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NORTH AMERICAN TECHNICIAN EXCELLENCE

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NATE Advantage March 2012

09 May 2012
The NATE Advantage
Jackson Systems  

Yellow Jacket

2012 NEWS Directory

 

 

 

 

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We hope you’re enjoying your subscription to The NEWS. Visit us online at www.achrnews.com for daily news updates and the latest product information.

NATE News: ANSI Accreditation Achieved

ANSI AccrediationARLINGTON, Va. — American National Standards Institute (ANSI) officially recognized North American Technician Excellence (NATE) as an ANSI-accredited certification body. ANSI has served as the coordinator of the U.S. private sector, voluntary standardization system for more than 90 years.

In early 2011, NATE formally applied for ANSI/ISO/IEC 17024 accreditation, which involved a review of all practices and processes in place. Based on the 17024 requirements, NATE implemented a wide range of updates and enhancements to strengthen its processes and ensure that the integrity of NATE certification is upheld at all levels.

On December 13, 2011, the ANSI Personnel Certification Accreditation Committee (PCAC) met to review NATE’s assessment report. Upon their review, PCAC granted NATE ANSI/ISO/IEC 17024 accreditation as a qualified Certification Body.

“The entire NATE family has spent countless hours working towards this accomplishment, and we could not be more proud that NATE has achieved ANSI accreditation,” stated Peter Schwartz, NATE president and CEO. “ANSI accreditation validates NATE’s ongoing commitment to meeting the highest professional standards of examination development, further establishing NATE as an unrivaled certification body in the HVACR certification arena.”

Don Frendberg, chairman of the NATE Board of Trustees, said, “NATE is the only certification organization developed and supported by the entire HVACR industry, and this impressive achievement exemplifies why NATE is the true leader in certifying technician excellence.”

ANSI provides a neutral forum for the development of policies on standards issues and serves as a watchdog for standards development and conformity assessment. The ANSI Federation also accredits qualified organizations, whose standards development process meets all of ANSI’s requirements, to develop American National Standards. Through these efforts, ANSI aims to enhance the competitiveness of U.S. businesses, while helping to assure the safety and health of consumers and the protection of the environment.

For more information visit www.natex.org or www.ansi.org.


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NATE Test Question
A technician measures the return air temperature of a 100,000 Btuh output furnace to be 65°F and the supply air temperature to be 135°. What is the cfm?

A. 690
B. 1,211
C. 1,323
D. 1,428

Read the explanation to find out the answer below or

scroll to the bottom of this e-newsletter to see the answer.

Don’t Underestimate Airflow Calculations

The importance of airflow cannot be overstated. When selecting equipment based on the OEM specification guide, none of the values listed mean a thing unless the airflow matches what’s listed in the guide. By the same token, troubleshooting a system by measuring actual operating values such as superheat and subcooling cannot be counted on to provide an accurate diagnostic snapshot for the unit unless the airflow in cfm (cubic feet per minute) is known. For all these reasons the sensible heat formula must be known, used and understood by every service technician in the HVAC industry. As shown below the formula can be stated in a variety of ways.

Btuh = 1.08 x CFM x TD

TD = Btuh x (1.08 x CFM)

CFM = Btuh/ (1.08 x TD)

The most common question about this formula is: Where did the constant 1.08 come from? It’s a property of air at sea level based on .076 pounds of air in a cubic foot multiplied by .24 which is the specific heat of standard air at sea level multiplied by 60 which is the number of minutes in an hour.
To use the formula we need to know two of the values to calculate the third. In our question above, we know the TD is 70º (135º – 65º = 70º) and the Btuh (100,000). So we apply the formula to get the following:

CFM = 100,000 / (1.08 x 70)

CFM = 100,000 / 75.6

CFM = 1,322.7 (rounded up to 1,323)

 

That makes the correct answer to our question above “c”. Keep in mind that any calculation made in the field is only as accurate as the values taken. As an example, if there are two supply ducts coming off the plenum, take a temperature reading in both, add them together and divide that number by two to obtain better “averaged” temperature rise. Also, allow the system to run in heat at least 15 minutes before taking the temperatures to allow the system to equalize. Check the temperature sensors you’re using and if they are not displaying the same temperature when placed in the same place, use only one of them to measure both the supply and return. And when using this formula on a natural gas furnace, remember the value to use is “output”, not “input” and of course the furnace should be fired properly so verify the firing rate by checking manifold pressure and clocking the meter.

Another way to utilize this valuable formula is with electric heaters. To calculate Btuh on single phase electric heaters, measure the voltage at the heater and the amperage of only the heater, so don’t include motor amps. Volts x amps x 3.415 will provide Btuh, you then calculate temperature rise (TD) which gives you the two values needed to apply the formula above to obtain cfm.

Remember, system capacity, performance, life expectancy of the components and occupant comfort are directly tied to proper airflow. Always verify airflow prior to adjusting refrigerant charge.

For additional application and troubleshooting help or to find a wide range of instructional PDFs you can download at no cost, visit http://www.virginiaair.com/technicalservicesupport.php?section=forms.

NATE Tip: Website Navigation

Here’s a hot tip to help you find exactly what you are looking for on www.natex.org. Check out the search box in the upper right hand corner. Type in the topic you want to know more about and click “Submit.”

You will be directly linked to a page of information on the topic of your choice. If you don’t find it the first time, try using a broader search term.

NATE Home Page

Update Your NATE

How important is it to keep up to date with NATE? Very! It is important to keep all of your personal information current with NATE including your email, home address, and employer information. This is how we stay in contact, and inform you of new information pertaining to NATE such as test results, renewal notifications, and e-newsletters like the NATE Advantage. If your email isn’t up to date, how will you receive this information?

And, if you don’t update your employer information when you switch jobs, we can’t approve you for the consumer contractor technician listing. The NATE certification belongs to you, so make sure you update your information to take full advantage of it.

To update your information, log on to www.natetesting.com, click “Candidates” and use your NATE ID and PIN or log in with your MyNATE username and password.

Managing Airflow with Zoning

Many homes around the United States have only one centrally located thermostat, and unless it’s a very small home, that single thermostat almost guarantees that the occupants will not be comfortable in every part of the house.

One solution to this problem is to install a zoning system. A properly installed zoning system will ensure that the correct amount of airflow is delivered to each zone, so that occupants in every part of the house are comfortable at all times. There are several methods by which airflow can be managed, and it is up to the contractor to decide which technique should be used, depending on the application in question.

When installing zoning, it is always necessary to employ some way to relieve the excess air pressure that may build up in the system.

A static pressure bypass routes the extra air from supply to the return through a bypass loop. The volume of bypass air is controlled by a barometric weighted damper or a motorized damper controlled by a pressure switch. Bypass not only ensures that the right amount of air is delivered to each zone, but it also ensures good airflow over the heat exchanger or a coil and prevents noise at the register.

In some cases, the bypass method may overheat or overcool the delivered air. In this scenario, some manufacturers recommend a discharge air temperature sensor, which senses the temperature of the discharge air. If it gets too hot or cold, it will turn off the equipment but continue to allow the blower to drive air into the calling zones until the discharge air temperature moderates.

Using a discharge air temperature sensor is generally considered a good idea for many applications. However, it is subject to the individual design and must take into account the size of the zones being served.

A bypass isn’t the only method available, especially if there are only two zones that are evenly split. If that is the case then a contractor can upsize the ductwork, making a bypass damper unnecessary. If oversizing the ductwork isn’t possible, however, contractors may introduce velocity and throw problems.

Another way to relieve the excess air pressure is to allow the zone dampers to leak. This method, which is often used when there is no room for a bypass, prevents static pressure from rising when few zones call, as the excess air will bleed into non-calling zones.

Dump and wild zones are areas in a home where the excess air is delivered to relieve static pressure. As with oversizing ductwork and damper leakage, dump and wild zones do manage airflow, but they often generate complaints and callbacks because occupants are not comfortable.


NATE Test Answer:

A technician measures the return air temperature of a 100,000 Btuh output furnace to be 65°F and the supply air temperature to be 135°. What is the cfm?

C. 1,323

 

 

AHR Expo

NATE supports the AHR EXPO.

It is the largest event that brings together all facets of HVACR industry under one roof for three exciting days.

www.ahrexpo.com

 

Links

Technicians

To find a NATE testing organization

To find NATE training resources

Information on NATE recertification

Contractors

To sign up for the free NATE contractor locator as featured on

www.hvacradvice.com click here

To update your listing (recommended at least twice a year) click here

To visit the NATE consumer web site http://www.hvacradvice.com

 

NORTH AMERICAN TECHNICIAN EXCELLENCE

www.natex.org

2111 Wilson Boulevard, Suite 510 • Arlington, VA 22201

877-420-NATE or 877-420-6283 toll free • 703-276-7247 phone • 703-527-2316 fax

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