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Discussion Starter #21
So looks like the options are as folllowing:

1. Do nothing. Continue using: Filtrete 14x20x1, MPR 2800, MERV 13. (because of availablity might open the 16x25x1 instead).

2. Upgrade the 2" filter Grille like this:
https://www.plumbersstock.com/shoemaker-920fg2-14x25-14inx25-filter-grille-2-filter-fixed-bar-blade.html
pair with:
Aerostar 14x25x2 MERV 13. It says MERV 13, but in description: 3M Filtrete MPR 1500 to 1900. This makes me question all the rating thing.

3. Upgrade to larger opening. Due to Filter availability, thinking about 20x25. 4" or 5", something like this:
Nordic-Pure 20x25x4, MERV 15
or
Nordic Pure 20x25x5, MERV 15
That's maybe an overkill, but there are lots of options for MERV ratings and would be able to change between filters on as needed basis.
 

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Discussion Starter #22
If the unit is 2.5 ton or larger add a second return that same size then you can run those higher MERV filters to better clean the air for the equipment and your unit will be glad you did.
The unit is 3 ton. TBH adding second return might be way harder and more involved.
 

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Discussion Starter #23
^it can be a lot of work.

14x25 is very small - the desirable size depends on equipment size and filter used.

bigger is better - if you can put a 25x25 grill, any filter would be far less restrictive.
I can't find a good 25x25 filter. Leaning towards 20x25x4 or 20x25x5.
 

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Option one will kill your ecm blower eventually - 14x25 is way too small for any 1" pleated filter when you have a 3 ton a/c.

16x25 is also too small.

Option 2 - 2" is not thick enough if you want to use merv 13, it may start okay with a larger opening.

You need to enlarge the opening or put another return, or switch to something completely non-restrictive and use room air cleaners*.

*On the cheap, a couple of box fans with very high merv furnace filters taped on may work.
 

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Discussion Starter #27
Option one will kill your ecm blower eventually - 14x25 is way too small for any 1" pleated filter when you have a 3 ton a/c.

16x25 is also too small.

Option 2 - 2" is not thick enough if you want to use merv 13, it may start okay with a larger opening.

You need to enlarge the opening or put another return, or switch to something completely non-restrictive and use room air cleaners*.

*On the cheap, a couple of box fans with very high merv furnace filters taped on may work.
Well, I've already got the box thing done. Its a solution during wildfires. But I needed a permanent solution for the rest of the time.
 

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Your filter box is too shallow for a 4" filter. So getting that grille is a waste of money, unless you double the height of the return box.
 

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A 4" pleated filter has MUCH less flow resistance than a 1" pleated filter (especially a Filtrete). If you are going to use 1" Filtrete filters, you are going to reduce the airflow significantly on what already appears to be an undersized return.
 

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Discussion Starter #31
Your filter box is too shallow for a 4" filter. So getting that grille is a waste of money, unless you double the height of the return box.
I'd get the box replaced to a bigger one. How deep should the new one be to take 4" filter?
 

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So looks like the options are as folllowing:
One more option. See if you can find a filter conversion kit for your electrostatic filter. Lots of others are doing the same thing as you.

Goggle "Make-and-model-of-my-electrostatic-filter filter conversion".

I put a big paper filter on my friend's furnace where her electrostatic filter died and she was running no filter at all. A while later, my HVAC guy was at her house for another issue and explained that the sheet metal shop just down the road (literally walking distance) makes a conversion kit. The HVAC guy was not particularly thrilled at how well my filter fit in the housing, but said it would be OK as is, so left it the way it was.

He said just tell them the make of the electrostatic filter and the nominal size.

I am not sure exactly what the kit consisted of. Maybe a permanent sleeve to put in the housing. Maybe something that you put the filter into and then slide into the housing. Maybe a filter housing for replaceable media.
 

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Discussion Starter #33
One more option. See if you can find a filter conversion kit for your electrostatic filter. Lots of others are doing the same thing as you.

Goggle "Make-and-model-of-my-electrostatic-filter filter conversion".

I put a big paper filter on my friend's furnace where her electrostatic filter died and she was running no filter at all. A while later, my HVAC guy was at her house for another issue and explained that the sheet metal shop just down the road (literally walking distance) makes a conversion kit. The HVAC guy was not particularly thrilled at how well my filter fit in the housing, but said it would be OK as is, so left it the way it was.

He said just tell them the make of the electrostatic filter and the nominal size.

I am not sure exactly what the kit consisted of. Maybe a permanent sleeve to put in the housing. Maybe something that you put the filter into and then slide into the housing. Maybe a filter housing for replaceable media.
I'm sorry but i couldn't follow. What is an "electrostatic filter" ? What kind of conversion are you referring to?
 

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I'd get the box replaced to a bigger one. How deep should the new one be to take 4" filter?

Min of 10 inches. Should have at least six inches from top of the air filter, and the duct opening.
 
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I live in NorCal where it's been very smoky (including 2 days of orange skies) the last few weeks. I changed out my 4" filter ~3 months ago before the fires started, below you can see what it looks like now. I keep my house clean so that isn't dust, it's smoke particulate. When it is smoky enough to sting your eyes outside the air inside inside is vastly better, I leave the recirculation fan on low 24/7 when it is smoky. Also, you can run a higher MERV 4" filter than you can 1-2" without sacrificing significant airflow, you will be happy with the upgrade, I know that I sure am.





 

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You must have a very "leaky" house, or go in and out the doors all the time! That filter filters interior air - outside air isn't drawn into the house by the HVAC system.
 

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You must have a very "leaky" house, or go in and out the doors all the time! That filter filters interior air - outside air isn't drawn into the house by the HVAC system.
Both of the above. 1952 house with original metal frame, single pane windows that don't seal well. Scraping money together to replace the windows next year I hope.
 
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