Inaccurate supply and return grille temperature averages – To avoid this, find average grille air temperatures, take grille temperature measurements to the nearest tenth of a degree, add them together and divide by the number of readings taken.
Hitting the wrong numbers on your phone is way too easy for most of us. Confirm your calculation twice.
No outdoor ambient or entering wet bulb readings – Outdoor dry bulb and equipment entering wet bulb readings in cooling mode are both required to determine current equipment rated capacity. Unfortunately, since we don’t do any math with these two temperatures, we only plot their equipment-rated capacity; it’s easy to skip collecting them in the field.
Two Possible Airflow Inaccuracies
Airflow at the equipment – It’s often difficult to find a good airflow traverse location near the equipment. Ideally, you will build your systems with reliable traverse locations. You can measure static pressure and plot fan airflow, but at times this may not be accurate enough to satisfy your equipment Btu calculation needs.
Airflow at the supply registers – Total airflow entering a building through supply registers is required to calculate system delivered Btu. A balancing hood is easy and accurate when you can get to all the registers. When you can’t, traverse the grilles and be sure to make a custom field correction factor.
Overcome Btu Obstacles
Although you learned the basics of Btu measurement when you were certified, you’ll discover that your accuracy regularly improves as you practice, gain experience, and grow your skills.
I remember the day when David Richardson had less than one month of Btu measurement experience under his belt and hit his first barrier. His opening words on the phone were, “I have learned system testing doesn’t work for me.” When I asked why, he responded, “I just measured 122% of equipment rated Btu on a system, and that’s impossible!”
You will face many obstacles as you learn to measure system Btus accurately. The question is, will you be like David and overcome and learn from each obstacle? Or will you be easily derailed by a few barriers you will undoubtedly face as you take your career far beyond the rest of the industry?
Meet Rob Falke at NCI Summit 2022
Rob “Doc” Falke, president of National Comfort Institute (NCI) will provide hands-on Performance Town training at NCI’s Annual High-Performance HVAC Summit in Scottsdale, AZ from March 27th to 31st. So if you want to see this article come to life, join us there. You can learn more about Summit 2022 at our website: gotosummit.com.
You can still save hundreds on your registration costs. And don’t forget to book your hotel. Go to ncilink.com/WeKoPa22 to reserve your rooms today. If you have questions, be sure to call 800-633-7058 and ask for a Customer Care Representative.
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