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One room not cooling...tips?

Posted on 7/30/20 at 10:34 am
Posted by lynxcat
Member since Jan 2008
24139 posts
Posted on 7/30/20 at 10:34 am
I've got one bedroom that isn't cooling on the 2nd floor. The rest of the house and floor is cooling. I've checked the vent and it looks open. Other things I should look into before calling an A/C repair company? Thanks
Posted by gumbo2176
Member since May 2018
15086 posts
Posted on 7/30/20 at 10:37 am to
You may need to get in the attic to see if there is a damper on the supply line where it comes off the plenum. It should be open all the way but sometimes they loosen and can close a bit, cutting down the amount of air heading that way.

Look for a wing nut looking gizmo under the insulation no more than about 6 inches from where the line hooks into the plenum. That is how you loosen/tighten the damper and get it in the proper position to allow air to flow.


ETA: What type ductwork do you have, metal wrapped with foil back insulation or that flex-duct plastic crap?

If flex-duct, I've seen rats and squirrels eat holes in that stuff allowing the cool air to dump in the attic.
This post was edited on 7/30/20 at 10:50 am
Posted by humblepie
Member since May 2008
536 posts
Posted on 7/30/20 at 10:40 am to
I had an AC duct get crushed by a pipe in one of our homes. The plumber was lazy I guess...
Posted by Geauxld Finger
Baton Rouge
Member since Jan 2005
31707 posts
Posted on 7/30/20 at 10:40 am to
has this one room always had issues cooling?

could be that its the farthest out from the run so it doesn't get the best airflow.

you could have a leak in the duct work
Posted by MikeBRLA
Baton Rouge
Member since Jun 2005
16455 posts
Posted on 7/30/20 at 10:51 am to
quote:

Look for a wing nut looking gizmo under the insulation no more than about 6 inches from where the line hooks into the plenum


Also look at every fork in the duct. There should be a damper there as well so you can control airflow at the fork.
Posted by lynxcat
Member since Jan 2008
24139 posts
Posted on 7/30/20 at 10:55 am to
quote:

has this one room always had issues cooling?



Bought the home 2 weeks ago, so just learning. Issue did not come up in the inspection. Home is under 3 years old.
Posted by Geauxld Finger
Baton Rouge
Member since Jan 2005
31707 posts
Posted on 7/30/20 at 11:05 am to
quote:

Issue did not come up in the inspection


i don't think that is anything that would come up in construction, also depends on the time of year the inspection is done.

how old is your unit? is it a separate upstairs unit?
Posted by Clint Torres
Member since Oct 2011
2662 posts
Posted on 7/30/20 at 11:11 am to
quote:

You may need to get in the attic to see if there is a damper on the supply line where it comes off the plenum. It should be open all the way but sometimes they loosen and can close a bit, cutting down the amount of air heading that way.


Yup; I bought new construction and had to have the HVAC installer come out and balance everything after we moved in. In some rooms, you could hear the air rushing out of the vents and in others there was next to zero airflow. They fooled with those dampers and it's been great since.
Posted by NYCAuburn
TD Platinum Membership/SECr Sheriff
Member since Feb 2011
57002 posts
Posted on 7/30/20 at 11:18 am to
Is there air flowing? if so, much as other rooms? As cold?
Is there a return in the room? do you leave the door open?
Posted by lynxcat
Member since Jan 2008
24139 posts
Posted on 7/30/20 at 11:40 am to
Single unit for total house. House is less than 3 years old so the unit will be too.
Posted by lynxcat
Member since Jan 2008
24139 posts
Posted on 7/30/20 at 11:41 am to
No air flow at all in the room. All other rooms on first and second floor appear to have good air flow.

When the door is open, it’s able to stay pretty cool but when the door is closed for a longer period then it warms up.
This post was edited on 7/30/20 at 11:42 am
Posted by Geauxld Finger
Baton Rouge
Member since Jan 2005
31707 posts
Posted on 7/30/20 at 12:32 pm to
A two story home now a days has two units. Was this a spec home type thing? Often times I have seen that the unit they put in is not really sized for the house.

What happens is the room that's farthest away at the end of the run suffers the most especially with the door closed. Adding an upstairs unit would alleviate it. Not really sure what else it would be aside from a leaking duct. It's really hot and the unit isn't strong enough to really cool the house, especially those new construction homes with undersized units
Posted by LSUengr
Baton Rouge
Member since Sep 2005
2332 posts
Posted on 7/30/20 at 1:26 pm to
quote:

When the door is open, it’s able to stay pretty cool but when the door is closed for a longer period then it warms up.



The door is too close to the flooring if this is the case. The air from the room is not getting back to the return air so it creates a pocket of trapped air that creates pressure not allowing air to flow from the vent. That is why it cools when the door is open, no pressure pushing back. You need to cut the bottom of the door off. Need around 1" between flooring and door bottom.
Posted by NASA_ISS_Tiger
Huntsville, Al via Sulphur, LA
Member since Sep 2005
7981 posts
Posted on 7/30/20 at 1:29 pm to
What's the temp of the air coming out of the vent in that room?

I see you say no airflow...does that mean zero airflow...if so then that's pointing to a duct restriction or collapse. You might see if there is dampners in the ducts and see if they've been overridden somehow. Previous owners might have bypassed some dampers in the system to force more air somewhere else. Or if a single unit for both floors...you might have a controller issue.
Posted by i am dan
NC
Member since Aug 2011
24717 posts
Posted on 7/30/20 at 2:01 pm to
quote:

I'm curious to know how the shocks held up on both vehicles.


We have a bedroom on our 2nd floor that gets pelted with direct sunlight on that side of the house all day. Really heats the windows and wall up, double paned energy windows too. We have black out curtains that help a bit, but that room is the warmest room in the house. It doesn't get hot hot, but you can tell a little difference when you walk into the room.
This post was edited on 7/30/20 at 2:05 pm
Posted by BoogaBear
Member since Jul 2013
5559 posts
Posted on 7/30/20 at 2:48 pm to
quote:

I'm curious to know how the shocks held up on both vehicles.


We have a bedroom on our 2nd floor that gets pelted with direct sunlight on that side of the house all day. Really heats the windows and wall up, double paned energy windows too. We have black out curtains that help a bit, but that room is the warmest room in the house. It doesn't get hot hot, but you can tell a little difference when you walk into the room.


Well how did the shocks handle it?
Posted by i am dan
NC
Member since Aug 2011
24717 posts
Posted on 7/30/20 at 2:54 pm to
quote:

Well how did the shocks handle it?


Quoted the wrong post..
This post was edited on 7/30/20 at 2:56 pm
Posted by East Coast Band
Member since Nov 2010
62759 posts
Posted on 7/30/20 at 4:23 pm to
I had to add a pass through vent in a room to allow air to return.
Made a big difference

ETA: I did this, but I put mine above the door

This post was edited on 7/31/20 at 8:16 pm
Posted by KajunKouyon
White Castle, LA
Member since Jun 2012
2377 posts
Posted on 7/30/20 at 9:20 pm to
Check all dampeners coming off of each duct line at the plenum. I’d block off half way to the bathrooms and stuff.
Posted by fishfighter
RIP
Member since Apr 2008
40026 posts
Posted on 7/31/20 at 8:11 am to
quote:

We have a bedroom on our 2nd floor that gets pelted with direct sunlight on that side of the house all day. Really heats the windows and wall up, double paned energy windows too. We have black out curtains that help a bit, but that room is the warmest room in the house. It doesn't get hot hot, but you can tell a little difference when you walk into the room.


Had this problem for over 26 years in the master bedroom. Besides that, that room is sound proof. Had just fixed this problem a few months ago installing a return duct. All that was needed was a 12"x12".
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