Understanding Variable Speed Cooling

July 17, 2019by admin0

Variable speed cooling provides maximum comfort for your home. It is a technology that has been available for sometime, but in the last 5 years has been truly embraced by HVAC manufacturers. In time, all air conditioners will become variable speed, allowing them to match cooling loads precisely. Like a modulating furnace, or the inverter technology used in ductless systems, a variable speed compressor communicates with the fan in your furnace as it changes speeds.  “Variable speed” refers to the speed at which the compressor outside, and fan portion of your furnace are operating – thereby controlling the flow and frequency of air that is generated – supplying cool or temperate air throughout your entire home. They run longer, usually at lower capacities, moving cool air to the far reaches of your home. Because of their longer runtimes and often slower speeds, variable speed ACs are amazing dehumidifiers. They are also very quiet and have SEER levels of 18+.  Unlike a single stage AC, a variable speed compressor can move in increments as small as 0.1% in a range from 30%-100% capacity; that’s 700 Stages!!!

When you decrease them temp on your thermostat by half a degree, a single stage air conditioner comes on at full blast, often overcooling the space and not running long enough to dehumidify. For such a small delta, a variable speed compressor will come on at only a very low capacity (say 30%) and the blower in your furnace will also move at a low speed. This means that temperature in your home rarely would be more than half a degree away from setpoint, and humidity will always be in check. For a higher delta, the VS compressor engages to make a more significant temperature adjustment and the fan increases its speed and air flow accordingly to ensure that cool air enters your rooms at an increased rate.  This air flow variability ensures even temperatures and an overall, more comfortable cooling solution.

Variable Speed Air Conditioners:

Utilize Communicating Technology

They must be paired with a communicating furnace or air handler, with a digitally controlled variable speed ECM blower motor. They must also be paired with a properly matched communicating control (thermostat).

Provide the benefit of “zoning” in your home

Variable speed air conditioners lend themselves to homes with zoning dampers installed. Because they can run at such low capacities, if only a single zone requires cooling, the AC can match the load precisely.


Master humidity challenges

When coupled with a smart thermostat, variable speed air conditioners allow you to more precisely control the amount of humidity in your home during the summer.


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