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Using an Air Conditioning Calculator Before Upgrading Your Cooling

Calculator and plans

Every one's looking for ways to increase property value. Smart investments include landscape, heating and cooling, paint, and adding new appliances to the kitchen. When it comes to cooling the types you can choose from are endless; however, with the need to increase resale value comes the need to find energy efficient systems that are beneficial to your home.

There are two options to choose from central air conditioning units and room air conditioners. So how do you pick one and about how much do they each cost?

When considering a central air conditioning system you should first know which type you want. There are two types of central air conditioning units: split-systems and packaged central air conditioners.

In a split-system an outdoor metal cabinet contains the condenser and the compressor while an indoor cabinet contains the evaporator. Insome cases, the indoor cabinet also contains a heat pump or furnace. If your home already has a furnace but no AC, then this is probably the least expensive option.

In a packaged unit, the evaporator, condenser, and compressor are all located in one cabinet. This unit is usually placed on the roof or a concrete slab next to the foundation. Air supply and return ducts come from indoors through the home's exterior wall or roof to connect to the package outdoors. These units also include electric heating coils or a natural gas furnace. This combination eliminates the need for a separate furnace indoors.

When considering a room air conditioner, look to a windowor portable AC. These are the most efficient. Each type of cooler provides single room cooling and can be quite cost effective. They usually include window kits to make set up easy. Compared to a central AC unit, room coolers are less expensive to purchase and a convenient option when your home doesn't have a central unit already in place.

Choosing a Cooling System

Napoleon HVAC unit

Comparatively speaking, a central AC is much more efficient than a room one. Moreover, they are conveniently out of the way and easy to operate. When it comes to investing in an upgrade, one of the deciding factors is the cost of ductwork.

If you already have a central unit and you're looking to upgrade for efficiency then it's recommended that you contact a contractor to make sure the new compressor is matched to the indoor unit. With all the new technology available, it might be best to replace the whole unit instead. Today's models use 30-50% less energy than models made in the 1970s. Even if your AC is only 10 years old, you can save from 20-40% on cooling energy.

Next, consider proper sizing. Proper sizing and installation determine efficiency. Too large a unit won't remove humidity and too small a unit won't make you feel comfortable on hot days. Look for a model with a high efficiency rating. Central units are rated by their seasonal energy efficiency or SEER. Older systems bear a rating of 6. Today, a good rating is at least 13 or greater. The higher the SEER, the greater the savings.

As of January 23, 2006, new AC standards went into effect. Anything manufactured beyond this date must have an SEER of at least 13. These standards don't require you to change your unit, but it could be a bone of contention when you go to sell your home.

If you opt for a room AC then you want to be sure it can meet your needs. These units cool rooms rather than an entire home. For this reason, they can be less expensive to operate. Typically, they plug into a standard 115V 20A household circuit, and there's no ductwork necessary.

A room AC's efficiency is measure by the energy efficiency ratio or EER. A unit from the 1970's will have an EER of 5. Today's models have an EER of at least 10. Using a new model will decrease energy costs by half, so when buying a new unit, look for an EER of 10 or more.

The required cooling capacity of a unit depends on the size of the room. They range from 5500 BTU/hr to 14,000 BTU/hr. A common term used by the manufacturer is ton. An air conditioning calculator can help you select the proper size. This measures the room length, width, and height so you know exactly how many BTU you need to cool a space efficiently.

Before you install your unit be sure your home's electrical system can meet the unit's requirements. Some more powerful units require 230V.If you're mounting your unit, be sure it's in a spot that can reach the desired area you want to cool. Other features to look for include:

  • An easy to change filter
  • Simple controls
  • Digital readout & thermostat setting
  • Built-in timer


Contractor looking up

If installed properly your unit will run efficiently. If not installed correctly, modern units can operate as poorly as old ones. Energy.Gov suggests making sure your contractor does the following:

  • Allows adequate indoor space for the installation, maintenance, and repair of the new system, and installs an access door in the furnace or duct to provide a way to clean the evaporator coil
  • Uses a duct-sizing methodology such as the Air Conditioning Contractors of America (ACCA) Manual D
  • Ensures there are enough supply registers to deliver cool air and enough return air registers to carry warm house air back to the air conditioner
  • Installs duct work within the conditioned space, not in the attic, wherever possible
  • Seals all ducts with duct mastic and heavily insulates attic ducts
  • Locates the condensing unit where its noise will not keep you or your neighbors awake at night, if possible
  • Locates the condensing unit where no nearby objects will block airflow to it
  • Verifies that the newly installed air conditioner has the exact refrigerant charge and airflow rate specified by the manufacturer
  • Locates the thermostat away from heat sources, such as windows or supply registers
  • If you plan to replace a split-system, be sure the evaporator coil is replaced with a new one that matches the condenser coil in the new unit exactly. There won't be any efficiency if the old coil is left in place

You don't need a contractor to install your room air conditioner unless you can't do it yourself. All the instructions are included and most units come with everything you need for easy set up. With these units, you can benefit from effective cooling almost immediately. The following tips from Energy.Gov will help your unit run more efficiently.

  • The unit should be level when installed so that the inside drainage system and other mechanisms operate efficiently
  • Don't place lamps or TV's near the thermostat. If the thermostat senses heat from the appliances, it'll run longer than necessary
  • Set your AC's thermostat as high as possible in the summer.The less difference between the indoor and outdoor temperatures, the lower your overall cooling bill will be
  • Don't set the thermostat at a colder temperature than normal, it won't cool the room any faster and might result in excessive expense
  • Set the fan speed on high except on humid days. When it's humid set the fan on low. The low speed will cool the home more effectively and remove more moisture from the air because of slower air movement through the cooling equipment
  • Use an interior fan with the room air conditioner to help spread cooler air through the room without greatly increasing electricity use

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