Do Most Improperly Size a System?
He referred to a study of 55,000 air conditioning systems by the Proctor Engineering Group (PEG), which found that refrigerant levels were wrong 62 percent of the time. In another study, the figure was 68 percent.
The PEG study also revealed that the speed and the volume of air moving through air conditioning systems were incorrect (usually too low) in about 72 percent of units tested. “This was due partly to mismatched indoor and outdoor units, which occurs more often on retrofits than on new installations because only the exterior compressor/condenser unit typically is replaced,” said Green.
In his article, Green noted that ducts are the least expensive part of the system and frequently are given short shrift. “A properly designed duct system begins with determining the cooling load for each room (not based on the square footage), which can vary greatly,” he said. “Duct runs need to be as short as possible; they need to be insulated; and when possible, they should be installed within conditioned space. Ducts also should be sealed. Leaky ducts waste energy, and in the right conditions may draw dust, spores, or combustion gas from a gas appliance back into the house.”
Mary Marble of Marble Mechanical Systems LLC addressed each of the three reasons for faulty installation.
“We all agree that refrigerant levels are very important in a/c systems,” she said. “I think we have to maintain systems properly to prevent leaks which will affect levels. I think that any good service technician can get the proper refrigerant charge into a system no matter what the line set length or if it is a retrofit project. The new 13 SEER systems have bigger cooling areas and you need to be careful with changing out the old system to the new. Typically old evaporators will not work well with 13 SEER condensers.
“Low air will be an issue with freezing up evaporator coils, although again, I think good maintenance is a key with keeping the filters changed and evaporator coils clean of dirt and debris assuming that everything else is designed properly.
“If you do not have proper airflow across an evaporator coil, you are going to have issues down stream with cooling the space and keeping a good air balance between supply and return side.
“All in all, air conditioning sometimes is not an easy task. You have to make sure you have the right equipment, refrigeration, and duct installation and controls to keep your customer comfortable.”
CONSULTANTS RESPOND TO THE TOPICThe topic of poorly or incorrectly sized systems is a very passionate one for many HVACR contractors, especially NEWS’ consultants. It strikes a nerve and gets a lot of attention because, according to the consultants, it is one of the leading reasons why the trade is criticized for its lack of professionalism. Here’s what a few of the consultants had to say about the topic.
Arthur Pickett of Royal Air Systems said it is a constant struggle to battle the “bigger is better” mentality and put the topic into a historical perspective. “Twenty years ago most guys stocked 3-5 ton units,” he said. “Even today we will run a load and size a job, only to discover the customer went with someone else because they offer a bigger machine. It’s difficult to get the American male to stop thinking bigger is better.
“You run the load calculation and size the equipment to a 3-ton unit. Then you find out the customer bought a 5-ton because he got it for the same price. When on a sales call it takes 30 minutes to educate the customer about what he needs and why, but even this doesn’t always work.”
Larry Taylor of the AirRite Air Conditioning Co. has been a strong advocate of properly designing and installing HVAC systems and he believes that most systems are installed based on price only and therefore a true quality installation cannot happen. He added another item that greatly impacts system installation: the lack of understanding and professionalism in the HVACR industry.
“As long as contractors have employees leaving to start their own businesses without the proper knowledge and training, we will continue to see this type of work,” Taylor said.
“I personally do not think that our industry has the overall desire to stop this type of work - but rather continues to complain about this type of work while allowing these actions to continue pulling down the professionalism of our industry. Until our industry is fed up with these type of installs and moves as a consolidated group with the effort to ensure that systems are designed, sized, installed, verified, and maintained to ACCA QA/QI standards, we are getting what we deserve and it will continue.
“The country and customers are the real losers in this process because of excess energy waste and poor indoor environments. We can either stand up or we need to shut up - but do one or the other and get off the fence!”
Ann Kahn of Kahn Mechanical supports what Taylor said, adding, “Two factors are the cause of faulty system design and improper installation. One is insufficient training and lack of knowledge on the part of the designers and installers, and secondly, hasty installations almost always result in poor quality workmanship.”
Dave Dombrowski of Metro Services/ARS also blames poor training and poor workmanship for the industry’s woes. “I absolutely believe that we are our own worst enemy when it comes to design and installation,” he said.
“There was a time in our industry that heating and air conditioning systems were installed by professionals who apprenticed in the trade and took pride in the design of the duct systems, their ability to form metal, the matching of equipment and a full understanding of all factors involved in heating (and later cooling) a home.
“With the strong growth in construction, the HVAC system became a commodity, items could be pulled from a box, slapped together, oversized, and allowed to leak since the homes all leaked air and it did not matter since energy was cheap. This is a new era of tight homes, high energy costs, and tighter money.
“We reacted to this not by becoming more efficient and more professional for our customers and then selling value. We reacted by cutting cost in training, design, and putting people into homes who do not have the skill sets to do the jobs. There are people still sizing jobs on the old “600 square foot per ton rule.” This is a joke and a bad one.
“ACCA has provided Manuals J and D to answer the load and duct issues. However, I challenge NEWS’ readers to go pull the last 10 installation jobs in their group and see if a Manual J or D was completed. Areas like checking airflow and refrigerant levels are part of the basic installation requirement and should not even be a topic for discussion. We all know how to do this (and if we do not know, then ACCA has the tools for everyone). We must decide to execute this as professionals or we are no better than the fly-by-night contractors who currently give us all a bad reputation.”
Ken Bodwell, Innovative Service Solutions, believes the biggest culprit in poor system design is the airflow problem, often because of “production line home building mentality.”
He added, “During a period where tract homes were being thrown up and manpower was short, I have no doubt shortcuts were taken. I think the issue in the South in residential application is more likely airflow: whether it is low airflow or a poorly designed system. Many tract homes were built using flex ductwork in place of duct board, and as a result static pressures are wrong and accurate air balance impossible. Most of these installs did not use balancing dampers unless you call a tie wrap a damper.
“I think Florida has taken some very positive steps to provide code enforcement and guidance but if the consumer is trying to get a low-priced install and utilizes unlicensed contractors, then let the buyer beware. The down side is that this ‘shoddy’ workmanship gives our industry a black eye.”
“On the commercial side, we certainly see questionable duct installations, but I think the refrigerant issue is the most valid. Typically on the commercial side, the ductwork is sized and laid out by engineers or trained professionals, however very few of the technical schools adequately teach airflow so technicians are not comfortable diagnosing airflow issues.
“There are certainly issues surrounding airflow in space build outs, but the practice of using balancing dampers is commonplace and minimizes most airflow issues. The installers and startup technicians need to understand the pressure-temperature charts and use either superheat or subcooling depending on the application. On multistory buildings and long runs, the refrigerant piping configuration is critical.”
Hank Bloom of Environmental Conditioning Systems, whose market is 100 percent commercial said, “The purchase process is poor. The general contractor gets the job on the correct HVAC number and then sends the bid process back out for rebid and finds someone to do it for much less. The general contractor has the extra money in his pocket and plays dumb. This means the scope gets cut, shortcuts are taken, pieces and parts are missing, and at the end, the customer loses. The other issue is that most contractors just use rule-of-thumb design. This can really get you into trouble.
“We actually have been called in to fix many of these jobs, which is sad. It gives us all a black eye in the industry.”
THERE IS HOPEBodwell doesn’t necessarily agree with author Green about incorrectly sized systems. “I think the blanket statement that most a/c systems are installed improperly is not correct,” he said. “I hope there are enough quality contractors across the U.S. who are proud of their work and who care about the finished product.”
Pickett said his state is trying to address the problem. “Massachusetts has started to look at the whole picture through the utilities,” he said. “When doing a changeout the utilities should offer a rebate to downsize the system to the proper size.”
But Taylor remains pessimistic - for now. “Each time an employee leaves a contractor without being forced to meet industry standards for HVAC work, we take a step backwards,” he said. “This is why I made the comment “Will the real HVACR industry stand up and take charge of our future.”
Publication date: 06/30/2008