OK to use highest rated filter?

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tomtheelder2020

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We had a new Bryant HVAC system installed last summer. In response to an email, the installation company owner told me it is OK to use any FPR/MERF rated filter - but it came with only a moderatly rated filter. I would like to use MERV 10 filters but am concerned they would put extra stress on the blower motor, potentially shortening its life. Is that concern realistic?
 

Steve123

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No that concern is not realistic.

My Armstrong manual specifically states to use a minimum MERV 11 filter.
 

kok328

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I would not expect the unit to be shipped with a high end filter as the cost will add up for the manufacturer.
Using a filter within the recommend MERV ratings for your specific unit should be fine.
Using a filter with a MERV rating higher that what is recommended by the manufacturer will definitely increase wear and tear on the blower motor as well as increase your utility cost to run the unit.
Working with my media supply vendor, on average, this curve can be expected at and above MERV-14.
 

Eddie_T

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I don't know about airflow but with well pumps they say work equals force times distance so less flow means less amperage.
 

havasu

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W = F x D?

Hmm, never heard that before.
 

Steve123

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W = F x D? Hmm, never heard that before.
From a Middle School online lesson - below :
But it is important to note that there must be motion for work to have been performed. If you just push on the back of a truck, no work has been performed if it does not move. If you don't have motion, one can invert the W to an M and say M=FxD (moment). Not sure what any of this has to do with air filters, though.

Work 2.jpg
 
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havasu

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Very similar to the E = MC (squared)

However, a thicker air filter is akin to placing a block of concrete in front of a car, and pushing it down the street. The force is greater, therefore the work is harder, causing motors to blow sooner.
 

Eddie_T

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I don't know if pneumatics work the same as hydraulics but consider this post from an engineering forum;
For a radial flow centrifugal pump . . . . The work done by the pump is the volume moved and not the pressure developed, although the relationship between pressure (head)capacity (volume)and power are all interdependent. For a fuller understanding search for "affinity laws" Basically for a given set of circumstances:
Reduce flow by increasing discharge pressure = lower power
Increase flow by reducing discharge pressure = higher power
Reduce speed = lower discharge pressure, lower flow and lower power
Increase speed = higher discharge pressure, higher flow,and higher power
Different rules apply for axial flow centrifugal pumps and constant displacement pumps
If you have an amp meter it's easy to run a rest. One person did on another forum yielding these results for a squirrel cage blower;
With it operating as unrestricted as possible at full speed. 4.8 amps

With it operating with only the the inlet blocked at full speed 3.8 amps

With it operating with only the outlet blocked at full speed 3.7 amps
If a filter severely restricts air flow it can impact the refrigerant flow (suction and head pressures) and that's a whole 'nother story.
 
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ajaynejr

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I unscientifically suggest: If the store has 3 grades of the same filter brand, choose the lowest. If 4 grades, choose the second lowest.
 
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