Look Before You Leap

Oct. 1, 2008
Before replacing HVAC equipment, how many of us take time to assess the performance of the existing duct system? Although the number is small, the idea
Before replacing HVAC equipment, how many of us take time to assess the performance of the existing duct system? Although the number is small, the idea of checking the duct system before replacing the equipment is catching on fast. Or, to put it another way, do you look before you leap? The reason more contractors are taking the time to check the duct system is two-fold. First of all, best practice requires it. Secondly, many are finding a new opportunity during these tough financial times by addressing the entire system and assuring high efficiency system performance, not just high efficiency equipment. Why Pre-Assessment? Today’s furnaces may require up to 50% more airflow. The National Comfort Institute (NCI) recently reviewed the ACCA Quality Installation Standard and found that this new industry standard is pulling together the basic processes needed to set a minimum bar the industry can follow to improve the quality of our installations. Our primary concern is that the specification lacks a solid pre-assessment process before replacing equipment. NCI research shows the average system performs at only 57% of equipment rated capacity. Typically poor system performance is the result of changing out boxes without a pre assessment procedure. Following a well defined pre-assessment procedure will assure adequate system diagnostics and will give the homeowner an opportunity to see that more is needed than simply installing new equipment. Performing a duct renovation with testing, adjusting, and balancing not only increases the revenue of the equipment change-out ticket, but also increases the average performance of the system by an average of 35%. By experience we know there’s no other way to achieve such high efficiency anywhere in the industry. Preparation One valuable step in a pre-assessment process includes conducting a comfort survey. The primary purpose of this short interview is to discover system defects that the consumer is aware of. Their experience may prove more valuable than what your testing instruments can prove. Current mild weather conditions may mask defects while they’ve lived though them year after year, so ask questions. Continue to educate your customers as you collect the nameplate data from the equipment. Gather the model and serial numbers as well as blower size, rated static pressure and equipment capacities. Take this information into consideration while determining total airflow as well as room-by-room CFM, and it will provide some clues on how to select new replacement equipment. This may be a great time to drop hints that the unit may be oversized, and to point out visible system defects. Then draw out a floor plan of the home or building. Keep your customer engaged in the process and record information that may be helpful when completing your load calculations once you have a signed agreement. We don’t recommend performing computerized load calculations during the same visit due to the time it takes and the distraction from the selling opportunity. Make sure to do the required calculations and keep them on file for documentation. Field Testing Now bring out the HVAC test instruments, inviting the customer to participate. This is a valuable learning experience for them. A knowledgeable customer assures you’ll get the job over 70% of the time, so teach. Measure airflow from each grille comparing the estimated airflow to actual airflow. Typically 10% of the registers will have zero airflow. That’s good for you. Many rooms will have below 50%, some over 200%. You’re looking really smart about now. Static pressure measurement averages .82-in. on a .50-in. fan across the country, so pressure is a shocker too. Filter pressure drops are typically 2 to 3 times higher than they should be. Measure temperatures to the nearest tenth of a degree to assure accuracy and to make a brilliant impression on the customer. Record each reading and compare results to the manufacturer’s engineering data or to industry standards. Comparison enables excellent diagnostics and pinpoints exact system defects. Carefully make recommendations for system performance improvement during the testing process. Calculate and Diagnose Airflow x the system’s temperature x the BTU constant = the system delivered BTU. Actual CFM from supply and return duct leakage can be calculated, BTU loss or gain from the ducting can be determined and quantified, as well as specific blockage in the duct system, and the resistance of existing filters and coils can be pegged. Each of these calculated values identifies system performance and pinpoints exactly where the system needs repair. Good diagnostics is completed by pouring the gathered data into performance formulas with the gripper being the system’s performance rating. Those that use this method claim its power to persuade the customer to add duct renovation to the change out and generate closing rates higher than any other sales method available. Prescribe Solutions Now that you’ve assessed the ability of the duct system to receive the new equipment, create a proposal that addresses the entire system. Pour the solutions into a proposal and mix it up with a price that thrills and delights your customer. Then give them the documented performance they’re looking for and you’ve baked up a prize-winning recipe for success. Rob “Doc” Falkeserves the industry as president of National Comfort Institute a training company specializing in measuring, rating, improving and verifying HVAC system performance. If you're an HVAC contractor or technician interested in receiving an HVAC system pre-assessment test procedure, contact Doc at [email protected] or call him at 800-633-7058. Go to NCI’s website at nationalcomfortinstitute.com for free information, technical articles and downloads.
About the Author

Rob 'Doc' Falke | President

Rob “Doc” Falke serves the industry as president of National Comfort Institute an HVAC-based training company and membership organization. If you're an HVAC contractor or technician  interested in a building pressure measurement procedure, contact Doc at [email protected]  or call him at 800-633-7058. Go to NCI’s website at NationalComfortInstitute.com for free information, articles and downloads.