Thermostat Buying Guide

Efficiently controlling the temperature inside the home not only keeps you comfortable, but it can also save money on utility bills. Whether you’re installing a new heating and cooling system, or just replacing your thermostat, this guide will help you choose the right control for your home. And if you’re having issues with your current thermostat, explore common problems and solutions below.

Where to Install Your Thermostat

A number of factors in and around your home can cause inaccurate temperature readings and make your thermostat switch on or off when it shouldn’t. For the most accurate temperature reading, install your thermostat on an interior wall near the center of your home, and make sure it’s placed away from heating/cooling vents, drafts, and direct sunlight.

System Compatibility

Not all thermostats work with all HVAC (Heating, Ventilation, and Air Conditioning) systems. HVAC systems are either single-stage or multi-stage.

Single-stage HVAC systems are basically on/off operations. Regardless of the temperature in the home, they blow heated or cooled air at full blast. When the thermostat registers that the room has reached the desired temperature, the whole system shuts down.

Multi-stage HVAC systems blow air at varying intensities. A two-stage system could be thought of as low/high, and a three-stage system as low/medium/high. Multi-stage systems put out varying levels of power depending on need. If the temperature only has to go up or down a couple degrees, the lower power level is used, saving energy.

Single-stage and multi-stage systems have different wiring, so the correct thermostat must be installed. Once you’ve determined what type of HVAC system you have, shop for a compatible thermostat. The thermostat packaging and documentation will indicate if it is for use with a single-stage or multi-stage system.

How Electromechanical and Electronic Thermostats Work

Before exploring modern thermostats, it’s important to understand how the different types work.

Electromechanical Thermostats

Electromechanical thermostat devices are older and more basic than the modern examples, operating on very simple mechanical principles.

A strip of two different metals joined together rests just under the cover, sometimes in the shape of a coil. This strip, or coil, will expand and contract with the fluctuating temperatures, activating the contacts on either one or both sides of the metal. If the unit controls the heating and cooling functions, it will have contacts on both sides; if it only controls one option, it will have a contact on only one side.

In a dual-controlled unit, this switch will tilt one direction if it is hot and the other if it is cold, creating contact with the appropriate side to activate the heater or the cooler to turn on. This system is sometimes joined with a mercury switch, which is a tube filled with mercury that also tilts as the coil expands or contracts, causing the mercury to move from one side to the other and thus opening or closing the points of contact.

Electronic Thermostats

Modern types of thermostats are electronic and function like a small computer. Often these are programmable, allowing you versatile flexibility in how you set temperature controls, timers and preferences.

Unlike electromechanical thermostats, which require manual adjustments, electronic versions allow you to set the temperature for a different setting when you sleep, wake up, return home and even for different days, such as on weekdays and weekends. This is a much more convenient setup than the simpler models, but it also means that there are more pieces that can break and maintenance work is more difficult and expensive. There are often inexpensive electronic models, making it often more feasible to simply replace your unit than try to fix it.

Discover the different types of electronic thermostats to find the best choice for your home and comfort.

Millivolt Thermostats

Millivolt thermostats work with low-voltage systems that get their power from the device they’re controlling—such as the pilot light on a gas fireplace.

How Does a Millivolt System Work?

Millivolt systems include thermocouples and thermopile sensors. When heated by the flame from a pilot light, the thermocouple produces a tiny amount of electricity (approximately 20-30 millivolts), which is enough to power the control system. A millivolt is one one-thousandth of a volt (1/1000).

Programmable Thermostats

Automating the temperature in your home is a smart way to save time and money. Rather than wasting energy by heating and cooling an empty house, a programmable thermostat can be set reduce usage when you’re away at work or while you sleep. You can program your heating and cooling schedule in advance, then let the thermostat take over. The programs can be adjusted if your schedule changes, and it’s easy to override the system for one-time events like a day off work.

Scheduling Programs

Many programmable thermostats have preset programs based on typical usage over the course of seven days. Here are some popular presets:

• A 7-day program allows you to set a different heating and cooling schedule for each day of the week. This is ideal for people who need flexibility because their work or school schedule varies from day to day.
• A 5-2 program lets you set one schedule for Monday through Friday and a second schedule for the weekend.
• A 5-1-1 program uses one heating/cooling schedule for Monday through Friday, another for Saturday, and a third for Sunday.

Tips to Get the Most Out of Your Programmable Thermostat

• Set your ideal-comfort temperature for the hours when you are home and awake.
• Adjust the thermostat to reduce energy use when you’re away or asleep.
• Plan for which events you want to adjust the temperature, for example: waking up, going to bed, leaving for work, and returning home.
• Set temperature adjustments in advance of events: reduce heating and cooling about 30 minutes before you leave the house each day or about 60 minutes before bedtime, and set the thermostat to your desired temperature 20-30 minutes before you’re scheduled to return home.
• Remember to override regular temperature programming when you’ll be away from home for an extended period of time.

Smart Thermostats

Smart thermostats are Wi-Fi-enabled for maximum convenience and flexibility. Each comes with an app to control the temperature from anywhere or get reports on your usage. These thermostats also can be connected to virtual assistants, such as Alexa or Google Home, so you can adjust the temp with your voice.

Select smart thermostats don’t rely on preset programs for efficiency. Over time, they actually learn your schedule and preferences. Users manually adjust their preferred temperature over a period of days, then the thermostat uses that data to automatically create an energy-efficient program.

Manual Thermostats

These low-tech thermostats use a dial or lever to set the temperature. Users must manually adjust the thermostat anytime they want to change the temperature. Though these units have a much lower upfront cost, they do not provide the convenience or long-term energy savings of programmable models.

Zone-Control Panels

Zone-control panels allow you to individually control the temperature in separate rooms (or levels) of your home. Each zone has its own thermostat, and all zones are controlled from the centralized panel. The ducts leading to each zone are outfitted with dampers that open or close to regulate airflow and adjust to the temperature in that zone as set at the control panel. The advantage of this type of setup is that you won’t waste energy heating and cooling unoccupied areas. It’s especially useful for multi-story houses, or large homes where certain areas are infrequently used.

Thermostat Covers

Thermostat covers let you limit who can adjust the temperature in offices, commercial buildings, or multi-resident dwellings. The covers fit over an existing thermostat and include a locking mechanism so only the keyholder can open the cover and adjust the settings. Typically, these covers are made of a durable, clear plastic, which allows you to view the thermostat but prevent tampering. Steel guard covers are also available for maximum control. Thermostat covers are vented to allow air to flow inside so the temperature can be accurately read.

Troubleshooting Your Current Thermostat

When the temperature inside is suddenly freezing cold or burning hot, most homeowners will do just about anything to fix it and restore a comfortable environment. Before you call a professional to repair your HVAC system, make sure the thermostat isn’t the problem. Below, we outline some things you can do to check its functionality and ensure you have a working thermostat.

While some fixes require a trained professional, there are several issues you can resolve on your own. Here are a few common problems and solutions that could be helpful:

#1: Furnace Won’t Start

Being caught in the cold winter months with a faulty furnace is a situation that nobody wants to be in, but there are things you can do to remedy the problem on your own. Here are some suggestions to try if your furnace won’t turn on:

• Check the power source, looking for issues such as blown fuses, tripped breakers, and dead batteries.
• Check for dirt, dust, spider webs, and nicotine buildup. These can coat the inside of the thermostat and cause the mechanical and electrical components to malfunction. To clean, use a soft brush, like a clean paintbrush, to gently brush the interior components. Compressed air is also useful in cleaning out the thermostat.
• Check for loose screws and corroded or loose wires inside the thermostat. Be sure to cut the power before you remove the thermostat cover, and check the owner’s manual to ensure correct wiring schematics.

While performing these simple fixes may not correct the problem, they can help you narrow down the issue to make it easier for the repair mechanic to quickly determine the problem and cause.

#2: Room Temperature and Setting Don’t Match

Another function to check before calling a professional is whether the thermostat keeps the room at the correct temperature or not.

To do this, tape a small thermometer on the wall next to the thermostat, being sure to place a paper towel behind the thermometer so that it won’t be affected by heat or cold transfer from the wall. Wait at least 15 minutes to ensure that temperature is stabilized and giving a correct reading, and then compare it to the reading on your thermostat.

If the numbers are more than a degree apart, the thermostat is likely giving an inaccurate reading. Before calling in a professional for repair, check a few other things:

• Make sure the inside of the thermostat is clean.
• Check if the thermostat box is level, since being off-center can alter the accuracy of the internal component.
• Check your box’s location, since placement in direct sunlight or in front of drafty windows and doors can greatly affect correct temperature regulation.
• Determine if the anticipator is set correctly. If you have a mechanical thermostat, check for a little metal tab that is mounted to a round dial on the inside. First, try pushing the tab lightly in either direction to see if that solves the issue. If not, you may need to set it to the furnace’s ampere setting. This is most easily accomplished by consulting the owner’s manual or directions indicated on the unit’s service panel.

#3: Unit Won’t Turn Off or Constantly Switches Off and On

Having a furnace or cooler that won’t turn on can be frustrating, but finding that yours won’t turn off can be equally difficult. Try these simple fixes to get your unit functioning properly again:

• Again, check for dirt and residue buildup. This is often the cause of many problems.
• Check to see if the box is level.
• Adjust the temperature higher or lower to see if that has any effect on the length it stays on or its likelihood of shutting off.

Having a thermostat that functions correctly is vital to keeping your interiors comfortable and livable during any weather. Many of the problems require simple fixes and can sometimes be taken care of on your own, but more complicated issues will need the help of a mechanic or even require replacement. After taking a look at the problems and solutions listed here, you should be able to determine the difficulty of your issue and whether or not you’ll need a professional.