W8710A EQUIPMENT MONITORING SYSTEM
68-0256
14
5.
When the temperature rise between the return and sup-
ply sensors is measured and is higher than 75°F, a High
D/T Alert Report is generated.
6.
When the temperature rise between the return and sup-
ply sensors is measured and is lower than 35°F, a Low
D/T Alert Report is generated.
7.
For cooling systems, the calculated temperature fall, D/
T, of air passing over the evaporator coil varies depend-
ing on the percentage of relative humidity. In this exam-
ple, the calculated cooling D/T is 18°F at 50 percent
humidity.
8.
As the relative humidity decreases, the sensible cooling
temperature increases. For example, at 50 percent rela-
tive humidity, the computer calculates that the system
temperature difference is 18°F. If the relative humidity is
lower than 50 percent, the temperature difference is
greater than 18°F.
Supply Air
Temperature
-20 Tolerance Range
Calculated 55
Temperature Rise
Return Air
Temperature
+20 Tolerance Range
Above 75
High D/T Alert Report
75
Gas Heat
Supply Air
Temperature
-20 Tolerance Range
Calculated 55
Temperature Rise
Return Air
Temperature
+20 Tolerance Range
Below 35
Low D/T Alert Report
35
Gas Heat
Supply Air
Temperature
Return Air
Temperature
0%
50%
Relative Humidity
100%
18 Calculated
Temperature Fall
Cooling
Supply Air
Temperature
Return Air
Temperature
0%
50%
Relative Humidity
100%
Calculated
Temperature Fall
Changes with
% Relative Humidity
Cooling
