HVAC Library

What is two-stage cooling?

Two-stage cooling uses a two-speed compressor which allows for two levels of operation depending on your cooling needs — full capacity or high speed for the hottest summer days or partial capacity or low speed for all the other days of the year. It can be a great energy-efficient option when compared to a traditional, single-stage or single-speed unit.

Two-stage cooling generally results in longer operational cycles, but at a low speed.  This may help to remove more moisture or humidity from the indoor air in your home, providing more comfort. The lower speed uses less electricity than single-stage systems which operate only at full on or full off modes. For better indoor comfort, two can be better than one.

What is variable speed cooling?

Variable-speed cooling (and heating with heat pump models) is driven by a variable-speed compressor. It provides high-efficiency cooling performance, which can result in lower energy bills and improved indoor comfort compared to air conditioners and heat pumps with a single-stage compressor. Now you have some variables to think about.

What is modulating heating?

A high-efficiency gas furnace with modulating gas valve and variable-speed blower provides outstanding efficiency and economical heating performance. Unlike single-stage gas furnaces that operate 'all ON' or 'all OFF,' a modulating, variable-speed gas furnace is designed to minimize energy use by running at its low fan speed setting to meet the temperature you selected at the thermostat or control system. It produces the right amount of heat to help maintain a steady, comfortable temperature inside your home.

Should I zone my house?

In ducted systems, zoning divides your home into areas with common heating and cooling requirements by using secondary thermostats and zone dampers installed in the duct system. Zoning allows you to adjust heating and cooling in parts of your home when they are not used, helping to save money on energy costs. A properly designed zoning system allows you to simply set the temperature in each zone to your desired comfort level. The equipment and zone dampers do the rest.

What is AFUE?

AFUE is the abbreviation for ‘Annual Fuel Utilization Efficiency’ ratio. AFUE is the percentage assigned to rate furnace efficiencies by dividing the ratio of heat output by heat input. This measurement describes how well fuel, natural gas or propane is consumed to produce heat by a furnace. As the AFUE percentage rate increases, the efficiency of your furnace also increases, which can help to lower your fuel costs.

What is HSPF?

HSPF is the abbreviation for the Heating Seasonal Performance Factor. The HSPF number identifies the heating efficiency of a heat pump. The higher the HSPF number, the more efficient the heating performance of the heat pump.

What do all those air conditioner and heat pump ratings mean?

The AHRI directory (your directory assistance of heating and cooling) contains rated values for air conditioners and heat pumps. These explain how a “split system,” which is an outdoor unit matched with an indoor unit and/or furnace. The AHRI Directory of Certified Product Performance provides information for all models still being sold, including those currently in production (“active”) and those that are no longer currently in production but are still available (“discontinued” or “production stopped”).

What is a “properly matched” system?

Because of a variety of factors for split systems, not every combination is a proper matched system. Our engineering team spends extensive time ensuring that the combinations we certify will work correctly in your home. Your local HVAC dealer can help you find your perfect pair for your home.

Why should I choose an ENERGY STAR® product for my home?

When it comes to energy efficiency, all ENERGY STAR® certified products shine. They have higher efficiency ratings than standard models and will likely cost less money to operate. ENERGY STAR® and the ENERGY STAR® mark are registered trademarks owned by the U.S. Environmental Protection Agency. ENERGY STAR® products are third-party certified by an EPA-recognized Certification Body. Products that earn the ENERGY STAR® prevent greenhouse gas emissions by meeting strict energy efficiency guidelines set by the U.S. Environmental Protection Agency (EPA). For more information, visit www.energystar.gov/.

Proper sizing and installation of equipment is critical to achieve optimal performance. Split system air conditioners and heat pumps must be matched with appropriate coil components to meet ENERGY STAR® criteria.

What is an AHRI-certified system?

AHRI is the abbreviation for the Air-Conditioning, Heating, and Refrigeration Institute, a trade association representing manufacturers of heating, cooling, water heating, and commercial refrigeration equipment. AHRI is an internationally recognized advocate for the industry, and develops standards and certifies the performance of many products, including the ones sold by Goodman.

In the case of an air conditioner or heat pump, an AHRI-certified system confirms the performance ratings of specific combinations of the outdoor unit, indoor unit, and/or furnace listed in the AHRI Directory of Certified Product Performance. AHRI’s voluntary certification programs conduct third-party laboratory testing to confirm performance ratings. The ratings associated with such combination are certified in the form of an AHRI Certificate of Product Ratings.

Why Must I Change My UV Bulb When it is Still Lit?

A UV lamp is not an ordinary light bulb. One of the most misunderstood things about a UV water treatment system is why the lamp should be changed even though it still appears to be working. Why is it that the useful life is typically defined as 9,000 hours, or about one year of continual use?

The problem arises from the fact that for most of us, our understanding is heavily influenced by our experience with incandescent lights. These are your garden variety bulbs, used in most household light fixtures, it is not necessary to change or replace this bulb until it quite literally burns out.

An incandescent light bulb works by passing electricity through a tungsten filament. This generates heat that causes the tungsten to glow. That glow is the visible light spectrum, so we see the light. The tungsten filament is deteriorated with use and eventually it becomes so thin that it quite literally snaps, and no longer lights.

A UV lamp, however, operates on a different principle, more like a fluorescent light. In this case, the electricity is still passed through a tungsten filament which heats up, but that energy “excites” the mercury vapor contained in the lamp. (Not to worry, only a very small amount of mercury is used, typically <10 mg, and it’s safely contained.) In this case, it is the mercury vapor that glows and, emits ultraviolet (UV) light. This is exactly what’s needed to inactivate any pathogens in your water supply. As you may know, UV light is not visible to the naked eye and is, in fact, quite damaging, so never look directly at a UV lamp while it’s on. If your system has a view port, you may see a blue glow from the lamp, but that’s not a result of the UV rays. Remember, UV light cannot be seen by the human eye. This glow is simply a by-product of the lamp’s operation. The useful life of the UV lamp is determined by the rate at which the mercury is consumed. That very small amount of mercury contained in the lamp will provide sufficient UV rays to disinfect the water for about one year. After that, although the lamp appears to be working, there is not enough UV produced to safely drink the water. Changing the lamp on time is critical to ensuring your safety. That’s why many UV systems have a timer that will count down from 365 days and then sound an alarm to let you know it’s time for a lamp change.