DAVIS Energy EnviroMonitor: Console - Manual (Page 14)

Weather Conditions Measured/Calculated
Energy EnviroMonitor Manual Page 7
Heating Degree-Days
Heating degree-days provide a measure for calculating the effect of tempera-
ture on the use of energy to heat a location. Essentially the opposite of cooling
degree-days, heating degree-days take into account the accumulation of cold
with passing time to calculate energy usage. One heating degree-day accumu-
lates when the temperature remains one degree below the threshold for 24
hours. One heating degree day
also accumulates when the temperature remains
24˚ below the threshold for 1 hour. The Energy EM calculates both normal heat-
ing degree-days and wind chill heating degree-days. Wind chill heating
degree-days uses apparent temperature (see “Temperature and Apparent Tem-
perature” on page 7) instead of outside temperature when calculating heating
degree-days.
• “Daily” Heating Degree-Days Sum (AutoClear)
• Heating Degree-Days Total for the period (Alarm: High/Low)
• Average Daily Heating Degree-Days over the period
• “Daily” Wind Chill Heating Degree-Days Sum (AutoClear)
• Wind Chill Heating Degree-Days Total for the period (Alarm: High/Low)
• Average Daily Wind Chill Heating Degree-Days over the period
Temperature and Apparent Temperature
The Energy EM has a temperature sensor built into the console which reports
inside temperature. You may use either the external temperature sensor, stain-
less steel temperature probe, or external temperature/humidity sensor (see
“Optional Sensors” on page 1) to measure outside temperature. Outside tem-
perature does not necessarily have to measure outside temperature, of course.
It measures the air temperature wherever you have located your temperature
sensor.
Temperature-humidity index (T-H index), commonly called heat stress, uses
the temperature and the relative humidity to determine how hot the air tem-
perature actually “feels.” When humidity is low, the apparent temperature will
be cooler than the air temperature since perspiration can rapidly evaporate into
the air. However, when humidity is high (i.e., the air is saturated with water
vapor) the apparent temperature will be higher than the air temperature.
Note: The Energy EM measures T-H index only when air temperature is above 68˚ F (20˚ C) because it is
a measure of heat stress which is not significant at lower temperatures. 125˚ F (52˚ C) is the high-
est T-H index for which calculation factors are available. Above 125˚ F (52˚ C), the system simply
reports that T-H index is “high.”