Phoenix Contact REL-MR-24DC/21AU Plug-in Relay Gold Contact

REL-MR-24DC/21AU: plug-in miniature relay with gold contacts for signal circuits

The Phoenix Contact REL-MR-24DC/21AU (order no. 2961121) is the signal-level variant of the slim REL-MR relay. It has one changeover contact with hard gold-plated AgSnO material, a 24 V DC coil and a 5 mm wide housing. AU stands for gold.

Seven Star LLC supplies the REL-MR-24DC/21AU as an independent supplier in Muscat for projects in Oman and the GCC, quoted against the exact part number shown here.

Technical specifications of the REL-MR-24DC/21AU

How the REL-MR-24DC/21AU works

The REL-MR-24DC/21AU is a plug-in miniature power relay: a coil that attracts an armature and moves one or two changeover contacts. When the coil is energised within the input range in the table, the common terminal changes from the normally closed to the normally open contact. The coil and the contacts are isolated from each other, with the winding/contact test voltage shown in the table, so a low-voltage control signal can switch a mains-level load. The relay has no socket of its own and is designed to be plugged into a compatible base, for instance a socket module.

Contacts are rated for a limiting continuous current of only 50 mA and a maximum of 30 V AC or 36 V DC, with a minimum switching current of 1 mA at 24 V. Interrupting rating is 1.2 W at 24 V DC. That makes it suitable for measuring and low-power signal circuits.

Where the REL-MR-24DC/21AU fits in a system

REL-MR relays are the replaceable switching element in many Phoenix Contact relay modules and in customer-built relay sockets. Ordering the relay alone is typical for spares or when a socket is already fitted. Family members differ by coil voltage, number of contacts, contact material and current rating, so the part number decides compatibility with the socket in your panel. Always check that the relay fits the socket series installed.

Use the REL-MR-24DC/21AU for signals that must be switched with low and stable contact resistance: analogue inputs, thermocouple selection, PLC feedback lines. Do not use it to switch power loads.

Selection and ordering checklist

• Confirm the coil voltage of the REL-MR-24DC/21AU against the control signal and its tolerance.
• Check the number of changeover contacts and the pin pattern of the socket.
• Check the load current and inrush against the contact data in the table.
• Use gold-plated contacts only for low-level signals, and power contacts for loads.
• Confirm the dimensions fit the socket and the DIN-rail space.
• Verify the ambient temperature.
• Confirm the load is a signal circuit of 50 mA or less.

Installation, commissioning and maintenance of the REL-MR-24DC/21AU

Plug the REL-MR-24DC/21AU firmly into a compatible socket, never into a socket designed for a different coil voltage. Check that the relay latches mechanically or sits fully in the retaining clip. Observe the mounting position: the datasheet permits any position. Replace the relay as a whole; do not attempt to clean or open it.

As with all gold-contact relays, never use the same contact to switch a load first and then a signal: it can wear the gold layer.

Typical applications in Oman and the GCC

In Oman and the GCC, plug-in relays are used in pump and valve controls, compressor panels, HVAC and lighting control and as spare parts in maintenance stores. Keeping a few spare relays per coil voltage shortens repair times considerably.

Instrumentation and control cabinets in the Gulf, where humidity and dust raise contact resistance, benefit from gold contacts for signals.

Comparison with related REL-MR plug-in relays

Information to send with an RFQ

• Full part number REL-MR-24DC/21AU and quantity.
• Socket or relay module in which it will be used.
• Coil voltage and load details.
• Operating temperature and duty.
• Delivery location and date.

Site conditions in Oman for the REL-MR-24DC/21AU

Control cabinets in Gulf plants often run hot, because many sit in outdoor kiosks or in rooms where air conditioning is not always reliable. Before you finalise the REL-MR-24DC/21AU, check the permitted ambient range and any derating stated by the manufacturer against the real temperature inside your panel, and leave the recommended spacing around the device so that heat can escape. Long cable runs between the field and the marshalling cabinet are common on large sites, so confirm the signal types, wiring limits and earthing arrangement early in the design.

It also helps to standardise on a small number of part numbers across a project. Keeping a few spare REL-MR-24DC/21AU units on site in Oman shortens recovery time after a fault, and documenting configuration settings makes replacement faster for the maintenance team.

Documents and quotation

Send us the part number REL-MR-24DC/21AU and the quantity you need, and we will confirm which official documents are available for this device. Seven Star LLC is an independent supplier in Muscat and quotes for projects across Oman and the GCC; we do not act on behalf of the manufacturer.

Please also tell us the delivery location and required timeline so that availability can be checked before you commit to a project schedule.