Trane CNT-SVX07C-EN, Zone Controller, N512 AI4 Universal 4-20 mA, Configuration Measurement range

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 low-coil-temperature protection when the fan is off. The controller enters the freeze avoidance mode when the outdoor air temperature is below the freeze avoidance setpoint (config- urable using the Rover service tool). (For more information, see “Freeze avoidance” on page 50.)

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 4–20 mA input	0–100%
	(4 mA=0%; 20 mA=100%)
CO2 measurement	0–2000 ppm
	(4 mA=0 ppm; 20 mA=2000 ppm)
Relative humidity (RH) measurement	0–100%
	(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 4–20 mA sensor must be hard- wired to the AI4 terminal. (Wiring is dependent on the specific applica- tion.) The sensor communicates a value of 0–100% to the BAS. This con- figuration has no direct effect on Tracer ZN521 operation. If a valid value

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