3 Minute Read
| Overview
With the 75F system usage globalization implemented, installers, facility managers, and users are allowed to set the preferred units for visualizing the building-level parameter data. Following this, the 75 system had the challenge to address.
The challenge is to convert and round off values from Fahrenheit to Celsius and vice versa, keeping the actual integrity of the preexisted system.
| Challenges Faced
The challenges faced were around the desired temperature, current temperature, and the tuners rounding off.
The desired temperature setting options in the devices and portals were programmed to increment or decrement in 0.5 Fahrenheit and when the similar increment and decrements were allowed for the Celsius mode of operation, the resultant values did not satisfy the conditions for a dual set point temperatures concept of the system (the 70F-74F, heating desired and cooling desired temperature concept).
To solve this, a reasonable rounding-off technique for the converted values had to be introduced.
| Rounding Off Strategy for Desired and Current Temperatures
The Rounding off a strategy that was implemented is a HALF_UP or HALF_DOWN rounding to be taken for Desired Temp changes.
Where the converted values are rounded off to the closest upward whole number when the converted value is with a .6/.7/ .8/.9
And at times the converted values are rounded off to the closest downward whole number when the converted value is with a .1/.2
Lastly, when the converted value is with a .3/.4 it gets rounded off to a .5
Below is a Common Conversion and round-off examples for current and desired temperature conversions when the values are converted from Fahrenheit to Celsius:
Fahrenheit Value |
Celsius Value |
Current Temp Round Off Value |
Desired Temp Round Off Value [0.5 based] |
Precision Percent Lost [Percent error] |
75F |
23.8889C |
23.9C |
24C |
0.41666666666667% error |
67.5F |
19.72222C |
19.7C |
20C |
1.5% error |
70.3F |
21.27778C |
21.3C |
21.5C |
0.93023255813953% error |
70.1F |
21.16667C |
21.2C |
21C |
0.95238095238095% |
50.4F |
10.22222C |
10.2C |
10C |
2% |
30F |
-1.11111C |
-1.1C |
-1.0C |
10% |
100F |
37.7778C |
37.8C |
38.0C |
0.52631578947369% error |
110F |
43.3333C |
43.3C |
43.5C |
0.45977011494254% error |
Below is a Common Conversion and round-off examples for current and desired temperature conversions when the values are converted from Celsius to Fahrenheit:
Celsius Value |
Current Temp Fahrenheit Value |
Desired Temp F Round Off Value [ O.5 based] |
Precision Percent Lost [Percent error] |
23C |
73.4F |
73.5F |
0.1360544217687% error |
23.5C |
74.3F |
74.5F |
0.26845637583893% error |
20C |
68F |
68F |
0% |
20.5C |
68.9F |
69F |
0.14492753623188% error |
26C |
78.8F |
79F |
0.25316455696203% error |
26.5C |
79.7F |
80F |
0.375% error |
28C |
82.4F |
82.5F |
0.12121212121211% error |
20.3C |
68.54F |
68.5F |
0.058394160583951% |
| Rounding Off Strategy for the System and Zone Level Tuners
When it comes to the tuners which deal with the temperature values, the conversion for the tuner values from Fahrenheit to Celsius is handled using the below concepts.
There are two kinds of conversions that are implemented, for the user preference of temperature for the tuners.
- Absolute Value
- Relative Value
The below table explains the concepts of absolute value and relative values with examples
Absolute Value: For tuners like the CoolingAirflowTemp, HeatingAirflowTemp, etc. which refers to one particular value which is absolute and there is no comparison involved, thus the conversion is done in the standard way as in the example. |
Example: CoolingAirflowTemp (⁰F) = 60 ⁰F; now to convert the same to Celsius it uses formula C = 5/9 x (F-32). Therefore, the CoolingAirflowTemp in (⁰C) = 16 ⁰C (approximated to the nearest whole number as per the Fahrenheit to Celsius Conversion of Current and desired temperature table shown above) |
Relative Values: For tuners like the coolingDeadband, unoccupiedZoneSetback, etc. which refer to a range and not a particular value and are thus considered relative, the conversion is done in as in the example |
Example: unoccupiedZoneSetback (⁰F) = 2 ⁰F; now to convert the same to Celsius it uses the formula C = F/1.8. Therefore, the unoccupiedZoneSetback in (⁰C) = 1 ⁰C (approximated to the nearest whole number as per Fahrenheit to Celsius Conversion of Current and desired temperature table shown above) |
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