Could be one of the following problems but not limited to:

A. Your ductwork could be leaking or separated.

B. If your system is zoned you could have a stuck damper, but on the return it is unlikely.

Please don't view my question as insulting, just trying to help.

Have you checked the return vents for filters that might need replacing? Some systems have filters located near the air handler, others have them right in the return vents.

Any chance of calling the previous owner to ask about this?

Cold air from second stories spills down any opening like water, while the hot air rises.

If the thermostat is downstairs, temperature will respond in the area of the thermostat and it doesn't care what you want upstairs.

If you have a seperate thermostat upstairs controlling its own cooling unit, than the answer is to !!! CLOSE ALL SPILLWAYS !!! (stairs, balconies, sliding poles, etc.) to the downstairs. If you don't want to put up permanent walls, use curtains that extend from ceiling to floor and watch the performance of your system improve.

I would recommend a small window unit for your upstairs bedroom(s).

Ruudman

Ruddman... until they determine why the returns are not pulling air, your standard, pasted reply will not assist them.

cookie_14... are you sre they were working with the heat on? Can you turn the heat on now, briefly, and see if they start to work? Just put a tissue over them and see if it "sticks."

The only other thought that comes to my mind is that the returns downstairs are so large that they pull everything before the negative pressure ever has a chance to travel far enough upstairs to do any good. But, that is just my layman's observation.

You're probably on to something dallasbill. cookie14, just run the fan to try this, no heat or A/C. Block off all the returns on the first floor then see if your drawing air on the 2nd floor. If you are, as Bill says, your returns are proabaly just not balanced,

Thanks for the responses! To answer your questions, I have checked the filter in the unit. It's new. There doesn't appear to be a filter near the air handler. I'm trying to avoid having to deal with the previous owner. (Long story!) The vents were working when the heat was on, but the pull was less than the downstairs vents, which we atributed to the fact that the upstairs returns are so much farther from the furnace than the downstairs vents.

I will try running just the fan again to see if this works. (We've done this in the past to try to circulate the cold air, and I don't believe the upstairs returns worked this way either. But I will do this again to verify. I will also try the heat and try blocking off the returns on the lower level with the fan on. Thanks so much! I'll let you know what I find.

cookie... as mr.hvac clarified, you don't have to turn on the heat.

Just turn your a/c & heat switch (or whatever it's called on yout t-stat) to 'off.' Then, after you have covered the downstairs returns, turn the fan to 'on' on the t-stat and go upstairs and see how much more pull you are getting there. I bet it's a lot more.

My guess is that you notice it more in the summer, and thinks it's not working as well as winter, because you notice the increased warmth and humidity up there (vs. the warmer, drier upstairs in winter.)

I blocked the downstairs returns and turned just the fan on. The upstairs returns worked! But when I uncovered the downstairs returns, the upstairs returns stopped pulling.

Well... now you know... you returns are not balanced. Return air never has a chance to get pulled in from upstairs. As a result, air doesn't move and rooms get warm... cold air settles and hot air rises and nothing mixes much up there.

You need to get a pro out to check it and suggest re-balancing. Simply closing off returns yourself is usually not a good idea. You risk freezing your coil that way.

I'll let the HVAC experts chime in more on that.
Good luck!

cookie 14, how many returns do you have on each floor and what size are the grills?

Dallasbill:

Air, like anything else in life takes the path of least resistance.

Any spillways from the second floor to the first floor are going to let a lot more cold air drop down them than the fans can suck down the return ducts of the second floor.

Mr HVAC's test recommendations have proven that. When you block the intakes on the first floor, any air coming down the spillways isn't being sucked through the returns on the first floor and therefore the returns on the second floor become the path of least resistance.

You and Mr. HVAC are also correct that the air distribution system isn't properly balanced. The problem with balancing the system is going to be a question of how big will the ducting to the second floor have to be to offset the easier path offered by the spillways in the house?

My repetitively pasted response to questions of this nature is the cheapest way to resolve the problem and one the homeowner can do themselves. If the homeowner has to do massive reducting, it will take them more time, cost more money and may still not make them happy with the results.

Curtains are easy to remove once you can afford to spend the money for balancing the existing ducts or upgrading to larger ducts.

Based on the claimed severity of what Cookie 14 is describing in her situation, I am guessing he/she will have to do major expensive reducting to achieve the results they want.

Ruudman

I don't know ruddman, it may not be all that costly. I wouldn't recommend a layman do this but somebody with a little knowledge of things could probably damp down the 1st floor returns a little by partially blocking them off. A little tweaking here and a little twisting there and you might get buy with just a few hours labor. I wouldn't recommend anyone doing that though without checking system pressures, temperature rise, blower motor amp draw and maybe static pressure if they have a manometer. I think all cookie wants is to eliminate the air stagnation in her system she's experiencing now. Hardly something that would break the bank .

Dampers in returns are against code.

Then how do you explain fire dampers? Up here they use a 135 degree fusible link in the return and 165 in the supply duct.

Fire dampers are normally open. Operated from heat that should NOT be present. The curtain should be out of the air stream. Type B high hat. They are not used to balance a system and restrict air flow to operating equipment. Fire dampers in returns are more common in the smoke/fire style. If smoke or fire is detected the damper will close shutting down the equipment fan. If a balancing damper becomes loose and closes or you choke the return to much you will damage the equipment.

Balancing dampers and fire/smoke dampers are totaly different items. They are not to be substituted for each other. It's like mixing apples and oranges.

The only time you use dampers in a return air application is when the equipment has some kind of fresh air or economizer option (commonly called face and bypass). If the return air damper is 10% closed the fresh air damper will be 10% open.

Heating and cooling equipment should be balanced from the supply side. Not the return side.

'The only time you use dampers in a return air application is when the equipment has some kind of fresh air or economizer option (commonly called face and bypass). If the return air damper is 10% closed the fresh air damper will be 10% open'
Sorry guy but an economizer set up is not face and by pass. Face and by pass is used to normally by pass air around a hot or chill water coil. It has nothing to do with an economizer.
The point I'm trying to make here is something can be done econnomically for cookie 14 short of a complete and costly total return duct job.

Face and bypass dampers are used in more applications than just chill water coils.

I am very much aware of that. But face and by pass is not the terminology used for an economizer set up. There is no air by passed anywhere in the air handler and no air blowing against a closed or partially closed damper.

Cookie,
Forget about the returns. It has nothing to do with your problem. An HVAC doesn't care where it gets its return. All that's required is an unobstructed path from the supply outlets back to the return grille. If you have an open stairway to the 2nd floor, what better duct could you have to convey return air? (yes a hallway is a duct)

The real problem is that you are not getting enough cool air supplied the second floor to meet the demand of the heat gained by the structure. In the winter, this is usually not a problem, since hot air rises from the first floor. But in the summer, its a different story.

If the 2nd level is too hot, you have two solutions: (1) reduce the heat gain of the 2nd floor of the structure and/or (2) increase the supply of cool air to that zone.

You reduce the heat gain by first making sure there are no hidden energy leaks in the attic above, like dropped ceilings above showers and tubs, soffits above lavatories that allow hot attic air to migrate down into uninsulated interior wall cavities. Make sure your attic access door is insulated and substantially airtight. Knee walls with little or no insulation also add substantial heat to an adjoining room. Adding foil faced foam insulation (Thermax, Celotex or Tuff R) on the back of them not only addes insulation, but reduces radiant heat.

Then seal all accessible holes in the attic floor ie; plumbing, electrical wiring holes, interior top plate wall junctions. You want the attic floor complete airtight. Make sure you have adequate insulation in the attic. (this will save you $$$ as well in energy costs)

Window heat gain is determined by orientation, u value and the transmittance of the glass, It can be reduced by blinds, draperies, insect screens, exterior overhangs or applied tints or films to the glass. Once you have assured there are no huge heat gain violations and sensibly reduced heat gain through windows, then go about directing more airflow to the second floor.

Air is like teenagers, it seeks the path of least resistance. Thus, it is usually easier for most of your cool air to spill out the diffusers on the first floor. To get more air upstairs, you must impose artificial resistance to the air flow paths on the first floor. You do so by installing and adjusting balancing dampers.

Balancing dampers are adjusted to force air to other parts of the house where it doesn't naturally want to travel. Properly adjusted, balancing dampers will force more cooling to the second level to mix with the warmer room air and create more comfort. This procedure is called air balance.

Air from the diffusers can be measured with a garbage bag and the methods setforth here by Canadian Mortgage and Housing Corp.

http://www.cmhc-schl.gc.ca/en/co/maho/yohoyohe/inaiqu/inaiqu_003.cfm

Measure the airflow and record the data before adjusting any dampers. Then began the air balance and re-measure to check your progress. After seveal adjustments through trial and error, you should be able to solve the problem.

Then, take a sharpie and mark the position of the dampers, noting it as a cooling position. You will most likely want to go back and reverse the airflow in the winter time.

If you experience a windfall someday, you may want to install a zoning system, which will give you a second thermostat upstairs which automatically controls electric dampers.

Hope this lengthy post helps.

I am having a similar situation in our home. I wish I had read the last comment before I adjusted my dampers in the basement. It was an almost a 10 degree temp difference between the 1st and second floors in our just purchased (well in Nov 06) 20 year old colonial. WInter was fine with even heat throughout the home. I thought the upstairs actually should have been warmer than downstairs since hot air rises....now I am guessing that if hot air did not rise it would have been cold up there.

Anyway, now the AC is on and to make it comfortable upstairs, its freezing downstairs....setting the thermostat on 65 to get it at 73 upstairs.

Our Trane unit is 20 years old but seems to be running fine. We have estimates to replace it (because of its age)but were in no rush...I wanted to see what my heating / cooling costs would be before I upgraded....but I can not live the summer like this!

Anyway, at 6pm last night, I went to the basment and shut off most of the first floor duct dampers dramatically reducing the amount of air blown out on the first floor. It did not seem to make a big difference upstairs but perhaps it needs more than a few hours to tell. I too figured doing so would send more air upstairs but I wonder if there are dampers in the ducts upstairs that might be closed? I could not find or differentiate between the duct and returns that run to the second floor...except to say that I did not see dampers on them. All ducts upstairs seem to be blowing good except the ones in the bathrooms. I see no major air leaks, the attic e vented and well insulated, though there is no attic fan....which some have said could make matters worse by somehow sucking more heat up stairs throught the ceiling....?

I figured I'd let it run all day today and see if it was any different when I get home. After reading these responses I am bit concerned I did more harm than good though...should I run home and open the dampers back up?