Furnace Filter?

[that_guy]

Hey folks,

I have heard on 3 separate occasions recently, that people using the high end expensive furnace filters ($15+/filter) have too fine of a mesh restricting airflow which results in burning up the motors in the furnace. The HVAC guys who have been doing their repairs have commented that even if you change the filter at the recommended intervals you may still be doing harm.

The HVAC guys all recommended using lesser expensive filters and changing them every 3 weeks.

My current residence where I'm using a higher end filter, we have a bear of a time getting quality air movement to the upper level resulting in colder temps in the winter and warmer temps in the summer. This all has me thinking that if there is restricted airflow due to the filter, would there be a benefit to using a higher flow filter to potentially get more airflow through the duct work to the upper level?

I know the efficiency of the system is contingent on proper routing and installation of the ducts, but I figure any little bit can help, right?

Anyone have some thoughts on this?

Thanks in advance

[BobT]

I suspect there is some truth in what the HVAC guys are telling you. Air flow is essential to the efficiency of the system. The filters are used because forced-air systems tend to stir up dust and air-borne particles. Do the filters provide information about the amount of air flow they allow? It would seem to be important to know this answer before installing the filter.

[Kyhl]

I'm no expert but this is my

My understanding is that over restricted air flow would cause the motor to over rev because of lack of pressure (resistance). I really doubt this could happen unless the filter was plugged. Again,

I wonder if it would be worth looking into having a larger filter bracket installed on the side of your furnace. I wish I would have known about this when our furnace was installed. IMO, they put too small a filter on our furnace which is restricting air flow. In our case, I know that there is enough room to add a few inches of length and width.

Might be worth looking into.

[leech~~]

I use to buy the cheapest filters I could find, but my house would be full of dust and we were dusting all the time. I started using the more expensive filters and they really have helped keep the dust down and I have not notced any issues with my furnace or any cold spots since making the change. If I where you and wanted to increase the air flow to other area of my house, I would install some of the small booster duct fans you can buy and keep the better filters in.

[nobody05]

in no way shape or form should you put one of those pleated filters in a furnace that are only 3/4 or an inch wide. A: There surface area for catching particles is limited therefore plugging faster inhibiting air flow and efficency for both a/c and heating. To have a good filter surface area is key. That is why alot of new filters and air cleaners on furnaces are getting into these 4''or 5'' in wide filters and get best of both worlds. Good filtering capabilities and good air flow.

[RiverFish]

We just had a Carrier furnace put in last week. There is a 5 inch filter for the furnace. Furnace guy says they do a better job of keeping "garbage" out of the furnace.

[that_guy]

Sounds like I need to do some more research. The furnace I have at my current place only has room for the 3/4in filters. So I'm S.O.L. there.

I'm willing to dust more if I get better air flow.

Good stuff

[Dave]

My last furnace guy told me to ditch the pleated and just use the cheap ones. Less strain on the furnace.

[Dave]

You are adjusting the duct dampers, to allow more flow upstairs, correct?

[Tom7227]

Seems to me that very few folks are able to tell what the air flow is in the duct system at any given time, clean filter or not, unless they have some type of airspeed indicator or whatever the dojobber is called. Having a plugged filter would certainly reduce air flow but I don't see how that could impact the motor and cause it to burn out - unless things were so clogged that there was virtually no air flow at all and the motor started to overheat. Even if that were the case don't the motors have thermal protectors?

Just wondering, maybe some furnace types can help with this one.

[dougger222]

Two of the HVAC guys I know say to buy cheap filters and change monthly.

[Eric Wettschreck]

I work for a major pharm company. Even on the air handlers that scrub lab and clean room air we put on the cheapies and change them monthly. Granted, the air supply also goes through a HEPA at the clean room, but I think you get my drift.

Most motors have internal thermal overloads. If they get too hot, they'll trip and re-set when cool.

At home, I put in the cheapo and change it aboot every 3 weeks or so, when I remember to do so. Things inside the plenum and ducting are still clean, that tells me they're doing their job.

[that_guy]

You are adjusting the duct dampers, to allow more flow upstairs, correct?

Yes, I have shut all but one of the dampers on the main level to move as much air upstairs as possible. This has helped but only marginally. There is still a temperature difference opposite of what it should be right now.

I personally find it hilarious that given the fact that heat rises, why it's so much colder upstairs than downstairs.

[Eric Wettschreck]

I have the same thing in my house, so I'll ask a few questions.....

1. Do you if the furnace has a multi-speed motor? If so, what's the speed setting?

2. Do you have decent cold air returns upstairs? You can pump a ton of BTU's up there, but ya gotta get the cold air out at the same time.

My place used to be a country school. Super duper old and the house has it's issues. Recently when I did some remodeling after the kids moved out I put in cold air returns upstairs and that made a ton of difference.

[nofishfisherman]

What kind of insulation is overhead on the 2nd floor? Is the attic space properly insulated?

[cavalierowner]

Before I retired, if there was any kind of question or issue with any kind of material or equipment in a building, the first thing we did was tell people to read the manufacturer's literature. If the answer wasn't there, the next step was to contact the manufacturer's tech support. In theory anyway, nobody should know their product better than the manufacturer. And in most cases you had to follow the manufacturer's instructions to maintain a warranty. As far as frequency of filter change, it has to do more with how much dust, etc. is produced. With all the dogs in my house and the shedding, if I let my filter go a month, I'd have no airflow Well maybe a little exaggeration, but not much!

[SkunkedAgain]

My ignorant brain wonders if there is a ventilation leak somewhere preventing the warm air from reach upstairs through the vents. Then again, shouldn't it be able to rise throughout the house (assuming doors aren't closed) even if only being forced into the lower levels?

[that_guy]

What kind of insulation is overhead on the 2nd floor? Is the attic space properly insulated?

I'll have to poke my head through the access, I never thought to check on this before. It's a 20yr old place already so I'd imagine there has been some settling, or perhaps none if its been rolled out.

Skunked,

I agree, the warm air should rise to the top level, it just seems that there is a pretty significant temp difference the wrong way. I do intend on taping the ductwork that I can get to. I figure every little bit helps...

[Eric Wettschreck]

I understand your thinking........but.......the warmer (lighter) air has to overcome the colder (heavier) air that's upstairs. This is why I asked if you had cold air returns upstairs and if your furnace has a variable speed fan motor.

And you are correct, every little bit helps. Insulation, tight ducting, proper air diffusion, sealing up holes, etc.

[SkunkedAgain]

Make sure that you use ventilation tape and not just duct tape

[that_guy]

I understand your thinking........but.......the warmer (lighter) air has to overcome the colder (heavier) air that's upstairs. This is why I asked if you had cold air returns upstairs and if your furnace has a variable speed fan motor.

And you are correct, every little bit helps. Insulation, tight ducting, proper air diffusion, sealing up holes, etc.

We do have air returns upstairs, I should probably check to see if they are clean. I'll check on the variable speed fan. The manual is down there I think.

[Eric Wettschreck]

Also, is your warm air ducting insulated?

[that_guy]

Also, is your warm air ducting insulated?

In the basement the ducts are not insulated. I would hope the ducts are insulated in the walls since at least part of the duct work does run up exterior walls. I know this is potentially a big part of my problem, I didn't mention it sooner because there is absolutely NOTHING I can do about this.

If I insulate the ducts in the basement, would that reduce the heating of the basement? I understood that the heat in the basement results in 1) a vent on the furnace and 2) heat coming off of the ducts.

Right now, I have the vent in the basement closed off trying to force as much heat upstairs as possible. It's chilly down there, but not cold.

[gunmunky]

Last fall I had a bearing go out in my squirrel cage. I pulled the cage out and I couldn't believe how dirty it was. So I cleaned it with a pressure washer before replacing the bearing and when I turned the fan on it was amazing how much more air flow was coming thru the vents. If your furnace is very old it may be worth a look.

[Dave]

I personally find it hilarious that given the fact that heat rises, why it's so much colder upstairs than downstairs.

While I can't feel as much difference as you, I do know I need more ceiling insulation on the second floor. Have you checked that? Maybe the heat that's rising is escaping faster than the supply.