Blocking off high return air in winter

[MnDave]

My home was built in 1998. On the upper level of the two levels, the HVAC installer placed return air vents on the floor and also high on the walls. One large one in the ceiling even.

The other day I was staring at the medium sized return in the master bedroom which is high on the wall. I was wondering if there was any leakage into the attic. This is the room that is hardest to move the stove heat into. It is larger and vaulted.

I first measured the vent temperature with the IR handheld and to my surprise it was warmer than the adjacent wall temp by 4 degrees. So I went and got a piece of plastic wrap, the kind used for leftover food. As I moved it over the vent it literally sucked up against the opening. A few minutes later I measure the temp and it had cooled off to match the adjacent wall.

I then went to the high return in the ceiling of my dinning room. It is large and was almost 5 degrees warmer than the adjacent wall. When I placed wrap over it, the suction was even greater.

The remaining high return is in a wall that does not go to the ceiling. There was no temp difference there so I did not cover it.

There are plenty of floor returns on both levels so blocking these is not going to overwork my fan blower which almost never runs in the winter anyway.

I did this two days ago. I have noticed that the house has been a couple degrees warmer than usual in the morning.

MnDave

 

[jatoxico]

I was poking around my AC return the other day w/ an IR as well. It's about 32" square. Wondering how much heat I'm losing to it. When the vents are left open you can feel the cold air dropping below them when you stand under them.

 

[Machria]

There are plenty of floor returns on both levels so blocking these is not going to overwork my fan blower which almost never runs in the winter anyway.

Keep an eye on that, especially when the season changes and you switch to AC assuming the same returns are used. I replaced my AC compressore and blower last summer, and went through 3 controlk units (electonics in the compressor outside). An engineer came from the AC manufacturer to see what the problem was, since they hadn't had anyone blow the electronics before with the unit, espeically 3 times. Low and behold, the returns were not sufficient for the new unit, even though it was the same size unit (btu wise...). They added another return, and I have not had any issues since.

 

[MnDave]

They added another return, and I have not had any issues since.

How big is that return and where did they locate it?

It sounds like you were freezing your A coil solid. That will take out the blower. Do you keep your windows closed during the summer?

MnDave

 

[Machria]

How big is that return and where did they locate it?

It sounds like you were freezing your A coil solid. That will take out the blower. Do you keep your windows closed during the summer?

MnDave

The return they added is 24" x 12" in a floor with something like 12" or 14" flex duct., about 10' from the blower which is located under the house. The house is on stilts.

I wasn't blowing the blower (no pun ..., wait, ok, some pun intended!), I was blowing the electronics in the compressor, basically a computer board with the processores on it. It's a computer controlled system for high efficiency (variable speed compressor based on need...). I never understood the exact connection between electronics blowing, and not having enough return air. I would understand a motor, compressor, blower physically blowing from it, not blowing electronically. But it did fix the problem, and made the AC work better (aka colder air, faster...).

Windows are allways closed, yes. Except sometimes we open a small window at the top peak of the house in a loft, since that's where all the heat is trapped. Opening that window speeds up the cooldown process if we just turned the system on.

 

[heat seeker]

I was having a similar problem - one downstairs room was always freezing cold, even with the baseboard heat on. I discovered frigid air coming out the AC vent in the ceiling. Turns out the ductwork in the attic was cooling the air in the ducts, and it was dropping down into the lower level vents, and sucking heat out through the ceiling vents upstairs. We made some covers for the vents and Velcro them on in the winter - HUGE difference. Cold air was coming out the 1st floor vents, warm air going into the upstairs vents due to convection. I had blocked the return off already (upstairs) thinking that was enough. Wrong!

 

[heat seeker]

I Wondering how much heat I'm losing to it. When the vents are left open you can feel the cold air dropping below them when you stand under them.

In my case, it was a lot!

 

[jatoxico]

In my case, it was a lot!

I shut all the vents but I think you're right I gotta cover the return.

 

[heat seeker]

Shutting the vents may help, but mine leave a lot to be desired to sealing. Air still gets by. We made covers out of foam-covered cloth with Velcro around the edge for each vent. Nice and air tight now, and easy to remove/install.

ETA: I put a trash bag over the filter in my return, then put the filter back in. Easy & effective.

 

[MnDave]

The return they added is 24" x 12" in a floor with something like 12" or 14" flex duct.

Big but not huge. Glad it worked.

I never understood the exact connection between electronics blowing, and not having enough return air.

I agree. I think that you flushed out a bug in there hardware.

MnDave