I think many people have a mistaken idea of just how effective their electronic air cleaners are.
Newly installed and clean, they are very effective at cleaning the air going through your heating system. Most air cleaners have pre-filters associated with them that catch the large particles in the air stream.
The pre-filters allow the small particles to get through which are then “zapped” in the electronic field of the coils of the unit.
As these particles get zapped they are collected on the metal plates within the unit. As these plates become covered with this carbonized material the effectiveness of the unit falls off precipitously. These particles simply flow through the air-cleaner and into your furnace, into your supply duckwork, and onto your glass coffee table.
I have found electronic filters that only have been cleaned when the furnace was serviced—most of the time they do not even get cleaned then. Your filter blocks should not look like this:
I think many people look at the unit and because they “look” clean they figure they “are” clean. The coating of particles on the plates is so very fine that it may not look to you as if there is anything on the surface at all.
Go check your air cleaner. Turn off the power to the unit and then pull out one of the Pre-filters and make sure it is clean. If it looks like this next picture, shame on you or your HVAC service company.
Next, pull out one of the filter blocks and wipe the surface with your finger.
If your finger comes away black it needs to be cleaned. Dirty like you touched the damper handle on your fireplace.
The blocks are typically cleaned with soap and water—they are not recommended to be cleaned in the dishwasher. The pre-filters can be hosed out and run through the dishwasher if you choose. Don’t forget that there will be two blocks and two pre-filters that need to be cleaned and put back in their proper places. The pre-filters should be in the slot away from the furnace and the electronic blocks have an arrow that should point in the direction of the furnace.
If all else fails, follow your manufacturer’s instructions (tongue firmly in cheek).
How often do these need to be cleaned? That depends on a lot of factors–but certainly as often as a throw away filter would need to be thrown away. Check it once a month. If your finger is black after a month it needs to be cleaned more than once a month. If it is clean after a month–try two months. You, yourself will have to figure out how often it needs to be cleaned. How often these filters need to be cleaned has more to do with lifestyle and other factors than it does with the unit itself.
Many modern thermostats can be programmed to remind you to clean the filter or change the filter.
By Charles Buell, Real Estate Inspections in Seattle
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