nVent RAYCHEM GM-TA Thermostat

Precautions!

The nVent RAYCHEM GM-TA is an electronic thermostat designed to control heating cables for roof and gutter snow melting applications. nVent recommends its use for roof and gutter heating circuits up to a maximum length of 30 meters.

• Electrical installation and commissioning must be performed by authorized personnel.
• Installation and commissioning must comply with local safety and electrical regulations.
• Do not exceed the maximum electrical ratings for the product.

The GM-TA is intended for DIN-Rail mounting within an electrical enclosure for indoor installation. The ambient temperature sensor, GM-TA-AS, should be installed outside the building but protected from direct sunlight.

Functional Description

The heating system activates based on the user-defined temperature range. The control relay switches the heating cable ON when the ambient temperature drops below the set point (default: +2°C). If the temperature falls below a lower temperature set point (e.g., SP1: -10°C), the control relay switches the heating cable OFF.

Installation

The GM-TA thermostat is designed for installation within a distribution panel and requires a 230 Vac electrical supply, in accordance with local electrical regulations. Heating cable and earthing connections must be made as per the circuit wiring diagram (Figure C).

Outdoor installation of the GM-TA thermostat is possible using the nVent GM-TA-OUTDOOR-BOX (PCN 1244-017966), which offers IP65 protection.

The GM-TA-AS sensor must be installed outdoors, securely fastened to a wall (preferably facing north) (Figure B). The sensor connects to the GM-TA thermostat via a sensor cable (e.g., round 3 x 1.5 mm², maximum 100 m).

Display

The thermostat features an A-LED display for temperature and alarm indication.

Display Functions:

• 0 (Off): Heating cable is OFF.
• -On: Heating cable is ON.
• -Blinking: Indicates post-heating or test mode.

Control Buttons:

• 1: Program mode selection ON/OFF.
• 2: Reduce value (change set temperatures).
• 3: Increase value (change of set temperature).

Diagram Description: The front panel shows a 7-segment LED display capable of showing numbers and symbols. Below the display are three buttons: an upward arrow ⬆️, a downward arrow ⬇️, and a 'P' button ?️. The device is labeled "nVent RAYCHEM GM-TA".

Operation

Set Point Adjustment

The operation sequence for setting the temperature involves:

1. Displaying the firmware revision.
2. Entering the temperature set point adjustment mode.
3. Displaying and adjusting the set and actual temperature, which may alternate for 5 seconds.

Diagram Description: A sequence shows the display changing from firmware revision to temperature set point adjustment, then to alternating display of set and actual temperature.

Thermostat Control Relay: On or Off Mode

The thermostat's control relay operates to switch the heating cable ON or OFF based on ambient temperature relative to the set points.

Diagram Description: Visuals illustrate the relay status changing between ON and OFF modes, controlled by temperature conditions.

Parameter Settings (SP1, SP2, SP3) and Test Mode

Accessing and modifying parameters SP1, SP2, SP3, or initiating a test mode involves specific button press sequences, typically held for 6 seconds.

Diagram Description: Sequences of button presses (P, ⬇️, ⬆️) are shown, indicating how to navigate and change settings like low temperature set point (SP1), post-heating time (SP2), sensor correction (SP3), and initiating a 30-minute relay test.

Low Temperature Set Point SP 1

Allows setting the lower temperature threshold, typically between -25°C and -5°C, by pressing the 'P' and '⬇️' buttons for 6 seconds.

Diagram Description: Shows the process of setting SP1 using button presses, with the display indicating the range -25°C to -5°C.

Post Heating Time SP 2

Configures the duration for post-heating, ranging from 0 hours to 3 hours, using the 'P' and '⬆️' buttons for 6 seconds.

Diagram Description: Illustrates setting the post-heating time, with the display showing the 0 hr to 3 hr range.

Sensor Correction Value SP 3

Enables adjustment of the sensor reading by +/- 10 K. This is typically done by pressing the 'P' button twice, followed by '⬇️' and '⬆️' buttons for 6 seconds.

Diagram Description: Depicts the process for setting the sensor correction value, showing the range -10 to 10 K.

Test Control Relay – 30 minutes

Initiates a 30-minute test cycle for the control relay by pressing the 'P' button three times for 6 seconds. A manual test stop is also possible.

Diagram Description: Shows the sequence to start a 30-minute relay test and how to stop it manually.

Technical Data

GM-TA Thermostat (PCN 1244-017783)

Programmable Parameters

Enclosure Thermostat

Ambient Sensor GM-TA-AS (PCN 1244-017965) Included

Approvals

CE, UKCA, RoHS, REACH

Error Codes

Wiring Diagram (Figure C)

Diagram Description: The wiring diagram illustrates the connection of the GM-TA thermostat to a 230V AC power supply. It includes circuit protection (Max 10A, 30mA, 2A) and shows connections for Line (L), Neutral (N), and Protective Earth (PE). The diagram details the terminals for the GM-TA-AS ambient sensor (17-18), the thermostat's internal relay (K1) and alarm output, and the heating cable connections (4-9). It also indicates a maximum cable length of 30m for specific cable types like GM-2X(T), Frostop-Black, or GM-2CW.

Temperature Sensor Data (GM-TA-AS)

The GM-TA-AS ambient sensor uses a 202AT +/-1% NTC 2.0 K @ 25°C type. The resistance (R in kΩ) varies with temperature (TEMP. in °C) as follows: