Knowledge Center
The voltage drop when current flows through a resistor.
Power has to feed every transistor within a chip. That power is distributed around the chip using the metal layers. As fabrication technologies have become smaller, the size of the wires has also been getting smaller, while physical chip dimensions have stayed roughly the same. This means that wires have become thinner but have not gotten shorter. That leads to an increase in resistance per unit length. There is an almost 10X increase in resistance between a 28nm chip and a 7nm chip, and that will follow an exponential increase for smaller geometries. At the same time, the total power consumed by chip has also remained fairly flat.
As current flows through a resistor, the voltage drops – this is what is referred to as IR drop. When the voltage at a transistor drops, it becomes slower and this could impact the circuit timing. When this happens on a critical path through a design, it can also lead to a functional failure and thus needs to be avoided. Another trend in semiconductor design has been a reduction in operating voltage, meaning that small changes in supply voltage may represent an increasing percentage of the digital swing and potentially lead to incorrect logic values being seen.
A second problem is intertwined with IR drop: electromigration. When large currents flow through these thin wires, molecular displacement can happen. This means that molecules of the metal migrate along the wires over time, causing a further shrinking of the wire at certain points and thus an increase in the resistance. So, over time, electromigration can make IR drop worse. It thus becomes necessary to analyze for IR drop over the intended life off the device coupled with electromigration analysis.
IR drop, while causing an increase in delay for a digital transistor, can have an even bigger impact on analog circuitry. Not only can timing change, but it can directly cause functional failures. Given that the current draw of a wire is influenced by activity in other areas of the chip, it is often seen as a source of noise for the analog circuitry and this has to be taken into account when doing circuit analysis.
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It’s quite common for professional HVAC technicians to hear residential owners ask if it’s okay to let their furnace fan run continuously in “ON” mode, and whether there are any advantages or drawbacks to this practice. Some people think that a furnace fan running all day is a telltale sign of a faulty unit. However, this doesn’t always indicate that something alarming is happening with your furnace system.
In this article, Bill Reynolds Heating & Air Conditioning, a reputable furnace installation contractor in Ohio, sheds light on the matter and discusses the specific considerations you should keep in mind when running your furnace fan.
What Is a Furnace Fan?
Also called a furnace blower, a furnace fan is the main component of a furnace system that’s responsible for pushing air into the areas of a home where heating is needed. In this day and age, most central heating systems are forced air systems, and therefore require the presence of air in order to move in a certain direction. A furnace fan is one of the simplest methods to accomplish this.
Most times, furnace fans come with a motor that’s one horsepower or less. The appropriate dimensions of the corresponding motor depend on the size of the furnace. There are times when the motor size hinges on the square footage of the location being heated, including the total number of openings or vents present in a home.
While most models of furnace fans are capable of moving at 1,200 revolutions per minute [RPM], some spin at a slower rate. For residential furnace installation units, the maximum speed of most fans is typically 1,500 RPMs.
Why Is Your Furnace Fan Always Running?
Oftentimes, the furnace fan in your home is running around the clock because of the current setting on your thermostat. Note that most types of thermostats have two fan settings: “AUTO” and “ON.” The former setting will command your furnace system to turn on the fan when it needs to circulate heated air, while the latter will force your furnace fan to run nonstop without a hitch.
However, a furnace fan that won’t stop spinning can also be the result of a defective fan limit switch or one that’s set to manual override. If you suspect a technical problem of this nature, it’s best to call a team of professional HVAC technicians who can lay things out accordingly.
Benefits of Running Your Furnace Fan
Running your furnace fan all the time isn’t exactly a bad thing. In fact, there’s no need to worry about the fan wearing out or breaking down because it’s designed to run continuously, and there’s an array of benefits connected to this. Here are some of them:
Better circulation of heated and cooled air. Since hot air is much lighter than cold air, hot air will naturally rise up to the ceiling and attic, and cold air will plummet down to the ground. In an enclosed space like your home, this process is called the “stack effect.” It’s the same process that allows your fireplace to draw smoke out of the chimney. This is the reason why many houses have perpetually chilly basements and warm upper floors, according to an air conditioning repair specialist.
Your heating and cooling system can help balance out these issues; however, it doesn’t run all time. A furnace fan that’s running day in and day out can offer assistance by regularly pulling cold air from the lower level and warm air from the upper level and fusing them together. Then it will redistribute a more stable, even temperature throughout the interior space.
Lower utility bills. If you possess a newer, ENERGY STAR-rated furnace unit, it will have a variable-speed motor that’s designed to run nonstop. Since ENERGY STAR products meet strict energy efficiency guidelines set by the U.S. Environmental Protection Agency, your furnace will consume less energy performing the same task, which helps eliminate energy waste and lower your utility bills in the long run.
An energy-efficient unit also brings a heap of unique advantages, including reducing greenhouse gas emissions, bringing down demand for energy imports and lowering costs on household- and economy-wide levels.
Prolonged lifespan of the furnace unit. Unfortunately, many homeowners are still under the impression that running their furnace fan all the time will cause it to fail too soon. A furnace and air conditioning repair expert says that this isn’t the case at all. As previously mentioned, newer models of furnace systems include fans that are designed to run continuously. Assuming that your heating equipment was properly installed by a professional and has correctly-sized ductwork, letting the fan run continuously may actually help extend its service life.
Keep in mind that the most stressful part of any motor’s life is the moment it starts. It’s much easier on the motor to run constantly than to be subjected to on-again, off-again operation.
Improved air quality. By running the furnace fan all the time, you’re also running air through the furnace filter constantly. Moreover, if you have a highly-efficient filter and UV light, you’re also constantly filtering and cleaning the indoor air, resulting in less dust on your furniture and other personal belongings and, more importantly, fresher and healthier indoor air for your family and guests to breathe.
According to a heating service professional, running the furnace fan can also help reduce the humidity levels in your home during cold, frosty weather by running air through the evaporator more consistently, which allows the system to pull more moisture out over time.
When Is Running Your Fan Not a Good Idea?
There are a couple of situations where you don’t want to run your fan all the time.
If it’s the middle of summer and you have ductwork in the attic space. Temperatures can reach as high as 140 degrees Fahrenheit in the attic in the summer. Even if your ductwork is well insulated, it can only do so much to fight off those temperature levels. Running the fan when the air conditioner isn’t on can actually result in excessive heat getting pulled out of the attic and into the main part of the house.
If your ductwork is leaking. Most newly-constructed residential homes are required to have all ductwork sealed and tested for airtightness. Sadly, most homes built before 2015 may have very leaky ducts, so make sure to have yours professionally inspected to avoid problems in the future.
Call Us for All Your Heating and Cooling Needs
If you’re looking for high-quality HVAC repair, installation or tune-up services to upgrade your living situation at home, Bill Reynolds Heating & Air Conditioning is more than ready to help you. Our company is recognized as one of the premier sources of professional air conditioning and heating services in the state of Ohio.
To set up an appointment, call us today at [440] 298-4698 or fill out our contact form. Our top-rated technicians are committed to providing a safe, comfortable living space that every homeowner deserves through industry-leading products and services.