Where to put the intake/filter, in ceiling or down by the floor?

MossonarockFebruary 13, 2014

You'll have to forgive my use of terms here. I don't really know what the standard names of the different parts of a heat pump system is called by the industry.

Hot air rises right? Cold air settles down by the floor or so it seems to me. I took high school physics and that's what I learned. Hot air ballons wouldn't work otherwise right? So, if one were to install a heat pump system, sometimes also known as an HVAC or central air system, for the primary purpose of heating a house, it seems one would want the intake/filter to be down by the floor. That way the intake sucks in all that cold air down by the floor to have it heated by the air handler. Then, the air handler blows that now warmed air out the return vents back into the rooms of the house. Does this make sense? Or is there something I'm not realizing here?

Round here, most HVAC installers put the intake up in the ceiling. I can't figure out why. That's what they did in my house and I didn't want it that way. I've been trying for months to have the intake down by the floor where I want it. I have a nice place for it. For some reason, the contractor just does not understand why I want the intake down by the floor instead of up in the ceiling "like everyone else." At the same time, most people who have HVAC systems complain that their house always feels chilly ever since they had their HVAC system installed. I'm thinking its exactly because their intake is up in the ceiling drawing in the warm air up by the ceiling and warming it some more by the air handler and blowing the rewarmed warm air back into the rooms of the house. Meanwhile, there's all that cold air down by the floor that never gets warmed. It just gets very warm air blown at it. So, the people feel that cold air. Sure they feel the warm air coming out the vents as I do in my house. But that cold air down by the floor never gets warmed. And so they develop this idea that HVAC systems aren't any good because their house still feels cold. I think that their problem isn't the HVAC system but rather that it wasn't set up well in their house. Is any of this making sense? Am I totally off my rocker here?

I even did some experiments in some places that I rented. One apartment I was in had the intake/filter up in the ceiling and I had that "the house is cold sensation" that everyone remarks upon. So, I put up some boxes around the intake to "lower it" down towards the floor. I managed to get it to within 2 feet of the floor. The cold sensation disappeared. The HVAC system didn't run as frequently any more. And, best of all, my electric bill went down. Why? sucking up that cold air down by the floor made the whole system work better and more efficiently.

I highly recommend that if you plan to install an HVAC system and plan to use it mostly for heating that you put the intake/filter down near the floor. It will work better.

Oppositely, if you are I a warm climate and need to cool your house more months of the year than you need to warm your house, having the intake up by the ceiling is where you' want it. That way it sucks in the hot air to have it chilled.

An ideal system, imo, would be to have two intakes. One up in the ceiling and one down by the floor. That way you can close the upper one and open the lower one in winter for heating. Then, in the summer you can reverse it by having the upper intake open and close the lower one for cooling. Seems brilliant to me and I can't understand why this doesn't get done. Can anyone fill me in here as to why this doesn't get done?

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mike_home

I think you are right that ideally there air return should be near the floor in the winter and near the ceiling in the summer.

I could see installing the air return close to the floor would present some problems. it creates a spot where you can't place furniture. I also think it would create a potential draft if you sat between a supply and return. The moving air could cause a wind chill effect.

Ask the contractor to cut a second intake near the floor. It should be easy and not cost very much. Most air returns are undersized, so a second intake will help.

    Bookmark   February 13, 2014 at 10:02AM
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klem1

"Can anyone fill me in here as to why this doesn't get done?"
Mossy,know what? That is a question to be answered on a long list of issues. It has simply become the American way because " only good enough" looks great compared to the rest of the world. Here are a few imho that demonstrate the mind set.
Automobiles have been progressivly desighned so it requires less skill to operate them. Driving a mud/ice obstical course,I wager I can maintain control and stop in less distance with abs disabled on a 100k + mile vehicle than majority of those who learned to drive abs equiped cars driving one where abs remains connected.
If you become bored and without anything fun or constructive to do,try this. Call any federal agency that supposly works exclusivly with a single day to day issue. They exist but they don't actualy do anything other than issue printed material talking about the work they don't preform.
The concept you spoke of was used in some homes built 50 years ago. A simple butterfly diverts return air flow between high and low intakes. In some floor plans,esp two story,the duct not carrying return at the time is carrying supply.

    Bookmark   February 16, 2014 at 2:29AM
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Mossonarock

Thanks for the replies and the assurance that I'm not just imagining things.
The return would be in a hallway. So, there's no sitting next to it or anything. The spot is an old linen closet. Seems like it would be simple to convert it to hold the return and duct. The air handler is literally just above and to the side of the linen closet- in a word, perfectly placed. The current return that the hammer swingers installed is in the ceiling of the same hallway. This Wednesday, I'm supposed to meet with the contractor who installed it and hopefully he will finally listen to me and change it to how I want it.
Most returns are undersized huh? How does one determine if their return is properly sized?

    Bookmark   February 23, 2014 at 8:17PM
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mike_home

Here is link which shows minimum sizes for duct work. You need about 400 CFM of air flow for each ton of AC cooling. The filter should be one square inch for each two CFM of air flow.

Here is a link that might be useful: Rules of Thumb for Duct Sizing

    Bookmark   February 23, 2014 at 8:29PM
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Mossonarock

"The concept you spoke of was used in some homes built 50 years ago. A simple butterfly diverts return air flow between high and low intakes. In some floor plans,esp two story,the duct not carrying return at the time is carrying supply. "

Durn, that's awesome. Sounds like a smart person was kicking around somewhere at sometime. If you could provide a link to such butterfly designs, I would be very grateful.

    Bookmark   March 4, 2014 at 7:45PM
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wwu123

By chance are your supply registers also in the ceiling? Possibly it means the heat pump equipment is in the attic, and it's easiest to have properly sized supply and return ducts in the ceiling. To have a return either high or low in the wall, you'd need it to be much larger than the space between a pair of wall studs, so you'd need a vertical duct between the wall the size of a small closet, robbing potentially valuable living space or closet space.

Of course if you are building your own custom house you can design the floor plan any way you want...

    Bookmark   March 5, 2014 at 12:29AM
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bus_driver

Filters near the floor collect debris much quicker than those in the ceiling. Whether that is good or bad is a matter of perspective.
I recently did some work on a house to convert the return intake/filter to the ceiling. The HVAC guys did the ductwork. The previous had the filter in the furnace in the crawlspace with the return grilles in the walls near the ceiling of 3 rooms. And those original returns were too small in total area. Filters are relatively easy to change on the ceiling.

    Bookmark   March 5, 2014 at 7:48AM
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