With the recent shift in attention from HVAC equipment efficiency ratings to operating system efficiency ratings, my office has been bombarded with inquiries from contractors, utilities, researchers and government entities searching for the “silver bullet” to make installed HVAC systems work better. The hunt is on for that one magic repair that can make an installed system immediately perform perfectly.
Sorry friends, there’s no silver bullet.
The truth is that a typical 20 SEER 3 ton air conditioning system usually delivers less than 20,000 BTUs into the envelope of its building on a hot summer’s day. Yes, that’s below 60% of equipment rated capacity. The typical state or federal energy efficiency system average will beat that by only about 2,000 BTUs.
So what’s the big secret? The ability to effectively measure the delivered BTUs into the building is the beginning to the solution. There’s no quick answer that solves the efficiency problem. The answer is found through the process of HVAC testing, combined with genuine hard earned knowledge gained through some pretty tough training followed up by the rigors of practice and field experience.
Add that to the idea that the process is still not perfected, and that with practice, better test instruments and industry advancements, we’ll be better at improving system performance by next summer; and you’re on your journey to efficiency heaven.
Air is the fluid that plays the most essential role in moving the heat in and out of buildings. Superheat and sub-cooling mean little unless airflow is correct. In heating mode, unless airflow is verified, temperature rise numbers are relatively meaningless.
Static pressure is just like blood pressure; it can be measured and compared to standards. The standard is written right on the nameplate of the air moving equipment. If it’s higher than the nameplate pressure, then the fan can’t afford that high efficiency filter and it needs to be removed. If the fan can’t afford the matched high efficiency coil, it also needs to be removed.
Measuring total external static pressure will be your best teacher. Take five minutes and follow the manufacturer’s installation recommendations and simply measure system pressures at each start up. This skill takes 10 tries or so to master if you’ve been trained correctly. Soon a whole new dimension in quality installation becomes evident.
By following these guidelines your fan, coil and filter selection process will change, your duct sizing will increase, and installers will quickly alter their duct installation methods. Not because of some regulation or committee’s standard, but because of new knowledge and understanding of the results of their installation methods.
To simply seal a duct system without verifying airflow by measuring static pressure will rarely save energy. No static pressure measurement, equals no energy savings in my book.
Delivering the airflow, without the required temperature change will result in operating efficiency failure.
Airflow moves through the ducting, and ducts have to be tight, but unless the size is right (make them bigger) and the insulation is adequate (in some cases more than R-8), you may not get enough of the BTUs from or back to the equipment. Performance measurement will diagnose duct temperature loss or gain and reveal the need for insulation that far exceeds code.
Exceed code? Sure. Code rarely considers system operating efficiency. Code earns you the grade of D-. Congratulations, you just barely passed. This typifies the low bid, low quality work of our industry today. If you’re ready to move beyond the pack in quality and profits, measure and diagnose the performance of your systems. Then exceed code and current industry standards and exceed current industry profits. This is a solid and tried idea. It works.
The list is endless. The general idea is that each system repair project is customized for each system. Each requires testing and accurate diagnostics to identify what is needed; one system at a time.
Equipment inlet and discharge fittings often cause excessive system effect. Temperatures leaving a furnace may not mix well, and more air turbulence may be needed. Duct suspension systems need far more attention than they receive to survive years in unconditioned space.
How many summers will flex duct survive a 140F attic? Unless you test performance, defects may be invisible. Do registers and grilles need upgrading? Sure they do, because that’s a part of the system that the customer sees most often. Nearly every residential system can benefit from additional return duct capacity to reduce system static pressure. Balancing the system is always beneficial. Once airflow is changed, the refrigeration charge needs adjusting. The list is endless.
The list of new products that can be found and literally created by your company at premium profit margins with little or no competition is available everywhere. We’ll always have equipment to replace, but never stop there. Differentiate yourself from your competition.
Rob “Doc” Falke serves the industry as president of National Comfort Institute a training company with technical and business level membership organizations. If you're an HVAC contractor or technician interested in receiving a free listing of performance improving repairs, 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.