GENERAL | Technical Reference
AOTA72LALT / AOTA90LALT External Input & Output
Low noise, peak cut, error status, compressor status and base heater connections
Electrical safety: This work must only be completed by appropriately qualified personnel. Isolate the outdoor unit before connecting or disconnecting plugs, and verify all field wiring against the applicable installation manual and local electrical requirements.
Applicable outdoor units: AOTA72LALT and AOTA90LALT. External input and output functions require the correct connector, field wiring and outdoor PCB configuration.
1. Connection summary
| Function | Type | Connector | Purpose |
|---|---|---|---|
| Low noise mode | Input | CN131 | Reduces outdoor unit operating sound. |
| Peak cut mode | Input | CN131 | Limits compressor current and power demand. |
| Error status | Output | CN136 | Provides an external fault/alarm indication. |
| Compressor status | Output | CN136 | Indicates whether the compressor is operating. |
| Base heater | Output | CN115 | Energises a base heater in low ambient conditions. |
2. External input functions — CN131
2.1 Low noise mode
Low noise mode reduces the operating sound of the outdoor unit. It is activated by applying an external contact signal from a timer, BMS interface or maintained ON/OFF switch.
| Input ON | Low noise mode active |
| Input OFF | Normal operation |
| Performance note | Available capacity may reduce depending on outdoor temperature and load. |
2.2 Peak cut mode
Peak cut mode suppresses the outdoor unit current value. It is enabled through the same external input connector arrangement as low noise mode.
| Input ON | Peak cut mode active |
| Input OFF | Normal operation |
| Configuration | Set the required peak cut level using the outdoor PCB push-switch settings. |
CN131 electrical requirements
Supply voltage: DC 5–24 V
Current capacity: approximately 100 mA
Switch contact: maintained-contact switch rated for at least DC 10 mA
Maximum distance from PCB to connected device: 10 m
Supply voltage: DC 5–24 V
Current capacity: approximately 100 mA
Switch contact: maintained-contact switch rated for at least DC 10 mA
Maximum distance from PCB to connected device: 10 m
| Control voltage | Recommended resistor |
|---|---|
| DC 5 V | 470 Ω, 1/4 W |
| DC 12 V | 1 kΩ, 1/4 W |
| DC 24 V | 2.2 kΩ, 1/4 W |
Important: The input circuit is field powered. Insulate any unused conductor individually. Do not apply voltage outside the stated range.
Optional input lead: UTY-XWZXZ2 — red / white / black.
3. External output functions — CN136
3.1 Error status output
Provides a signal to an external monitoring device when the outdoor unit detects an air-conditioning fault.
| System condition | Output |
|---|---|
| Normal | OFF |
| Error / alarm | ON |
3.2 Compressor status output
Provides a signal showing whether the compressor is operating.
| Compressor condition | Output |
|---|---|
| Operating | ON |
| Stopped | OFF |
CN136 output limits
External supply voltage: DC 24 V or less
Maximum load: DC 20 mA or less
Maximum cable length: 10 m
Optional output lead: UTY-XWZXZ2 — red / white / black
External supply voltage: DC 24 V or less
Maximum load: DC 20 mA or less
Maximum cable length: 10 m
Optional output lead: UTY-XWZXZ2 — red / white / black
4. Base heater output — CN115
The base heater output is intended to operate a heater that reduces ice accumulation in the outdoor unit base.
| Output ON | Outdoor temperature falls to approximately 2°C or below |
| Output OFF | Outdoor temperature rises to approximately 4°C |
| Supply | AC 240 V |
| Direct-connected load | 25 W or less |
| Connector pins | Connect to pins 1 and 3 only. Do not connect pins 2 and 4. |
Loads above 25 W: Do not connect the heater directly to CN115. Use the output to operate a correctly rated contactor or relay, with the heater supplied through an appropriate external circuit.
| Field-supplied item | Specification |
|---|---|
| Connector housing | VHR-4V-BK |
| Contact pins | SVH-21T-P1.1 × 2 |
| Wire | Select wire size to suit the connected load and installation requirements. |
5. Installation and commissioning checklist
| 1 | Confirm the exact outdoor model and applicable connector location. |
| 2 | Isolate power before connecting CN131, CN136 or CN115. |
| 3 | Confirm the external power supply and load are within the published limits. |
| 4 | Keep input and output wiring within 10 m of the outdoor PCB unless otherwise approved. |
| 5 | Insulate all unused conductors separately and secure wiring away from sharp edges and high-temperature components. |
| 6 | Set low noise or peak cut levels using the outdoor PCB push-switch procedure. |
| 7 | Function-test each input and output and confirm the expected ON/OFF state. |
| 8 | Record connector, function, control voltage, field-device details and test results in the job notes. |
Key takeaway: CN131 is used for low noise and peak cut inputs, CN136 provides error and compressor status outputs, and CN115 supplies the base heater output. Correct field power, load limits and PCB setup are essential.