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The FILTERSCAN WiFi® Home affordable airflow sensor and differential pressure monitor sends you a text or email when it's time to change your home's air furnace filter.

    How to Select the Best HVAC Air Filter Monitor

    Posted by CleanAlert Blog Team on Dec 10, 2014, 11:14:00 AM

    Some of today's cooling/heating systems, or programmable thermostats, feature a "filter change" reminder.Wondering how to select the best HVAC air filter monitor? Although monitoring the efficiency of your heating and cooling system isn't new, air filter monitors are not all created equal.

    The best HVAC monitor is one that provides you with accurate information about the state of your air filter. That way you know the best point to replace your furnace filter.

    Dirty or clogged filters strain your furnace, which increases your utility bills and shortens your HVAC (heating, ventilating and air conditioning) equipment’s life. At the same time, replacing air filters that don't need to be changed gets expensive, too.

    Let's explore the different types of air filter monitors available so you can select the best one for you.

    Monitoring How Long Your Air Filter Has Been in Place 

    Some of today's cooling/heating systems, or programmable thermostats, feature a "filter change" reminder. These gauges measure the length of time the filter is in place, or the amount of time the furnace is in use. The problem with these timers is that they don't measure if the filter is clean or dirty; only that time has passed.

    • If your home is well sealed, you have no pets, no dust-prone furnishings like carpet and fabric-covered furniture, and you dust and vacuum frequently, you won't have to change HVAC air filters often.
    • Also, filters only load up with contaminants when your HVAC system is running. If you don't turn on the heating or air conditioning for a month or two, the air filter will not become clogged during those months.

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    Should I replace my filters every 90 days?

    Someone decided long ago that 90 days is the optimal period between filter changes, and so most timers are set to issue reminders at 90 day intervals. Unfortunately, there is nothing special about the number 90, other than it’s a convenient way to divide up the year.
    Some mechanical furnace filter gauges cannot work with today’s high efficiency furnaces that use multiple blower speeds.
    So what happens if 90 days go by when it’s mild outside and you’re not running your system? You will still get a reminder to change the air filter, even though it is not needed.

    On the flipside, an extended heat wave or cold snap can result in your system running for 30 days straight. In that instance, the filter will probably become clogged much sooner than normal.

    Time doesn’t matter for air filters. It’s what happens in your home that matters.

    Monitoring How Long Your HVAC System Has Been Running

    Other gauges rely upon operation "run" time (i.e., how long your heating/cooling system is running) to determine if a filter is clogged. The thinking goes that after your system has run for a certain amount of time, your filter must need replacing. Here again, the gauge does not measure the state of the filter, but merely the passage of time.

    In addition to timers that cannot differentiate between clean and dirty HVAC air filters, there are also mechanical air flow gauges that sense pressure changes. The premise here is that as the filter fills up with contaminants, the differential air pressure in the system changes. This change in differential pressure then causes a needle on the gauge to move.

    Measuring the change in the air pressure over time as a filter becomes used is much more accurate than measuring the passage of time. Unfortunately, these mechanical gauges cannot differentiate between the change in pressure caused by a clogged air filter and that caused by a change in the speed of the blower. Multiple blower speeds are common in today’s high-efficiency heating and cooling systems These mechanical gauges can also get stuck or yield different readings if tapped with a curious knuckle.

    Scientifically Monitoring Changes in Internal HVAC Pressure Using a Clean Filter as Baseline

    More sophisticated air filter gauges use patented differential pressure technology and advanced circuitry to determine the very point when a filter becomes too clogged to perform effectively. These advanced filter monitors take a scientific approach to filter maintenance by continuously and automatically measuring the change in internal air pressure using a clean filter as the baseline reading.

    As a filter becomes dirty, the system’s pressure level changes due to the increasing resistance from particulates caught in the filter. Once this pressure reaches approximately two times the initial baseline level, the air filter monitor alerts the homeowner that a new filter is required. And, unlike some mechanical gauges, today's premium electronic monitors automatically compensate for changes in system blower speeds, making them compatible with most variable air volume (VAV) systems.

    This type of HVAC air filter monitor is ideal for telling you exactly when to change your home air filter.

    So before purchasing an air filter monitor to check for clogged  filters, make sure you know exactly what it measures and whether or not you will get your money’s worth. A cheaper product that works poorly may not be worth the savings. 

    Have questions about how to select the best HVAC air filter monitor? Let us know. 

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    Here are additional resources regarding home air filters:

    Topics: Home Air Filters, Home Maintenance, Air Filter Monitoring