# New HVAC -filter keeps collapsing inside?



## adgjqetuo (Oct 21, 2011)

Anyone know why this keeps happening and how to prevent it? The system is new and the original filter was a very basic filter - practically see through.

I replaced the original filter with one claiming to have a little more filtration in attempt to help my daughters allergies some but it keeps collapsing inside the housing. Is it too restrictive? Do I have other options or do I have to stick to the low end filters?


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## roughneck (Nov 28, 2014)

What size filter, and what BTU equipment?
The filter is likely too restrictive, and based on the equipment size the return may be too small causing excessive velocity within the duct. 
Stick to cheap fiberglass throw away filters unless you can upgrade to a 4" or 5" media filter.


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## adgjqetuo (Oct 21, 2011)

20x25 and I believe 85k BTU 

Unit is a Reem R96VA

Thanks - that's what I was afraid of - maybe I can look into upgrading in the future.


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## yuri (Nov 29, 2008)

There are 6 or more grades of filters and the industry norm is called MERV. min efficiency reporting value.

You cheapo 1 dollar filter is a Merv 3ish. Then you go up to merv 7 and 8 and 11 or 12 up to 16 which is HEPA grade.

I would try a Merv 7 True Blue from HDepot and see if it collapses. If so your ductwork is undersized and they may have the fan running on too high a speed.

3M does not use the Merv system so it could be a lot higher w/o knowing as they have some very tight expensive filters.


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## adgjqetuo (Oct 21, 2011)

Thanks for the information. Here is the filter that's currently in now - it's a FPR 9 (10 is the highest). 

http://m.homedepot.com/p/Honeywell-...eated-FPR-9-Air-Filter-90901-012025/203145831

Maybe I should try the 4 or 7? I feel like the 7 would have similar results? These are the only 3 options I really have at my local HD for my size. I could maybe try Lowes though? 

http://m.homedepot.com/p/Honeywell-...eated-FPR-7-Air-Filter-90701-012025/203145812

http://m.homedepot.com/p/Rheem-20-i...eated-FPR-4-Air-Filter-64100-012025/203140811


You may also be right about the undersized duct work, I noticed with this filter the static pressure according to the stat hovers around .90-1.0 where as before it was closer to .70. The unit also has a slight whistle sound with this filter too.


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## yuri (Nov 29, 2008)

You have a variable speed ECM blower the maximum static pressure it is recommended to work against is .8""WC versus the .5" of a regular PSC motor in an basic furnace.

Point being you don't want to go over .7-.8" as it decreases the life of the motor/overworks it.

Ideally you should try get the ductwork fixed, more returns added.


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## beenthere (Oct 11, 2008)

Try the 4.


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## adgjqetuo (Oct 21, 2011)

I'll pick one up today - thanks!

EDIT - I meant to ask, the installer also put in a UV light right before the filter on the return, does that help any filtration wise? Are the 7 and 9 filters considered more of a waste of money? I noticed they are triple the price of the 4.


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## beenthere (Oct 11, 2008)

The UV light will help kill Bactria. The 7 and 9 are too restrictive for the amount of air your furnace needs to move. You would need 2 filtered returns to use those filters and get enough air flow not to bend/bow those filters.


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## adgjqetuo (Oct 21, 2011)

Just curious, you mean adding filters to the return vents directly? Why only 2? We have 7 return vents throughout the house (5 upstairs, 2 downstairs) but the grates don't have support for filters I believe.


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## roughneck (Nov 28, 2014)

adgjqetuo said:


> Just curious, you mean adding filters to the return vents directly? Why only 2? We have 7 return vents throughout the house (5 upstairs, 2 downstairs) but the grates don't have support for filters I believe.


Not return grills, but as in 2 main returns to the furnace itself. Basically 2 of what you have now, where the filter is located. The added surface area would not only support additional CFM, it would greatly decrease velocity within the duct.


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## beenthere (Oct 11, 2008)

adgjqetuo said:


> Just curious, you mean adding filters to the return vents directly? Why only 2? We have 7 return vents throughout the house (5 upstairs, 2 downstairs) but the grates don't have support for filters I believe.


Sorry. Didn't give thought to my post being cryptic as to what I really meant. 

As said above, 2 returns like you have at the furnace to use that type of air filter. 

Most likely, your current 7 individual returns in teh house are not enough or too small already.


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