GESTRA TRS 5-50 Safety Temperature Limiter, SIL 3

A SIL 3 safety temperature limiter for boiler superheaters and hot-water plants

The GESTRA TRS 5-50 is a temperature switch used with a Pt 100 sensor of the TRG 5-6.. family as a safety temperature limiter or monitor in steam boilers and pressurised hot-water plants. When the maximum admissible temperature in a superheater or inlet line is reached, it opens its safety circuit and switches the heating off. Two seven-segment LED displays show the adjusted switch-off temperature TMAX and the actual temperature, and the rotary button sets the limit, simulates an alarm and resets the device.

It is configured as a safety temperature monitor, which closes the safety circuit again once the temperature has fallen below a fixed hysteresis, or as a safety temperature limiter, which interlocks the heating off until it is reset manually or externally. The companion type TRS 5-52 covers a different sensor group.

Technical specifications

An automatic self-test monitors the safety functions in the switch and the sensor. A fault in the sensor, wiring or switch is shown on the display and the output contacts open, so the heating is switched off. The equipment must not be used in potentially explosive areas.

Wiring and commissioning points

Feed the switch from a SELV 24 V DC supply where the DC version is used, and use screened multi-core cable of at least 0.5 mm2, for example LiYCY 4 x 0.5 mm2, up to 100 m to the sensor. When the unit is used as a safety temperature limiter to EN 12952 or EN 12953, a wire link is fitted on site on the safety-circuit terminals so that the interlock applies. The actuator, such as an auxiliary contactor in the safety circuit, is installation specific and must be considered separately in the SIL calculation for the whole safety function.

Other boiler safety and level equipment is listed under temperature instrumentation and level instrumentation.

How the GESTRA TRS 5-50 works

A Pt 100 sensor sends its resistance to the TRS 5-50 over a three-wire line. The device turns that signal into a temperature and compares it with the limit set on the rotary button. When the limit is reached, the safety circuit opens and the heating is switched off. Two LED displays show the limit and the actual value.

Where the TRS 5-50 is used

• Steam boiler superheaters
• Superheater inlet lines
• Pressurised hot-water plants
• Heating systems that need a safety cut-off
• Plants that follow EN 12952 or EN 12953

Selection checklist for the TRS 5-50

• Limiter or monitor function
• Matching TRG 5-6.. sensor type
• Switch-off temperature needed
• Supply voltage, 24 V DC or 100-240 V AC
• Number of safety contacts
• Need for a 4-20 mA output
• External test and reset buttons
• Panel space for the housing

Installation, commissioning and maintenance notes for the TRS 5-50

Wire the Pt 100 sensor with three poles and the screen. Connect the supply with the external fuse. Set the switch-off temperature with the rotary button. Use the alarm simulation to check that the heating switches off. Repeat the function test at each proof test interval.

Requesting a quotation for the GESTRA TRS 5-50

Please send the sensor type, the limit temperature and the supply voltage. Seven Star LLC serves industrial customers in Oman and the GCC and replies with a quotation based on the information provided.

TRS 5-50 sensor input

The TRS 5-50 takes one Pt 100 input from a TRG 5-63 to 5-68 sensor.

TRS 5-50 limit range

The limit range is 0 to 600 degrees C.

TRS 5-50 hysteresis

The switchpoint hysteresis is minus 2 degrees C and fixed.

TRS 5-50 safety circuit

The safety circuit has two volt-free make contacts.

TRS 5-50 contact rating

The contacts carry 6 A at 250 V AC.

TRS 5-50 supply voltage

It runs on 24 V DC or on 100 to 240 V AC.

TRS 5-50 display

Two three-digit LED displays show TMAX and the actual temperature.

TRS 5-50 signal output

A semiconductor output gives 24 V DC at up to 100 mA.

TRS 5-50 analog output

An optional 4-20 mA output covers 0 to 650 degrees C.

TRS 5-50 operation

One rotary button sets the limit, simulates an alarm and resets the device.

TRS 5-50 monitor function

As a monitor, it closes the safety circuit again once the temperature falls below the hysteresis.

TRS 5-50 limiter function

As a limiter, it keeps the heating off until a manual or external reset.

Safety records for the TRS 5-50

Record the set limit, the sensor serial number and the date of each proof test.

Choosing the right TRS 5-50 function

Choose the limiter function where the heating must stay off until an operator resets it.

Documents and quotation

The attached GESTRA data sheet 819216 lists the safety figures, technical data and order specification. Send the sensor type, supply voltage, whether a limiter or monitor function is needed and any 4-20 mA output requirement for a quotation, and confirm approvals for your boiler code before ordering.