Noisy duct - http://www.hvacmechanic.com/ Forums
Original message
| Rooky
 |  "Noisy duct"
, posted Fri 15 Aug 17:35  
I have a Trane Gs furnace Model TUD100R9V5K4 with variable speed blower. The outdoor unit 's Carrier Strait A/C Model 38TKB048350 R-22.
Homeowner says the unit ( this one ) is noiser thant the previous one. We replaced it about a year ago. The old onwe was exactly a four ( 4 ) tons unit just as this trane is. The dip switches are set up to move 1600 CFM ( 4 Tons At 400 CFM per ton )The Return duct measures 14X20. I used the duct calculator and I came up with 2000 CFM ( 0.1 Friction for every 100 feet of duct ( galvaized ). There are two ( 2 ) supllies. One measures 12X8 @ 0.1 friction gives me 500 CFM and the second one a 10X14 @ 0,1 friction gives me 800 CFM. My split temperature was about 23 degrees. The outdor temperature was around 79 degrees and the indor temperature was about 74 degrees. Subcooling and Superheat, do'nt have them now. I would post them next time if they are needed.
My question is this. Do I have an air restriction ? I think that my supply duct can't handled that much air. The other thing I did not mention is that the install has a Trane CleanEffect Electronic Air Cleaner install. Wouldn't it cause static pressure to go high. Am I mistaking Friction rate with Statice pressure? If not , what would have to be the friction rate tp be use to calculate the CFM at the supply, and what would have to be the one at the return ( Remember I have a EAC installed , Do not have Spec's for this EAC so I do not know the prassure drop it creates). Plz! could you post your opinions and experience ( I'm a rook.
Thanks !
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Replies:
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| RCLAOAC
| "Re(1):Noisy duct" , posted Sun 17 Aug 13:22
Not enough ductwork. Is that rectangular metal duct that you have? Or are you talking about he size of the registers/diffusers?
Be a Man!
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| pbreazeale
| "Re(1):Noisy duct" , posted Sun 17 Aug 08:25
You need to lower the fan speed.
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| Jojo98
| "Re(1):Noisy duct" , posted Fri 15 Aug 23:21
A 23deg split is an indication that the A/c is not moving enough air. Also, if the supply is moving 1300cfm, you have to dump another 300cfm somewhere.
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| | Rooky
| "Re(2):Noisy duct" , posted Sat 16 Aug 11:05
I completly agree with you. I think that the supply is no capable of moving that much air. I told the customer that I could set the blower to move 350 CFM per ton but I would have to adjust the system's cahrge since the air flow through the evaporator is going to be less and the suction pressure would drop some, how much ....I do not know.
By the way, here is the actual readings. System TXV
Outdoor temp: 80.6 Degrees
Liquid line Temp; 93.9 Degrees
Head Pressure: 200 PSI It gives me about 102 Degrees
subcooling is: 8 Degrees.System desing: 15 Degrees
Suction: 56 PSI it gives about 31 Degrees.
Suction line temp: 57.7 Degrees
SuperHeat: 26.7 Degrees.
Compressor: RLA( 24.4) It runs at 12.3 Amp.
Return: 69.0 Degrees..Supply: 46.5 Degrees
Split temp: 22.5 Degrees.
Rooky.
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| | Freon
| "Re(3):Noisy duct" , posted Sun 17 Aug 07:34
Your post says Noisy Duct. You need to determine the source of the noise. If it is whistling at the supply and return registers, then air flow is too high. But if the noise is from vibration then your method of solving that kind of noise would be completely different.
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| | Rooky
| "Re(4):Noisy duct" , posted Mon 18 Aug 19:05
Ye, It's metal Duct ( RCLAOAC), the noyse is Whistling ( Freon ). That's why I agreed with Pbreazeale , I need to move less air ( Low the blowers speed to 350 CFM and then correct the charge to this new setting ( the suction preassure is going to change. It would be lowwer. I'll call back this customer and I would propose to lower the spped ( again ) and adjst the charge. SHe told me not to do it the first tine I was there.
Thhanks
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