please help 10 degree difference on vent inside home on central a/c


  #1  
Old 07-24-09, 07:50 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
please help 10 degree difference on vent inside home on central a/c

The ac vent in my master bedroom and bathroom are 10 degrees higher around 72 to 74 with ac on than the vents in the rest of the home they all run around 60 degrees. The pipes are the first 2 drops of the square pipe before it connects to the round pipe that feeds the rest of the house. we added a air scoop to the duct work on one vent and it changed it by about 2 degrees any suggestions. and for a little more info its in the attic comes out of the top off the furnance into a square sheetmetal box thats insulated on the inside and feeds the round pipe. the 2 hot vents are on the square box. I can get pictures if needed
 
  #2  
Old 07-24-09, 08:22 PM
M
Member
Join Date: Jan 2008
Location: Tennessee
Posts: 438
Upvotes: 0
Received 0 Upvotes on 0 Posts
Too Hot

That is a lot of temperature difference, my first guess is that there is not actually any air movement (dampers closed or air blowing by the first few taps due to improper sizing) and you are measuring ambient air temperature. Are you feeling any air moving in the warmer ones.
 
  #3  
Old 07-24-09, 08:31 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
yes you can feel the air blowing out of the warm vents it stronger out of the one we added a scoop to but still warmer than the rest of the system
 
  #4  
Old 07-25-09, 07:23 AM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
they are getting heat from somewhere
 
  #5  
Old 07-25-09, 09:21 AM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
we went taped the seams on the box and around the the fittings we could feel the air moving around still no luck
 
  #6  
Old 07-25-09, 02:47 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
I mean the duct is getting heated up form somewhere. Take air temp readings along the duct starting at the beginning. Pop a small hole, insert a stem type thermometer, let it stabilize and take a reading. Insert a sheet metal screw into the hole and move down a few feet.
 
  #7  
Old 07-26-09, 12:13 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
I checked the piping to the master bedroom it was about 75 degrees I checked a pipe going to a cold vent in the hall it was 65 degrees
 
  #8  
Old 07-26-09, 02:46 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
What I mean is, check all along one of the warmer ducts. From where the duct starts to the end at the room.
 
  #9  
Old 07-27-09, 03:56 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Thats what I done in 4 places they were all between 75.2 to 75.4. I then done another vent that blows cold and it was between 65.2 to 65.6.
 
  #10  
Old 07-28-09, 04:49 AM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
Interesting

Somehow those ducts are not being fed air properly at the takeoffs. I'm having a little trouble understanding how the ducts connect but I don't think the takeoffs are in the mainsream area of the main duct. Pictures would help.
 
  #11  
Old 07-28-09, 07:11 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
Its late now I will get you some up tomorrow afternoon thanks for your help so far
 
  #12  
Old 07-29-09, 06:18 AM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
Sounds good, thanks. hat I'm wondering is if you have a horizantal coil and the ducts in question come off the top of the plenum box with just a T connection, that's a high pressure drop fitting. Also, if the plenum box is metal, maybe some insulation on the inside has worked loose?
 
  #13  
Old 07-30-09, 07:04 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
here are the pictures
Picture 1 in this picture the pipe that 90s out of the side of the box goes to the bathroom and blows around 74 ~75 degrees the one that elbows out of the top towards the bottom of picture goes to the bedroom and blows about a degree maybe 2 cooler



Picture 2: is a different angle of the same thing the one on the side is to the bathroom and the one on the top is to the master bedroom


picture 3: is the rest of the house that blows cool


picture 4: is a picture of the main system
 
  #14  
Old 07-31-09, 12:14 AM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
If you stick the thermometer into the metal box those 2 ducts are connected to, what temperature do you read? How is the main duct connected? Does it come out the front of the box?
 
  #15  
Old 08-02-09, 11:35 AM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
inside the box it reads 62 degrees there are no obstructions inside and the main tube comes out if the end of the box straight to the rest of the hose no bends or anything
 
  #16  
Old 08-02-09, 12:38 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
well you may have to disconnect the 2 ducts in question and take a look inside the box. Losing 10* + at the connection is weird.
 
  #17  
Old 08-02-09, 02:16 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
I done that there ws nothing in there the insulation was all still stuck to the sides I couldn't see anything that would cause it. It has me and a neighbor of mine stumped also
 
  #18  
Old 08-02-09, 04:13 PM
D
Member
Join Date: Aug 2007
Posts: 1,851
Upvotes: 0
Received 0 Upvotes on 0 Posts
So if you take a temp right after the connection, it's in the 70's?
 
  #19  
Old 08-02-09, 05:22 PM
M
Member
Thread Starter
Join Date: Jul 2009
Posts: 10
Upvotes: 0
Received 0 Upvotes on 0 Posts
in the first picture I posted earlier you see a piece of tape on the insulation that was the second hole I drilled there was one more before the elbow above the top of the box and they were all in the 75's.
 
 

Thread Tools
Search this Thread
 
Ask a Question
Question Title:
Description:
Your question will be posted in: