The TECSYSTEM T538 is a temperature alarm unit designed for monitoring and protection applications, particularly for transformers. It functions as a protection relay, continuously monitoring temperatures and triggering alarms or trips when predefined thresholds are exceeded. The device is designed for panel mounting and features a digital display for temperature visualization and programming.

Function Description:

The T538 unit primarily serves as a temperature alarm and trip unit. It accepts inputs from Pt100 RTD sensors, allowing it to monitor temperatures across multiple channels. The device is equipped with two alarm relays (ALARM-TRIP) and one alarm relay for sensor fault or working anomaly (FAULT). These relays can be programmed for either Fail Safe or NO Fail Safe operation, providing flexibility in how the system reacts to temperature excursions or sensor issues.

The unit features a 13mm high, 3-digit display for showing temperatures and 8 LEDs to indicate the reference channel, alarm/trip status, and fault conditions. It supports temperature monitoring from 0°C to 240°C and allows for two alarm thresholds to be set for each input channel. Sensor diagnostics (Fcc-Foc-Fcd) are integrated to detect damaged Pt100 sensors.

Programming of the T538 is performed via frontal push buttons, allowing users to set alarm limits, configure relay functions, and manage other operational parameters. The device also includes features such as automatic output from the programming cycle after 1 minute of inactivity, automatic display of programmed data, and the ability to set manual channel scanning or display the hottest channel. It can store maximum temperatures and supports a programmable number of channels.

An optional AUX.1 relay (FAN) can be integrated, with its values for FAN OFF and FAN ON set during the programming procedure. The unit also offers an optional RS232/485 Modbus® RTU output for communication, enabling integration into larger control systems.

Important Technical Specifications:

Auxiliary Power Supply:
- Rated voltage: 24-240 Vac-dc
- Maximum ratings: 20-270 Vac-dc
- Vdc with reversible polarities
Inputs:
- 8 inputs RTD Pt100 sensors (3-wires, removable rear terminals).
- Input channels protected against electromagnetic noises and spikes.
- Sensor cable compensation up to 500 m (1mm²).
- Optional: 8 analog inputs 4-20 mA (range 0-240°C).
Outputs:
- 2 alarm relays (ALARM-TRIP).
- 1 alarm relay for sensor fault or working anomaly (FAULT).
- Output contacts capacity: 5A-250Vac res.
- Arranged for output relays test.
- ALARM & TRIP programming for Fail Safe and NO Fail safe.
- Optional: Relay AUX.1 (FAN).
Displaying and Data Management:
- 1 display, 13mm high, 3 digits for displaying temperatures.
- 8 LEDs for displaying reference channel.
- 8 LEDs indicating alarm or trip.
- LED indicating fault.
- Temperature monitoring from 0°C to 240°C.
- 2 alarm thresholds for each input.
- Sensors diagnostic (Fcc-Foc-Fcd).
- Maximum temperatures storage.
Tests and Performances:
- Assembling in accordance with CE rules.
- Protection against electrical and magnetic noises: CEI-EN50081-2/50082-2.
- Dielectric strength: 2500 Vac for 1 min. (relays to sensors, relays to power supply, power supply to sensors).
- Accuracy: ± 1% full scale, ± 1 digit.
- Ambient operating temperature: -20°C to +60°C.
- Humidity: 90% no-condensing.
- Housing: ABS self-extinguishing NORYL 94VO.
- Burden: 3VA.
- Data storage: 10 years minimum.
- Digital linearity of sensors signal.
- Self-diagnostic circuit.
- Optional: Protection treatment of electronic part.
- Optional: Frontal plastic protection.
Dimensions:
- 96x96mm-DIN43700-Prof. 150mm (with rear terminals).
- Panel cutout: 92x92mm.
Communication:
- Optional: Output RS232/485 Modbus® RTU.

Usage Features:

Mounting: The unit is designed for panel mounting, secured by fixing blocks.
Power Supply: The T538 has a universal power supply (24-240 Vac-dc), which simplifies installation. It's crucial to ensure the correct Vac or Vdc power supply is provided and that the ground cable is firmly fixed. The unit is protected against high-intensity overvoltage.
Electrical Connections: Connections are made via a removable terminal board. It's important to ensure correct wiring for Pt100 sensors, power supply, and output relays. The manual provides detailed diagrams for these connections, including specific terminals for each channel, power supply, and communication interfaces.
Programming: The device can be programmed using the frontal push buttons (PRG/SET, ▲, ▼, ENT/RESET). The programming sequence allows setting alarm and trip limits, configuring Baud rate for communication, setting RS485 address, and defining fail-safe functions for relays. A "HOLD FUNCTION" (HLD-YES/NO) can be set to keep ALARM and TRIP relays energized until manual reset, even if the temperature falls below the alarm thresholds.
Display Modes: The display can show the hottest channel (HOT), manually scan channels (MAN), display the maximum temperature reached (TMAX), or automatically scan channels every 2 seconds (SCAN).
Alarm Relays Test: A built-in test function allows users to verify the working status of the relays (Fan, Flt, Alr, TrP) by pushing the TEST button for 5 seconds.
Alarm Relay Exclusion: The alarm signal can be temporarily excluded by pushing RESET. The relay de-energizes, and its LED lightens. The exclusion system automatically disconnects when the temperature falls below the ALARM threshold.

Maintenance Features:

Faults Diagnostic: The manual provides a comprehensive table for diagnosing common faults and their remedies. This includes issues like the unit not switching on, damaged sensors (FOC=sensor open, FCC=sensor in short circuit), relays energizing during main switch maneuvers, wrong temperature indications, and power supply problems.
Sensor Cable Requirements: All Pt100 measure signal transport cables must be separated from power cables, shielded with twisted conductors, have a minimum section of 0.5 mm², be firmly fixed, and have tinned or silvered conductors. TECSYSTEM offers a special cable (mod. CT-ES) meeting these requirements.
Warranty: The unit comes with a 12-month warranty from the delivery date, covering production faults or insufficient calibration. The warranty is void if the unit is tampered with, damaged by wrong sensor connection or power supply, operated outside working limits, or affected by excessive transitory voltages.
Test Description: The unit undergoes several tests during production, including PC board test, input test, relay contacts and outputs test, key test, lamp test, calibration at 100 and 200°C (Range 0-240°C), software test, and a minimum 24-hour burn-in test.
Programming Rehabilitation: In case of a blocked programming (Prg no), a specific procedure involving pushing PRG and keeping TEST pushed is provided to re-enter the programming mode.

TECSYSTEM T538 - Page 2

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