Did you know that clogged air filters are the primary cause of heating and cooling system problems? Dust and debris in a home air filter restrict air flow, which forces your furnace to strain and use more energy to heat or cool your home. Just like replacing your car engine’s oil and air filter every 3,000 miles, a clean HVAC air filter protects your furnace system from becoming damaged and, ultimately, failing entirely. But how can such a simple and relatively inexpensive component have such a big impact on energy consumption, equipment life and air quality? In other words, how can a $15-30 filter protect a $2,500-$3,500 heating and cooling system? To answer this question, we first need to understand how your home is heated and cooled and then how air filter clogs prevent your system from operating efficiently. A forced-air system, which is the most common heating and cooling system, uses a heat exchange to heat or cool incoming air that is then blown through metal/flexible ducts to the various rooms in your home.

As the warmed or cooled air flows into the rooms, the unit’s fan pulls existing air out of the rooms via a separate set of “return” ducts and toward the heat exchange (where it is again heated or cooled). This circular cycle continues until the desired temperature is reached. Here’s a good guide on how often you should change your air filter. When your air filter is clogged, your air handler must work harder to compensate for the blockage of air flow. In addition to driving up your utility bill, the reduced air flow through your heating and cooling system can cause your heat exchanger to overheat and shut off too quickly, preventing your house from warming up. If that happens too often, the electronic "limit switch" safeguard can fail, and then the furnace won't fire up at all. This service call and new part can easily cost you $175. So what’s the big deal? Does an air filter really matter?  In an effort to answer this, let’s take a look at what happens if you do not routinely change your heating and cooling filter. 

Here are some clogged furnace filter symptoms: Because the system relies on the constant recirculation of air, the performance of your heating and cooling system’s blower fan can have a big impact on your home’s energy consumption. The harder this fan has to work to draw air throughout your home, the higher your energy bills will be. In fact, a clogged filter can use 15% more energy, according to the Department of Energy. This inefficiency increases quickly as the filter becomes more and more clogged, or until the filter is serviced. If your air filter clogs during the summer cooling season, this can cause the evaporator or cooling coil to freeze up because not enough air is moving past the coil to dissipate the condensation that is normally produced during the cooling process. Lack of adequate airflow causes this condensation to freeze – reducing the unit’s ability to remove heat from the air (e.g., cool your home) and, most likely, eventually causing your air conditioner to break down.

Blower fans push the air through the filter. If the filter becomes too clogged with dust, dander and debris,then the blower has to strain harder to pass the air through a clogged filter. With reduced airflow you can experience hot and cold spots in your home, and it can be difficult to reach your desired indoor temperature levels.2001 honda civic ac compressor diy With less air flowing through the system due to the clog, the central air conditioning and heating system will run longer in an effort to heat the home, raising energy usage. freon for window ac unitIn fact, according to a study by the Florida Public Service Commission, the number two cause of high energy bills in the summer was a clogged air filter.lattice to hide ac unit

A clogged air filter will allow all that dust and debris that should be filtered out to be re-circulated back into your home. This can cause chronic allergies and especially be dangerous for people with asthma or other respiratory conditions. If you own pets or keep many chemicals around the house, the indoor air quality will be even worse with a clogged filter. You might not notice a sniffle here or there, but over time, poor indoor air quality will impact your health in a very negative way. Can a clogged air filter cause a heater to stop?  The answer is yes, and likely the costliest result of an improperly changed air filter may be the internal damage it deals to your central air conditioning and heating system. According to the Diamond Certified Organization, a clogged furnace air filter is the primary cause of equipment failure. Essentially, that overworked air blower discussed above may give out entirely, causing the whole system to fail, an outcome that can cost thousands of dollars to repair!

Here’s a good guide to know how to change your home air filter. Check out how valuable clean air filters are for your home: When you think how much can go wrong when you have clogged air filters, you take to heart the benefit that an air filter clog detector offers. Nest Learning Thermostat: Installation, battery issues, and the importance of the "C" wire My furnace's control board. The "C" terminal has no connection to the thermostat in this picture. (The white wire on the C terminal goes to the A/C.) I connected the unused blue wire (bottom center) to the C terminal. The Nest now confirms the active "C" wire. I recently bought and installed a Nest Learning Thermostat to replace my old non-networked thermostat. I show the installation, demonstrate control from mobile devices, and provide a general review in the above video. It's been about a month since I installed the device, and I found one important issue yesterday. My Nest dropped off the network for 7 hours, and upon investigation I discovered that the battery was low and it turned off the Wi-Fi radio to save power.

Many other people have reported problems with the battery, which is scary because your thermostat is one device that you absolutely want to work 24/7 -- you don't want your pipes freezing when you leave town and the Nest decides to run out of juice! It turns out that my thermostat wiring, like in many homes, does not provide a "C" wire (common 24VAC) for completing a circuit that provides constant power to the unit. This sort of wiring worked great for old-fashioned mercury thermostats -- it provides a red 24VAC power wire, and "call" wires for turning on the fan, heat, and air conditioning. When the thermostat needs to turn on one of those appliances, it simply closes the circuit between the red wire and the relevant call wire. Smart thermostats rely on batteries to power their smartness when no circuit is closed. When an appliance is running (i.e. one of those three circuits is closed), it can perform "power stealing" to sap power from the closed circuit for its operation and recharging the battery.

For simple programmable thermostats, power stealing is probably sufficient. However, for a power-hungry device like the Nest that needs to operate a Wi-Fi radio, this mode of operation can be problematic for several reasons: If you live in a nice place like Colorado where you can open the windows and go days without using the heater or air conditioner, the control circuits are never closed and the Nest's battery doesn't have an opportunity to recharge. Power stealing is an imperfect backwards compatibility hack, and can't necessarily provide enough current to recharge the battery even when the appliances are operating. This is because the current may be limited by resistance in your furnace's control board. When the HVAC appliances are not running and the battery needs to be charged, the Nest performs an even worse hack than power stealing: it pulses the heater call circuit on and off very quickly to steal some power, and hopes that the pulses are short enough to keep the furnace from activating.

I haven't noticed any problem with this, but at least one person has found that this wrecks havoc on their heater. The Nest uses a "Power Saving Mode" of Wi-Fi to reduce the power consumption of the radio and prolong the battery life. (And hopefully require less overall power than it can steal from the call circuits.) Nest indicates that some non-conformant wireless access points may not fully support this mode, thus causing the Nest to consume more power. (Perhaps more quickly than it can be replenished.) I was lucky that my thermostat wiring contained an extra, unused (blue) wire, and my furnace's control board provided a 24VAC common terminal for a "C" wire. After hooking up the blue wire at the furnace and the Nest's base, I now seem to have successfully provided a 24VAC "C" wire to the Nest, and hopefully my battery issues are behind me. I do think that Nest is perhaps overly optimistic about their power stealing and circuit pulsing being able to provide adequate power to the device.