[WAYNE3298]

What is the design clean filter pressure drop at design airflow of the filters normally installed in residential installs?

 

[Core_d]

Even at .55” not including drop of the filter is not very good static. None the less a great improvement from over 1” of static.

Thats likley the difference between a system that will function and will not function.


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[WAYNE3298]

Core_d would you restate your last post? I'm not sure I understood it like you meant. Thanks0

 

[knave]

Even at .55” not including drop of the filter is not very good static. None the less a great improvement from over 1” of static.

Thats likley the difference between a system that will function and will not function.


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Where he was measuring the static gave no indication of airflow, in other words if he had put a piece of cardboard where the filter went his measure static would’ve been zero

 

[WAYNE3298]

ASHRAE has studies concerning filter rating and associated pressure drops. Their studies confirm that if you want better filtration you have to live with the increased pressure drop and resulting loss of airflow or increase the filter surface area to limit pressure drop. Due to space restrictions in residential applications increasing filter surface area to slow down the face velocity isn't feasible and in many cases not possible.
It is not uncommon for clean filter pressure drop to consume 1/3 to 1/2 of the available fan static pressure and that causes the airflow to go almost straight down. If the fan is too short of airflow there is nothing you can do to get more out of it. ASHRAE says that depends on the type of fan you have but I have never seen any type of residential fan that allows increasing airflow above the airflow you get as delivered.

 

[Adlerberts-Protege]

Where he was measuring the static gave no indication of airflow, in other words if he had put a piece of cardboard where the filter went his measure static would’ve been zero

The filter was pulled out.

 

[RMSG01]

Are you in the Shreveport area???

Most of my family is buried in that large cemetery downtown...

Nice area... if you can stand the humidity... grin...
I should be talking... I grew up in Houston...

Yes I'm in Bossier City, have family in a few cemeteries around here and I'm not sure which is worse, Shreveport or Houston, I have kin around the Houston, Katy area, I've thought about heading to Dallas and start my business there, Shreveport going more liberal and it's trickling into Bossier as well.

 

[Poodle Head Mikey]

This is one of the reasons that I have long favored electronic air cleaners. They really remove a substantial amount from the air, their cost of operation is low, and they never negatively impact the air flow performance of the system.

PHM
------------

ASHRAE has studies concerning filter rating and associated pressure drops. Their studies confirm that if you want better filtration you have to live with the increased pressure drop and resulting loss of airflow or increase the filter surface area to limit pressure drop. Due to space restrictions in residential applications increasing filter surface area to slow down the face velocity isn't feasible and in many cases not possible.
It is not uncommon for clean filter pressure drop to consume 1/3 to 1/2 of the available fan static pressure and that causes the airflow to go almost straight down. If the fan is too short of airflow there is nothing you can do to get more out of it. ASHRAE says that depends on the type of fan you have but I have never seen any type of residential fan that allows increasing airflow above the airflow you get as delivered.

 

[WAYNE3298]

I agree Poodle. The last house I did was for a real rich guy. He had six heat pumps with electronic filters and they worked well with not much dp. I forgot what they cost but they were not cheap.

 

[knave]

Not to start a new argument, but some of the dirtiest systems that I had to clean out whether it was the a coil or the secondary heat exchanger or the blower, have been coupled with electronic air filters that did not get maintenance

 

[WAYNE3298]

I don't know anything about how they are or if maintained. The only ones I have seen were new. Other than cleaning what do they need?

 

[knave]

I don't know anything about how they are or if maintained. The only ones I have seen were new. Other than cleaning what do they need?

There are different styles, most only need cleaning per the manual. Many lose efficiency drastically after 1-2 months of runtime. The old Honeywell “snapper” style ones were only as good as the pre and post filter. (A washable metal mesh filter)

The Accuclean (and Clean Effects) haven’t performed all that well even with maintenance. (In my experience)

 

[WAYNE3298]

How do these compare to electrostatic precipitators? What happens when they get dirty? Do they quit filtering or does the dp increase or both?

 

[Core_d]

Core_d would you restate your last post? I'm not sure I understood it like you meant. Thanks0

all im saying is with the filter in place the TESP would still not be very good after the repair. Probably around .7 or .8 Far from ideal but would relieve a multitude of issues compared to over 1” static.

Where he was measuring the static gave no indication of airflow, in other words if he had put a piece of cardboard where the filter went his measure static would’ve been zero

thats true but, the measurement is not useless. There is info available on the pressure drop of the filters at various cfms. Just add that to your measured static to get a good idea of what the TESP is.

This is one of the reasons that I have long favored electronic air cleaners. They really remove a substantial amount from the air, their cost of operation is low, and they never negatively impact the air flow performance of the system.

PHM
------------

Not somuch the with the trane clean affects. They have a significant pd.


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[knave]

How do these compare to electrostatic precipitators? What happens when they get dirty? Do they quit filtering or does the dp increase or both?

Not familiar with the term “electrostatic precipitator”.
When they get dirty they no longer attract dirt, air continues to flow. My assumption has been they hold a certain amount of dirt “in suspension” but when the blower kicks on they lose several grams, and then spend the next 30 minutes replacing those grams of dirt. I suppose the delta p would slightly increase, especially if the pre or post filters would get dirty. Usually the “collection cells” do not get clogged with dirt, just a light coating of dust.

 

[WAYNE3298]

Electrostatic precipitators are used in coal fired power plants. I haven't dealt with them for years and don't remember a lot about them.

 

[Adlerberts-Protege]

Bottom line. A cheap fiberglass filter positioned properly in the return drop at a proper angle is the best?

 

[BBeerme]

In my home, I have a cheap fiberglass filter before the pleated. Change the fiberglass one maybe once a year, after it gets pretty well plugged, and the pleated maybe once every few years.

As you can tell, I'm real picky about that whole maintenance thingy.

 

[knave]

The Aprilaire 2210 has a .11” pressure drop at 1200 cfm. (With MERV 10 filter)

Keep in mind the cheap 1” filters are great for pressure drop right up until the system gets clogged with dust or the a-coil turns into an a-shaped wall of filth.

 

[knave]

In my home, I have a cheap fiberglass filter before the pleated. Change the fiberglass one maybe once a year, after it gets pretty well plugged, and the pleated maybe once every few years.

As you can tell, I'm real picky about that whole maintenance thingy.

That’s not a bad idea as long as the first one is really cheap.... a couple years ago I ran a call where an rtu was freezing up. They had filled the 2” slot with a double layer of pleated 1” filters. Coincidentally shortly thereafter the airflow seemed poor and the convenience store got warm.