AFCA Forums Home
Home Search search Menu menu Not logged in - Login | Register

 Moderated by: Steve Cunningham, Rod Rogers, Larry Hancock
New Topic Reply Printer Friendly
Adding Filter to Window Fan  Rate Topic 
AuthorPost
 Posted: Sat Mar 24th, 2018 04:11 pm
  PMQuoteReply
1st Post
Jac Chandross
Guest
 

Joined: Wed Nov 12th, 2014
Location:  
Status: 
Offline
I live in a city and want to add an air filter to a window fan to avoid bringing in pollen, dust, diesel particulates, etc.  I did a forum search but turned up nothing which would answer this question.

My idea was to construct a simple box out of sheet steel which holds a washable metal-mesh pre-filter to large particulates and keep out rain, then a plastic electrostatic filter which adds minimal drag but removes most of the coarse dust, then a conventional pleated furnace filter with large surface area for the lowest drag.

I am aware that fans work better on pull than push, so the filter would be on the fan intake.

I was hoping to be able to keep the fan size down to something manageable, such as the conventional 12 inch window fans with a round opening and three to four blades.  This will fit in the window and can be removed in the winter or have a cover for insulation, much like an air conditioner which is permanently mounted.  Since I must store the fan when removed in the winter, I want one which is as small as possible.  The filter housing could be constructed to disassemble and be flatpack stored.  This is not the most difficult part of the task, of course; that is determining if the fan will pull sufficient air to make it work.

I'm uncertain how to calculate the drag, and am unsure if this project is simply doomed from the start.  HEPA filters are generally not used in HVAC applications because the drag is too high for a whole house system.  Since the size is standardized, I can use try an HEPA and see if it is too high and then drop down.  I do not believe adding the two coarse mesh pre-filters would add significant drag.

I point out that a car cabin air system uses a coarse pleated-paper filter and a very small fan motor, far less powerful than the window fan unit.  I just replaced my cabin air filter with a washable unit with fine mesh which works in an electrostatic fashion, similar to the furnace filters.

Do the smaller window fans, such as the Vornado, Lasko, Eskimo, etc. have sufficient power for this purpose?  I am open to a single or double fan.  I thought a double might be the optimal solution.

I also considered using two fans: the intake with the filter on one side of the apartment, and an exhaust fan, obviously with no filter, on the other side.

As an side issue, I will, of course, completely clean the motor and re-lubricate so the additional force on the motor will not have the added burden of animal fat lubricant crosslinked into wax.

Has anyone done this?  Thoughts?  Comments?

Back To Top PMQuoteReply  

 Posted: Mon Mar 26th, 2018 06:29 pm
  PMQuoteReply
2nd Post
Michael Rathberger
AFCA Member


Joined: Tue Nov 15th, 2005
Location:  
Status: 
Offline

I'm going from memory, but GE made a window fan that had a filter element in it, it was an odd design, but basically the fan unit sat mostly outside, drew air from the bottom, through the filter and into the room through vents if I remember right. The profile in the window was about 8-12" only. I have one buried away somewhere that I wish I didn't. A member here may remember the thing and give a better description than I can. It's been 10-12 years since I even seen the thing.

Back To Top PMQuoteReply

 Posted: Mon Mar 26th, 2018 07:32 pm
  PMQuoteReply
3rd Post
George Durbin
AFCA Member


Joined: Fri Nov 2nd, 2012
Location:  
Status: 
Offline
I buy $10-$15 box fans from Wally world that are 20x20 and tape 20x20 furnace filters to them in my wood shop... works great... very little expense and way cheaper than the other stuff u can buy... I have done this in my wood shop for nearly 40 years! 

Geo

Last edited on Mon Mar 26th, 2018 07:33 pm by George Durbin

Back To Top PMQuoteReply  

 Posted: Mon Mar 26th, 2018 07:37 pm
  PMQuoteReply
4th Post
George Durbin
AFCA Member


Joined: Fri Nov 2nd, 2012
Location:  
Status: 
Offline
I keep 2 or 3 new fans in box on a shelf and when they seize up I tossem and drag out a new fan... I keep 2 fans running 24/7 with filters... I get about 1.5 - 2 years out of them running in my basement...

Don geo corleoni...

Last edited on Mon Mar 26th, 2018 07:38 pm by George Durbin

Back To Top PMQuoteReply

 Posted: Mon Mar 26th, 2018 08:51 pm
  PMQuoteReply
5th Post
Rod Rogers
Administrator


Joined: Sun Nov 13th, 2005
Location: Salina, Kansas USA
Status: 
Offline
I also use this system for spraying paint & laquer. Set the fan up on a bar stool & it's about the right height to stand behind it. Most of the overspray gets trapped in the filter instead of all over the shop!

~Sparky~

Back To Top PMQuoteReply  

 Posted: Tue Mar 27th, 2018 01:06 am
  PMQuoteReply
6th Post
Jac Chandross
Guest
 

Joined: Wed Nov 12th, 2014
Location:  
Status: 
Offline
Michael Rathberger wrote:

I'm going from memory, but GE made a window fan that had a filter element in it, it was an odd design, but basically the fan unit sat mostly outside, drew air from the bottom, through the filter and into the room through vents if I remember right.


I believe that would be the GE Ventoglide.  Very rare.  I had found a reference to that one and looked it up before posting to see if I could derive any useful information about how thick that filter was and what the airflow was like.  Nuthin'.  I got nuthin'.  Thanks for the pointer, though.  That is the sort of gizmo I am thinking of building.

Here's a video of one: https://www.youtube.com/watch?v=5KV2nWFaeEM

Back To Top PMQuoteReply

 Posted: Tue Mar 27th, 2018 01:12 am
  PMQuoteReply
7th Post
Jac Chandross
Guest
 

Joined: Wed Nov 12th, 2014
Location:  
Status: 
Offline
George Durbin wrote: I keep 2 or 3 new fans in box on a shelf and when they seize up I tossem and drag out a new fan... I keep 2 fans running 24/7 with filters... I get about 1.5 - 2 years out of them running in my basement...
Is the short life because of the added force the filter puts on the motor or because these are shoddy fans with sleeve bearings and poor quality construction?

I have two inexpensive fans which have been running 24-7-365.  One is a Bionaire column fan.  I take each apart twice a year, same as my other fans, wash the blades and cage, and lubricate the bearings and gearbox.  I had the Bionaire seize on me after a single season of continual use.  The oil in the motor had turned to sludge.  After cleaning and regular lubrication it has flawlessly worked.

My original oil was a lightweight turbine oil for HVAC, but lately I've been using synthetic oil with PTFE (brand name Teflon) for the bearings, and silicone grease with PTFE for the gearbox, both of which makes a big difference in the longevity, fan speed, and noise.

Back To Top PMQuoteReply  

 Posted: Tue Mar 27th, 2018 01:20 am
  PMQuoteReply
8th Post
George Durbin
AFCA Member


Joined: Fri Nov 2nd, 2012
Location:  
Status: 
Offline
These fans from Wally world are non oilable and are sealed bearings... all plastic very cheap 20 inch fans... with furnace filters attached by duct tape I think last pretty good considering the abuse they get... This winter I bought 2 fans for $12 each...
Geo...

Back To Top PMQuoteReply

 Posted: Tue Mar 27th, 2018 01:21 am
  PMQuoteReply
9th Post
Jac Chandross
Guest
 

Joined: Wed Nov 12th, 2014
Location:  
Status: 
Offline
Thanks for the datapoints on adding simple filters. That says the pre-filters I want to use should be fine.

The filters being used are, however, far more porous than the HEPA main filter I want to use. I know I could use such a filter with a squirrel cage blower, but with a 12" window fan? Hmmmmm.

Does the window fan motor have that much power on the draw to pull air through a pleated HEPA furnace filter?

Does the loading tend to overhead the windings?

Is a reduce air flow going to increase motor heating leading to issues?

I can find no answers to any of these questions. :( I do, however, have some educated guesses.

I called Honeywell to ask about loading and the response was don't stack multiple filter if the filters offer significant air impedance, and that the coarse electrostatic filter would be acceptable provided it isn't dirty, but it likely isn't necessary for a house. I was specifically told that stacking HEPA filters doesn't make super-duper HEPA, which is what I expected.

Given that I am pulling in NYC air, I think I want to have some particulate filters to remove the worst of it before it clogs the pleated HEPA filter.

The coarse metal for particulates isn't going to add much, that's mostly to keep out rain and large airborne awfulness, and neither will the lightweight electrostatic furnace filter as long as it is regularly cleaned.

Because the HEPA filter has many pleats the surface area is very high, so the impedance, provided the filter is not clogged, should be low enough to not cause problems.

Back To Top PMQuoteReply  

 Posted: Tue Mar 27th, 2018 09:27 am
  PMQuoteReply
10th Post
Lane Shirey
AFCA Member


Joined: Wed Apr 30th, 2014
Location: Downingtown, Pennsylvania USA
Status: 
Offline
... or you could just move to somewhere with cleaner air.   :D

Seriously, any obstruction will impede air flow which can then cause the motor to heat up due to the additional load. The more the "blockage" the more heating. 

Personally, I'd model the system used in furnaces. A higher horsepower squirrel cage blower and proper ducting. I have an old furnace blower in my shop that I've fabricated a wooden box to fit. I use it as a dust collector and it's bolted to the ceiling. I use a double filter arrangement. An outer one that's washable and looks like synthetic coconut fiber. The inner one is a small particle pleated filter. Both are designed for furnaces. But this blower has the HP to suck through both filters and does not heat up. Perhaps you make a decorative wood box to sit on the floor and just run a duct to the window for an intake . Would be far more practical and you can probably get the blower/motor for free from a furnace installer. And they are multi-speed motors. Use a 4 position toggle to switch it. Steal the control board also out of the furnace. You won't need it, but if you leave it connected till you get home, you'll know which wires are for which speeds. Usually the wire colors/speeds are listed on the board. 

I've used cheap box fans for painting as well, and I think they usually die due to contaminants and grit getting into the bearings as well as the paint-clogged filters. 

Last edited on Tue Mar 27th, 2018 09:28 am by Lane Shirey

Back To Top PMQuoteReply

Current time is 10:04 pm  
AFCA Forums > Antique Fan Collectors Association > Post-1950 (Vintage) > Adding Filter to Window Fan Top



Beige Theme By: Di @ UltraBB
UltraBB 1.17 Copyright © 2007-2008 Data 1 Systems
Page processed in 0.3216 seconds (49% database + 51% PHP). 29 queries executed.