[jczst21]

I'm not an HVAC professional just a home owner so please excuse if this question is far fetched.

An HVAC professional told me i have a return air problem for the 2nd floor.

On the first floor there is a huge long 30" return grate. The 2nd floor has a return but it's a regular size vent probably 12x6 size i think,

Can i cut the wall longer and put a larger grate for the return or do i need to make the whole duct all the way down larger to suck the air from the second floor. It appears in the basement they used the floor runs as the duct...i ordered a camera online to look down the return to see if anything is blocking it. I stuck the camera from my phone on video mode to look in a little and seems you can see under the floor from in the duct so looks like there is not a liner in the wall.

 

[beenthere]

Will need to open another wall cavity to gt more return air from the second floor. 16" OC 2x4 wall is only good for a max of 145 CFM.

 

[jczst21]

Ok thank you.

I thought i could extend the return vent on this one all the way to it's max of 16" and then make another return somewhere on the second floor.

In the basement, and i've read this on other sites, that it's not up to code, but it seems previous to my ownership they have used the floor joist runs in the basement as the duct work for the returns. One coming from the first floor in the living room and the other is the one that is on the second floor.

There is a third huge 30 inch long return on the first floor and the return pretty much goes right into the unit.

I'm trying to think of where to put this extra return. If i put it into the second bedroom, it brings me down over the garage where the return would come down it would be where the garage door opens.

I thought of an interior wall on the second floor in the hallway and when i tried to determine where it would come out in the basement i think it would be where the back wall of the house is and i run into the basement steps and such.
The only option would be in the master bedroom putting a second one.
I would think two returns in the same room would create an imbalance of air flow but maybe cut in right next to the exisiting one and make one big grill for it.
Not sure.

 

[stick\shift]

You should have at least as much return area as vent area so a good start is to take stock of all the vents in the house. Keep in mind you have to count the smallest area as the size, which is why adding another return upstairs without adding a duct would do no good, as that would not increase the cross sectional area as the duct would be the bottleneck.

 

[jczst21]

There are three vents upstairs. One in bathroom, one in master bedroom and one in guest room.
Each vent is a 12x6.
There is one return in the master bedroom. It is 14" x 6.

There are tons of vents on the 1st floor.
2 in the den, 1 in kitchen, 3 in living room.
Returns are in living room. 2 of them.
The big 30" one and another one that is 12x6.

The 1st floor is frigid and then the 2nd floor is like going into the attic.

 

[Bud9051]

Speaking of going into the attic, what is up there for insulation and ventilation?

By leaving the bedroom doors open you would be simulating more return flow. If you do that and nothing changes, then the return issue may not be the reason for it being hot up there.

Bud

 

[jczst21]

I had the HVAC people come in and they did a air flow test from all the vents and they said i have good flow from each...i just doing understand why it's so darn hot up there...he said i needed more returns...
i wonder if my return vent is clogged.

I ordered a camera snake on amazon to try to see what's going on. It's supposed to be delivered today.

 

[BayouRunner]

Anytime you have a two story system it's generally going to be warmer upstairs. I haven't read through the whole thread but if you could move your thermostat upstairs that might work for you as well.

 

[Bud9051]

jczst: "i just doing understand why it's so darn hot up there.."
1. Your attic is filled with 150° air.
2. Probably insufficient insulation up there.
3. The ceiling/attic floor has not been air sealed increasing the air exchange through the whole house.
4. You mentioned a "panned return" where a floor joist cavity and probably wall cavities are being used as air ducts. That method also pulls air from that hot attic and forces cool air out other places to balance the flow.
5. The issue you are looking at is contributing, but only a small part. In winter the warm air naturally collects upstairs making the work of the furnace easier. In summer, that natural air flow continues concentrating the warmer air upstairs, working against your cooling system. In the summer, your delivery of cool air to the upstairs needs to be double the volume of warm air that is delivered in winter.

Bud

 

[beenthere]

Adding a return in the landing of the second floor would help a lot.

As you think, 2 returns in 1 bedroom won't help that room or any of the other second floor rooms when the door is shut.