returns

[bcb]

My returns are on the wall at the floor if the wall cavity is hollow would there be any advanges to move the inlets to the top of the wall?
If it makes any difference we have a couple of dogs that leave a lot of hair on the floor.

Thanks
bill

[tinknocker service tech]

it would help with colling by pulling the heat off the cieling. this will lower the cooling bill some. also you should leave some at the floor to pull the cold air off the floor in the winter.
the best is to have high and low returns witch you can do by useing the same bay. one high and one low.

[amickracing]

Originally posted by tinknocker service tech
the best is to have high and low returns witch you can do by useing the same bay. one high and one low.

Nothing personal against you, but I don't get it when people do that.

#1, a wall cavity will only flow so much.
#2, air follows the lazy rule, aka the path of least resistance.

If the hole was cut in the bottom of the wall (through the floor to the return duct), and you had 2 registers, say 14/8, in the wall, one high and one low. I'd be willing to bet you could hold a flame or cig by the top one and it wouldn't be sucking anything.

Maybe I'm wrong though, what do y'all think?

[jiminator]

I found this thread after doing a search to find more information about "hi-lo" returns. So, I thought I'd revive it and ask a question or two.
At a recent duct sizing seminar I went to, the instructor told the class that the whole "hi-lo" approach is a bunch of hooey (to many gasps of disbelief from the class)and that the thinking that "put 'em low in the basement to suck the cold air off the floor" or even "put them high on the second floor to suck the hot air off the ceiling in the summer" was baloney, too! His justification was "provide a clear path for the proper amount of return air back to the furnace and THEN the properly sized and placed supply registers will do the rest to ensure comfort." He went on to say that the return location in a room has little to do with the air circulation pattern in that room. Air circulation (and therefore comfort) was accomplished with carefully placed and sized supply registers, again, assuming there is a clear and sufficient path for return air to the furnace, regardless of that return's location.
Here's the analogy he gave-Take a shop vac and put the hose on the outlet. You can easily blow the papers off a desk from across the room. Now put the hose on the inlet and try to suck the papers off the desk from across the room. Can't do it, right? This was his example for showing how little an effect return grille placement within a room has on comfort and that if the air in a room is so stratified that you're placing a return hi or lo to counteract this stratification you have much bigger issues with the system!
He loved good quality supply registers saying the stamped cheapo standard ones were basically garbage and couldn't be adjusted to each room's special requirements for air throw and spread.
He hated under-cut doors (so do I, BTW). Under cut a 30" door by an entire 1" and you've only given that return air 30" square to squeeze thru on it's way back to the furnace. That's not really enough, is it, especially since many rooms have 100's of CFM pumped into them? For that reason, he did advocate putting properly sized returns in each room, again only to provide a clear path back to the furnace.
I should say too, that the guy was an ACCA certified instructor and of course was a huge advocate of Manuals J and D. (As he, and everyone, should be! The J and D thing, I mean)
Everything he said seemed to make so much sense, even though it ran against everything that I'd learned in the past (and have read on this board!)about returns.
So what's the deal? What do you all think about this? I'd love to hear some other thoughts about this, preferably with some examples or justifications for your positions.
Just sort of "stirring the pot" as it were,
Jim

[dash]

Originally posted by amickracing

Originally posted by tinknocker service tech
the best is to have high and low returns witch you can do by useing the same bay. one high and one low.

Nothing personal against you, but I don't get it when people do that.

#1, a wall cavity will only flow so much.
#2, air follows the lazy rule, aka the path of least resistance.

If the hole was cut in the bottom of the wall (through the floor to the return duct), and you had 2 registers, say 14/8, in the wall, one high and one low. I'd be willing to bet you could hold a flame or cig by the top one and it wouldn't be sucking anything.

Maybe I'm wrong though, what do y'all think?


Very close to sorrect,it might pull a little air at the top.

If the the system supply side is properly desigigned the location of returns,high versus low ,will have little effect.

[dash]

Originally posted by jiminator
I found this thread after doing a search to find more information about "hi-lo" returns. So, I thought I'd revive it and ask a question or two.
At a recent duct sizing seminar I went to, the instructor told the class that the whole "hi-lo" approach is a bunch of hooey (to many gasps of disbelief from the class)and that the thinking that "put 'em low in the basement to suck the cold air off the floor" or even "put them high on the second floor to suck the hot air off the ceiling in the summer" was baloney, too! His justification was "provide a clear path for the proper amount of return air back to the furnace and THEN the properly sized and placed supply registers will do the rest to ensure comfort." He went on to say that the return location in a room has little to do with the air circulation pattern in that room. Air circulation (and therefore comfort) was accomplished with carefully placed and sized supply registers, again, assuming there is a clear and sufficient path for return air to the furnace, regardless of that return's location.
Here's the analogy he gave-Take a shop vac and put the hose on the outlet. You can easily blow the papers off a desk from across the room. Now put the hose on the inlet and try to suck the papers off the desk from across the room. Can't do it, right? This was his example for showing how little an effect return grille placement within a room has on comfort and that if the air in a room is so stratified that you're placing a return hi or lo to counteract this stratification you have much bigger issues with the system!
He loved good quality supply registers saying the stamped cheapo standard ones were basically garbage and couldn't be adjusted to each room's special requirements for air throw and spread.
He hated under-cut doors (so do I, BTW). Under cut a 30" door by an entire 1" and you've only given that return air 30" square to squeeze thru on it's way back to the furnace. That's not really enough, is it, especially since many rooms have 100's of CFM pumped into them? For that reason, he did advocate putting properly sized returns in each room, again only to provide a clear path back to the furnace.
I should say too, that the guy was an ACCA certified instructor and of course was a huge advocate of Manuals J and D. (As he, and everyone, should be! The J and D thing, I mean)
Everything he said seemed to make so much sense, even though it ran against everything that I'd learned in the past (and have read on this board!)about returns.
So what's the deal? What do you all think about this? I'd love to hear some other thoughts about this, preferably with some examples or justifications for your positions.
Just sort of "stirring the pot" as it were,
Jim



He was right,the old rules of "dumb" are wrong,thank the heavens someone is spreading the word!!!

[trane]

Dash, I read this earlier today and wondered not if but when you would reply. I knew you couldn't resist. LOL

[dash]

Wow,now on top of all my other problems ,I'm predictable too.LOL!!