Two PVC pipes leaving furnace/AC unit connected correctly

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Old 05-18-14, 04:24 PM
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Two PVC pipes leaving furnace/AC unit connected correctly

Hello,

We recently had our a/c units cleaned and it looks to me like we are missing parts on the pvc piping. On the first two pictures, there is a pvc pipe coming out of the overflow tray and exits out of the side of the house. Name:  P1040004.jpg
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Size:  43.0 KB The second pipe comes out of the unit itself and runs along the floor to the second ac unit. The pipe sticking up, blows cold air into the attic when the ac is running. The other hole in the unit has nothing coming out of it. Name:  P1040005.jpg
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The second AC Unit, has no open pipes, yet it does have the same vertical pipe. (Not sure if this one blows cold air out when the ac is on, as this one is only used for the second floor) Name:  P1040006.jpg
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Just wondering if this is correct, or if I need to get someone out here. Our AC in Texas is astronomical, and I really don't want to cool the attic.

Thanks for the help.

mark
 
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Old 05-18-14, 05:47 PM
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I'm not an expert, just a homeowner, however I believe that the open vertical pipe is there for cleaning purposes (allows you to pour bleach into drain lines). I believe that you can cap the pipe, however I wouldn't permanently attach the cap, as you may need to remove it sometime in the future to clean the pipes.
 
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Old 05-18-14, 07:34 PM
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The drain piping from the cooling unit needs a "loop seal" (aka trap) before the open vent. The depth of the seal is dependent upon the pressure differential between the cooling unit enclosure and the atmosphere.
 
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Old 05-18-14, 08:24 PM
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The cold air you feel coming out of the pipe in the first photo is from the cold water flowing out the pipe. It will not affect your cooling cost. The open pipes are for what Bob says, pouring in some bleach to keep the pipes clean.
 
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Old 05-18-14, 08:39 PM
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Sorry, Fred, but the open pipes are vents for the downstream piping. True that many people DO use them to attempt to clean the piping by pouring a bleach solution down them but the REAL purpose is that of a vent.

AND, the cool air coming out of the vent is not because of the cool condensate but is indeed cooled air that should remain in the ductwork. Would you punch a 5/8 inch hole in a supply duct and then tell the homeowner it has no effect on their cooling costs?
 
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Old 05-18-14, 08:44 PM
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Well, you may be right, but my clean-out PVC pipe is capped; so, it couldn't be acting as a vent. I'll have to do some research on this. If you're right, then I probably should remove the cap.
 
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Old 05-18-14, 08:52 PM
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Sorry Champion but I was probably wrong with my assertion that the cold air was from the cold water draining in the pipe. See this: https://answers.yahoo.com/question/i...7175430AAOiM2o
 
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Old 05-18-14, 10:02 PM
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According to this site ( Let's Concentrate on Condensate | The ASHI Reporter | Inspection News & Views from the American Society of Home Inspectors), the two pipes should be plugged. And, there should be a trap for each unit.

"The primary purpose of a condensate trap is to prevent air from moving in or out of the coil box or air handler during operation." So, adding a trap for the first unit should stop the cold air exiting the vertical pipe. It's not clear to me in the second photo whether the pipes form a trap or not because some of the pipe is covered by insulation.

Regarding the vertical pipe serving as a vent, this says that this is not its purpose: "There are a number of piping mistakes made when installing a condensate trap. In my opinion, an open clean-out between the trap and coil is the number one mistake. I believe itís made because installers think leaving the pipe open will help the system drain, working much as a vent does on the house plumbing. When in fact, an open clean-out at this location allows air to bypass the trap altogether. This mistake is easily corrected by placing a cap over the clean-out pipe and only removing it for cleaning purposes."
 
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Old 05-19-14, 12:03 PM
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My Trap

Here is a picture of the trap the Trane folks installed on my upstairs evaporator unit. You could model this to add a trap to the unit in your first photo.
 
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Old 05-19-14, 06:00 PM
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The vent goes downstream from the trap. Any piping from the coil pan to the trap should be closed to the atmosphere.
 
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