Home Energy AC Pro Guide 2011 : Page 5

air-conditioning ▪ ducts that leak over 20% of the air they carry; ▪ low-quality brazed joints that leak refrigerant; ▪ refrigerant contaminated with air, moisture, oxidation, and particles; and ▪ callbacks, warranty costs, and frustrated customers. It is worth paying extra to have a duct system that is tested and shown to have less than 10% leakage (a new duct system should be built and tested to leak less than 6%). It’s also worthwhile to have the installation commissioned and verified. These two steps alone will pro-duce an average energy savings of 24%–35%, depending on the local climate and on air conditioner usage. “If I’m not comfortable, it’s the HVAC contractor’s fault.” A contrac-tor’s ability to make a homeowner comfortable is severely limited by the performance of the house and by the willingness of the builder or homeowner to pay for a high-quality installation. In some ways, buildings have gotten much better over the last 15 years. Insulation is more com-This means that your new air conditioner will do a poor job of remov-ing moisture, will have low airflow across the inside coil, will be noisy, will cost you more to purchase, and will increase your utility bill for 15 to 20 years. Contractor Misconceptions It’s not just the homeowners who are confused. Here is the contrac-tors’ side of the equation. “Customers will not pay for quality; they want the biggest air con-ditioner for the least money.” There will always be customers—and builders, too—who just want the lowest price. However, there is a growing rec-ognition that smaller air conditioners do a better job of dehumidification, and that better installations save energy and money. Installation specifications are being enforced in some states and are under consideration by EPA for Energy Star products. One of the biggest hurdles you will face is finding a way to convince the customer that you are doing a better job PROCTOR ENGINEERING mon, low solar heat gain roofs are available, and newer, high efficiency glass can block much of the heat gain during the summer. In many homes, 50% or more of the heat gain at the hottest part of the day comes through the windows. When low solar heat gain windows are used, the air conditioner can often be downsized by as much as 1 ton. None of these improvements has reduced the amount of moisture gen-erated in the home or the amount of moisture entering the home with outside air. As the heat gain through walls, roofs, and windows is reduced, moisture removal becomes a larger and larger part of the cooling load. Simply put, if you live in a leaky house, most thermal improvements will make your house more suscep-tible to moisture problems. Therefore 4-ton 3-ton kWh PROCTOR ENGINEERING than your competitors. Some of the most exciting results we have seen involve contractors who take pride in doing a bet-ter job and are comfortable with ethical third-party verification to their customers. These contractors refuse to sell business-as-usual jobs. They are paid for their higher value, have high customer satisfaction, and experience very few callbacks and warranty calls. “If I use ACCA Manual J , I have to use higher outdoor temperatures than it speci-fies and lower indoor temperatures than it specifies. And I have to add a fudge factor at the end just to make sure there is enough cooling.” This is a very common misunderstanding among contractors. To figure out whether Manual J produces load estimates that are too small, we monitored homes in three states. We found that, on average, the actual sen-sible load was two-thirds of what Manual J Proper installation takes time and competent technicians. Air Handler kWh Figure 3. In a side-by-side test of identical homes, the 3-ton air conditioner ran 30% more than the 4-ton unit. The 3-ton air handler still used 27% less energy. reducing house air leakage is a very high priority in moist climates. “My contractor can tell what size air conditioner I need just by cal-culating the floor area.” If you let the contractor use this method, he will probably oversize your air conditioner by a ton or more. In order to use the floor area method, contractors have to deal with all the differences between homes by always installing large air conditioners. estimated. This means that Manual J actually overestimates a home’s air conditioning needs. Simply put, if the contractor uses Manual J without any fudge factors and selects an air conditioner to just meet the sensible and moisture removal loads, the air conditioner will be properly sized. In addition, it will provide good comfort even when the weather is scorching hot. www. homeenergy.org 5

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