National Comfort Institute Inc. : Performance-Based Contracting : Knowledge Base

N A T I O N A L C O M F O R T I N S T I T U T E, I n c .

Search NCI Online

Contractor Home

Training Programs

Technical Excellence Membership

Business Leadership Membership

The Summit 2012

Regional Conferences

CO Monitor Reseller Program

Technical Excellence Member Features

Technical Downloads

Marketing Materials

Air Balancing Training Programs

CO/Combustion Training Programs

Home Performance for HVAC Professionals

NCIOnline University

National Comfort Institute's Knowledge Base

National Comfort Institute's Knowledge Base is a collection of questions and answers to help NCI members and industry professionals. The knowledge base is open to both NCI members and NCI Online users.

Access Levels
Each question has an Access Level, NCI Member Only and NCI Online User. NCI Members can view all questions and answers in the knowledge base. NCI Online Users can read NCI Member Only questions but cannot access the answer. NCI Online users can only access NCI Online User level questions. Both NCI Members and NCI Online Users can ask knowledge base questions.

Asking a Question
Even though Knowledge Base questions are answered by both National Comfort Institute and trusted Industry Professionals, all questions and answers must be approved by National comfort Institute.

Question Category:

Search Knowledge Base:

Sort Knowledge Base By:

Question Category: Testing

NCI Member Only

Question: Twinned furnaces I have 2 80,000 btu/3ton blower twinned. Measuring static and calculating is this actually supposed to be a 6 ton blower? when measuring we found that tesp was the same through both totaling .1 Other job, separated systems with common return. static is ok when only one system running. when both are running static goes off the charts to 1.2 or 1.5 How do we calculate for Heat/coolmax. - To view, please click on the question.
Asked Date: 08/17/2011

Question Category: Air Flow

NCI Member Only

Question: It seems to me one could determine airflow CFM with a pitot tube and anemometer if we took enough readings to get a representative average. That is what a traverse measurement is, correct? Of course the location in the air flow changes the value. By the same token does not changing the location of the static pressure tube in the air flow also give you different values and should we not also take several readings to get a representative average? - To view, please click on the question.
Asked Date: 07/24/2011

Question Category: HeatMaxx & CoolMaxx	NCI Online User
Question: Can we determine duct leakage based on the values in the CoolMaxx report, if so how? - To view, please click on the question. Asked Date: 07/24/2011

Question Category: HeatMaxx & CoolMaxx	NCI Member Only
Question: On the CoolMaxx report, section 1 system pressures where exactly do we measure the 2 pressures to add to obtain a total staic pressure? - To view, please click on the question. Asked Date: 07/24/2011

Question Category: Static pressure

NCI Member Only

Question: When refering to fan rated pressure either from a manufacturers chart or the generic table is this for the total static pressure from behaind the fan (I always refer to a direction of from return to supply) to after the furnace element, before the coil or the total system from before the return register to after the supply register? Or what? - To view, please click on the question.
Asked Date: 07/24/2011

Question Category: Air Flow	NCI Member Only
Question: In the equation for CFM = Area times Velocity and indeed many other equations the variables or input values are affected by elevation, temperature and relative humidity and perhaps other influences. Is there a chart, equation/s or program that integrates these affects to give a result based on all known influences? - To view, please click on the question. Asked Date: 07/24/2011

Question Category: Air Flow

NCI Member Only

Question: I am a California HERS rater. I realize the standard we test for is a minimum and you folks would like to achieve greater overall efficiency. But for now it is what it is. I took the first 4 day and the second light comm. 2 day course. There was a lot of technical details to digest and I have a number of questions to be answered so I can fully understand the diagnostics you have introduced me to. I will ask them one at a time. First, regarding velocity pressure and CFM is this equation correct? CFM = area times 4005 times the sq. root of (Total pressure - Static pressure). - To view, please click on the question.
Asked Date: 07/24/2011

Question Category: Duct System Renovation

NCI Member Only

Question: I have a question about "cheese boxes" / remote plenums. On page 66 #3 states to use sheet metal wyes, which I know and understand, but I need something to show to a customer why this needs to be done. We just discussed this in class, but I can't find anything about the equivalent length of a "cheese box". Where do I need to look? Thanks - To view, please click on the question.
Asked Date: 06/07/2011

Question Category: Air Diagnostic	NCI Member Only
Question: Is the pressure drop across a clean filter constant with an increase in cfm's or velocity? We are a new memeber and are learning so please bear with us. Thanks, Don - To view, please click on the question. Asked Date: 05/25/2011

Question Category: Duct System Renovation

NCI Member Only

Question: Is putting turning vanes in return air drops advisable on replacement furnace and ac systems, as long as the drop and as much of the ra duct has been up sized to keep our statics in line? We are in the replacement side of Hvac and hi static is a big issue. We do alot Heat Pumps and low air flow due to hi static was a problem. I feel they are a good thing the Boss has the other view but open to any thingt that can help. Thanks Bob Hollingshead McCarthysOne Hour HVAC - To view, please click on the question.
Asked Date: 04/29/2011

Question Category: Duct System Renovation

NCI Member Only

Question: Duct Work Design- When designing a duct system using a ECM motor is there any special notes to address. What is the design static pressure. Currently everyone uses .05,.06,.07 and .1 static. What do you recommend? Also I'm told some of the older ECM's if they rev to far, they will over amp and shut down. Please keep in mind we do alot of zoning / design JD - To view, please click on the question.
Asked Date: 02/24/2011

Question Category:	NCI Member Only
Question: Stack temps? Steel fire tube steam boiler with power burner, what should my stack temps be running? Joe - To view, please click on the question. Asked Date: 01/10/2011

Question Category: Air Balancing	NCI Member Only
Question: I'm looking for the balancing dampers that can be installed in round duct through a hole. I remember them as a fabric damper with a spring edge that made them collapsible. Where can I find them or something that will work as well? - To view, please click on the question. Asked Date: 11/02/2010

Question Category:	NCI Member Only
Question: Which hot water pilot orifice drill bit? I see that 4 different ones are listed for natural gas. Which one do I use? Joe Heritage Ralph's Heating Service Inc. - To view, please click on the question. Asked Date: 08/16/2010

Question Category:

NCI Member Only

Question: A service tech has come across a 15-ton air handler that someone has dampered the return and added a fresh air return also with a damper. The problem is that they try to use it as an economizer. They shut off the return air and open the fresh air damper which only handles about 900 CFM. The unit is tearing up the blower wheels. Can this be caused from a shortage of airflow? - To view, please click on the question.
Asked Date: 05/13/2010

Question Category: Business Management	NCI Member Only
Question: Do you have any Encouragement Sales Classes Available anytime soon? Might have 2 People too Signup! - To view, please click on the question. Asked Date: 04/19/2010

Question Category: Combustion

NCI Member Only

Question: Re: combustion analysis question. Ran across an older (1960's) commercial Bryan water tube atmospheric boiler with the following readings. 02 = 9% stable CO= 10ppm stable flue temp = 645 degrees? draft = .05 temp rise across boiler 22 degrees. The high flue temp is what has me scratching my head. everything appears normal. Could this old boiler just be that inefficient? Thanks Joe - To view, please click on the question.
Asked Date: 03/04/2010

Question Category: Air Diagnostic	NCI Member Only
Question: How can I measure air volume on a system with a 12-inch air sock as the duct? The customer has gone through 2 heat exchangers in three years. - To view, please click on the question. Asked Date: 12/28/2009

Question Category: Testing

NCI Member Only

Question: Last year a member asked the best way yo charge a heat pump in the heating mood in the winter.At that time jim davis gave an answer to the effect of put a digital thermomater on the discharge line between the compreser and the reversing valve an add 126 degree above ambient temperture. I have serched for this question and answer but cant find it any where this year jim tell me if this answer is still avelable and where can i find it. - To view, please click on the question.
Asked Date: 12/21/2009

Question Category: Technical	NCI Member Only
Question: Hot air goes to cold and wet goes to dry? right? - To view, please click on the question. Asked Date: 09/29/2009

Previous Records | 1 2 3 4 5 6 7 8 9 10 | Next 20 Records

What's active on National Comfort Institute

News Updates

Current Newsletter Button

Upcoming Training Programs

Air - Columbia, SC
Air - Cincinnati, OH
Air - Phoenix, AZ
Air - San Antonio, TX
Air - Sacramento, CA
Air - Cleveland, OH
CO - Detroit, MI
CO - New Orleans, LA
CO - Chicago, IL
CO - Dallas, TX
CO - Cypress, CA
CO - Las Vegas, NV

ContractorsIMAGE

CO In The News

Carbon monoxide scare forces residents from home - 2/3/12

Carbon monoxide leaks reported - 2/3/12

Carbon monoxide victim showing signs of improvement - 2/3/12

Carbon monoxide detector rules to be examined - 2/3/12

State carbon monoxide death prompts look at regs - 2/3/12

More CO News Stories

Top Of Page Go to the top of National Comfort Institute

Go to the top of National Comfort Institute