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Old 07-25-2010, 12:11 AM   #1
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Stop Whining Blower


This is a new system, just install a few weeks ago. I noticed that there are two types of noise. One type is the regular wind blowing noise. The 2nd one is the whinny noise. I have 1000 square inches for the filter area. That's more than required by the user manual. However, the filter is the 5 inches pleated type, with Merc 12. When I take out the filters, the system stops making the whinny noise. My understanding is that pleated type filter would provide much larger penetration surface. But high merc rating would offset that. My question is should I get a filter of similar dimension (with 5 inches thick), and 8 Merc to help this issue? Or should I go with 1 inches (with a filter box adaptor)? Do you think the blower and motor is responsible? Do Goodman replace things like this when it makes noise, but runs fine?

Thanks.

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Old 07-25-2010, 04:39 AM   #2
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This is a new system, just install a few weeks ago. I noticed that there are two types of noise. One type is the regular wind blowing noise. The 2nd one is the whinny noise. I have 1000 square inches for the filter area. That's more than required by the user manual. However, the filter is the 5 inches pleated type, with Merc 12. When I take out the filters, the system stops making the whinny noise. My understanding is that pleated type filter would provide much larger penetration surface. But high merc rating would offset that. My question is should I get a filter of similar dimension (with 5 inches thick), and 8 Merc to help this issue? Or should I go with 1 inches (with a filter box adaptor)? Do you think the blower and motor is responsible? Do Goodman replace things like this when it makes noise, but runs fine?

Thanks.
I would try a MERV rating of a lower range. If it cures the problem you can either stick with the lower rated filter or make modifications to correct the noise of the MERV 12.

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Old 07-25-2010, 06:19 AM   #3
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What size furnace and A/C did you install.

What size is/are the return air grille/grilles.

What CFM is it set to move.
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Old 07-25-2010, 07:23 AM   #4
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The system is 3 tons AC. The furnace's blower is supposed to handle up to 5 tons. The return air grill's sizes are 350 sqrt innches, 350 sqrt inches and 100 sqrt inches, which makes it 800 sqrt inches. The return air filter area is 1000 sqrt inches.
The current CFM is 1800 CFM. I will reduce it down to 1200 CFM following 400 x 3 tons = 1200 CFM guide to see how it goes. However, it seems to me that at 1800 CFM, air going through the supply grills in each room are at a good rate. By "good", I mean I can feel them coming out well, but not blowing like a strong fan or anything like that (without the grill on). It's also not blowing stronger than other houses I looked at (at the supply grills). Air in each grill are distributed very evenly, so I don't have to touch the damper yet (which means less restriction).

The main supply trunks total cross area is 192 + 160 + 91 = 443 sqrt inches
The main return trunks total cross area is 380 sqrt inches.

One thing though, the supply trunks goes perpendicular to the furnace, right on top of the coil (due to the furnace and the coil is 70 inches height, I don't have much room above it in the basement). Do you think that adding turning vanes to the 3 supply trunks right above the coil would help? I know it does, but is it significant or not?

Also, using my hand, I turned the blower's fin (with the system off) real fast, I heard some noise, and not the wind noise type. That surprised me because it shouldn't make any noise like that. However, I don't have much experience on that. What do you think?

Last edited by vdu; 07-25-2010 at 07:27 AM.
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Old 07-25-2010, 07:51 AM   #5
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Your return grilles are sized for a 2 ton unit at 300FPM, or barely a 3 ton unit at 400 FPM. Trying to run 1600 CFM through them would require a face velocity of over 700FPM.
Your 188CFM is way to high for a 3 ton A/C.

Set your blower to 1200 CFM, and probably most of your noise will go away.
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Old 07-25-2010, 09:17 PM   #6
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I set it at 1200 CFM, and the whining is still there. Not as loud. The wind noise from the return grill goes down dramatically.
I then tried 1400 CFM, and the whining is gone from the 1st floor. Standing next to the unit, it's barely noticeable. Strange isn't? However, if I close the basement's return, about 100 sqrt inches, the noise goes back up again.
What's really strange is this, when first installed about 3 weeks ago, it was cool. However, today, not as hot as yesterday, I ran for several hours, and it was at 79 degree F. I went outside, around 5:30 PM, and my car showing outside temperature was at 80 degree. I think the refrigerant is leaking somewhere. I have to call the installer to check this out. What do you think?
Also, the manual says set the high cool CFM, but low heat CFM. Why in setting the CFM for heat, using the low values versus high? I heard for heating, the fan doesn't run as fast. Does that mean it will run in the low mode (this is dual speed) most of the time? For my current settings, in the winter, if it goes with the high mode, it would blow at more than 1800 CFM. That doesn't sound right if heating suppose to blow slower than cooling.
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Old 07-25-2010, 10:56 PM   #7
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I think your misunderstanding the manual.

You don't set a 3 ton A/C to use 1800 CFM for heating or cooling.

Don't know if your system is leaking or not. The whining noise may stop if you adjust the vane of the return grilles.
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Old 07-26-2010, 12:03 AM   #8
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My question was why the manual says for cooling, set the high CFM, while for heating set the low CFM.
I didn't say I should set 1800 CFM for 3 ton A/C. It was there by default. I have changed it to 1400 CFM, and no more whining or noisy return grill.

My issue right now is that it used to be able to cool the house down to 75 degree F from outside temperature of 95 degree F. The machine also stop once awhile.
After I posted above, at 10:42 PM, outside temperature was 80 degree. Inside was 78 degree, which is the same temperature as the programmed value. I lowered it down to 70 degree F. After 1 hour 47 minutes, at 12:29 AM, the machine didn't stop running, and the temperature is at 75 degree F. Outside temperature is 78 degree F.
That is definitely not good. Since it was able to cool the house down before, I would assume the machine at 3 tons can handle the the outside temperature of 95 degree F. So the calculation at least is not wrong there. However, with 80 degree outside this afternoon, and later 78 degree, it still not able to go down to 70 degree, or even 74 degree after 1 hour and 47 minutes.
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Old 07-26-2010, 03:36 AM   #9
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Quote:
Originally Posted by vdu View Post
My question was why the manual says for cooling, set the high CFM, while for heating set the low CFM.
I didn't say I should set 1800 CFM for 3 ton A/C. It was there by default. I have changed it to 1400 CFM, and no more whining or noisy return grill.

My issue right now is that it used to be able to cool the house down to 75 degree F from outside temperature of 95 degree F. The machine also stop once awhile.
After I posted above, at 10:42 PM, outside temperature was 80 degree. Inside was 78 degree, which is the same temperature as the programmed value. I lowered it down to 70 degree F. After 1 hour 47 minutes, at 12:29 AM, the machine didn't stop running, and the temperature is at 75 degree F. Outside temperature is 78 degree F.
That is definitely not good. Since it was able to cool the house down before, I would assume the machine at 3 tons can handle the the outside temperature of 95 degree F. So the calculation at least is not wrong there. However, with 80 degree outside this afternoon, and later 78 degree, it still not able to go down to 70 degree, or even 74 degree after 1 hour and 47 minutes.
You started off with an air flow noise question that has now evolved into a cooling issue.

I would contact the installer. All the motor related noises are warranty problems that should cost you nothing.
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Old 07-26-2010, 05:21 AM   #10
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As above. Your original post said it runs fine. And you have now added that it doesn't run fine.

What is the model number of the furnace, and the outdoor unit.

Was any refrigerant added when it was installed?
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Old 07-26-2010, 09:39 AM   #11
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It's my bad that the thead get twisted a bit. Initially, I thought the system was running fine, and it did. 2 days ago, I started seeing the problem, but thought it was a record hot day. Then yesterday, was a mild day, especially at night, not even hot outside, and the house was not currently hot (78 degree F), so I thought pushing it down to 70 degree F to see if it would be able to handle that. It couldn't.

The furnace model is: GMV950905DX*
Condenser: SSX160361
Coil: CAPF4860D6

I didn't know if they added the refrigerant. I think they did (I hired an HVAC guy to do it). I'll ask him to come by, but I need to be knowledgeable, and make sure he does it right.
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Old 07-26-2010, 11:38 AM   #12
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Ok.

You set high cooling speed. And for your system, that should be 1195 CFM.

You set low heat speed/CFM. The furnace knows what speed to use for high heat after that. If you set low heat to 1125 CFM, it uses 1620 for high heat CFM.
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Old 07-27-2010, 02:38 AM   #13
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Quote:
Originally Posted by vdu View Post
It's my bad that the thead get twisted a bit. Initially, I thought the system was running fine, and it did. 2 days ago, I started seeing the problem, but thought it was a record hot day. Then yesterday, was a mild day, especially at night, not even hot outside, and the house was not currently hot (78 degree F), so I thought pushing it down to 70 degree F to see if it would be able to handle that. It couldn't.

The furnace model is: GMV950905DX*
Condenser: SSX160361
Coil: CAPF4860D6

I didn't know if they added the refrigerant. I think they did (I hired an HVAC guy to do it). I'll ask him to come by, but I need to be knowledgeable, and make sure he does it right.

If you are knowledgeable enough to know if it's done correctly than maybe you should take a crack at fixing it yourself. I think it would be counter productive to have you second guessing the tech. Techs have been known to walk on HOs if they try to tell the tech how to do his job.

No sarcasm intended but your first post said the system was installed some few weeks ago. Your post above concerning freon sounds like you had a different guy aside from your installer put freon in.

Could we at least get the events into the correct chronological order so we can better help you?
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Last edited by hvaclover; 07-27-2010 at 02:40 AM.
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Old 07-27-2010, 07:20 AM   #14
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I understand I shouldn't offend the guys. There are two of them working together. One of them didn't do the duct connecting to the machine right, and left a gap 1/2 inch wide, and 23 inches long along the bottom. They also crushed one of my top take off and flex pipe (without even telling me). So, as conventional wisdom goes, the more I know, the better it is. But, I do appreciate your advice and not offending them.
The freon leak was just a wild guess.
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Old 07-27-2010, 09:35 PM   #15
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After the installer came and check, he said the system is running fine. The pressure is good. He said I need to have the system running at higher CFM. He said the house is 82 degree F, but return temperature of the freon is 55 degree F. The pressure is also good. I asked if would use a cheap filter with lower Merc help? He said it won't help. He showed me by pulling out the filters. He said with less friction, the fan just blow even slower due to variable speed motor. I asked him what about the whining noise. He said variable speed motor works like that. Many of his customers complain, and then they replace another one, with same old noise.
So, in conclusion, if I turn the CFM higher, the house get cooled, but there is whining motor noise, and there is not much I can do about that.
I wonder if my supply duct is too big, and the system detects low friction, so it doesn't turn the fan as much, which reduces CFM. In principle, the CFM should stay the same, it just reduce the speed so that not more CFM is blowing through.
What do you think?

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