[Stickman42]

I have a geothermal split system - heat pump in basement, air handler in attic, one central return in upstairs hallway ceiling which has about 6' of flex connecting it to the return plenum. I currently use a 1" pleated filter in the return grille. MERV 8, costs $10 for 3, changed monthly.

I understand the merits of using a 4" or 5" pleated filter. I did purchase a 5" deep one with 1" lip that will fit in my return grille. Price delivered was about $45. I've read that I should only have to change this filter every 6-12 months. What I would like to know is how I can best determine when to change the filter? Besides just looking at it, can I take pressure readings somewhere when the new filter is installed, then check again after some time has elapsed?

Overall , I want to figure out if using the 5" filter is going to be much more expensive than the 1". (I've got a dog that's been shedding straight through winter, but haven't seen any fur in the filter.) my only other option is the available slot in the air handler for a 2" deep filter.

 

[Bob Sanders]

Personally I'm not a big believer in higher merv filters.

Filters were originally designed to protect the equipment and the straight old fashioned fiberglass style filters did a pretty good job at that with minimum resistance, but of course we figured why not treat the system as an air purifier too, which is primarily why the higher merv filters come into play. What people aren't aware of is that they can and most often do drop overall efficiency a little because of the increased efficiency. Particularly if you have an ecm motor which (some) will actually increase in rpm (and amperage draw), in effect costing you more money.

Pretty good article here, but to answer you question (from the article):

We also expected to see a lower pressure drop for the deeper 2-inch and 4-inch filters, because of the increased surface area and the reduced velocity of air passing through the media. Surprisingly, the 4-inch Filtrete 1550 (MERV 12) was only marginally better than the 1-inch Filtrete 1700 (also MERV 12) and the two other MERV 11 filters of the same brand (1000 and 1085).

http://www.homeenergy.org/show/article/id/667

As fir measuring devices... you need a manometer. You can get them hand held, mechanical like the one below (just an example), or electronic.

http://www.ebay.com/itm/78075-manometer-H23-606-/141809771452?hash=item21048563bc:g:GA4AAOSw5VFWKoZv

You can even make your own little manometer with some tubing and a bit of water filling the tube.

 

[SeniorSitizen]

Don't want to hijack Stickman42's thread but in the study I found this interesting, especially I've been using a electrostatic ( not a Web ) as a pre-filter in conjunction with 1" fiberglass .

"The Web Lifetime, a electrostatic filter, was the best Hi-Merv performer. Its Merv 8 rating is surprising, given the relatively open appearance of the media compared to replaceable filters".

 

[SeniorSitizen]

I sure hope no one falls for the e-bay manometer deal at that price.:surprise: A 3 dollar rain gauge and a couple of bucks for the tubing and fitting at Ace Hardware should do it.:biggrin2:

 

[Stickman42]

I sure hope no one falls for the e-bay manometer deal at that price.:surprise: A 3 dollar rain gauge and a couple of bucks for the tubing and fitting at Ace Hardware should do it.:biggrin2:

Yeah, $55 seemed a bit high. I saw this one and thought it would be better because it could be mounted

http://www.ebay.com/itm/DWYER-INSTR...337039?hash=item58b657ea8f:g:msUAAOSwoydWrC48.

Or I think I have a manometer at work I can hijack. Where in my system would be the best place to take a reading?

 

[Bob Sanders]

Yeah, $55 seemed a bit high. I saw this one and thought it would be better because it could be mounted

http://www.ebay.com/itm/DWYER-INSTR...337039?hash=item58b657ea8f:g:msUAAOSwoydWrC48.

Or I think I have a manometer at work I can hijack. Where in my system would be the best place to take a reading?

Yeah, I just grabbed the first one I saw as an example. $1.25 worth of tubing and you can make your own

 

[jomama45]

Yeah, $55 seemed a bit high. I saw this one and thought it would be better because it could be mounted

http://www.ebay.com/itm/DWYER-INSTR...337039?hash=item58b657ea8f:g:msUAAOSwoydWrC48.

Or I think I have a manometer at work I can hijack. Where in my system would be the best place to take a reading?

I have had that exact Dwyer mounted to my chimney, tied into my wood furnace pipe, for a few years now, and can tell you that it's very easy to use and works great........

 

[Bob Sanders]

Yeah, $55 seemed a bit high. I saw this one and thought it would be better because it could be mounted

http://www.ebay.com/itm/DWYER-INSTR...337039?hash=item58b657ea8f:g:msUAAOSwoydWrC48.

Or I think I have a manometer at work I can hijack. Where in my system would be the best place to take a reading?

If you're talking about filter measurement then you need to place it across the filter.

 

[SeniorSitizen]

If I read correctly, the .org test folks found it surprising the depth of the filter pleats mads little difference in air flow when testing clean filters. I have a thought for them but they would probably say " who the hell is that guy ".

 

[Stickman42]

If you're talking about filter measurement then you need to place it across the filter.

Could you please specify exactly how/where to accomplish this? The attached is a sketch of my equipment layout.

 

[jomama45]

That Dwyer has 2 ports on the top, Hi & Low ports. You hook one hose on the cold air return, before the filter, and the other to the trunk. I'm sure a pro can elaborate a little more, and let you know how much static pressure is acceptable..........

 

[beenthere]

Don't want to hijack Stickman42's thread but in the study I found this interesting, especially I've been using a electrostatic ( not a Web ) as a pre-filter in conjunction with 1" fiberglass .

"The Web Lifetime, a electrostatic filter, was the best Hi-Merv performer. Its Merv 8 rating is surprising, given the relatively open appearance of the media compared to replaceable filters".

Your better off testing its actual pressure drop. Then hoping its close to that test/survey.

 

[Stickman42]

That Dwyer has 2 ports on the top, Hi & Low ports. You hook one hose on the cold air return, before the filter, and the other to the trunk. I'm sure a pro can elaborate a little more, and let you know how much static pressure is acceptable..........

Before the filter is open space, not in the duct system. I could see if my filter was at the air handler how I could probe it before and after. With my setup, I don't see how I can measure pressure before the filter.

 

[jomama45]

Before the filter is open space, not in the duct system. I could see if my filter was at the air handler how I could probe it before and after. With my setup, I don't see how I can measure pressure before the filter.

I guess you're just trying to measure "draft" then, which is how I use it on my chimney pipe. In that case, I guess you just hook to the "low" port to measure draft/restriction??

 

[Stickman42]

I guess you're just trying to measure "draft" then, which is how I use it on my chimney pipe. In that case, I guess you just hook to the "low" port to measure draft/restriction??

So I take baseline measurements with a clean 1" and 5" filter, then check the reduction in draft later on. Sound like a reasonable plan?

 

[DOUG1111]

Frequently the air return grill is smaller than it should be. Their for use the cheap filters & change them more often. The $$ you saved on filters put to a in place coil clean once a year. Pending size filters @ walmart 3 for $4.00

 

[supers05]

Filters of the same MERV rating but thicker will have longer life expectancies. (ie. Your 1" merv8 compared to the 5" merv8.) The thicker filter will last longer with almost no impact on the overall system)

The manometer will be placed "across" the filter. In your case, high port is open to the free space of the room, and low port to the ductwork. (It can also be remote mounted, where you'd be better off using tubes on both ports, running to the same locations)

You'd want to change them somewhere between 0.1"WC to 0.3"WC would be where I'd change it. It depends on the system, since some systems are already near their lower flow limit. In the article below, they found some running higher then 0.68"wc. They then replaced those low merv filters with merv16 and retested.

http://eetd.lbl.gov/sites/all/files/lbnl-6144e.pdf


Cheers!

 

[Stickman42]

I read and re-read Bob Sander's and supers05 articles, and this is what I come away with:

- there's not a major pressure drop differential between CLEAN 1" and 4-5" filters of the same MERV rating
- since I have an ECM blower motor, my blower consumes more power as the installed filter becomes more dirty/restrictive

And now my own conclusions:
- a 1" MERV 8 filter at $3.50 changed monthly (my month-old filters are not collapsed, nor do I see much dust in the flex return duct post-filter) has essentially the same pressure drop as a 5" MERV 8 filter costing me $45
- twelve 1" filters costs less than one 5" filter; 12 months seems to be the most common maximum interval of replacement of deep filters
- a 1" filter that is not overwhelmed with dirt by month's end exerts no major influence on system performance/cost to operate; the effect of degradation of airflow/performance of a deep filter can only be assumed to be gradual as the 12 months go by
- twelve 1" filters cost $42; one deep filter costs $45

Therefore, in MY situation, it appears that 1" filters are the best strategy. Would you agree?

Edit: I should mention that I am filtering only for equipment protection. If I was looking for IAQ improve,net, I would have considered higher MERV filters, probably with a different conclusion

 

[beenthere]

- there's not a major pressure drop differential between CLEAN 1" and 4-5" filters of the same MERV rating
- since I have an ECM blower motor, my blower consumes more power as the installed filter becomes more dirty/restrictive

If your comparing a 3M 1" to a 3m 4 or 5", not much difference.

Compare some of Honeywell's 4" media filters, and you'll see they have lower pressure drops then many 3M media filters do.

A Honeywell FC100A is 23 bucks. So basically, 2 years for the price of 1 year of the 1" your looking at.

 

[Stickman42]

My comparison was for Rheem 1" FPR 4 filters from HD (http://www.homedepot.com/p/Rheem-30...PR-4-Air-Filter-3-Pack-64300-012430/203584167) vs. a Honeywell FC40R1177 (https://www.filtersfast.com/P-24x30-Honeywell-FC40R1177-Air-Grille-Filter.asp). The Honeywell is a return grille filter. Do media filters cost significantly less than return grille filters? I do not have a media filter cabinet at this time, so I'm working the best possibilities with my current setup.