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Rick
Rick, HVAC Supervisor
Category: HVAC
Satisfied Customers: 19533
Experience:  40+ yrs. experience as a licensed oil & gas technician.
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We are getting condensation back into the heating area on the

Customer Question

We are getting condensation back into the heating area on the outside of the 3in PVC. The 2in vent is surrounded by the 3 in PVC and then a 4in PVC through the roof. I need some details as to how the system operates in order to figure out my difficulties. The moisture system that removes condensation to the crawl space seems to be working correctly.
Submitted: 1 year ago.
Category: HVAC
Expert:  Rick replied 1 year ago.
Let's see if I understand your description. It sounds like you have a gas condensing furnace with a paired AC coil and you're getting condensation on the outside of the concentric 3" PVC vent/intake piping while you're running the AC. I have a theory as to what's happening. If your furnace has a sealed combustion chamber then my theory would be more viable.
Customer: replied 1 year ago.
It's not the AC it's the heating .
Expert:  Rick replied 1 year ago.
You have condensation on the outside of the vent piping when the furnace is firing?
Customer: replied 1 year ago.
Correct
Expert:  Rick replied 1 year ago.
I don't see how this is possible. The inner pipe which is the exhaust, will have exhaust gases that are moisture laden and which can condense into water liquid. The outer pipe only draws in air from outside for combustion. The air outside would have to be considerably colder and the air inside (where the condensation occurs) would have to be considerably warmer and humid for condensation to occur. During the winter the outside air is indeed much colder but I've never seen condensation on the outside of concentric piping even then.
Customer: replied 1 year ago.
There are 2 , 3in pic pipes from the furnace. The one that has the condensation problem has the 2in pvc inside . The other pvc goes straight up thru the ceiling in the proximity ( 4 in) of the other pvc. I've seen illustrations of this system and the 2, 3in pipes are joined by a 45' joint. In this case it would be above the ceiling line. The 2in vent and the 3in are encased by the 4" coming through the roof.
Expert:  Rick replied 1 year ago.
What's the model number of your furnace? If you have 2 3"PVC pipes connected to your furnace then 1 would be exhaust the other combustion air intake. If this is the case then you would not/should not have concentric piping (2" inside of 3") since this is only used when the intake and exhaust are piped together (not what you seem to be describing. Maybe some pictures of your installation, including where you're seeing condensation might help You can post a picture here by clicking on the paper clip icon in the tool bar at the top of this dialogue box. You can only post from a PC or a Mac not a phone or a tablet. If that doesn’t work for you then you can upload a pic to a file sharing service like https://photos.google.com/ OR https://www.dropbox.com and post the “share”link to your picture here or you can email the pic to customer service but the last option can take quite a while to get to me. Click on the CONTACT US link to contact customer service. http://ww2.justanswer.com/contact-us
Customer: replied 1 year ago.
The model number is ***** BWT. Nordyne. I'll try for some pics later today.
Expert:  Rick replied 1 year ago.
Ok
Customer: replied 1 year ago.
I went by the job site and opened the unit. No water condensation because the stat was turned down. The two 3" pvc have a 2" pvc pipes that run to the unit inside. The exterior roof penetration is 4" with a 3" and 2" inside. I've taken pics but don't know if I can get them to you successfully. If you Google the make and model you may pick up the drawings of the pvc details showing the pvc exiting the right hand side of the unit . When the 2 ,3" pvc enters the unit it goes back to 2"(both units). I'll try the pics but don't wait too long.
Expert:  Rick replied 1 year ago.
This is the first mention of 2 units (if I'm understanding you). Like I said before condensation inside the exhaust is normal. This type of config is pretty standard ( I did check the install manual). On the outside of a 3" concentric vent is not. You haven't given me any info so far that would inform me as to why this might be happening. I can only speculate that they aren't installed properly.
Customer: replied 1 year ago.
Should there be a 4" pvc on the roof penetration? Could this be the cause of the condensation of moisture at the 3" through the penetration of the roof. The top cap of the roof penetration looks to be designed for a 4"pic. The previous illustrations didn't include the 4" but showed the 45 degree transition between the two 3".
Expert:  Rick replied 1 year ago.
What you're describing isn't typical but that doesn't necessarily make it wrong but if the 4" is capped (has some type of weather cap)then it might be possible for the condensation to collect on the cap and run back down the outside of the 3"
Customer: replied 1 year ago.
Haven't heard from you in a couple of days and was wondering if you have come up with any phenomenal conclusions? The cap I mentioned was PVC which included the 4". it allowed the the 3" to breath and the 2" to vent to the outside. It was tent shape and allowed the 4" to be protected from the environment.
Expert:  Rick replied 1 year ago.
I gave you the only likely scenario based on the info you provided. Like a said before a picture might provide more insight into your situation
Customer: replied 1 year ago.
I'm not very computer literate regarding forwarding pics. I think that is not an option even though I have several good pics. Sorry about that.
Expert:  Rick replied 1 year ago.
Well, all I can do is answer based on the info you provide and all I can come up with (based on your description) is that the condensation is collecting under the 4" cap and running down the outside of the 3". The thing is that with this type of furnace the type of roof termination you describe is not typically used.
Customer: replied 1 year ago.
The e mail software doesn't cut it. Your conversations are not included. I'm at a loss on how to resolve the problem and keep the integrity of the ceiling and leaking with the condensation problem. Sorry about the pics.
Expert:  Rick replied 1 year ago.
Maybe if you contact customer service they can help you iron out your problems with the interface. I can't tell you specifically how to resolve your problem when I can't see what it is. All I can tell you is that it sounds like you have an atypical vent termination and it will probably have to be replaced with one that complies with the install instructions to resolve the problem.