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Old 05-07-2009, 12:28 AM   #1
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Duct work issue


I have a 3 year old 2 story home w/ flex duct through out. It uses only one 5 ton A/C unit to cool both the upstairs and downstairs. I know I'm creating static pressure behind the air handler, but I have to close the vents downstairs in order to get the air upstairs. I ussually hear hissing / whistling from the vents downstairs. Today the A/C has been running constantly and I don't hear the hissing / whistling coming from the vents. What just happened? Obviously the thermostat is not turning off b/c of the lack of cooling. I believe I created a leak in the ductwork. It's a cheap house and I've been told that builders often don't install the ducts correctly. I cannot fully access the attic where the ducts come from downstairs. I went around looking / feeling for leaks, but lack the tools and know how to do so. How can I inexpensively determine my suspicion?

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Old 05-07-2009, 05:08 AM   #2
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Duct work issue


Is the blower running.

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Old 05-07-2009, 10:29 AM   #3
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Duct work issue


Yes. Everything is working. Cold air comes from the vents, but not as much. I use the cheap blue filters as to not restict flow and they are new / clean. The return seems to be sucking as much as it use to, though I have no way of measuring it. It appears the air is going somewhere other then out the vents. I've opened all the vents downstairs were the thermostat is, so that atleast it will be cooled and the system doesn't run continuously. By doing so it is pretty uncomfortable upstairs. I've would like to reduct the whole house, but money is an issue. It would be nice to isolate the leak and fix it for now. Then fix the big problem when times are better. Is there anything I can do, or do I need a professional? Blower door & infared audits seem pretty expensive. I might as well have the house reducted.
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Old 05-07-2009, 10:46 AM   #4
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Duct work issue


Could be a dirty coil.

If you have a big air leak, it should be easy to find.

Just have the A/C running, and check you duct, including any chases it might run through.

Could be a leak, disconnected duct in the air handler location.
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Old 05-07-2009, 10:53 AM   #5
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Duct work issue


You can use tissue paper or a candle flame to detect airflow too small to feel.
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Old 05-07-2009, 11:13 AM   #6
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Duct work issue


It's a big leak. Again the vents use to hiss when closed, now you can bearly feel the flow when opened. I checked everything I can see, air handler, attic ducts, ... They appears to be sealed tight. There is a portion of the attic not accessible where the ducts come from downstairs. I got on the roof and checked the gable vent to feel if there was any cool air, but I doubt if I would be able to feel / hear the difference. I remember having the ceiling open to plumb in a water softner a couple years ago. Then I could feel cold air blowing from inside the walls. I'm almost positive the vents were not sealed properly by the builder. Now the issue is worse. I'm about to rip out drywall to investigate. Tell me I don't need to do this!
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Old 05-07-2009, 11:21 AM   #7
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Duct work issue


It seems to me there is an odorant you can put in the air handler and use it to detect downstream leaks. The name maybe has something to do with "green."
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Old 05-07-2009, 11:57 AM   #8
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Could use a laser thermometer.

Turn on the A/C. Wait a couple minutes and see if walls start to show a temp difference.
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Old 05-07-2009, 12:10 PM   #9
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"Oil of wintergreen" but it's to check heat Xchangers. My bad.
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Old 05-07-2009, 12:44 PM   #10
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Duct work issue


Great idea, didn't think of detecting a leak w/ an odorant. I should be able to detect a big leak from the non accessible attic space from outside the gable vent. Depending on my sinuses. I don't know how close it will get me to the leak, but I would rather now where in general it is leaking before tearing through the ceiling. Wish I had a laser therometer. I'll probably pick one up before this is through.
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Old 05-07-2009, 02:09 PM   #11
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Quote:
Originally Posted by kfrome View Post
Wish I had a laser therometer. I'll probably pick one up before this is through.
They're $50 and up and they work better on dull surfaces [high emissivity] than on shiny surfaces.
I guess it'll pay for itself on this one job.
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Old 05-07-2009, 04:35 PM   #12
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Well I used some peppermint oil my wife uses for making soap. Man the stuff made the whole house smell. I closed off all the vents to aggrevate the issue, turned the A/C on, threw a saturated napkin against the intake, and went investigating. Checked the attic, roof & gable vents, garage, any hole I could find and couldn't smell peppermint except inside the house.

Yesterday the A/C ran for so long the high pressure line was frosty, and the house was not cooling off. This makes me feel it could be the coil. I can't imagine the coil getting clogged so quick. One day no problem the next no flow. Would a dirty coil effect the flow of air or just the temperature?
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Old 05-07-2009, 04:48 PM   #13
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Duct work issue


Went outside and no water is dripping from the pipe. I poured a cup down the trap to make sure it wasn't clogged. It's flowing fine. Then I started pulling tape off the evaporator and took a peek inside. The whole thing is frozen! Sorry for the confusion. Looks like my evaporator coil needs to be cleaned. Thanks for all your help.
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Old 05-07-2009, 11:51 PM   #14
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Well I cleaned the coil. It took all day, and it wasn't the problem. Now the compressor cycles on and off every 5 seconds. I believe there is a freon leak. I'm going to get a professional. Pisses me off, I just had a guy out 1 month ago. Told him I suspected a leak were I saw a constant wet spot on the condensor. He said it was fine, then charge me $150.00 bucks for a run capacitor and for him to hose off the condensor. The wet spot is back again. Any suggestions? Does anyone fix a leak or am I looking at new compressor / condensor?
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Old 05-08-2009, 04:25 AM   #15
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Depends were the leak is.

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