Cooling System F.A.Q.

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Should the outdoor unit of a split central air system be covered for the winter?



Modern split AC units are designed to withstand winter conditions without a cover. In fact, a cover can retain moisture that may cause premature system corrosion.

What is two-stage cooling, and what are the benefits?



Two-stage operation means that the heat pump or air conditioner can operate at a fraction or its maximum capacity on milder days, and full capacity only when needed. This results in longer system cycle times, lower sound levels, more consistent indoor temperatures, and enhanced dehumidification.

What is a variable speed compressor?



This refers to the type of compressor in your air conditioner or heat pump. When combined with a variable speed indoor air handler or furnace, it creates the cooling capacity for your system. Variable speed compressors allow a unit to run at virtually any speed between 30% and 100% based on the needs of the conditioned space at any point in time. This ensures maximum efficiency, comfort, and dehumidification rates.

What is a heat pump?



A heat pump is like a central air conditioner, but includes a reversing valve that allows the system to provide winter heating in a single efficient package. There are several heat type types:

  • Ducted split heat pump: The most common heat pump system includes and outdoor unit, combined with an indoor air handler or furnace.
  • Ductless mini split heat pumps: Typically an advanced variable speed, highly flexible heat pump system that combines and outdoor unit combined with one or more indoor units.
  • Geothermal or ground source heat pump: A heat pump system that utilizes a ground loop as the outdoor source of energy in heating season, and as a thermal dump in summer. Because ground temperatures are far more consistent and moderate than air temperatures, ground source heat pumps are generally more efficient than air source heat pumps.
  • Dual fuel heat pump System: an air source heat pump, typically combined with a gas furnace. The heat pump provides efficient heating during moderate winter weather. During more extreme cold the gas furnace takes over the heating load for the conditioned space.

What is system zoning?



System zoning allows different parts of a conditioned space to be controlled independently with their own thermostat and operating conditions. The primary benefits of system zoning are improved comfort and energy savings. There a four common ways to provide system zoning in a conditioned space:

  • Ducted systems with zone dampers: Dampers within a duct system allow airflow to a portion the heating and cooling system to be regulated and redirected air to specific areas of the home. Each zone is controlled with its own thermostat.
  • Multi-zone mini split heat pump systems: A single outdoor heat pump unit feeding heating and cooling to two or more indoor units that are control independently.
  • Heat only hydronic systems: A natural gas, LP, or oil boiler, combined with an indoor distribution system that includes two or more heating zones. Heating zones can each be controlled by their own thermostat and controlled either by zone valve, or zone pumps. Distribution methods can be combined, and include hot water baseboard, hydronic unit heaters, or radiant floor heating.
  • Heating and cooling hydronic systems: A natural gas, LP, or oil boiler, combined with two or more ducted hydronic air handlers, also typical containing refrigerant based cooling coils for summer comfort. Outdoor condenser(s) are added to provide summer cooling operation.

What is the best way to size my central air conditioning system?



  • For a system replacement replacement: The last thing you should do is replace your existing AC system with one with the same capacity. Many existing AC systems are significantly oversized. An oversized air conditioning system results in a more uncomfortable indoor environment with wide temperature swings, large temperature differences from room to room, noisier operation, and significantly poorer indoor dehumidification. If you are considering a AC system replacement, make sure your contractor carefully evaluates your application and performs a complete, accurate air conditioning design load in order to size your system.
  • For new construction, heat gains are typically much smaller than in the past. Make sure your contractor performs a room by room heat loss / gain to ensure that your heating and cooling system is properly sized in every room.
  • Bigger is NOT better when it comes to heating and cooling. Most air conditioning systems are over-sized. An oversized furnace is noisier and less comfortable, louder, and less efficient. An oversized cooling system will also not dehumidify properly.

Can central air conditioning be added to any existing home?



  • If you have an existing duct system, there is a great chance conventional split central air conditioning can be added. You definitely should have a training HVAC technician evaluate your duct system, and do a proper room by room heat gain in order to ensure a properly designed system.
  • If you do not have an existing duct system, great central air conditioning is still within reach with a ductless mini split system from Mitsubishi. These single or multi-zone systems only require a 3" lineset between the indoor and outdoor system. They come in either a single zone system, or are available with up to 8 indoor zones from a single outdoor unit.

How long does a typical air conditioning system last?



Many air conditioners can last 15 to 20 years, if maintained properly.

How is air conditioning efficiency measured?



Central air conditioning efficiency is measure by the SEER (Seasonal Energy Efficiency Ratio) rating. The SEER rating is derived by dividing the annual estimate cooling output (in btus) by the electric energy input. The higher the ratio, the more efficient the AC system. The United States Department of Energy (DOE) requires all new air conditioning units to meet minimum efficiency ratings identified by these SEER numbers.

I have an older central AC system. Event though it's still operating, should I consider replacing it now?



  • If your existing system is 10 - 15 years old, or older, it is likely nearing the end of its service life, and it is significant more expensive to operate than a new system would be. A system installed more than ten years ago probably has a rated SEER efficiency (Seasonal Energy Efficiency Ratio) of 10.0 or less. New Lennox air systems are available with SEERS as high as 26.0. So a new AC system reduce operating cost by 50% or more.
  • If your existing AC system dates back to about 2004 or earlier, you system may operate with an obsolete refrigerant (R22). R22 is damaging to the environment, and can not be economically serviced in a residential application so you should strongly consider a system upgrade.
  • A planned AC system replacement will probably save you money on the cost of the replacement system. Performing an emergency air conditioner replacement during the peak of summer heat may require overtime labor. Replacing your system in a scheduled fashion during regular business hours will ensure an efficient installation process.

Will I have to replace my indoor coil if I upgrade my outdoor air conditioner?



In general you should replace both the outdoor and indoor sections of your AC system during a replacement.

  • Current AC systems are rated as "matched systems." This means that in order to operate a peak efficiency, the indoor unit and the outdoor unit need to be design to work together. If you have an older existing AC system, your indoor coil is definitely design for a less efficient system, and will not provided appropriate efficiency with a new outdoor unit.
  • Your older system my be design for older R22 refrigerant. R22 coils are not appropriate form use with modern R410A systems.

How often should I have my AC system professionally serviced?



All air conditioning manufacturers recommend that your AC is serviced every year by a trained HVAC professional. If used as part of a complete heating and cooling system, it should be serviced in both the spring and the fall. Annual maintenance, including a thorough examination and cleaning of the parts that commonly malfunction, like the air filter, the outdoor fan, the indoor blower, the refrigerant lines, and any condensation removal systems will ensure safe operation, prolong equipment life, and sharply reduce the possibility of unanticipated failures.

If my AC system isn't running, can I fix it myself?



There are things you can check if your AC system does not turn on properly:

Check System Power:

  • Check you circuit breaker panel to ensure that your heating system breaker is "ON".
  • Check your indoor furnace or air handler system switch. Make sure your "SYSTEM SWITCH" is set to "ON". This switch is typically a traditional toggle switch that may have a RED cover-plate.

Thermostat Settings:

  • Make sure your thermostat is "ON", is set to "COOL", and the desired room temperature is set lower than the current ambient temperature.
  • Batteries: If your thermostat has batteries, change them now.

Indoor Airflow Issues:

  • Is your furnace or air handler filter clean? Change your furnace filter and re-start your system.
  • Check your duct system inlets and outlets. Are almost all open and clear of obstructions?

Other Issues:

  • If you thermostat or the system power was off, after turning the system on give it a few minutes; many AC systems have a time-delay function on start-up.
  • If your system is blowing cool air, but not cooling as well as it should, check your outdoor unit to ensure there is nothing blocking airflow through the outdoor coil. PLEASE NOTE: Be very careful not to damage the fines on your outdoor coil and call us if you need help!
  • If your AC system utilizes a condensate pump, check if to make sure that it is not completely full or water. If it is check the power to the condensate pump. Then if possible empty the condensate pump. If the AC system restarts you may need to have a professional AC tech replace the condensate pump.

My air conditioning system starts up and runs for a while, but then ice or frost forms on my indoor coil and refrigerant lines. Why?



This is often caused by a lack of airflow across the indoor coil during cooling operation. Check and change your indoor air filter. Check to make sure that almost all of your indoor grills are registers are open and clear. If it turns out that the filter or closed registers was the problem, turn the system on to "Fan Only" for a few minutes to speed up the thawing of your indoor coil before restarting your AC system.