Probably an easy fix but not sure

Old 05-30-17, 02:15 PM
Thread Starter
Join Date: May 2017
Posts: 1
Upvotes: 0
Received 0 Upvotes on 0 Posts
Probably an easy fix but not sure

I'm new here so apologises if this should have been posted elsewhere. I have recently had a new ducted HVAC system installed in the house and I've noticed that upstairs approx 4 rooms don't seem to be receiving any hot air. When I have gone into the roof cavity (where the unit is installed), I can see the plenum. The plenum feels warm and blows air to a distribution point which is then meant to distribute the air to approx the 4 rooms. Interestingly the plenum has about 2 other shoots and one of these services the other upstairs rooms and they receive air particularly the rumpus room so I believe the plenum would be working correctly.

I can't understand why the air would not be flowing correctly. The piping is flexi pipe and is hung from the roof rafters.

I have checked for leaks around the plenum on the main distribution HVAC line and there is a small leak (or at least it probably could have been a little tighter fit) which is leading to the distribution point for those 4 rooms, but surely that wouldn't stop all the heat missing from those 4 rooms?

Is there a blanking cap in the distribution point that could stop air flowing into it? How could all points not be receiving air? There appears to be a little panel on each of the outlets on the distribution point before the pipe runs to the room does that need adjustment?

I'm doing my head in as the unit seems to work, air is flowing from the plenum but not coming out at the other end? If someone could help or offer some advice that would be much appreciated


Old 05-30-17, 03:59 PM
PJmax's Avatar
Group Moderator
Join Date: Oct 2012
Location: Jersey
Posts: 65,451
Received 4,051 Upvotes on 3,634 Posts
Welcome to the forums from down under. (Should put non-US in your bio information.)

So your HVAC equipment..... furnace and A/C is in the attic..... I'm guessing since you don't have a basement.

You said distribution point. That could have adjustable dampers in it.
The system is working but you're not getting air out of all the registers. If there isn't an adjustable damper then something else is causing a blockage.

I've noticed things done much differently in different parts of the world from how we do it.
Since it's a new system.... might be best to get the installer back.
Old 06-01-17, 04:28 AM
airman.1994's Avatar
Join Date: Dec 2005
Location: VA
Posts: 5,491
Upvotes: 0
Received 8 Upvotes on 8 Posts
If dampers are not closed in each line then the duct is not sized / installed correctly.

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