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mainstreetprod 01-15-2009 06:12 PM

Poor airflow to living room
 
I have a two story home with upstairs and downstairs HVAC units. There are
3 ducts in the living room, but each has very low airflow compared to other rooms. Best I can determine, all 3 have very long runs from the trunkline, causing the poor airflow. The gas fireplace has to run continuously to keep the room as warm as the rest of the house. What change can be made to the duct system to correct this?

beenthere 01-15-2009 06:54 PM

Besides bigger duct.

Need more info how the duct is run.
And the sizes of the duct, plus info on your return duct.

Have you always had this problem.
Have you changed the air filter lately.
Was the A/C coil cleaned in teh last year or 2.

Winchester 01-15-2009 07:36 PM

Are there any baffles?

mainstreetprod 01-15-2009 09:09 PM

Besides bigger duct.

Need more info how the duct is run.
And the sizes of the duct, plus info on your return duct.

Have you always had this problem.
Have you changed the air filter lately.
Was the A/C coil cleaned in teh last year or 2.

(Concerning the 2nd story unit)
The duct is probably adequate size. I'm a homeowner - but know a bit about HVAC and am reasonably sure it is adequate. The return has a 14 x 30 filter and is only a couple of feet from the furnace, which is in the upper story attic. Any of the vents to 2nd story rooms can be opened and to get plenty of airflow, enough to heat the rooms thoroughly. I have many of them partially closed to try and force the air to the lower story. There are
about 5 ducts going downstairs, airflow is weak to very weak on all. To the
point that you can place your hand over the vent and feel a bit of heat,
but virtually no airflow.
I've had the house two years, it is 8 years old, 3400 sf. The filters are new, have not had the coil cleaned, but as I said, upper story rooms have
strong airflow.

(Concerning 1st story unit)

Only one vent from here goes to the LR. Airflow is good on all vents except LR, which is weak, but a bit more than from upstairs. The coil on this unit may need cleaning, judging from the amount of dust inside the filter housing The return on this one is at least 30 feet from the furnace. This unit is half the size of the upstairs unit.

beenthere 01-16-2009 06:32 AM

Sounds a bit like the ducts from the second floor unit to the first floor are all just a bit too small for their length.

And you basically may have the same problem with the first floor unit.

No idea, why the first floor is getting heat from both units.

mainstreetprod 01-16-2009 08:45 AM

It's an unusual setup, the first floor gets all its heat from the
very large upper story unit, except for the master BR suite which has its own unit (with one additional duct going to the LR).


So hypothetically lets say most of the duct going to the registers is
7". All the runs going to the upstairs are 10- 15 feet and the runs to
downstairs are say 25 feet. Should the installers have run say 8" to downstairs? How difficult to retrofit?
I'm also wondering if some of the duct was pinched in the process of running it to downstairs .
One other question: My bathroom, which is fairly large, has a small size register typically put in bathrooms. If the register is small, is the duct
running to it smaller than that running to a larger register?

AllanJ 01-16-2009 11:01 AM

Try it yourself -- close some of the other vents partially to force more air to the outer reaches of the system namely your living room.

If your house does not have an open floor plan and there is no return duct in the living room, then open the doors from the living room to the rest of the house so air can circulate better.

beenthere 01-16-2009 03:54 PM

They should have allowed for the length of the run to the first floor, and increased size, of number of runs.
May mot be easy to run larger now.


The master bath run may have a smaller duct, or it may not.

mainstreetprod 01-16-2009 08:13 PM

Just out of curiosity - does a duct that is attached to the end of the trunk line have stronger airflow than one attached to the side?


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