# Thread: More Returns Than Actually Needed ???

1. Originally posted by dash
Originally posted by Carnak
Originally posted by dash
Originally posted by Carnak
X is right about air going from 'positive' to 'negative'.

Think of a well pump, straight suction lift, be the biggest pump in the world and it is going to be limited to under 34 ft of lift, 25 is doing good.

Drill a 200 ft deep well and drop the pump down there and it will push water all the way up and build up pressure in a tank.

There's more weight involveds with water,think about it.

Why do exhaust fans work,why are you all afraid of correcting Robo,he's clearly wrong in this post,are you all afraid????
Contrary to popular belief you cannot suck a golf ball through a garden hose but you could most likely blow it through.

Pumps, vacuum cleaners, exhaust fans are all limited on how much suction they can create. This maximum suction is ultimately a perfect vacuum although none of these will do this. When you have a perfect vaccum and then break it, atmospheric pressure pushes the air inside.

The well pump can only suction lift as high as atmospheric pressure will push it. If you had a one inch by one inch column of water 33 ft and change high, it would weigh about 14.7 pounds and since this weight is pushing down on a square inch the pressure you could measure with a gauge would read 14.7 pounds per square inch. You can drop a pump down the well and it can push as high as the impellor and the horsepower will allow.

The first barometer was a big tube, closed on one end, filled with water and then quickly flipped upside down into a bucket. The water was 33 feet and so many inches high maybe it was 33.9 feet. It did not spill out, atmospheric pressure was pushing it up.

So when you have an inlet into the fan, it creates a lower pressure than atmospheric, and the atmosspheric pressure pushes the air into the fan.

You seem to have a vendetta against robo,I do not fear robo nor you.

Though this is not the case here,does the pump suck or pull ??

Or does atmospheric pressure push or allow the water to get get from the well to the inlet of the pump as Robo,would claim.

You aren't even addressing the issue,just defending your buddy, by trying to change and confuse the issue,just as he constantly does.

When it is a suction lift, atmospheric pressure pushes the water up out of the ground.

When the pump is down in the water below the ground, the pump pushes the water up out of the ground.

2. In both cases above, atmospheric pressure pushes the water into the pump inlet.

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Originally posted by RoBoTeq
Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.
Lets focus on what was said and see if anyone but Dash and I agree that the above post is incorrect. I have already said the first sentence I agree with so lets move on.

Lets say we have a down flow furnace with supply under the house and return ducts in the attic. If you took an 8 inch pipe off the supply and run it through the foundation to outside, according to Robo the return would not notice this because it only gets air that's being pushed back to it from the supply. Anyone that thinks that is correct tell me why.

I only questioned Robo in the beginning and he would not answer or backup the above post.

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Got back from a Thanksgiving trip last night, I was hoping for a few replies to my original post of this question. When I seen the number of replies I instantly new I wouldn't find a simple answer to what I though was a simple question. After reading all the replies I've come to the conclusion that I should rip out my forced air system and replace with baseboard hot water. Not really....the conclusion that I'm drawn to is that having unnecessary return runs(qty 2) doesn’t have any substantial negative impact on my homes heating and cooling system. I won’t rip them out . Thanks

5. Originally posted by trane
Originally posted by RoBoTeq
Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.
Lets focus on what was said and see if anyone but Dash and I agree that the above post is incorrect. I have already said the first sentence I agree with so lets move on.

Lets say we have a down flow furnace with supply under the house and return ducts in the attic. If you took an 8 inch pipe off the supply and run it through the foundation to outside, according to Robo the return would not notice this because it only gets air that's being pushed back to it from the supply. Anyone that thinks that is correct tell me why.

I only questioned Robo in the beginning and he would not answer or backup the above post.
The return would not notice it pulls air from the easiest place, but the house would notice.

Where I would disagree with Robo, with respect to what you have quoted him as already saying, is that atmospheric pressure pushes the air into the vacuum cleaner too. I already stated this fact without having to single him out, until now, however you and dash find this necessary to do.

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## I have to agree

with Carnak, and we can over complicate things quite easily

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Carnak, if you read the first page you will find that I only asked him to explain his thinking on his post or change it. He responded by saying THINK WHAT YOU WANT and nothing to support his opinion. Anyone giving false information on this site will get questioned and I did not know Robo was exempt from this. Dash and Robo may have issues but that has nothing to do with me or my replies.

8. Originally posted by trane
Originally posted by RoBoTeq
Other then not having a required static at the unit, there is basically no such thing as too much return.

The return air portion of an HVAC ducting system does not "pull" or "suck" air...it allows the higher pressure of air introduced into an area to "return" to the units blower.

HVAC systems do not have negative pressure blowers. These blowers do create a negative pressure within the direct area of the blower, but it is not like a vacuum cleaner that actually "sucks" or "pulls" air to the blower.
Lets focus on what was said and see if anyone but Dash and I agree that the above post is incorrect. I have already said the first sentence I agree with so lets move on.

Lets say we have a down flow furnace with supply under the house and return ducts in the attic. If you took an 8 inch pipe off the supply and run it through the foundation to outside, according to Robo the return would not notice this because it only gets air that's being pushed back to it from the supply. Anyone that thinks that is correct tell me why.

I only questioned Robo in the beginning and he would not answer or backup the above post.
My remarks are certainly being scrutinized quite a bit more then I thought of how to express myself. What you are getting out of my post is not precisely what I stated. As a matter of fact, you and dash are completely altering the intent of my statements by adding all kinds of factors that were not in my statement and do not apply.

This is a matter of your not comprehending my statements and not a matter of me stating what you are claiming I have. Carnak has expressed what I have stated very well. I never claimed that an air system would not "recognize" a condition where there was a negative pressure created inside of the home because I know that air systems are "stupid". They cannot recognize anything. The higher pressure of the outdoors will "push" the amount of air not being supplied into the dwelling, back into the dwelling.

Overall, we are stating the same thing. Dash and Trane are simply not understanding that the physics of the process is that the higher pressure air zone is "pushing" air back to the lower pressure air zone. There are blowers that are designed to "pull" air. They are called vacuum systems. I have installed many negative pressure cyclone dust collecting systems in the 1980s when the government required them to be installed in all solid waste type of manufacturing plants, and there is a big difference between a negative air system and a positive air system.

The fact is that if you have a house with a central return and you close off a room that has no way for air to get out of it, air will not enter that room from the supply. Exactly the same, if you seal off a room that has the only return in it, that room is not going to go into a vacuum. The blower motor will soon overheat from lack of air, but the room will not be sucked into the air handler. If an opening is then made into this room, the higher pressure air from outside of the room will "push" into the room.

The reason it is important to know the difference between whether the air is being pushed or pulled is that it determines the best place to locate return paths back to the air handler. Otherwise, it really is a matter of semantics whether or not the air is being pushed or pulled.

By the way, a negative type of system requires the blower motor to be out of the air stream so that it is not affected by the lack of air. In the case of moving solids in a negative system it is required that the entire blower section actually be out of the main airstream so that solids in the system do not hit the blower. I demonstrated this effect to a furniture warehouse worker by putting a mouse in one of the dust collecting hoses that pulls saw dust and bits of wood chips to a turbine collection box. You could hear the mouse thumping through the spiral ducting into the collection box. I opened the collection box and scooted a not so happy but basically unharmed mouse out onto the floor. Don't try that with a furnace blower.

9. Originally posted by dash You aren't even addressing the issue,just defending your buddy, by trying to change and confuse the issue,just as he constantly does.
For your information dash, my initial comments about "X" and the well pump were directed to Robo, in response to his jest concerning "the Equalizair", a product that Robo and I have carefully examined.

You may not be familair with X or his product, and you are also unaware that it is a running joke with Robo and myself. Therefore you would not have been aware that my response was to Robo as I did not quote him.

You then disucussed the issue with me and I hopefully clarified it for you.

So when you accuse me of "defending my buddy" and "confusing the issue" decide first whether you are confused or the issue is confused.

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I understand how an airflow system is supposed to work in a home. What I don't understand is how you keep saying a blower will not suck air in on the return side but only relies on the supply to create pos. pressure which forces it back to the neg. blower. Any blower will suck or try to suck an equal amount of air that it is putting out on the supply side.

You saying that the pos pressure outside will force the air back into my model house is also not how I see it. The neg pressure inside the house created by the blower due to the 8 inch pipe going outside will be more of a factor as to why air is trying to get in.

11. Originally posted by trane
What I don't understand is how you keep saying a blower will not suck air in on the return side but only relies on the supply to create pos. pressure which forces it back to the neg. blower. Any blower will suck or try to suck an equal amount of air that it is putting out on the supply side.

A fan will discharge the same volume of air as it returns.

There is a big difference in the velocity of the airflow between the supply grilles & return grilles but the same volume of airflow should still be moving through the duct system.

Every home I have tested for dominant duct leakage outside the envelope the effect was the same depending which side the ducts leaked in. The only difference was which way the pressure of the building envelope went.

12. Originally posted by davidr
Originally posted by trane
What I don't understand is how you keep saying a blower will not suck air in on the return side but only relies on the supply to create pos. pressure which forces it back to the neg. blower. Any blower will suck or try to suck an equal amount of air that it is putting out on the supply side.

A fan will discharge the same volume of air as it returns.

There is a big difference in the velocity of the airflow between the supply grilles & return grilles but the same volume of airflow should still be moving through the duct system.

Every home I have tested for dominant duct leakage outside the envelope the effect was the same depending which side the ducts leaked in. The only difference was which way the pressure of the building envelope went.
This is better expressed then the way I have been stating this, but exactly the same as I have been stating. Again, I really think we are puffing our chests based mostly on semantics while thinking the same basic principals of air traveling from a high pressure to a low pressure created by the same mechanical device.

The term "return" is a very accurate term in the fact that the "return" ducting provides a path for the amount of air being pushed into an area to "return" to the blower that is producing that amount of air.

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The suction of a blower (like a vacuum cleaner) is what allows us to pressurize a building with outside air. If the blower did not have this suction capability there would be no need to run outside air ducts.

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