Duct Dynasty: Do Your Tuneups Perform?
Properly Diagnose System Performance Using These Simple Measurements
Across the country, the spring maintenance agreement season has begun. Many contractors have revised the title of their maintenance agreements in their marketing to performance tuneups. These two services are technically different, yet the same routines are being performed in many instances. The big question is, are your customers really getting better performance as a result of your performance agreement? Or are you just insinuating they are? Is there a possibility you could add something more to increase the value of this service to your customers?
If you’re using the term performance tuneup, how do you know if you changed the performance of the equipment or system? Let’s take a look at how a standard performance tuneup is often handled and how it can be turned into something special.
The Yup Check
When you look at many service invoices and checklists used for performance tuneups, they are nothing more than “Yup Checks” from the days of basic maintenance agreements. Yup Checks are an endless series of check boxes to give the appearance the customer is getting what they invested in.
You may have seen these Yup Checks, or you may be using them and not even be aware of it. An example of a Yup Check being used on a maintenance agreement would be a (insert any number here) point checklist of your HVAC system. Some contractors will use 15 points, 20 points, etc., and most of these points involve checking to see if the thermostat is level, drain is clear, or the motor is oiled.
While all of these are important points, they are only maintenance tasks being conducted. They don’t ensure that an improvement in performance will magically occur.
Static Pressure Testing
One of the essential tests that should be performed during a performance tuneup is a baseline static pressure test. Think back to the last time you visited the doctor’s office. One of the first tests performed was a check of your blood pressure. This is a key indicator of your overall health, just as static pressure reading is a key indicator to the overall health of an HVAC system. Measured static pressure should be compared to nameplate fan-rated astatic pressure.
As an industry, we have gotten into a bad habit of assuming the duct systems we see on a daily basis work properly. In many instances, the duct system might get examined at the time of an equipment change out. All too often, it is missed at that point in time. What if you could give a duct system an annual checkup?
Think about this. How many of your service agreements cover the distribution portion of the HVAC system? Are you seeing an opportunity here?
Total external static pressure is one of the most valuable and simplest measurements you can perform on an HVAC system. In less than five minutes, the amount of information you can gain is invaluable. This test is the entry test for determining the overall health of your customers’ HVAC system — just as blood pressure is a key indicator in your own personal health. By adding just this one test to your agreements, you’re adding the first steps of performance to your tuneups.
By referring to the manufacturer’s fan-performance data, you can determine fan airflow by using the measured total external static pressure. This gives you an approximate amount of airflow that the fan in the equipment is moving. You can use this to show how much fan airflow was being moved before and after cleaning the system.
Filter pressure drop will help give you an idea how restrictive the existing filter is. This 1 minute test can lead you to filter-rack upgrades simply by taking two pressure measurements, determining if a filter is too small or if the existing filtering media is too restrictive. It can also show the impact of a clean filter compared to the old filter that was in place.
Coil pressure drop is a quick way to determine if an indoor coil is restrictive. Instead of tearing into a piece of equipment, this measurement can allow you to determine whether a visual inspection of the coil will be needed to see if it is impacted with dirt and debris. If a coil cleaning is needed, the before and after pressure drop measurements can be compared to one another to verify cleaning was achieved.
Supply Register and Return Grille Temperatures
Many tuneups do a fantastic job of measuring supply and return temperatures at the equipment. By adding average supply register and return grille temperatures you get a look beyond just the equipment and a glimpse at the duct system. Looking at the equipment temperature change, or ?T, is a valuable test.
By taking supply register and return grille temperatures, you can get a more accurate gauge for how much cooling is being lost through the duct system. Taking these readings will open the door for many opportunities to correct issues that have gone uncovered for decades.
The Sum of Its Parts
With the two measurements that were just covered, you can measure an improvement in the performance of your tuneups. This allows you to determine how the equipment was operating before your tuneup and after your tuneup.
By measuring static pressure and equipment temperatures, you can figure out approximate fan airflow and equipment-delivered Btu. This way, you can see how the cooling system is performing in live field conditions. As you can see, it doesn’t take much additional testing or time to achieve this. You can typically add something more to your tuneups in 15 minutes or less.
These procedures offer you a means of determining a percentage of improvement based on before and after test results. Now, in all good conscience, you can offer a performance tuneup and know it isn’t a Yup Check.
David Richardson serves as a curriculum developer and trainer at the National Comfort Institute (NCI). NCI specializes in training focused on improving, measuring, and verifying HVAC and building performance. Contact him at 800-633-7058 or at firstname.lastname@example.org.
Publication date: 4/7/2014