Ok, coming from a land of radiant heat systems, forced air is relatively new to me. But I'm still an idiot based on this situation!

I had the furnace changed maybe 18 months ago, and sort of figured that was me all set for a few years.

Ah, but the filters. (wasn't ever a thing in Scotland - damn!)

So I went poking around in the basement, and the place where the filter is was not part of the new furnace. Never knew that. There was a 20x25x1 filter in there, but it was collapsed, and looked as though t was maybe forced in. See, the opening is only 18 inches, so there must have been a little persuasion used.

There is no brand name on the box, it just says that it's an Electronic Filter. Behind the door is a gaping hole, around 27 x 18 inches, with a channel that is just over 6 inches wide.

Can I buy something to fit this????

Thanks in advance. :-)

Hugh

 

So there are no electrical components in there, like somebody removed all the guts from a prior electrostatic filter system?

Cartridge filters or conventional furnace filter would have to be checked for size but I bet it needs to be replaced with a new cartridge filter to fit the existing gap between furnace and return duct!

 

Nothing inside, I'm guessing some sort of filters resided in there. Somewhere in the back of my mind, I hear the guys that installed the new furnace telling me that parts they pulled out were now obsolete, and I needed to source filters. I think. There's something in there. :-)

As far as electrical components go - they are probably in the "door" of this thing. It's pretty heavy, and about 3.5 inches deep. But there doesn't seem to be any power to it, probably disconnected by the furnace installer.

I did consider building a plywood sleeve to house a more standard size filter. I could get a 4 inch filter into a couple of sheets of half inch ply, with windows cut out to let the filter work.

It sounds clunky, but I could easily basically reduce the overall housing size to suit.

Sound like a plan?

Thanks for your reply!

Hugh

 

Might be easier overall just removing and adding a new cartridge assembly, they are not very expensive!

https://www.famcomfg.com/product/fur...4aAp98EALw_wcB

 

Measure the area where the electronic elements once were, your local big box stores will have a wide filter element that fits in there. I converted mine when I had a new A/C installed last year.

 

Hi, at the bottom of that enclosure there appears to be a track, what is the dimension between that and how high is it ? I don’t believe I would be putting any plywood in there.
this link suggests the pre filter size which I would think would be the size of a regular 4” or 5” pleated filter.
https://www.appliancefactoryparts.co...h/part/276965/
Geo

 

Hi,

the height is 18.5 inches, just over 6 inches wide, and the depth is 28 inches.

Thanks for the link, I'm off to check that out! :-)

Hugh

 

Hi, at 18.5 inches high, it's an in between size, not readily available in the two stores I visited. Looking elsewhere now.

Thanks!

Hugh

 

this issue is growing arms and legs. :-)

So I found filters that are closer to the required size, 17 1/5 inch by 26 1/5, and I cut a pice of ply to slip in place as a visual guide. Image below.

The ply is hard against the back wall, and could move forward 2 inches before getting to the edge of the furnace opening.

The actual hole in the side of the furnace is 24 x 16 inches.

Worth trying to modify?

Marq1 The Furnace Rack you linked to is 7 inches wide, mine is 8.5. I'm unsure whether that inch and a half would present problems, as I would have to bring the ducting closer, and that might create an angle I can't seal.

I did think about taking off what's there, and trying to make alterations internally to suit. As of now, the whole thing is badly sealed in addition to it being a pain in the butt.

Kill me now!

Hugh

 

Yes I think that is what you will have to do.

The furnace filter has to seal to the furnace side so that air cannot get around it.

Hopefully it will not be a pain to pull out so you can work on it.

The suggested holder or something similar might word by attaching and sealing it to the furnace side.
Then use sheet metal to connect it to the cold air return.
It is the furnace side seal that matters, a little air leakage on the cold air side is usually not that big of a concern.

 

Filters not needed there anymore. The filter should be in your return grill..

IMO your wasting your time.. Call the HVAC gut and have that filter box removed if it bothers you.

I see gaping holes in the back side anyway. I would call the company back. Have them remove and put a piece of square duct there.

18 months and no filter change? Oh geez...

 

lawrosa Thanks for the reply.

When you said "Filters not needed there anymore. The filter should be in your return grill.." you lost me a little.

Do you mean not in that box?

Isn't that the return grill, that the box is attached to?

Sorry, as I said in my OP, I'm used to radiant heat and no filters/ducting - this is a learning curve for sure. :-)

Hugh

 

You would have to have filters custom ordered/made to re-use that old eac assembly.

I would have it removed and replaced with a 16x25 media filter cabinet. Some duct modification may be required.

Return air grill filters are generally used when the equipment is in an attic or crawlspace.

Attic/crawlspace systems are common in the southern us where basements are uncommon.

Otherwise, it's actually much better to have the filter at the furnace as return ducts leak.

 

check the return grill

 

Are you sure this wont fit?? That size filter fit nice and snug in my electronic air cleaner.
https://www.homedepot.com/p/Honeywel...2025/203781265

And if not, cut a piece of plywood that fits the space tight, then cut out a hole in that plywood insert, basically leaving just a frame the correct size for a standard filter. Use a little velcro to hold everything in place.

 

lawrosa Ah, gotcha.

No, I don't have that anywhere in the house. The system is in the basement. There is just what's in my photos, and no filter present.

I'm heading down now to pull it out to see what can be done. (I can order another part, but can't get it delivered until the end of the month)

Thanks!

 

tomf63 Hi, no, that filter you mention is too tall, the mouth of the box is just over 18 inches.

Funny, I mentioned in a post yesterday about perhaps making a plywood sleeve to reduce the opening to a standard size, but another member didn't think that was the thing to do.

That got me wondering why. The glue in the ply perhaps introducing something into the air? Probably not an issue.

So I'm about to pull it out and have a look. I have all I need to work with wood - table saw, routers, basically a garage full of woodworking stuff. That may be my best path, though I'm also going to look at sheet metal.

Fingers crossed!

Hugh

 

Quick question gentlemen,

with the box now removed, it may be easier for me to create a solution that involves in some way using wood, ply or solid.

Any reason why you wouldn't do this?

Thanks!

Hugh

 

Wood is considered combustible so not allowed as part of duct system.

 

Get yourself a media filter - https://www.honeywellhome.com/us/en/...r-f100f2025-u/

 

There must be a return grill in the home somewhere.

Or several return grills in the rooms..

Really? Look where you air comes out of those grills. There should be a bigger return somewhere...

 

^maybe in your area return grill filters are common but in the northeast the filter is at the furnace when it's in a conditioned basement!

 

Hi, another thought is that by down sizing the filter, you are creating a restriction to air flow which could problems with Hi limit safety , and also Cooling issues if not enough air is moving over the coil.
Geo

 

I would suggest you get the filter you want to use before starting.
Then you can fit it properly and know for sure that the fit is correct.

 

ok guys, here's how it all ended up.

I pulled out the box and set about modifying it. The final opening is only marginally smaller than the opening cut into the furnace. This is what I did.

1. A Raised Platform. This needed to lift the filter up almost 1.5 inches from it's previous position . To do that, I used L channel. The difficulty was being able to fit it without going through the sides of the box, with the screws which would impede the connection to the furnace.

In the end, I had screws protruding into the right hand channel where the filter would slide. The solution was to use and angle grinder to take down the protruding threads. That channel was fitted upside down so the filter could slide in, then move a little to the right to nestle against the side of the box. Problem solved.

The left hand channel was a bit more challenging. I ended up using shelf brackets bolted through the box bottom. As the box sits an inch off the floor, the bolt heads would not be in the way.

2. A New Box Side. I used a sheet of steel and sized it to the overall box, then cut it out where my filter would sit. Sealed onto the box, and to the furnace with fire resistant sealer.

3. A Filter Guide. I attached a piece of L channel to the back of the box, with a flat length of aluminum attached to that. The aluminum has a bend to it.

So, when the filter slides in, it hits the aluminum and follows it's curve, pressing the filter tightly against the box side at the end of it's travel.

As an extra method of snugging up the filter I used a 6 inch section of L channel, and hammered it into a U shape. I can drop this into the bottom left of a fitted filter to press the filter tight to the side. Probably not needed, but it really does firm everything up. (I have a tendency to over engineer things)

When fully home, the filter is ice and solidly in place, and can't be rocked from side to side. This gives me as airtight a seal as I would imagine I could get from a furnace filter.

Other places were sealed as I went, including the outer joints, which received both fire resistant sealer, and then duct tape.

Here's some images of the result.

Guys, I absolutely appreciate all of your advice. It helped a lot.

Hugh

 

Looks good !!! - twentyfivecharacters

 

Looks like a professional job to me.

Not sure about the duct tape you used. Often the glue on this stuff dries out over time and it fails.
But that may very by brand.
If this does happen replace it with something like the following.
https://www.homedepot.com/p/Nashua-T...7794/100048600

 

tomf63 Thank you. :-)

manden Thank you. The duct tape - I already had a roll, though it's been lying around for a few years. So I bought a fresh one from the ducting section in Lowes. It's this.

https://www.lowes.com/pd/Nashua-All-...ape/1000428297