YOUR remarks about "short circuiting" are shown to be less than accurate when viewed in the light of a concentric diffusers.
Your observation about short circuiting are intuitive. unfortunately, there are a number of areas in this biz that are COUNTER-INTUITIVE.
Another example of this is burying duct work in loose fill insulation
Your advice about more returns are better also does not take into account that the return GRILLS are not adjustable and won't pull the amount of air you calculated. They will pull the most air from the easiest path. Therefore you waste either duct material OR use more fan horsepower using your advice.
So is your advice about putting return grills at the top of the list is also WRONG. No one here has said return is not important, we continue to say that the air needs a LOW RESISTANCE PATH back to the unit.
You ignore that because the "others" don't make it #1 We keep telling you supply air is #1
Again, there is more to the story than your simplistic approach. Unfortunately you are so fixated on being right and holding to your discovered, flawed ideas, you won't allow yourself to learn and evolve your thinking. Picking sub contractors who only follow your instructions because you want to be the smartest guy on the job doesn't help you learn either.
When I'm not annoyed with your tactics, I feel sorry for you
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
An answer without a question is meaningless.
Information without understanding is useless.
You can lead a horse to water............
http://www.mohomeenergyaudits.com
I think the major point that most are trying to get at, is that return placement is far, far down the list of critical factors in a system design. Its' probably the last thing you woudl consider, so much so that I woudl consider it a nice-to-have feature. If I had to choose between 2 stage or vairable capacity equipment, better sealed ducts, Better quality supply duct distribution/design... the list goes on.
He** in my house, I would have been happy if the installer (PO's put in the system) knew what mastic or foil tape was, or had even bothered to use PVC cement on the furnace exhaust piping.
I don't think anyone is saying return placement is irrelevant, but it's not worth paying so much attention too. There's better, easier and more effective ways to solve air distribution problems. At work, I've solved them twice now by just downsizing equipment as well as installing better quality ceiling diffusers.
Just because there is such a thing as concentric diffusers, window ac’s, or mini-splits doesn’t mean they use the best return path. They shed no light on our discussion.
Huh? Again, off topic.Your observation about short circuiting are intuitive. Unfortunately, there are a number of areas in this biz that are COUNTER-INTUITIVE.
Switchable high/low returns do have louvered/adjustable registers. And, if ducted correctly they would have graduated ductwork.Your advice about more returns are better also does not take into account that the return GRILLS are not adjustable and won't pull the amount of air you calculated. They will pull the most air from the easiest path. Therefore you waste either duct material OR use more fan horsepower using your advice.
A low resistance path can take many paths. The question of this thread is which of those many setups is best?So is your advice about putting return grills at the top of the list is also WRONG. No one here has said return is not important, we continue to say that the air needs a LOW RESISTANCE PATH back to the unit.
This thread is not about effects of supply air, it about which type of return configuration is best. But if you want to bring up supply air and mixing then yes, it is more important that return location.You ignore that because the "others" don't make it #1. We keep telling you supply air is #1
Saying supply air only needs a path back to the unit is the simplistic approach.Again, there is more to the story than your simplistic approach.
When you can show you understand quotes like this I will begin to think you are getting it:Unfortunately you are so fixated on being right and holding to your discovered, flawed ideas, you won't allow yourself to learn and evolve your thinking.
ASHRAE quote- “an intake can be located to return the warmest air in cooling season". Hence Cherokee.
Btuhack quotes - “The most appropriate application of return will be determined by the situation, whether conditions dictate hi/lo or central/independent, and will perform better. Not primarily because of it's influence on distribution, but because of it's clever collection of the most offensive room air”
And
“…but practical common sense tells me that return accumulation can influence things dramatically when applied areas of stratification.”
So rather than drifting the topic and slinging your insults tell us what you know about those wise quotes and how they apply to this discussion.
Brian, I don't need any assistance when it comes to looking stupid, so please don't cherry pick my quotes or ashrae's strategies to fit all situations. I tossed in a few pro and con quotes for you to digest due to you being an industry outsider, and to make it a fair fight, but you chose to accept only those that fit your preconceived ideas. You let me down and I'm disappointed.
You'll notice from my posts that the ideas and strategies wander around. Why? You don't care but I'll say it anyways, because buildings and systems can offer a variety of challenges, each unique and constantly changing.
"a fully mixed system creates homogeneous thermal conditions throughout the space. As such, thermal gradients should not be expected to exist in the occupied zone."
"If return location matters, which it easily could, then alot of other things are wrong."
"The ideas are situational and good judgement and reasoning need to be applied."
You are in the fringe of the deep end here with a lot of guys with long/successful careers, so...
to sum it up:
A) You could do all the right things for all the right reasons
B) You could do all the wrong things for all the wrong reasons
C) You could do all the right things for all the wrong reasons
D) You could do all the wrong things for all the right reasons
Your quoting privileges have been officially revoked and you must cease and desist immediately.
Quote:
Originally Posted by genduct
YOUR remarks about "short circuiting" are shown to be less than accurate when viewed in the light of concentric diffusers.
Just because there is such a thing as concentric diffusers, window ac’s, or mini-splits doesn’t mean they use the best return path. They shed no light on our discussion.
Quote:
Your observation about short circuiting are intuitive. Unfortunately, there are a number of areas in this biz that are COUNTER-INTUITIVE.
Huh? Again, off topic.
Brian, you can't even recognize giving you the benefit of suggesting that the short circuiting thing is thought to be true of many in the Industry because it seems to make sense. I guess even an attempt at civility is misunderstood
Quote:
Your advice about more returns are better also does not take into account that the return GRILLS are not adjustable and won't pull the amount of air you calculated. They will pull the most air from the easiest path. Therefore you waste either duct material OR use more fan horsepower using your advice.
Switchable high/low returns do have louvered/adjustable registers. And, if ducted correctly they would have graduated ductwork.
Quote:
So is your advice about putting return grills at the top of the list is also WRONG. No one here has said return is not important, we continue to say that the air needs a LOW RESISTANCE PATH back to the unit.
A low resistance path can take many paths. The question of this thread is which of those many setups is best?
I answered the question, you didn't agree
Quote:
1You ignore that because the "others" don't make it #1. We keep telling you supply air is #
This thread is not about effects of supply air, it about which type of return configuration is best. But if you want to bring up supply air and mixing then yes, it is more important that return location. Do I see a glimmer of hope, does this mean you have evolved
Quote:
Again, there is more to the story than your simplistic approach.
Saying supply air only needs a path back to the unit is the simplistic approach. There is elegance in a simple truth
Quote:
Unfortunately you are so fixated on being right and holding to your discovered, flawed ideas, you won't allow yourself to learn and evolve your thinking.
When you can show you understand quotes like this I will begin to think you are getting it: If understanding means agreeing with you then it's hopeless since I will then never understand
ASHRAE quote- “an intake can be located to return the warmest air in cooling season". Hence Cherokee.
Btuhack quotes - “The most appropriate application of return will be determined by the situation, whether conditions dictate hi/lo or central/independent, and will perform better. Not primarily because of it's influence on distribution, but because of it's clever collection of the most offensive room air”
I think we mentioned about the commercial emphasis of ASHRAE
And
“…but practical common sense tells me that return accumulation can influence things dramatically when applied areas of stratification.”
So rather than drifting the topic and slinging your insults tell us what you know about those wise quotes and how they apply to this discussion.
CAN WE JUST AGREE TO DISAGREE
I THINK I AM GOING TO HAVE TO ADD YOU TO MY PRAYER LIST
Maybe St Jude, the Patron Saint of hopeless causes can intercede
Best, Mike
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
I know people tried to answer the original ?? but ended up with examples that posed other ??.
In commercial offices I've seen short circuiting. It was an extreme install but when a small water source heat pump used a perf grill and a return grill 4' away, I had 95degF return temps.
So it can happen.
About stagnate air a return could help but as for stratification, supplies will be the best approach.
I base this on how a grill/diffuser is designed. It's based on vena contracta. Just for those unfamiliar with this term it means when air leaves a diffuser/grill static pressure falls to zero and the jet of air draws into itself and in turn draws in room air something like a paint sprayer. This is how the mix of supply air and room air solve stratification.
Problem with resi is fans don't run all the time like they do in many commercial applications and stratification returns in time. But along with this a different return design wouldn't help either.
Like others, I don't like undercut doors or use transfer grills. I also don't like noisy central returns. But don't expect GC's to care when they can save a buck. That's why so few GC's go green w/o kicking and screaming.
So what's better? Depends on who is asked. For the GC, the cheap one. For someone that doesn't like the loss of privacy through undercut doors and transfer grills that allow noise to pass. A return in every room.
We are here on Earth to fart around ......Kurt Vonnegut
You can be anything you want......As long as you don't suck at it.
USAF 98 Bomb Wing 1960-66 SMW Lu49
I did not suggest those quotes fit all situations. I read your other points and agree with them. I just asked that Genduct expand on those particular quotes, which he chose not to do.
How air of different temperature moves through a structure while a unit is running and while it is off is very complex (and invisible). Where cold and warm supply and infiltration air migrate to in the winter vs. the summer is a science of its own. I am convinced that it is not taught in the industry, otherwise more here could speak in detail about it, but they won’t (or can’t).
I may be an "outsider" but I have spent about fifteen years closely observing air movement within structures. I believe I could hold my own on this topic, especially to those who speak in generalities which, btw, is not you. You wrote concise, educated posts that I take not issue with.
"Better tell the sandman to stay away, because we're gonna be workin on this one all night."
"Dude, you need more than 2 wires to a condenser to run a 2 stage heatpump."
"Just get it done son."
Dad adjusted
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
I hope this remains a place to express opinions (by anyone ) vs. give advice to homeowners.
There are many who have not gone to the PRO thing for whatever reason who are thoughtful and contribute. If this area was shut off then there would be no way to move to PRO if they wanted to do that IMO
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
You won't even explain your point of view or show you understand or can take apart my point of view.
Constantly repeating the same thing – “jump ducts, provide an air path and fix it with more supply air” are such general statements it doesn’t convince me you understand air distribution. You’ve had many opportunities to step up and speak from both sides of the fence like Btu has but you seem incapable of it.
If you want to sound convincing and continue to talk down to me as though you are an authority on this topic, step up and explain why the limited results I’ve observed are wrong.
Ok I caught up to at least what I think the base argument is about.First it is always a good idea to take care of any infiltration problems first, however in the real world alot of people need real fixes right now and dont always have the money to spend thousands on top of the hvac bill.And from my experiance adding a return ar in some cases suppy vents will give immediate comfort and a happy customer. I have added returns on houses like were stated with great results. And always informing the homeowner to take care of their infiltration problems. Which most will do IN TIME and as their finances allow.So in essence your both right and if you could see past your argument you may even agree. The RIGHT answer is both in my opinion, but to homeowners the simplest or least expensive and invasive makes them happy. And thats what were after right? Somethng ive learned over the years is mosthomeowners dont care about having the perfect system but making theirs work its best and Keeps them comfortable. Further more we as professionals should strive to be able to go into any home and regardless of desighn flaws should be able to make the nessicarry "fixes and get their system to work its best within the customers finacial capabilities.In other words if you are in a mansion with well off homeowners then they will want it all done, but when your in the poorer parts of town we should be able to work within their budget and give them options that are reachable if at all possible, if we can do this we will be better off as a trade.
I speak with 30 years of expierence, it is you who is putting on the mantle of authority. I am not the ductwork or airflow Policecontinue to talk down to me as though you are an authority on this topic,
After sharing lots of explanations,( which you have ignored or discounted) I think it only fair that you answer the 2 questions:
1. Is the concentric diffuser example enough to change your mind about short circuiting?
2. How about the question you managed to ignore about the furniture and drapes affecting the kind of commercial rules that ASHRAE suggests for air distribution?
Your last admission that supply "may" trump return seemed to indicate progress, but we have seen you revert to your old drumbeat in the past. Please don't persist in your statement that commercial is irrelevant when it is the physics that we are talking about (as you already know)
Your answers to these simple question will indicate if there is any hope for an adult conversation
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
If you derive relevance from those questions we are talking about two different topics. Concentric diffusers do not provide the best supply-to-return path to model anything after and drapes and furniture do not significantly hinder general airflow paths back to a return situated across a residence. If there is such a thing as a good question, those are bad questions.
Your inability or unwillingness to speak in detail on this subject is bringing this discussion to an end. If you refuse to grasp or respond to my posts then try re-reading Btu’s or Stickinittothman’s. There is good, wise, open-minded stuff in them.
Why is a concentric diffuser terrible? I could see it being the most effecient design. If located in the center of a square room, it's would distribute air in a perfectly symetrical flow pattern. Any other design would heat and cool unevenly.
It's not used in residential because of aestetics, the use of ceiling fans and light fixtures in the center of a room ceiling and cost. Most builders will want ot put in a apir of $5 registers and grills than a $50+ cocentric diffuser.
Brian, have you ever owned an aquarium? How much does it matter where you place the filter inlet vs. the discharge? What impacts the water movement more. Did you know air is a fluid and behaves virtually THE SAME as water? The placement and number of inlet on hte filter have almost no impact on water flow. Debris can literally float past the inlet within 1" and often not get sucked in. But if the same debris comes anywhere near the discharge , it's will get thrown halfway across the aquarium. I can even place the inlet pipe directly aross form teh dischanrge and it will have minimal impact on the water movement. It would only "short circuit" probably about 10% of the water.
There's nothing that return placement can do for airflow that supply size, shape, placement and design can't do better. There's how's that for a statement?
Please, do yourself a favor and go look at hte air distribution patterns (throw) of some registers on the HArt & Cooley website and you'll se that even placing a return almost directly opposite the supply on an opposite wall 10' away will have minimal impact. Its' still poor practice. As a matter of fact, it's pretty common ot have a return on a sidewall near the ceiling across the room from a supply, and it's only 18' away. Place it on the floor and it's only 26' away. Actually, if you palced it next t othe supply on the floor, it's would then be actually 36' away, not 6". Air with velocity isn't going to make a sharp U-turn. Come to think of it, from that standpoint, the best return placement might be just a couple feet away from a supply on the same wall or floor. It's the point farthest from the airflow.
Short circuiting does happen and it's not always due to return distance.
I gave one example of short circuiting (SC) in post 88. SC is almost always due to supply velocity too low.
When concentric supplies were mentioned, what needs to be remembered is they are dependent on supply velocity to work. I've seen them not work and freeze the evap coil due to plugged filters or a badly slipping belt. The supply air does get sucked up the return. Concentrics are usually chosen for large open spaces like a big box store and installed $$ savings not efficiency as w/o maintenance they fail.
Here's an example where distance was the pronblem. When Lennox introduced the Pulse furnace, instructions for outside termination said "do not install the exhaust discharge closer than 3 feet from the air supply. OK, Then it froze. Lennox said " No further than two feet, Froze again. Last time Lennox said
12" from supply. This worked. At 12" the velocity of the exhaust was too fast to make the bend and return to the supply.
This example of further is worse shows there are situations where other physics exist. Even the choice of design diffuser/grills can make a difference.
It gets even worse with large spaces where the ducts need to be way up there.
So far, as I see it, no one is all right and no one is all wrong. Just sayin.
We are here on Earth to fart around ......Kurt Vonnegut
You can be anything you want......As long as you don't suck at it.
USAF 98 Bomb Wing 1960-66 SMW Lu49
You must understand my simple approach to the problem from my posts.
You demand answers, but are unwilling to give any answers, especially when the answer would need you to adjust your thinking.
So, I can only conclude I am not up to the task!
I hope you can find someone up to your standards to advise (agree with) you and your theories.
You have got to learn from other people's mistakes! Because God knows you don't live long enough to make them all yourself !!!!!!!!
That is a true statement if you’re talking about mixing a particular room. Right, a return will not help mix a room. That is up to the supply placement, throw and velocity. Where return placement comes into play is here:
Take a two story house, two units, both central returns on the upstairs ceiling because units are in attic. When downstairs furnace turns on it heats the whole downstairs evenly. But, by the return being upstairs, the sum total of all supply air is being pushed up and out of the condition zone by being pushed up the stairwell. It ends up heating the upstairs along the entire path back to the return.
It gets worse. If the downstairs has a warmer stratum of air along the ceiling due to imperfect mixing, that will be the air that gets lost to the upstairs first, leaving the colder air on the floor. And, it can get worse than that when the unit goes to lower speeds of operation and the velocity isn’t there to mix the air properly. Then you can be assured there will be a warm stratum of air along the ceiling to be lost to the upstairs "pulling" action.
None of these scenarios would exist if the return was downstairs on the floor while heating. The entire cycle of heating would be contained downstairs rather than the supply air being pushed out of the conditioned zone and half way across the house.