HVAC filters
#11
I recently had my ac serviced. The tech stated that I would be better using a cheaper filter I use the dupont 9600 premium with a merv of 12.
My unit seems to handle it well enough.
Is there a good basisis for using a lower price filter?
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#12
(07-22-2018, 09:02 AM)Jack in omaha Wrote: I recently had my ac serviced. The tech stated that I would be better using a cheaper filter I use the dupont 9600 premium with a merv of 12.
My unit seems to handle it well enough.
Is there a good basisis for using a lower price filter?

The higher the merv rating the more resistance to air flow.  Here is a article about it.

Resistance to Airflow: The rule of resistance to airflow is the higher the filter’s MERV rating, the greater its airflow resistance, and the greater the airflow resistance, the less air moved by the HVAC fan. When airflow becomes too low, efficiency drops and equipment can be damaged. A filter’s resistance to airflow is measured in pressure drop across the filter in inches of water column (IWC). Unless the entire system is designed for filters with a large pressure drop, it is good practice to use filters with pressure drops of less than 0.10 IWC. In almost all cases this will limit your choices to filters with a MERV rating of less than eight. Don’t assume that a filter with a MERV of eight will have pressure drop of less than 0.10 IWC. Many hardware store filters have pressure drops in excess of 0.2 IWC, and are not suitable for residential equipment.
 I can tell on my furnace a high merv will cut air flow to the farther rooms which results in unit running longer.  Roly
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#13
I had my house inspected for energy usage last fall. I had 11 MERV filters and it was recommended to use a MERV 8. I haven't noticed much difference.
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#14
(07-22-2018, 10:48 AM)cndamm Wrote: I had my house inspected for energy usage last fall. I had 11 MERV filters and it was recommended to use a MERV 8. I haven't noticed much difference.

You may not notice but your fan motor might.

An alternative is installing a 4" filter box and use a higher MERV rated filter. The greater surface area of the 4" pleated filters makes up for the lower airflow... so it's a wash. You get cleaner air and don't sacrifice airflow.
Neil Summers Home Inspections




" What would Fred do?"

... CLETUS











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#15
(07-22-2018, 03:47 PM)Snipe Hunter Wrote: You may not notice but your fan motor might.

An alternative is installing a 4" filter box and use a higher MERV rated filter. The greater surface area of the 4" pleated filters makes up for the lower airflow... so it's a wash. You get cleaner air and don't sacrifice airflow.

 Fan motor would draw less amperage with more restriction, however evaporator may not see enough air flow and freeze up and heat exchanger would get hotter.  Roly
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#16
(07-22-2018, 09:02 AM)Jack in omaha Wrote: I recently had my ac serviced. The tech stated that I would be better using a cheaper filter I use the dupont 9600 premium with a merv of 12.
My unit seems to handle it well enough.
Is there a good basisis for using a lower price filter?

I have been using the higher merv filters for several years thinking they would catch a little more dust.   This house is a Lindal Cedar Home with lots of glass and exposure.  The thermostat selected temperature would not be maintained and the house would over shoot by perhaps 6 deg.  This year I started using the cheapest filter and the temperature inside will be much closer to seletected. FYI
Regards,

Regards, Bill
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#17
My neighbor was just telling me today that his furnace shut down in the past because he was using too high a MERV... apparently the system is designed to not but out the motor. I'm guessing it is designed to not run when too dirty, but resistance to air flow is resistance to air flow.
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#18
The only protection the motor has is the furnace breaker and an internal overload switch that shuts the motor off if it gets too hot internally.  As Roly mentioned, a blocked filter will actually unload the furnace motor.  Your friend's furnace was overheating at the heat exchanger and the high limit switch was shutting it off to prevent gross overstress of the heat exchanger or a potential fire.  I easily see a couple dozen calls a year for systems that are malfunctioning due to excessively restrictive filters.  To go along with that, a lot of folks believe the 3 month life statement that a lot of filters carry.  Pure hogwash.
Blackhat

Bad experiences come from poor decisions. So do good stories. 


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#19
(07-25-2018, 10:57 PM)blackhat Wrote: To go along with that, a lot of folks believe the 3 month life statement that a lot of filters carry.  Pure hogwash.

I've always assumed the filter needs to be changed when it's too dirty, no matter how long it's been there.
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#20
How do y’all decide when the filter is too dirty?
Gary

Please don’t quote the trolls.
Liberty, Freedom and Individual Responsibility
Say what you'll do and do what you say.
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