Air Conditioning - dirty coil?
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rpatzer
01-10-08, 09:54 PM
Can a dirty coil cause a reduced air flow to one room only? That duct comes directly off the plenum. The other runs have good CFM.
I have changed the duct from the old metal-covered duct to a flex-duct and the CFM did not improve. Also the AC is warmer than the rest and the heat is cooler than the rest to this room.
I have changed the duct from the old metal-covered duct to a flex-duct and the CFM did not improve. Also the AC is warmer than the rest and the heat is cooler than the rest to this room.
pflor
01-11-08, 02:29 AM
Can a dirty coil cause a reduced air flow to one room only?
Nope! but a partially (or fully) closed damper [at the branch takeoff location, by the plenum] could. How'bout the damper blades at the register itself...are they open?
I have changed the duct from the old metal-covered duct to a flex-duct and the CFM did not improve. Also the AC is warmer than the rest and the heat is cooler than the rest to this room.
You have switched from metal to flex? Kinks and/or sagging could also restrict airflow thru a flex-duct branch line, as would an undersized duct section too.
Although may sound hard to believe, the duct/branch closest to the furnace could offer a problem condition like the one you're reporting. The Static Pressure is at its highest there and the absence of a directional damper [scoop they also call them] may cause that the air in the trunk bypasses this branch altogether
Try reducing a bit the airflow in rooms further downstream from this register...that should improve things. And you should have a balancing damper at the beginning of this branch, by the trunk.
Nope! but a partially (or fully) closed damper [at the branch takeoff location, by the plenum] could. How'bout the damper blades at the register itself...are they open?
I have changed the duct from the old metal-covered duct to a flex-duct and the CFM did not improve. Also the AC is warmer than the rest and the heat is cooler than the rest to this room.
You have switched from metal to flex? Kinks and/or sagging could also restrict airflow thru a flex-duct branch line, as would an undersized duct section too.
Although may sound hard to believe, the duct/branch closest to the furnace could offer a problem condition like the one you're reporting. The Static Pressure is at its highest there and the absence of a directional damper [scoop they also call them] may cause that the air in the trunk bypasses this branch altogether
Try reducing a bit the airflow in rooms further downstream from this register...that should improve things. And you should have a balancing damper at the beginning of this branch, by the trunk.
mattison
01-11-08, 05:42 AM
That duct comes directly off the plenum. The other runs have good CFM.
If it comes off right at the airhandler plenum then the air may just be blowing by it. You can buy a take off collar with an air scoop on it which may help. Also you will get better airflow from metal duct than you will with the same size flex duct.
If it comes off right at the airhandler plenum then the air may just be blowing by it. You can buy a take off collar with an air scoop on it which may help. Also you will get better airflow from metal duct than you will with the same size flex duct.
mike n
01-17-08, 05:31 PM
The answer to the Question is no a dirty coil will not affect only one duct there is either a blockage in the duct (damper closed or foreign substance) or air is leaking out from a bad joint.
hcfcr22
01-17-08, 06:00 PM
Another possible solution, assuming you want a lot of airflow into that room and the duct is sufficiently undersized is to move your flexible duct takeoff to the top of the plenum.
(It is not a good practice, but flex duct will most likely dampen any turbulant noise).
Although flexible duct insures a sealed duct run you need to consider the velocity reduction created by it's ununiform surface.
A good sealed return throughout your system and a direct return being pulled from this room specifically are all possible solutions. Installing a good return air system and you can get away with a lot on the supply.
The 1st solution is most likely the easiest. It may be a good idea to install a damper in this solution.
Air takes the path of least resistance.
(It is not a good practice, but flex duct will most likely dampen any turbulant noise).
Although flexible duct insures a sealed duct run you need to consider the velocity reduction created by it's ununiform surface.
A good sealed return throughout your system and a direct return being pulled from this room specifically are all possible solutions. Installing a good return air system and you can get away with a lot on the supply.
The 1st solution is most likely the easiest. It may be a good idea to install a damper in this solution.
Air takes the path of least resistance.
rpatzer
01-23-08, 09:40 AM
Thanks all for the info- I am going to try the air-scoop idea. I think that might be the issue( air is bypassing this smaller duct opening and going to the 2 bigger ones)
Ed Imeduc
01-23-08, 09:46 AM
Like matt said . We put what we call a robber in the pipe sometime to get more air into it. Its just a small piece of metal and screw it to the metal collar to stick out in the duct air stream then put the flex pipe back on the collar there.
rpatzer
01-25-08, 09:23 AM
I did try it and nothing changed. I thought in the plenum would be air flow in one direction and my extension, "robber" would direct more air flow into this one duct, but the air seemed to be equally pressurized so I couldn't "grab" any more air. I would probably need to put a larger duct to that room. The air flow seemed to be adequate down to the grill opening, then it seemed to decrease.
mike n
01-25-08, 01:02 PM
If you have what you think is adequate airflow on one side of a grille and the grille is open then you have essentially the same airflow minus a negligible pressure drop, perhaps it just feels different due to the grilles diffusion effect or spreading of the air.
If you could tell me what size unit you have (I can tell from the model number) and what size and how many branch lines are on your unit and the configuration (Square plenum box with 4 taps on the top and 3 on the sides or 12' long 14" round trunk line with x amount of taps on it)
I will tell you exactly what is happening
If you could tell me what size unit you have (I can tell from the model number) and what size and how many branch lines are on your unit and the configuration (Square plenum box with 4 taps on the top and 3 on the sides or 12' long 14" round trunk line with x amount of taps on it)
I will tell you exactly what is happening