It is not too unusual to find missing or out of place furnace filters—-or even non-functional Electronic Air Cleaners. All furnace filtering systems need to be maintained and even more important they need to be there!
If they are not there at all, the same old air keeps circulating through the heating and cooling ducts. When not present the supply ducts can get very dirty and the dust will circulate back into the home. If you have air conditioning and/or heat pump components installed, the coils will become very clogged with this dust—-making the unit inefficient or possibly not functional at all.
Re-circulating this dusty air into the home works against most people’s disdain of dusting.
Take a look at this furnace installation. The blue highlighted arrow shows the flow of return air to the furnace as it arrives at the Electronic Air Cleaner.
With the Air Cleaner access cover removed we can see that the internal components of the filter are missing (pre-filters and Electronic coils). The orange high-lighted area is the opening into the furnace plenum below the blower area of the furnace above. That space left of the orange highlighted areas would normally be the location of the electronic coil components of the air cleaner.
What makes this installation “unusual” from what would otherwise be a very common place defect found in many heating systems, is the presence of another air intake that is the wrong side of the filters—-the filters that aren’t present.
This next picture—-high-lighted in green shows that return air intake that goes through the plenum to an adjacent space.
So even with all the proper components in place and well maintained, this air intake would likely be the major source of unfiltered air to the heating/cooling system.
How dusty is your house?
Charles Buell, Real Estate Inspections in Seattle
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