Analog inputs
Economizing (free cooling) is a function whereby outdoor air is used as a source of cooling before hydronic or DX cooling is used. The Tracer ZN521 uses the outdoor air temperature value to determine whether economiz- ing is feasible. Economizing is not possible without a valid outdoor air temperature. (For more information, see “Economizing (free cooling)” on page 45.)
The outdoor air temperature value is also used for the freeze avoidance function. This function is used for
If AI3 is configured as a generic temperature input, it can be monitored by a BAS. The controller receives the temperature as a resistance signal from a 10 kΩ thermistor wired to analog input AI3. The generic tempera- ture input can be used with any Trane 10 kΩ thermistor. The thermistor can be placed in any location and has no effect on the operation of the con- troller. The controller will generate a Generic Temperature Failure diag- nostic if the input becomes invalid or goes out of range.
Note:
AI3 is not polarity sensitive; you can connect either terminal to either sensor lead.
AI4: Universal 4–20 mA
The AI4 analog input can be configured in one of the three ways shown in Table 5.
Table 5. AI4 configuration options and associated measurement ranges
Configuration | Measurement range |
|
|
Generic | |
| (4 mA=0%; 20 mA=100%) |
|
|
CO2 measurement | |
| (4 mA=0 ppm; 20 mA=2000 ppm) |
|
|
Relative humidity (RH) measurement | |
| (4 mA=0% RH; 20 mA=100% RH) |
|
|
If this input is not needed for an application, configure it as Not Used. This will disable the generation of diagnostics.
Note:
AI4 is polarity sensitive.
For the generic input configuration, a
| 19 |
