I have an Aprilaire filter enclosure attached to my furnace which takes
a #413 filter. I believe it's designed to give 95% filtration.

https://www.amazon.com/Aprilaire-413...13+replacement


16" x 25" x 3 1/2"

It does a decent job but in this ancient house with two cats I'd like to
go all the way to a HEPA filter.



I have not been able to find a HEPA replacement so unless anyone has a
suggestion , looks like I will have to replace the entire enclosure.


Since I'm not a sheet metal expert, will have to contract this out.

On 02-Dec-17 10:19 AM, philo wrote:
I have an Aprilaire filter enclosure attached to my furnace which takes
a #413 filter. I believe it's designed to give 95% filtration.

....


I have not been able to find a HEPA replacement so unless anyone has a
suggestion , looks like I will have to replace the entire enclosure.

http://www.filtersamerica.com/Results.aspx

May have to do the search again in a new session; in same session new
window it reloaded results but I can believe that won't happen in a
completely new session.

Since I'm not a sheet metal expert, will have to contract this out.

Those were all 16x25x3; there wasn't a 3.5" choice in the dropdown.
But, since these have solid frames, shouldn't be difficult to fabricate
a 1" skirt around the edge to fill up the remaining space without
re-fabbing the whole plenum box.

--

On Saturday, December 2, 2017 at 11:20:05 AM UTC-5, philo wrote:
I have an Aprilaire filter enclosure attached to my furnace which takes
a #413 filter. I believe it's designed to give 95% filtration.

https://www.amazon.com/Aprilaire-413...13+replacement


16" x 25" x 3 1/2"

It does a decent job but in this ancient house with two cats I'd like to
go all the way to a HEPA filter.



I have not been able to find a HEPA replacement so unless anyone has a
suggestion , looks like I will have to replace the entire enclosure.


Since I'm not a sheet metal expert, will have to contract this out.

It wouldn't be worth it to me. You're probably looking at $500 plus. I bought a rheem filter housing when I put in a new furnace. That's 5" thick I think. I think they were going for under $200 on line, but an installer is going to likely charge you list plus labor. Labor and extras will depend on what it takes to get it in. Mine the work was the same with or without. If you have two cats, the existing filter will catch anything significant and no filter is going to catch most of the cat stuff because it will never make it to the filter.

replying to philo, Iggy wrote:
Very bad idea and won't do anything but harm your system and therefore you.
Notice the 4th picture down of the Amazon link, you currently have a MERV 13
and may only be able to go to MERV 15...your system may need the 7th Amazon
picture with just a MERV 15.

HEPA on the other hand is MERV 17-20 and will absolutely kill your system's
fan motor in very short order. Your current filter, the 413, is easily getting
all pets stuff as well as all the dusts, viruses, germs and bacteria that
would ever harm you in anyway, filters also catch more as they fill-up. Here's
a MERV breakdown http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf

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for full context, visit https://www.homeownershub.com/mainte...r-1152089-.htm

On Sat, 2 Dec 2017 10:19:59 -0600, philo wrote:

Since I'm not a sheet metal expert, will have to contract this out.

.... this could turn into a duct tape conversation (G)

Large HVAC contractors may have a fabrication shop close by.

On Saturday, December 2, 2017 at 5:44:15 PM UTC-5, Iggy wrote:
replying to philo, Iggy wrote:
Very bad idea and won't do anything but harm your system and therefore you.
Notice the 4th picture down of the Amazon link, you currently have a MERV 13
and may only be able to go to MERV 15...your system may need the 7th Amazon
picture with just a MERV 15.

HEPA on the other hand is MERV 17-20 and will absolutely kill your system's
fan motor in very short order. Your current filter, the 413, is easily getting
all pets stuff as well as all the dusts, viruses, germs and bacteria that
would ever harm you in anyway, filters also catch more as they fill-up. Here's
a MERV breakdown http://www.mechreps.com/PDF/Merv_Rating_Chart.pdf

--
for full context, visit https://www.homeownershub.com/mainte...r-1152089-.htm

That's a good point. I don't remember what MERV my 5" thick filter is,
but AFAIK, it's not HEPA. Are HEPA even available for a furnace?
IDK, but maybe not, because you can only pleat it so much to increase
surface area. And as you point out, as it filters finer and finer,
the pressure drop would increase to unacceptable levels if the surface
area is not also increased. That's why mine is 5" instead of 1".
And at that filtration level these filters cost ~$35 a piece to replace.
If you can get a HEPA, it must cost a lot more.

There are also electronic ones available. One advantage they have is
little pressure drop, but AFAIK those are not HEPA either. Maybe Philo
has a link to what he's thinking of using?

replying to trader_4, Iggy wrote:
Yeah, he's pretty much maxed-out for any furnace. HEPA's a tighter weave, so
from its start it's worse than a many years old completely filled
filter...maybe an exaggeration, but not far off. There's no HEPA option, the
fan motor might have to be twice the horsepower to pull the air through the
filter and of course it only gets tougher as it fills. I'm not sold on the
electronic filters, I had one and it was surprisingly good and cheap but I'm
not sure I can believe it zaps the air as clean as a top performer
paper/fabric filter.

--
for full context, visit https://www.homeownershub.com/mainte...r-1152089-.htm

On 12/02/2017 10:19 AM, philo wrote:
I have an Aprilaire filter enclosure attached to my furnace which takes
a #413 filter. I believe it's designed to give 95% filtration.

https://www.amazon.com/Aprilaire-413...13+replacement





OK, thanks folks


Think I will leave well enough alone