How would you answer this test question and why

Glenn Harrison_2

That had the following test question, and the two most appropriate answers.

What is the primary reason/bennifit of adding fresh air to a forced air heating/cooling system.

A. To improve customer comfort

B. To ballance Positive/Negative pressures between indoors and outdoors

(There were two other choices, but I don't remember what they were as they didn't apply IMO)

Now I know what the "Organization" considers the correct answer, based on the study packet they provided, but I don't agree with it, and I'm just curious how others feel about answering this question and why.

I will post my feelings in a couple of days, after I see your answers.

Thanks for the time guys. I think this should be interesting :)

don_42

Hmmm!!

they sure try and throw you off alot dont they? Is this a
nate test?

I would say B,only because most time in building they try and maintain a positive pressure inside the envelope.
And by doing so they keep the unwanted stuff out that would
be pulled in from a negative envelope.

Then maybe it could be A,I mean breathing fresh air would
make you comfortable one would think.

Its b,no A,long pulse.....ok B,yea B,..how much time is left? Shoot..ok my final answer B.

Arthur

Fresh Air

Hummm, Well imho, The answer should be A, To introduce fresh air to combat the vitiation of the air in the home, We all breath out CO2, Ok our breath is about 19% oxygen so we only absort about 2% oxygen we breath in (which is why Mouth to mouth resustion works) but in a closed area continual breathing in and out the oxygen level can get depeted over a period, Causing stuffyness, Can also lead to build up of CO as well.
I alway like to see some fresh air introduced to main a decent oxygen level in the home.
Just my penny's worth.

ScottMP

would be nice to

know answers C and D.

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Kal Row

the question is usually half the answer

so let's look at the question
"What is the primary reason/benefit of adding fresh air to a forced air heating/cooling system"

keywords “benefit” and “fresh” fits with answer A and keyword “adding” doesn’t fit with answer b’s “balance” – so I would have to go with A and the keyword “primary” would also point at A, except in very large commercial where pressure differential is a major issue


this is a classic example as to why a certification doesn’t in any way shape or form, indicate that you are a competent service person

dconnors

A & B

Fresh air is healthy but positive pressure keeps out what will make you sick? Well, maybe negative pressure will insure an adequate supply of fresh air so.............

Matt Clina

It depends

I think the question is poorly worded, and it might depend on what type of system.

On a residential system, the fresh air is added for indoor air quality reasons, which improves the breathability of the air, but I don't know if I would consider this comfort.

On a commercial system, it is primarily to make up for any exhaust that might be there: kitchen equipment, lab hoods, dust collectors, etc.. This would more closely resemble answer B.

Ken_8

'A.' - obviously

No one ever got a "wrong answer" out of, "To improve customer comfort." So that was rather obviously the correct answer.

With today's extra tight construction, 'A.' is also a better answer than 'B.' because of natural pollution issues from tight construction methods, etc. Customers who might die from tight construction would be dead customers or at least "sick." I cannot imagine a sick or dead customer as being "comfortable" (:-o)

Final answer?

'A.'



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STEVEN MARKS

My answer would have to be A mainly because the question is generic. I have worked in labs where the pressure has to be negative to prevent chemicals spilling into the rest of the building. This can only be done by exhausting more air then supply.
Steven

Robert O'Connor_7

Glenn..

The testing company is profit motivated so you fail, then return to re-test. In many cases the overall test is NOT to find out how smart you are , but your ability to adapt to different codes and standards and knowing which code your giving an answer for. An example of this was a ICS test I took years ago asking "According to CABO, what is the correct drainage pipe size for a shower?" now we all know the correct size to be 2" for a shower, but according to CABO (at that time) the size was 1-1/2", so if you answered 2", it would have been wrong...Robert O'Connor/NJ

Aidan (UK)

I think...

I'd say A.

Adjusting the positive/negative pressures between indoors and outdoors would be done by varying the air flow rates of the supply and/or extract, with an additional amount to compensate for infiltration or exfiltration. I've previously worked on both clean areas and laboratories (positive & negative pressures respectively) where the indoor/outdoor air pressure differential was critical.

Rob_16

Fresh Air

Where is Jim Davis this might even be from his test The reason for the fresh air is make sure the the building will not go into a negative pressure. This way all the vents in yhe building will work properly mainly the chimney. It will also stop ghosting have you ever seen the dark marks at the base of walls in the light colored carpets. The answer is B

Rob

bob_25

answer


I forgot to say why A is the correct answer IMO. When air is brought into a building to control the static pressure it is usually refered to as "make-up" air. bob

Unknown

Amen Kal

to that. It is one of the reasons I do not like certifications. My employer and my customer determine if I am qualified by my performance and ability to solve difficult and complex problems. I am all for testing but to certify simply becomes a marketing tool. I have stopped people who wear a "Gas expert" chevron and asked them three questions that any so called gas expert should be able to answer. No one has answered them correctly to this date.

By the way both answers are correct. It is a very poor question.

Just my humble opinion!!!

Mike T., Swampeast MO

Dissection

In a typical multiple choice question here are two distractors--likely the two you dismissed.

The remaining two often boil down to a single word that doesn't fit properly in a simple answer to the question. The "correct" answer need not be a complete answer to a complex question--it only has to be the one that is not incorrect.

The single word that does not fit is "comfort".

Think of it--that forced air heating/cooling system is operating because the outdoor air is considered somehow uncomfortable.

BUT COMFORT IS NOT REQUIRED FOR LIFE! For life, we need "in with the good and out with the bad."

Were thermal comfort the only thing required to live the correct answer would be "A".

The correct answer would be "B". Just add "to ensure the safety of the occupants" at the end of the answer. The writer didn't put this at the end because it would make the answer too simple.

S Ebels

Correct answer (SE)

B.

A, makes no sense because to improve customer comfort with a forced air system you rip it out and install HYDRONIC!!!!


YEEEHHAAAAAAAA!!!!




Sorry............, inhaled to much PVC primer today in a crawl space 18" tall.

Glenn Harrison_2

Sorry,Mr. Milne,

I honestly debated over the question and first two answers so much, that I have completely forgotten them.

My appologies.

Glenn Harrison_2

Tim, I whole heartedly agree with you and Kal.

I'm not really caring about the certification, other than my bosses sent us all to take the test paid for. I'm more interested in opinion, based on training of the "correct" (HA HA) answer.

By the way, Tim. I thought of the many things you and Jim Davis have posted and taught when I debated this question.

Glenn Harrison_2

Nate test, HMMMMM MAYBE

Glenn Harrison_2

No, not from Jim Davis' test dirrectly

But I did think of his teachings while debating the question, as I have attended his two day CO/Combustion class.

Ken D.

Test

I tend to think they both may be right, but the term comfort in "A" gives me pause. The intake air would have little impact on comfort as long as the system is running, as long as the intake was not oversized. Assuming the forgotten two answers are incorrect, I would say "B".

Glenn Harrison_2

You are so correct Mr. O'Connor.

The reason all us techs and installers were sent is that the scorched air manufacturers are pushing testing and certification from this "organization" and advertising it. Some are even starting to require a percentage of "Certified" techs/installers in a company to be able to purchase equipment (supposedly). I know every time I hand out a furnace of A/C brochure, the "organizations" Stamp is on the liturature.

Bob_19

If I

were to read into the answers I would have to remove "B" because we are trying to create an un-balance situation between the outdoor/indoor pressures.
"A" would make the most sense here.

eleft_4

B.... If comfort is out side why are you inside?

If it were heating why would cold dry air bring comfort?

If it were cooling why would hot humid air bring comfort?

I would say B.

al

Mark Hunt

OK. I waited a while.


First of all, you will NOT equalize the pressure between indoor and outdoor by adding an intake to the duct system. It doesn't happen and here is why.

Warm air rises and cooler air drops. If you were to measure the pressure at the lowest point of a structure in relation to atmospheric pressure, you would find that it is negative. Why? Because the cooler air is dropping in to replace the the air that was warmed and rose to the top of the structure. Now measure the pressure at the top in relation to atmospheric pressure. It will be positive. This is called "Stack Effect", and it happens year round.

Opening windows and doors just changes where the air change occurs, but it still occurs.

Now, think of it this way. Let's say we add a 6" intake to the return side of the duct system. With a .1 static pressure we can move about 110cfm/hr through that 6" pipe. What happens if the air infiltration rate is 400cfm? Will a 6" intake "equalize" the pressures? Nope.

I have tested literally hundreds of homes as a New York State Home Energy Auditor with the EnergySmart program, and I can tell you all this. 99% of the forced air systems I have tested are so out of balance it isn't funny. Truth be told here, I installed the same way when I first entered the industry. It's how I was "told" to do it.

Answer "A", "customer comfort", is ambiguous. What do they mean by "comfort"? Do we automatically add an intake on every system we install? What "comfort" are we targeting?

I wish you remembered the other two choices Glenn.

Mark H

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S Ebels

Seriously (SE)

The answer is B regardless of what the testing officials say. Cutting a hole in the side of someone's home and connecting said hole to the cold air return does nothing for comfort. In fact it will work against maintaining comfort in any application, be it heating or cooling. Why do you think they sell those little "backdraft dampers" for the "fresh air intake"?? (See eleft's answer above)

The purpose, at least the only logical purpose for the intake is to allow air into and out of the home in order to keep it at a neutral or ambient pressure.

The fresh air inlet cannot work as intended unless it is pulled to less than ambient pressure. This also assumes, erroneously, that the building is able to be "pressurized". I have personally monitored the operation of these systems to see what really happens. I found that during normal winter operation, the intake will go negative allowing outside air into the return when the fan is running for a short period of time. That period of time depends on how tightly the home is contstructed. After the home becomes "pressurized" to a certain point the intake quits "inhaling" even though the fan continues to run. It's reached the limit of the house to allow any more fresh air in.

Here's the good part, When the fan cycles off, the house actually exhales. The pressure in the fresh air intake goes positive, as measured with a Magnahelic. The house "breathes out" allowing nice heated air to escape.

Makes an indisputable case for an HRV don't you think?

Glenn Harrison_2

Mark, Interesting answer.

Let me ask you something. What is your opinion of the Field Controls Make up air system pushed by Jim Davis and NCI, that has an intake damper that can be set to maintain a nuetral to slightly positive pressure in a structure, assuming of course the intake pipe is large enough.

jerry scharf_2

I'll take B

I make several assumptions:

1) This test is only looking for "simple" answers. There will be nothing that requires deep thought.

2) the bent of the test writers are on facts that can be regurgitated.

with these, I make a simple picture that I have a kitchen and bath exhausts running at 100 and 200 CFM respectively. That air is going out a pipe, so the other air better come in a pipe somewhere. The lowest pressure point is the return air duct, so it has the best chance of inducing air flow from the outside. Answer B fits this perfectly!

Facts about this assertion actually working or other complicating factors can all be dismissed based on the assumptions above.

I'll bet a beer that my logic will produce the right test answer. May not be the right answer, but it will get graded as correct.

There is also the point made that these folks couldn't really care about comfort...

jerry

Weezbo

Hello...

I agree with Mark......Stack effect fricks up any chance of comfort...it is also dangerous in its own right in a Fire. the first answer to the question is not all togethr if you get my meaning. it should ask if the use of Hrvs in conjunction with forced air can be done correctly to aid with indoor air quality. it can and is possible:) balance is everything in forced air. even the placement of where and what to pipe in residential locations when tying the two together.so , i figure the answer is a Packaged response based on the reading of some class in your area . so i going to go with B and not liking either of the answers.

ScottMP

Steve

I am out of my league to debate this one, but I thought the whole answer centered around HRV.

Thats why I wanted to know the other two anwers. MArk gave a very good responce to the question and asked the same question I did, what were the other two questions. Its is possible that the answer is niether A or B.

Scott

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Glenn Harrison_2

Scott, you bring up another posibility,

as ERV's and HRV's never even crossed my mind while debating. I can asure you that when I looked at the study guide, that neither C of D was correct as far as the testing "Organization" is concerned. Now obviously a few here have made me realise that C or D could have been a correct answer, depending on training and job experiences.

I mainly posted this to see what others train of thought would be based on the question and two answers I dealt with. It's sort of an experiment on how others think.

Maybe I'm just looking to see if others are thinking out in left field like I was

Glenn Harrison_2

Ken,

Would you not agree, that as Mark Hunt stated, that if ou do not add a large enough fresh air intake, then there would still be a negative indoor air pressure, which could cause a chimney to downdraft, which could cause CO poisoning, which would also create an uncomfortable customer.

And as you said, with new homesbeing so tight, it makes it very easy to suck a house into a negative pressure, with a dryer running, kitchen exhaust, and mutliple bath fans in these 1 bathroom per occupant houses.

Look at the question this way, What is the FIRST reason to add freshair?

By the way, I'm not disagreeing with your answer either. I like your perspective, and as always, I'm trying to learn something.

Unknown

Glenn, I was recently asked

to evaluate an exam given for liscense and another one for certification. Test 1 had 100 questions, I eliminated 42 questions multiple choice because two of the answers were correct depending on what field you are in. 12 questions had no real correct answer, that is 54 questions the rest of the questions were okay but did not really test to find out if the individuals applying for that liscense knew what they were doing.

The certification exam was 150 questions 21 questions on that one also had two correct answers. Another forty (40) questions created confusion by how they were worded.

The interesting thing is those exams still continue to be given.

I have been creating exams for over 40 years now and I can tell you it is no easy task. It is harder to find wrong answers to use on multiple choice than the obvious correct one.

Glenn Harrison_2

That does not suprise me, Tim.

I would say that at least 10 out of the 50 questions on this test were either poorly worded, vaguely worded, or had no correct or multiple correct answers. Some questions were completly opinion based, and so to get it right, your opinion must match the organiztions.

I'm getting interesting answers here, and enjoying it. Some have even got me thinking differently than I did when I took the test.

Ken_8

Glenn, here's the problem with the question as well as

all our answers. The question has no parameters. Therefore we are forced to assume many things. Since we are all individuals, we will assume things differently.

My assumption was as follows:

If this is a replacement furnace, it already had code or manufacturer's combustion air plentiful and the new system will not later that condition.

Or, The new furnace would be in new construction - sans chimney and be direct vented and sealed combustion anyhow - making inside air a non-issue.

There is insufficient information to know anymore details than stated in the rather nebulous question in the first place. I assumed a few aspects apparently Mark and you did not. Like you suggest, that is neither a righ or wrong assumption. It does however reflect the realities I encounter daily. And that's why I wrote what I did.

As a rejoinder of sorts, what was it in the question that led YOU to assume something different than I?

Probably your experiences as well

Good exchange!

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Glenn Harrison_2

I instanly thought safety when reading the question as written..

Mostly due to the numerous service calls I have been on where negative indoor pressures caused furnaces, water heaters, fireplaces, etc. to backdraft and dump CO and/or fumes into houses, including one call that sent me to the hospital with CO poisoning due to the nature of the call not instantly making me think of CO as the issue.

I also have to thank my attendance of NCI's CO/Combustion class by Jim Davis, and their Air Balancing class, along with Tim McElwain, Rudy Leatherman, and Mark Hunt's CO and combustion air talks.

You are right, it is a poor and imcomplete question with no true correct answer. I also wrote this on the survey sheet provided to point out the question needs a lot of work, along with many other suckie questions they had.

Glenn Harrison_2

By the way, Tim.

could you possibly post your three questions here or e-mail me privately with them. I'm just curious what they are and if I know the answers.

glennhvacman@comcast.net

Unknown

I will do that Glenn

when I have some time. My wife is yelling at me to get off the computer so we can go out to dinner. I will post them later for everyone to answer. I had posted them back a year or so ago and no one at that time got them all correct. Many did however answer two out of the three. Folks here on the Wall tend to be sharper than your average expert!!!

Glenn Harrison_2

Glenn Harrison_2

Amen Tim!!!

Now take that lovely women of yours out and have a good time

Bob_19

Unless

we are talking about combustion air, which I believe were not, the answer is "A" (period).