No air return in Master Bedroom

ASnatchA

Problem:
- There doesn't seem to be any air flow from the air return vent in the master bedroom of my house I bought.
- Room is stuff at night and generally warmer then any other room with ac on.

Background
- I noticed the room being warm and stuffy at night so I started looking into it. There are 3 supply air ducts for the room and 1 return air. With the furnace fan running I checked the return air for suction with piece Kleenex and it seems to blow more then anything.
- Checked all the ducts in the basement and doesn't seem to be an issue.
- I opened the supply duct cover and took a look around in there and can't seem to see a duct connection in the subfloor. That's just looking around with my phone camera. I was thinking of getting a boroscope camera to see more what's going on.
- I put a temperature sensor in every room and the master bedroom, with 3 supply ducts wide open, is always a degree or two hotter then any room.
- I generally have been sleeping with that bedroom door cracked open which is becoming an issues.

If anyone has any ideas what I could do to figure this out that would be great.

Thanks

Charlie

Jamie Hall

Returns are so important... is there any possibility of something blocking that return inlet or duct? Or even had it disconnected somehow? Do you have a way of generating a small amount of harmless smoke -- incense maybe -- and seeing if it gets sucked in and, better, if it has a noticeable odour, if the odour reappears somewhere?

Lance

Ductwork design and air balancing is one of if not the weakest trained and practiced in the residential markets. Satisfaction starts with proper engineering from load demand to delivery, to how used, and testing the results under all conditions. Want to keep the door shut? Find another hole to let the hot air escape through the wall back to the blower. Or it could be as simple as thermostat cycling control or proper humidification control or all of the above. A poor design will always yield poor results.

ChrisJ

If there's no return you can either add one, or undercut the door so there's a bigger gap at the bottom.

They also make vents that insert into the door to allow more airflow.
For example : https://www.amazon.com/HVAC-OV-Grille-Sided-Ventilation/dp/B09V7QY7SY/ref=sr_1_1_sspa?crid=KV4VF8NL7POL&keywords=door+vent&qid=1692893334&sprefix=door+vent,aps,124&sr=8-1-spons&sp_csd=d2lkZ2V0TmFtZT1zcF9hdGY&th=1



I had considered these when installing my ductwork and just decided ot do proper returns. However I am still considering them to help the bathroom fans.

mattmia2

Does the return grill lead somewhere? Usually return ducts are just constructed of joist and stud bays that are enclosed by the drywall and plywood and sheetmetal and duct are used to enclose and connect the parts that aren't enclosed by other building materials. Maybe someone put in some blocking and blocked the return air path after the hvac contractor was done or someone removed some of the connecting ducting in the basement.

ASnatchA

I got as far as I could into the void space that the return air vent covers. It goes to a void space under the floor but as far as I see I couldn't find a duct opening in there. I am thinking they might have covered the return air duct when they got the flooring redone. That would be a shame.

I'm going to get my brothers inspection camera and take a better look.

I wonder if there's a way to cut a bit of the drywall out and cut a hole where I think the duct would be. Maybe drill a hole first and see if I get suction. That's all I can think to do right now.

Thanks for the responses.

mattmia2

Is this bedroom on a first floor or second floor?

hot_rod

These door vents are used at the bottom for problems like that

ChrisJ

hot_rod said:

These door vents are used at the bottom for problems like that

I had mentioned these but I guess it's not the route they want to take.

PRR

Low-effort test: put a radio against the 'return'. Go to the furnace, pull the filter, put your ear to it. Do you hear radio better in the filter slot or just down from above?

retiredguy

Back in the 1960's and early 1970's when I was still doing residential HVAC, every room except the bathroom and kitchen had a low wall level return. When an A/C unit was added high wall returns were installed to assist in the cooling in all those rooms. Today almost no new houses use this kind of ducting. Central return grills are all the rage as are short cuts to any installation.

ChrisJ

retiredguy said:

Back in the 1960's and early 1970's when I was still doing residential HVAC, every room except the bathroom and kitchen had a low wall level return. When an A/C unit was added high wall returns were installed to assist in the cooling in all those rooms. Today almost no new houses use this kind of ducting. Central return grills are all the rage as are short cuts to any installation.

The house I grew up in was built in 1958.
It had it's original Mueller Climatrol furnace even when my parents sold it in 2006.

It had a large return in the hallway wall by the bedrooms and then it had a very tiny one in the living room that was hardly even worth the effort. All of the doors were undercut by the floor.

Laziness, shortcuts and cheapness isn't new. Especially with forced air systems.

Proper, or even oversized returns in every room except bathrooms and kitchens are still recommended but just as in 1958, cheap is still all the rage.

pecmsg

I wouldn't say the returns were oversized as much as the furnaces then were high temperature low velocity air flow.

mattmia2

Most 50's houses around here inculuding my house that was retrofited around 1950 with forced air seem to have the supplies in the center of the house and the returns on the outside walls.

ASnatchA

So after the summer break of managing oy with keeping our door open at night I finally got around to getting a inspection cam. Looks like to me the master and room 2 return vents connect in the joists and then run to a drop that should go to the basement. Tries to follow with a camera and looks to be blocked by drywall. ****.

Checked room 3 and its air return has no suction either. All three rooms on the second floor essentially have no return vent. Wonder how that happened.....

Might have to go door vent solution or start busting drywall. The other 4 air return vents draw suction.

EBEBRATT-Ed

Drywall is cheap. Your only talking 3 rooms. Are the ducts connected in the basement and just blocked with drywall somewhere? Or do they not show up in the basement.

ASnatchA

Well the house is a split level 2nd floor, 1st floor, crawlspace. Looks like the joist gos into a hole that should run down a 1st floor wall and into the crawlspace.

I'm going to keep poking around tomorrow and get a better idea where everything is. Also know the contractor that did some Reno's for the previous owner so going to see if he knows anything.

ASnatchA

Update:

Opened the duct in the crawlspace and fount the suspected vent was clear. Followed the duct and it was a duct between the joists and looked like it dropped into the main return header duct..... except there was no hole in the main duct to connect them. So all the return vents just connected to each other and not the return vent.

Nice that I found my problem, going to cut a hole in it tomorrow and patch everything up. Excited to see how it effects the air in the house.

ASnatchA

So cut a big opening in the return duct and worked as planned. All the rooms upstairs and the office got return air back. One room still doesn't have return air so I have to follow it to see where it comes into the return duct.

Air feels alot better upstairs in my bedroom anyways, and temperatures have balanced out better so I take this as a success. Thanks for everyone's help

Question for those who read this:: I was looking at the furnace after the return air was added and it sounded and felt like it oscillating/vibrating. My first thought is that it was starving for air which I thought would be the way better with the return air change. I changed the filter and there was alot of suction. More then I remember before. Any idea what could be going on? Fresh air makeup was drawing in alot of air too.

Jamie Hall

There's something somewhere which is still blocking that return air. Good hunting.

bburd

Possibly the fan was set on a higher speed than normal to compensate for the restricted return air. The easiest way to tell is to check the temperature rise through the furnace after it's been running for a while. The spec should be on the rating plate. If the temperature rise is below spec, try reducing the blower speed.

ASnatchA

I checked the temperature rise and it was only 26F. Looked at the specs and it should be 35 - 65 so I dropped the air flow one setting and it brought the dT up to 41F. Nothing else seems different.

Still kinda loud and vibrating. I was thinking is there a chance with the air flow up higher the vent gas pipe is under sized or something? Looking at the manual it seems like it should be a 3inch and seems to only be a 2inch flu.

Another thing that's a little unclear after reading the manual is the difference between low fire and high fire modes. Mainly how can I tell tell which is active or control which one. Is it automatic? Does my thermometer tell it which to use?

I realize I've kind of transitioned from ducting questions to furnace questions. The furnace is a napoleon 9600, 120 btu/hr furnace. Model number NPV120T5B. Just in case anyone is familiar with the model.

Thanks all

bburd

A 2 inch flue pipe? Can you post some pictures?

ASnatchA

bburd

That looks like a 3 inch flue pipe but it's hard to tell without a tape measure or ruler.

The vibration most likely has nothing to do with the gas vent.

I'm not familiar with that furnace, but I would reduce the blower speed one notch further. Also look around for anything that is not properly secured and could be contributing to the vibration.