distributing heat through ac duct

[kykel]

I have a 2 story home and a lot of heat goes up the stairs. My ac returns are up stairs. If I turned on ac fan only, I get air blowing out of the registers. I tried this once but only felt cool air. In theory you would think the returns would suck in the warm air coming up the stairs and redistribute it through the registers. Question is am I losing to much heat in the cold attic before it moves through the rest of the duct work? Or should I have let it run longer. My wife was home during this experiment and wasnt happy about cold air coming out.

 

[St_Earl]

if it were me, unless the upstairs were uncomfortably hot (guessing the floor with the stove will be warmer), i'd just let the upstairs keep all it's heat.
it's pretty hard to move heat downward to any great degree.

it's hard to say not knowing your exact setup. it seems like if you left the fans run long enough the temps might/should equalize. but it just seems like once the upstairs is warm the rise of heat should slow and the warm 2nd floor will also insulate the first floor too.

i sympathize with having to conduct such experiments with the spousal variable coming into play.
but it's a factor that must be accounted for one way or another. lol

oh man that reminds me. once when my lady and i had only been together about a year, a friend came over without calling. he and his g/f were just out and about and dropped by.
i was having the "why are you pointing the fan out" argument that can come up during the summer. my friend saw my somewhat scowling face and asked me what was going on.
i said "oh nothing. just having a "discussion" about fluid dynamics."

she has since learned to trust me in all things air/heat/cooling related. when it was 106 in portland oregon where we lived, and i had the house at 85 with no ac, she pretty much decided i knew what i was doing

 

[St_Earl]

dangit. didn't mean to post again.

 

[kykel]

Good for you.

I will leave well enough alone. The heat does a good job upstairs so I cant really complain. Just like tinkering like many others on this post.

 

[St_Earl]

well. that's just my take. i know some folks use the furnace fan to spread heat around. but i'm pretty sure its for spreading into cooler rooms.

it would be good to hear what someone else with a similar layout to yours does.
tinker away though. that's how we get better at stuff.

 

[jtakeman]

Most local code doesn't allow ducts unless they are done to create proper fire stops. You might even need to jump thru hoops with your insurance company.

 

[DexterDay]

Because you are pulling warm air into cold ducts and trying to distribute it, you are cooling the warm upstairs, but doing very little to warm the cold areas. The ducts are cold and trying to warm them with 75* air does not work that well.

I tried it my 1st year. Not efficient for me. I actually made the house cooler overall because I had to use heat to warm the cold ducts. The colder it gets, the worse it is. I have all new insulated ducts. From furnace plenum to registers in the rooms.

Some people say that it works well for them. But more often it doesnt.

 

[heat seeker]

I think the OP is referring to the existing AC ductwork?

My AC ducts, while insulated, still cool off the air if the fan's not running. That cold air drops out of the vents on the first floor, chilling those rooms. We made cloth/velcro covers for the downstairs vents to stop the drafts. I suppose if the fan were running all the time, it wouldn't matter. The heat, however, does find its way upstairs via the stairway well enough, so we're happy with the status quo.

 

[kykel]

Correct heat seeker. Its an ac only unit with air handler in the attic. It sounded like a good idea since each room had a regester in it. Was just checking to see if anybody thought it might be feasable. We just leave the bedroom doors open a little and that works good