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The lower and upper limits must differ by at least three degrees. We recommend a six-degree separation. Most users don’t notice a few degrees of
difference as long as they are inside their comfort range. However, one degree outside the comfort range can be uncomfortable. Therefore, the
system’s priority is to keep every room inside its comfort range. This means that sometimes a room may be heated even if it is a few degrees above
its lower limit. Or it may be cooled when it is few degrees below it upper limit. It may receive circulation even if it is in the middle of its comfort
range. The reasons for this are described in the following section.
A narrow comfort range uses more energy than a wide comfort range. When there is only a few degrees between a
call for heating and a call for cooling, the HVAC equipment may heat a few rooms for a few minutes, then
immediately cool a few other rooms for a few minutes, then heat, then cool, and so on. The system does its best to
satisfy all comfort ranges, which may use a lot of energy. Most people prefer at least a few hours between heating and
cooling cycles. We recommend using the widest comfort range that maintains your comfort. This saves the most
energy. Many people use at least a six-degree range.
As outdoor temperatures decrease, rooms start to approach their lower limits. As outdoor temperatures increase,
rooms approach their upper limits. During transition seasons when little heating or cooling is needed, the rooms are
more evenly spread between their upper and lower limits.
One Thermometer Versus Many Temperature Sensors
A conventional thermostat has a thermometer plus controls for setting the temperature you desire. For heating, you use the controls to set the
temperature at which you want heating to start. When the thermometer reports a temperature below the set temperature, the thermostat calls for
heat. The thermostat continues to call for heat until the thermometer reports that the temperature is above the set temperature. With a
conventional thermostat, the temperature sensing is in the same location as the thermostat. Therefore, the area around the conventional thermostat
is the only area within the home with accurate temperature control.
Important Concepts
We recommend
using the widest
comfort range
that maintains
your comfort.
(continued)
