manage daily temperature settings. “Hold” or “vacation” features are best when you’re planning to be away for an extended period. Set this feature at a constant, efficient temperature (i.e., several degrees warmer temperature in summer, several degrees cooler during winter), when going away for the weekend or on vacation. You’ll waste energy and money if you leave the “hold” feature at the comfort setting while you’re away.
  • Cranking your unit up to 90 degrees or down to 40 degrees will not heat or cool your house any faster. Most thermostats begin to heat or cool at a set time, reaching set-point temperatures sometime thereafter. Units with adaptive (smart) recovery features are an exception to this rule.
  • Many homes use just one thermostat to control the whole house. If your home has multiple heating or cooling zones, you’ll need a programmed setback thermostat for each zone to maximize comfort, convenience, and energy savings throughout the house.
  • And this one should be a no-brainer – If your programmable thermostat runs on batteries, don’t forget to change the batteries each year. Some units will indicate when batteries must be changed.

Many Homeowners prefer to completely replace their old thermostats with the newer automatic and programmable thermostats. However, some devices can be placed over existing thermostats and are mechanically controlled to permit automatic setbacks. These units are usually powered by batteries, which eliminates the need for electrical wiring. They tend to be easy to program, and because they run on batteries, the clocks do not lose time during power outages.