Things To Know
In this time of ever rising utility costs and concerns for the environment, we all need to do our best to conserve. Like most any other HVAC professional, I will encourage the purchase of very high efficiency units. I will also encourage enhanced comfort and savings available from the INFINITY systems and INFINITY zoning. I consider the 2 stage variable speed zoned Infinity system the best choice available. The thing to consider is that although you may invest in the best of HVAC equipment, you may not get the super savings or high comfort you expect. There are other things the consumer needs to be aware of the can have a big effect on both economy and comfort.
House Envelope Leakage
Even minor air infiltration into your house can easily offset the savings from super efficient HVAC systems. For years we have had the mentality of adding insulation and reducing heat loss/gain. Air will easily go through thick layers of fiberglass insulation. Leakage must be stopped first, then add insulation. On new construction consider spray foam insulation. On all construction, search for, find, and stop, air leaks. Have the house tested with a blower door to help find these leaks, and then seal, seal, seal.
Get What You Pay For
When you do buy a HVAC system, be sure you are getting what you think you are getting. Units are manufactured in what I call families or series. A certain model family may be called 13 SEER or 15 SEER etc. The thing to know is that the efficiency of units in that series will vary with the size unit and the indoor unit or coil or furnace it is connected. For example, a 15 SEER family unit may be rated at 15.1 SEER in the 3 ton size when connected to a certain fan coil unit. Another unit from that same family in the 4 ton size may only be rated at 14 SEER. Also that same 3 ton 15 SEER family unit that was 15.1 SEER with a specific fan coil might be 14.9 SEER with a different fan coil, and may be 16 SEER when matched the yet another fan coil. This means that because the outdoor unit reads 15 doesn't necessarily mean you got 15 SEER. So how do you know? The true ratings of all brands of units in approved combinations are listed on the ARI website. Have your contractor to provide the actual full model number of the outdoor unit, indoor fan coil, or coil and furnace you are considering purchasing, go to the website and look it up yourself. Go to (www.ari.org). and click the certified HVACR equipment in the center column. If this gets a little complicated, ask you contractor to do this for you and provide a certificate that can be printed from the site with your exact models and combination.
The system needs to be like baby bears soup, just right. The system needs to be big enough to condition the space and small enough to run a lot. That's right, I said run a lot. Short run cycles in hot or cold weather mean a over sized system. An over sized system causes uncomfortable temperature swings with blasts of hot or cold air, reduced dehumidification in summer, and high bills due to repeated startups which just kill efficiency for both heat pumps and gas furnaces. Every installation should have a Manual J heat loss/gain worksheet run to determine the size system you need. The contractor should come out, measure and inspect the house, windows, insulation, roof color, and direction the house faces to get the information necessary to do this worksheet. If he doesn't get this information he is sizing your system either by rule of thumb, guessing or what he just got a "deal" on. If it is not the right size for your house it is not a deal to you. Often a larger unit cost on a little more to buy than a smaller one. The labor is often the same to the contractor. The duct cost only slightly more and often the units cost only slightly more. The 3 ton unit may sound like a bargain when price per ton is considered against a 2 ½ ton. But if these are single speed units the bargain to operate after it's bought is the one that is big enough but not too big. The 2 stage units can be an exception to this rule as they can run at ½ size as needed.
Seal The Duct Work
Just like the high efficiency you pay so dearly for can be lost through leaks in the house envelope, Leaks in the duct system will also. Make sure the duct is well sealed with proper fasteners and seal with duct mastic, not just tape.
Use Proper Size Duct
All systems have to move the proper amount of air to work properly. This is much harder for a home owner to verify. While the air flow can be tested, It can be a somewhat costly process if done by and outside authority. Choose a reputable contractor that you trust to do a proper installation. If someone offers a great "bargain" on an installation, be very careful. Most "bargains" come as a result of cutting or shorting something. Duct design is often where this happens. Tip: The CARRIER INFINITY system can check the airflow CFM and static pressure, display it on the user interface, adjust the fan speed to help compensate, and notify you if it is outside of proper operating conditions.
Maintain Your System
A tiny layer of dust in the curvature of the blade on the indoor blower can reduce that critical air flow listed above by 30%. We have found severely neglected units where the blades were actually bridged with dust, dirt, hair, and anything else you can imagine. The indoor and outdoor coils are often clogged in a similar manner. Even when the coils are not clogged, they can be coated with a thin layer of sticky scum that is hard even to see. This coating works as an insulator on the heat transfer surface. Any of the above can kill that high efficiency we worked so hard and paid so dearly for.
The Moral of the Story
A couple $4.00 tubes of caulk, a little tape, a little time sealing the house, and proper maintenance of your system can protect your investment in high efficiency equipment.