# Supply and Return Ratio?



## luxbuildsmall (Jan 11, 2006)

Hey folks,

Could use some input with a situation I have with a client. I am going to do an energy audit due to a complaint that the second floor can't get cool enough and apparently they say its difficult to heat also. I can pretty much assume to close off the chimney affect by sealing the attic, and look at the addition of a whole house fan, and check if there is adequate ventilation. Once I do a heat load I'll check to see if there are enough tonnage for the second floor. But since they are also concerned that it doesn't heat up, being the second floor, I wonder if there is enough return? Is there a simple way to look that the return should equal the supply or is this something for you experts to look at? Thanks


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## NickTech (Feb 13, 2005)

the return is usually sized slighty larger than the supply (approx 20%) to decrease air velocity, the volume is the same but it'll be drawn in much slower with less noise. return velocity should be about 600 - 700 fpm.


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## Bestheating (Dec 3, 2005)

Common problem and not all houses have the same problems.
One example last winter, resulted in finding a cape cod with little or no insulation in the attic.
I am concerned that the 2nd floor does not heat either. There are a myrid of things that could cause that. Is the thermostat or heating equipment running short cycles and not properly circulating the air?
How about checking to see if some of the close runs are running full open and recirculating most of the available air. Oh, and don't discount the filter issue. An obvious but often overlooked issue. The list goes on.....
Spend some time, look more closely and the solutions will present themselves. That is why you have been hired.
Larry

I came back to edit this post. do a temperature rise over the furnace. See if the unit is running within specs. This is something that should be done much more often and it will tell you a lot, for being such an easy test. Is it possible the A/coil is restricted? That's a common and often overlooked issue.
Larry


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## Darwin (Apr 7, 2009)

readjust the dampers in ductwork throughout the house to send more air up to second story.


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## flashheatingand (May 3, 2008)

If the furnace is downstairs, it's very difficult to adequetly condition the upstairs. Usually, the supplies that go upstairs have too many obstacles. As many home designs do not stress ample space for the duct-work. Odds are the return thing is not the problem. It sounds as if the home owners simply aren't getting enough supply air upstairs. If installing a second unit upstairs isn't an option, a zone system is the next best alternative. Thats just my opinion.


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## NickTech (Feb 13, 2005)

try to midigate all heat loads, like attic insulation, solar exposure (blind/shades) and have a expert tech conclude proper cfm readings as per room load and duct. if the right amount of air is coming out, then most likely it could be that the warm unconditioned air is not being removed. air conditioning is not the introdution of cool air into an area but the removal of heat from the air in the space. returns are as important if not more important than the supplies. hope this helps, good luck!


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## Remco Air (Jan 12, 2009)

I would run a load on the house just to double check if the system the homeowner currently has is adequate for that particular house. Being said that it is a two story house, the upstairs is usually hotter than downstairs since heat always tends to rise, check the ductwork layout, to see if it is even sized right.I would suggest a zoning sys.


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## flashheatingand (May 3, 2008)

Like Nik said, having enough return air is critical. To test if R/A is the culprit, run the furnace with the filter rack open as well as the fan door off.. That way, you know there is enough r/a. If the problem persists, you know the problem lies in the supply lines. Also, it wouldn't hurt to make sure the indoor coil is clean while you are at it.


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## flashheatingand (May 3, 2008)

NickTech said:


> try to midigate all heat loads, like attic insulation, solar exposure (blind/shades) and have a expert tech conclude proper cfm readings as per room load and duct. if the right amount of air is coming out, then most likely it could be that the warm unconditioned air is not being removed. air conditioning is not the introdution of cool air into an area but the removal of heat from the air in the space. returns are as important if not more important than the supplies. hope this helps, good luck!


Midigate what theasaurus did you pull that word from? Anyhow, theres nothing better to "midigating" than a big ol' Cottonwood tree or something of that nature. Insulation is great for the winter, but it only can do so much during the summer.


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## flashheatingand (May 3, 2008)

Probably got it from his Anthropology 101 class;;


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## coolmen (Mar 25, 2006)

static pressure test at the system unt will give good info.


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## NickTech (Feb 13, 2005)

i got word of the day toilet paper for my b day,


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## NickTech (Feb 13, 2005)

insulate for winter, ventilate for summer.


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