(800) 853-2651
SHOP NOW

Air flow geometry

R

rrlund

Well-known Member
OK,forced air oil furnace. There's a rectangular duct running back under one part of the house. Feeds to two rooms,the toy room and our bedroom. It feeds two round ducts,one goes left to the bedroom,feeds one register,the other goes the other way to a register in the toy room,then the rectangular duct goes straight through to another register in the toy room. I keep the door closed to the toy room,so I had both of those registers closed in there. I haven't been able to get any heat out of the one in the bedroom for several years. The other day,just totally on a lark,I opened the one directly opposite it on the round duct in the toy room and danged if the one in the bedroom didn't start blowing hot air!

Now why the heck wouldn't it blow being the only one open? You'd have thought it would have had so much air flow behind it that it would have blown the register right out of the floor. No more cold draft coming across the floor out of the bedroom either.
 
Is there a return duct in the toy room and not the bedroom. Thus this would allow the to circulate.

Gary
 
There's not. I lifted it out of the floor to open it and dropped it back in. It's about the same distance from the rectangular duct as the one in the bedroom. That one's blowing fine and that room's warm now too. I'm not loosing sleep,just seems more than curious to me.
 
There is something in the duct to the bedroom. Either a dampener in the duct or foreign object. Dampeners can be adjusted to control air flow. This is not the vent with control at the air outlet into the room.
 
Just curious, did you close the one in the toy room again to see if the bedroom quits?
 
I agree. If you take out the register, you may be able to see/feel the blockage. I have put HVAC in 25 houses and only a real damper, or object, can redirect common air flow. There are highly engineered pneumatic switches and control systems that use flow directed with gate like ports, but this is not it. Jim
One example of what it is not.
 
Maybe guys,but this thing has been in there since the mid 60s. It was all installed by one old man who owned a motel north of town,not by some professionals. Hard to believe he'd have put anything fancy in there.
 
No,didn't want to press my luck when something's finally working. I wouldn't be tinkering with the trailer wiring if the brakes started working. lol
 
You can't blow warm air in, if the cold air can't get out. The balloon in the back of the house was full, so the hot air couldn' come in. As said check your cold air return ducting, If there is any there. It's just like a tractor with the rain cap stuck shut, It don't run too good.
Loren, the Acg.
 
Now you know that ain't right.
If it isn't broken you have to fix it until it is!
I would really have to try it myself, then if it quits
I'd have to try it with the other vent in the toy room!
 
The cold air duct works,and even more than that,the bedroom door is always open. That should have been letting the cold air out and warm in even if the cold duct wasn't working. Gonna be one of those mysteries of life I guess.
 
Maybe if I open the second one in the toy room,I'll get twice the air flow in the bedroom.
Afraid if I do that it'll be too hot to sleep though. lol
 
I was taught in trade school years ago. If you run your car's air conditioning and have the blower on low speed it will get colder because the air is in contact with the evaporator longer. So I would say this is what is happening in your case. With one register open the air flow volume is low. The air probably cools down in the ducts before it gets to your room. Having two registers open the air doesn't stay in the duct long enough to cool down.
 
I guess I can put this in a little simpler term. Say if you turn your hot water faucet on so it would barely run. The water coming out of the faucet would never be hot because the pipe was able to absorb and release all the heat before it reached the sink. Low volume of flow.
 
I see what you're saying. I kind of had in my mind that it was causing some kind of vortex or pillow of air that was just stopping the air at the front end of the duct in the first place.
 
I don't see where you guys think something is blocking it? Where's the blockage going when the duct in the toy room is open? The one in the bedroom works when that one's open.
 
Hey man.........just realize that you "fixed it". Why do you want to beat yourself up over this?? Just leave it alone...don't you DARE touch it again!
 
Like I told Royse,no plans to tamper with it. Just curious as to what the cause is or was. Not loosing any sleep,just thinking there must be some air cushion that develops from too much back pressure or something. After I thought about it,I remember pulling one of those registers up a year or two ago to see if air would come out of one. It did,and when I went and checked the one in the bedroom,it was working. It was like I "primed the pump" or something,but it was a one time thing as far as I know. Works all the time now with that one open though. One of the great mysteries of life I guess.
 
Sounds as if the duct feeding this part of the house is undersized. With only one register open the static pressure in the duct is too great to let much air flow. This air cools off before it enters the room. When you opened the second register the pressure in the duct was lowered allowing more airflow and carrying more heat into the room. If this duct is comning off the side of the main duct than the air may be flowing by this duct takeoff. You could put a scoop to force more air down this duct. DH
 
With one of the registers open and the other closed, half the toys
are going to be warm and the other half are going to be cold.

They will then start trying to shuffle themselves from one end of the
room to the other, fighting over the comfortable middle parking spots.

But because of the condensation that is now built up in the transmissions
due to the temperature difference, the cold ones won't be able to move
well and will end up making a lot of noise which will keep you up at night.

I would go mess with it! :lol:
 
How does lowering pressure add air flow. Makes no sense.

I would think there is an obstruction that seals the bedroom run with too much air flow, but bleed off some air flow and the obstruction releases allowing a smaller amount of flow. Maybe some kind of loose flap that's just hanging in that bedroom duct run.
 
As is the case with all mysteries,you are leaving something out of the equation. Unlike old men who behave differently according to thier state of mind at the moment,the laws of sience and engineering behave the same today as they did in 1947.
To the question of wherether to"Look the gift horse in the mouth",shadetree tinkerers will say no and that is why they learn so little over a lifetime. Real mechanics remain a student thier intire life and would say"I'm not willing to leave well enough alone".
If the op was willing and desired to find out"WHY"I guarantee there is a completly logical reason for the air behaving as it does. Solutions are are found by systematicly testing not by guessing at and trying new things in hopes of hitting on the answer. This is why some garages throw parts at your car at your expense until it is fixed. A good mechanic will test until he knows what is needed then fix it right the first time.
Here is one of the possibilites and a simple test.
A damper missing the part that holds it in position after adjusting. One person sits by outlet while another turns furnace fan on. There would be a momentary burst of air as the damper closed.
 
I've broke a bolt turning it "just another quarter turn" way too many times. I know enough to leave well enough alone and quit while I'm ahead. lol
 
"A damper missing the part that holds it in position after adjusting. One person sits by outlet while another turns furnace fan on. There would be a momentary burst of air as the damper closed."

That's the type of thing I'm thinking it is.

Like a door that's been open all day and a sudden gust of wind blows it closed. Soon as the wind dies down, it swings open again
 
You're kinda hitting on what I was thinking. Undersized duct,maybe the wrong position from the main duct,who knows(?),but causing a "pillow" of air that stops the air from flowing that way when the small opening created by only one register being open. All I know is,it's warm in there and there's no cold draft coming across the floor from out of that room anymore.
Like I said,although the old guy did a good job,it wasn't a professional job. Just an old guy who gave Dad a good price on doing it back in the 60s. You can believe me or not,but for the furnace,ductwork and labor,it cost him $400 total in about 1966. The old guy started the job in early summer,finished in late November.
 
I am a Pipefitter that worked with a lot of Sheetmetal workers on many big jobs and their favorite saying is "Air don"t care!"
 
Is the cold air return blocked in the bed room or the toy room ? I would look down the bedroom 1st, see if restricted.
It's like your trailer brakes : I want know whats wrong with them also !!! Mark
 
You must log in or register to reply here.

Similar threads

S
Open flow dual air chuck.
Replies
3
Views
504
BarnyardEngineering
BarnyardEngineering
A
Pressure checking a Z series block
Replies
2
Views
223
Alan K
A
1
New furnace ?how to hook in booster duct blower
2
Replies
20
Views
657
Crazy Horse
Crazy Horse
2
air brakes
2
Replies
28
Views
944
sms
S
Hobo,NC
Freezer drain
Replies
10
Views
758
Hobo,NC
Hobo,NC
Tractor Parts Tractor Manuals

We sell tractor parts! We have the parts you need to repair your tractor - the right parts. Our low prices and years of research make us your best choice when you need parts. Shop Online Today.

Copyright © 1997-2024 Yesterday's Tractor Co.

All Rights Reserved. Reproduction of any part of this website, including design and content, without written permission is strictly prohibited. Trade Marks and Trade Names contained and used in this Website are those of others, and are used in this Website in a descriptive sense to refer to the products of others. Use of this Web site constitutes acceptance of our User Agreement and Privacy Policy TRADEMARK DISCLAIMER: Tradenames and Trademarks referred to within Yesterday's Tractor Co. products and within the Yesterday's Tractor Co. websites are the property of their respective trademark holders. None of these trademark holders are affiliated with Yesterday's Tractor Co., our products, or our website nor are we sponsored by them. John Deere and its logos are the registered trademarks of the John Deere Corporation. Agco, Agco Allis, White, Massey Ferguson and their logos are the registered trademarks of AGCO Corporation. Case, Case-IH, Farmall, International Harvester, New Holland and their logos are registered trademarks of CNH Global N.V.

Yesterday's Tractors - Antique Tractor Headquarters
Website Accessibility Policy

Back
Top