Air Handler move question


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Old 08-07-09, 08:23 PM
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Air Handler move question

Hey All: Been doing a lot of research after my compressor / Air handler was installed three years ago. I've been trying to figure out my my return grille is singing to me, yes there is harmonics coming from the return. When I open the return (bring down the grille), the harmonics stop. Well originally, I talked with the guy that installed it, he said that he installed a 5 ton unit but ducted for a 4 ton unit. He wanted to put in a bigger return. I needed to verify this and so my research began. I recently found out that he installed a 4 ton system, but has the air handler set for 450 CFM/ ton. This is all background, I recently ran into an HVAC guy that is friends with my neighbor who wanted to take a look. He described the supply duct as an octopus. The supply duct is indeed short with many flex ducts running off of it. He says that the short supply is creating a lot of static pressure which is causing the harmonics in the return. The air handler is located in the center of the house in the attic. He says the air handler should be over to the side of the house and the supply truck should be the entire length of the attic reducing in size as the duct get farther from the air handler. Then the supply will be taking off to make the runs as short as possible. My question (finally), Is this how it supposed to be done? Do all of you have an air handler on one side of the house and a long supply trunk leading to the other side? I tell you, the guys that put this system in, well you can't talk to them, so now I'm relying on others to help me through this. Thanks for any comments. -paul
 
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Old 08-07-09, 09:35 PM
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I don't know what cause your problem, but I can tell you one thing, my air handler is in the center of the attic. don't know how long is long for a supply trunk. but I have no problem.
 
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Old 08-08-09, 05:32 AM
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see if you can change the speed on the air handler to med hi(right from the wires coming off the motor) or add a second return half the size of the exsisting.the air being discharged into the rooms is balloning the house,and the return is out off sized for the return air the air handler is looking to pull back.forget about the location of the air handler if the ductwork is designed right the take offs should be as short and straight as possible...with minimal bends.he cheated on the supply duct and the result is the air being discharge doesn't have the lenght it needs to defuse down to a normal pressure then out into the space...the takeoffs are the only place it will drop.if the ruturn is connected to a boxed piece of duct on the back of the air handler running another flex from that to hall ceiling will add return
 
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Old 08-08-09, 06:31 AM
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Originally Posted by sminker
see if you can change the speed on the air handler to med hi(right from the wires coming off the motor) or add a second return half the size of the exsisting.the air being discharged into the rooms is balloning the house,and the return is out off sized for the return air the air handler is looking to pull back.forget about the location of the air handler if the ductwork is designed right the take offs should be as short and straight as possible...with minimal bends.he cheated on the supply duct and the result is the air being discharge doesn't have the lenght it needs to defuse down to a normal pressure then out into the space...the takeoffs are the only place it will drop.if the ruturn is connected to a boxed piece of duct on the back of the air handler running another flex from that to hall ceiling will add return

Thanks Sminker:

Changing the speed is no problem physically, it controlled by a series of DIPs. I can try that to do that, will I lose any dehumification?

I understand that the physical location of the handler is not important, I'm trying to figure out if the work the Neighbors friend wants to do is the correct path? I'd like to add more returns in the bedrooms (there are 3 of them), to fix the undersized return and he is willing to do that but he wants to lengthen the supply duct and remove the flex. My concern with the return duct work, will it work, if you tie three ducts 8" into the back of the airhandler, or would it be better to tie them into a box and tie the box into the existing return that is at the back of the air handler. I think the return box in the hallway is out of the question because the pipe is 18" which only takes 2000 CFM which is only 200 cfm less then the 1800 cfm's that the air handler is pulling @ 450 cfm/ ton.

About the supply, just so you know some flex is over 13ft long, which he said is not code. But those flex are huge, 7, 8, 9 inch round inch.

So, I think his plan is to move the air handler so that he can run the supply duct the entire length of the house and make short runs as you described, but it wont help the return unless a) the speed is changed b) more return is placed and how should it be done, a second box or three ties into the existing box?

Any comments? I'd like to keep the 450 CFM unless there will be no difference in dehumidification.

Thanks so much for the help!

-paul
 
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Old 09-07-09, 05:02 PM
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Hi All:

Just an update:

We changed out the supply duct, now instead of a 36 inch block, there is a long tube (anti matter chamber looking) in the attic.

When we fired up the system, we felt more airflow from the supply's. The air was much faster as the supply's blew harder, we actually had to turn down the last one on the line, which was originally silent, it was blowing loudly. It took a 30 degree turn to make it silent again.

We did not change the return yet, but the sound was still there. We bolted (2) 8 inch take offs to the plenum in the back of the air handler and sucked in attic air, just to see what would happen. The sound was quiter, much quiter but still present.

So we will be working on placing another return in the hallway, plus returns in each of the three bedrooms.

Hopefully this will be the end. Were using cork pads for vibrations, but not sure if there working so great. The air handler was over the laundry room, so I never knew what it sounded like.

-paul
 
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Old 09-08-09, 05:26 PM
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Hi There:

Does anyone know what a flashing CFM LED on an American standard air handler control panel means?

Thanks
-paul
 
 

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