Monday, February 16, 2015
Saturday, January 4, 2014
What are air filters supposed to do anyway?
The MERV rating also indicates the percentage of particles the filter will remove from the air passing through it. In general, a MERV rating of 6 indicates that the filter will capture up to half of the particles in the air; a filter with a rating of 8 will trap 70 to 85 percent of air-born particles it encounters; and a rating of 11 or higher means that the air passing through the filter is up to 95 percent cleaner when it comes out of the filter than it was when it went into it.
A properly sized, installed and functioning heating and air system circulates the air in your home every hour. In the process, it pulls that air through the filter. Just how much the filter cleans the air depends on the MERV rating of the filter.
MERV stands for Minimum Efficiency Reporting Value. MERV ratings indicate the size of particles that a filter can remove from the air passing through it. MERVs range from 1 to 16, with a higher number indicating a higher cleaning efficiency because it can filter smaller particles out of the air. The cheap, 1-inch (2.54-centimeter) thick, disposable filters made of jumbled fiberglass or natural fiber strands typically have a MERV rating of 1 but can go up to 4. Pleated filters made of nonwoven, disposable fabric have smaller pores, and the pleats increase the surface area of the filter so it can hold more particles than a flat surface can. These filters have MERV ratings of 3 and higher depending on the density of the fabric and the number of pleats. Some are charged with static electricity to attract and hold air-born allergens.
The particle catching efficiency actually goes up as the filter gets dirty; buildup on the fibers shrinks the openings the air passes through and allows the filter to capture more particles. This is good only up to a point. The particle-removing efficiency of the filter is inversely related to the energy efficiency of your heating and air system. A by-product of cleaning the air is a restriction of the air-flow through the system.
Think about times you've worn a dust mask while you worked on a project. It's harder to breathe through the mask than it is if you aren't wearing one. If you upgrade to the HEPA (high-efficiency particulate air) mask that filters out particles as small as 0.3 microns with up to 97 percent efficiency, it gets even harder to pull in enough air to keep you going. The same is true of your heating and air system. The denser the filter, the harder the system has to work to pull in air. A clogged filter may cause your system to run continuously, driving up your heating or cooling bills. That's why it's important to check your filters at least monthly and change them when they get dirty.
Monday, December 24, 2012
For any furnace, providing maximum comfort means achieving the proper amount of airflow. This is true for both heating and cooling operations. Unlike conventional single speed motors, a variable speed motor runs at a wide range of speeds. Using intelligent technology, it continually monitors incoming data from your heating and cooling system, and it automatically makes the adjustments necessary to meet your comfort needs. The motor varies the amount of air circulated, compensating for factors like dirty filters by increasing speed. Put simply, it delivers just the right amount of air necessary to provide the desired level of heating and cooling comfort.
--More Efficiency! Compared to a conventional single speed furnace, a variable speed furnace performs better and uses about two thirds less electricity. During cooling operation, variable speed technology typically results in an efficiency gain of 1 SEER (Seasonal Energy Efficiency Ratio). The higher the SEER, the lower
--Enhanced Humidity Control!! When moisture levels are high, there's a higher potential for mold growth and other pollutant problems. Compared to a single-speed furnace, a variable speed furnace is more effective at drawing moisture from the air for improved air quality and comfort.
Sunday, December 23, 2012
We've had a number of questions the last couple months on unpleasant odors associated with start-ups of heating systems this season. So we thought we would share some background on an odor issue generally associated with heat pumps referred to as "Dirty Sock Syndrome," because that name approximates the smell involved.
Dirty Sock Syndrome is caused by the growth of bacteria and/or mold on the indoor coil. As the surface area of the coil becomes more compact, as it does with higher efficiency coils, the coil fin spacing is going to be tighter (more fins per inch of coil). The depth of the coil may increase as well because manufacturers want to expose a greater amount of coil surface to the air stream in order to improve coil heat exchange and in the process improve system efficiency. So as the coils grow in size, depth, and fin density, the coil is even more likely to trap bacteria and mold on its surfaces.
Heat pump environments are the most likely systems to be associated with Dirty Sock Syndrome. The reason is pretty simple. When the heat pump is in the heating mode, the heat pump heating cycle for most heat pumps is not hot enough to kill the microbes that grow on wet coils in the cooling mode. So, when the unit goes into defrost (cooling mode), the likelihood that the indoor coil is wet or moist goes up, which causes any microorganisms or bacteria that were dormant to become active again. When the heat pump goes back into the heating cycle, it only warms the microbes to a level where they off-gas their odors. And that's where the odor associated with this phenomenon come from.
When the outdoor temperature drops below the thermal balance point for the heat pump, supplemental heat for the heat pump will be energized. At that point, the discharge temperature of the system is likely hot enough to kill the microorganisms or bacteria as they move from air handler or furnace. That is why many customers will note that the odor seems to go away when they put the heat pump system in emergency heat mode.
Controlling indoor relative humidity is key to maintaining a healthy indoor environment that is less susceptible to this type of phenomenon. Anytime relative humidity gets much beyond 40% to 45% during the heating season, conditions are right for bacteria and other microorganisms to begin forming on the indoor coil. Helping your customer understand the importance of indoor relative humidity is key to solving the problem for them. Don't forget to investigate other potential sources of excessive moisture. The indoor coil drain pan can also be a source of mold and bacteria, particularly if there is a problem with the drainage and disposal of condensate from the pan.
For purposes of indoor air quality control, ultraviolet lighting is a good addition to most any HVAC system. However, because there are so many choices within this area of IAQ technology, caution must be used when selecting and installing any UV system. All UV systems are sensitive to installation location and air stream CFM. Efficiency for some UV systems changes with air temperature. UV output levels very widely from one manufacturer to the next as does air stream exposure efficiency. UV light wave length can also impact UV performance. The UVC spectrum destroys the DNA of microbial contaminants while the UVV spectrum is primarily used for oxidation, which is most often associated with neutralizing odors in the air.
The fact that a customer has a UV light system doesn't necessarily mean that particular UV system will be effective in controlling odors for their home. Some manufacturers of UV equipment make UV lights specifically designed for coil and drain pan and odor applications. Take the time to investigate several manufacturers to ensure the right choice for vour customer.