Emergency Heat Indicator:
Many thermostats come with a light that turns ON when the emergency heat is ON
(indicating the heat pump isn't working when it should). This is a desirable
feature because it will let you know immediately when your heat pump needs
repair. NOTE: The terms "emergency heat", "auxiliary heat", and "supplemental
heat" are often used somewhat interchangeably since they all refer to the
heating unit that adds to, or takes over for, the heat pump when needed. Supplemental Heat Indicator:
This lets you know when the supplemental heat is ON. Unlike emergency heat,
supplemental heat is a normal occurrence. Supplemental Heat Lockout:
If you want to keep your heating costs low, it's important that your
supplemental heat does not come on when it's not needed. There are two ways to
prevent unneeded use of supplemental heat: 1) Outdoor thermostats sense the
outdoor temperature and lock out the supplemental heat unless the temperature
drops below a preset point. 2) Certain microprocessor-controlled thermostats
allow the heat pump to "ramp-up" to the desired temperature but won't turn on
the supplemental heat unless the heat pump alone is unable to keep the home up
to the desired temperature. Staging Supplemental Heat:
Staging refers to turning the supplemental heat on in two or more phases.
Important benefits of this are: it's more comfortable and staging may reduce
the on/off cycles of the heat pump, which can increase the longevity of the
heat pump compressor. Defrost Controls: There
are many types of defrost controls, but they can be grouped into two
categories. Time and temperature controls activate the defrost cycle at
specified intervals whenever the outdoor temperature reaches a predetermined
point (unfortunately, there may not actually be frost during the times
specified). Demand controls actually detect the presence of frost on the
outdoor coil. High Pressure Switch/Low Pressure Switch:
A heat pump should have refrigerant pressure sensors to prevent compressor
damage. Air Filter: Two popular
options are to use an "electrostatic" or an "electronic" air cleaner. These
types of filters can remove small particles from the air, including pollens. A
High Efficiency Particulate Air (HEPA) filter is a replaceable filter that also
removes very small particles. HEPA filters have a greater resistance to airflow
than other filters, which needs to be accounted for in the system design. Variable Speed Heat Pumps:
These are relatively new on the market. They're called variable speed because
they adjust output to match the requirements of the home. Scroll Compressor: Another
new heat pump development is a type of compressor called a scroll compressor.
It uses a rotary motion that reduces noise and has higher efficiencies at lower
outside temperatures.
