low air flow&humidity

[oldmillcj8]

Having problem with air flow & humidity. I live in a split level rancher. Heater is in the attic .there is a 10 degree difference from lower floor to upper floor .starting at the lower floor 65/70/75. Humidifier can not keep up. There is a noticeable difference in air flow, upper floor to lower with the lower floor having the least.

[filterchanger]

sounds like a poor setup,,are you new to the house

[oldmillcj8]

not new to the house. We just had a contractor install it.

[filterchanger]

are you saying there is one airhandler in the attic supplying 3 floors

[fat eddy]

How long of a cycle does the furnace run ?

[oldmillcj8]

its a single unit 3.5 ton. It comes out of the unit to 2 10inch ducts one 10inch duct supplies middle floor which supplies 6 vents and 1 return. Second 10inch duct feeds the upper floor which supplies 6 vents 3 returns and has another 10inch duct that extends from this one that feeds the bottom floor which supplies 4 vents and 1 return that is shared with the middle floor return.

[oldmillcj8]

it runs for about 10-15mins at a time. the thermostat and humidity control is on middle floor.

[rsmith46]

Are you saying 2 10" flex supply runs? If so you have real ductwork problems, need more like 2 10 x 12 metal trunklines. Tri-level's are hard to keep uniform temps, about all you can do is run the fan all the time. Did the old system work better?

[oldmillcj8]

there was no old system. My house was electric heat before. the 10inch duct work only runs for about 3 feet then its the hard square duct work and branches to the registers are 6 inch flex duct. Do you think that the fans that you can put in the 6inch flex duct really work to provide more airflow to the lower floor? Do you think the manual air control duct would work if it was put somewhere in the 6inch duct to the registers? I am not sure what this is called but it has a lever on the side that can block the air flow to the upstairs floor would it devert more air to the first floor. closing the regesters did not work.

[dmoneyc22]

NO YOU HAVE DUCT PROBLEMS AIR FLOW AIR FLOW AIR FLOW

[cem-bsee]

did you or contractor run load calc?
read lots here --

again, were you warm enuf with old system? is new furn same size as all baseboard addded together?

did someone say: "air flow"

how about assume 600sfpt?

[Edited by cem-bsee on 02-19-2005 at 06:30 AM]

[mayguy]

I agree with the guys. You have wrong sized duct(10") to feed the main trunk.

[filterchanger]

if you want it to work properly, i think you might have to start over

[fat eddy]

Unfortunately if the unit is running a fifteen minute cycle it will point more to a problem in the duct design rather than some type of equipment problem. We have to go with the fact that the stat is on the middle floor and that is the only floor that the unit will listen to or care about the other floors can be considered slaves to the middle floor. If the system fails to condition the other floors satisfactorally, then you have a ducting issue which may or may not be as simple as balancing it out. More than likely you will need to have the ducting modified to bring the other floors to some type of balance with the middle floor.

[fat eddy]

I just caught the part about two 10" supplies this defies any air flow chart ever made for a normal residential static pressure ? unfortunately or maybe fortunately the centrifugal blower in your furnace will peak out on its curve without moving the sufficeint air. You should have noticed in the cooling season that your suction line may have froze. You have to find a way to get the proper trunk connected to this thing. Is this furnace a lot louder than the previous one ?

[rsmith46]

Originally posted by fat eddy
I just caught the part about two 10" supplies this defies any air flow chart ever made for a normal residential static pressure ? unfortunately or maybe fortunately the centrifugal blower in your furnace will peak out on its curve without moving the sufficeint air. You should have noticed in the cooling season that your suction line may have froze. You have to find a way to get the proper trunk connected to this thing. Is this furnace a lot louder than the previous one ?

He just had it put in so hasn't run in cooling, no old system - electric heat before.