Intermediate relays for automation | for PLC and electrical control panels

Interface relays pass a weak control signal (PLC, timer, thermostat, sensor) to another circuit, isolate it galvanically and multiply the number of contacts. Relays here are arranged by coil (control) voltage – first choose the voltage you will control the relay with.

Selection in 30 s – what is your control voltage?
24 V DC
PLC, automation 12 V
gates, alarm, battery 230 V AC
timer, thermostat, mains 24 V AC
HVAC, transformer 230 V AC + 24 V
dual coil, DIN 18 mm Relay sockets
for plug-in relays
ELSprendimai recommends – full interface relay guide ↓

Interface relay guide: how to choose by coil voltage, contacts and load

An interface relay sits between a weak control signal (PLC, timer, thermostat, sensor) and the circuit that has to be switched. In this group relays are arranged by coil voltage – that is where correct selection starts. Below: quick selection by situation, solution levels, a matrix of all relays in the group, a wiring scheme and the most common mistakes.

Colour meaning: ■ information · ■ benefit, solution · ■ ⚠ check · ■ ⚡ safety, mistakes

Contents: What do you need? · Solution levels · Selection matrix · Coil voltage · Contact load · Relay, contactor or SSR? · Scheme · What to check · Common mistakes · FAQ · Related guides

What do you need? Quick selection

Situation	Solution	Where to look
A 24 V DC PLC output must drive a contactor coil or a valve	Relay with 24 V DC coil, 1CO or 2CO; suppression circuit across inductive loads	LANBOO ultra-slim with LED 1CO 6 A Finder relay 2CO 8 A Schneider Zelio relay 2CO 8 A
Many PLC channels, little panel space	Slim 1CO relays for signal interfacing	Phoenix Contact relay 1CO 6 A Finder slim relay 1CO 6 A LANBOO ultra-slim with LED 1CO 6 A
12 V system: gates, alarm, battery	Relay with 12 V coil	LANBOO ultra-slim with LED 1CO 6 A LANBOO mini 2CO 12 A GEYA modular 3CO, 12 V AC/DC
Control from a 230 V timer or thermostat, home panel	Relay with 230 V AC coil	GEYA modular 3CO 16 A Finder relay 2CO 8 A
HVAC controller with a 24 V AC output	Relay with 24 V AC coil	Finder relay 2CO 8 A Finder relay 4CO 7 A
Both 230 V and 24 V control in the panel – one model wanted	Modular relay with dual coil	GEYA modular dual-coil 2CO 8 A, 230 V AC / 24 V AC/DC
Four separate contacts needed from one signal	4CO plug-in relay + socket	Finder relay 4CO 7 A, 230 V AC Finder relay 4CO 7 A, 24 V AC Finder socket with clip
Load above 16 A, motor or three-phase circuit	Not an interface relay – a contactor driven by an interface relay	Contactors · Mini contactors

Solution levels: from accessory to industrial solution

1. Accessories: relay sockets
A plug-in relay needs a socket with screw terminals for the DIN rail. The socket is chosen by relay series.
Finder socket with clip Schneider Zelio socket Releco socket Phoenix Contact base

2. Compact 1CO signal relays
6–8 A, one changeover contact. For isolating PLC outputs, passing signals, driving small coils.
LANBOO ultra-slim with LED 1CO 6 A Finder slim relay 1CO 6 A Phoenix Contact relay 1CO 6 A

3. General-purpose 2CO
8–12 A, two contacts: one drives the load, the other returns status or interlocks.
Finder relay 2CO 8 A Schneider Zelio relay 2CO 8 A LANBOO mini 2CO 12 A OMRON with socket 2CO 10 A

4. Modular DIN 18 mm, no socket
Mount directly on the rail like a circuit breaker, with LED. Dual coil or 16 A contacts.
GEYA modular dual-coil 2CO 8 A, 230 V AC / 24 V AC/DC GEYA modular 3CO 16 A, 230 V AC GEYA modular 3CO, 12 V AC/DC

5. Industrial 4CO
Four contacts from one signal – for more complex logic and interlocks. Mounted in a socket.
Finder relay 4CO 7 A, 230 V AC Finder relay 4CO 7 A, 24 V AC

6. When a relay is not enough
Motor, three-phase or large load – contactor. Frequent switching – SSR. Push-button control – impulse relay.
Contactors · SSR relays · Impulse relays

Selection matrix: all relays in the group by coil voltage

Names highlighted in blue are links to products. "Plug-in" – the relay needs a separate socket.

Relay	Contacts	Current	Mounting / feature
12 V coil (DC, AC/DC)
GEYA modular (12 V AC/DC)	3CO	8 A AC1	DIN without socket, LED
LANBOO ultra-slim with LED	1CO	6 A	DIN, LED
LANBOO mini	2CO	12 A	compact
LANBOO mini with test button	2CO	8 A	test button
LANBOO mini	1CO	8 A	compact
LANBOO mini with test button	1CO	8 A	test button
24 V DC coil
LANBOO ultra-slim with LED	1CO	6 A	DIN, LED
Finder slim relay	1CO	6 A	slim
Phoenix Contact relay	1CO	6 A	fits Phoenix Contact base
LANBOO mini	1CO	8 A	compact
LANBOO mini with test button	1CO	8 A	test button
Finder relay	2CO	8 A	plug-in
Schneider Zelio relay	2CO	8 A	plug-in, fits Zelio socket
LANBOO mini	2CO	12 A	compact
LANBOO mini with test button	2CO	8 A	test button
OMRON MY2N, LED	2CO	5 A	plug-in, socket sold separately
Releco 2-pole	2CO	10 A	plug-in, fits Releco socket
ELESTA SGR 282 Z safety relay	2CO	6 A	PCB (solder), force-guided contacts
OMRON industrial	2CO	10 A	plug-in
24 V AC coil
Finder relay	2CO	8 A	plug-in
Finder relay	4CO	7 A	plug-in, fits Finder 94 socket
230 V AC coil
GEYA modular	3CO	16 A AC1	DIN without socket, LED
Finder relay	2CO	8 A	plug-in
Weidmuller relay	2CO	8 A	plug-in
Finder relay	4CO	7 A	plug-in, fits Finder 94 socket
Dual coil 230 V AC / 24 V AC/DC
GEYA modular dual-coil	2CO	8 A AC1	DIN without socket, LED

Coil voltage: how not to get it wrong

24 V AC ≠ 24 V DC. A DC coil on AC voltage works unstably, and an AC coil on DC voltage overheats. Only a coil marked AC/DC suits both.
A 12 V relay in a 24 V system will burn out, and a 24 V relay in a 12 V system may not pull in at all.
Dual coil: on the GEYA modular relay 230 V AC goes only to A1–A2, 24 V AC/DC only to A1–A3.
PLC output: check that its permitted current is higher than the coil current (coil consumption is given on the product card).
Tolerance: e.g. GEYA modular relays allow −15 % / +10 % of rated voltage.

Contact load: why 8 A does not always mean 8 A

Load type	What happens at the contacts	What to do
Resistive (AC1): heating elements	Easiest for contacts – the rated current applies directly	Choose a relay whose rated current is not lower than the load current
Inductive: contactor coils, valves	Switching off causes a voltage spike and an arc, contacts wear faster	DC – a diode, AC – an RC snubber or varistor across the load
LED drivers	Inrush current briefly exceeds the rated current many times – contacts can weld	For larger LED groups – a contactor, the relay drives its coil
Direct current (DC)	A DC arc is harder to break than AC	Check the DC limit on the product card: e.g. 24 V DC for GEYA modular, 30 V DC for Finder 40/55 series
Motors, three-phase load	Starting current is several times the rated current	Only via a contactor with thermal protection

KibirkštisI hung four LED floodlights on an 8 A relay – after a month the contact stuck. But the floodlights drew only 3 A?

FazėThe rated current is 3 A, but at switch-on LED drivers briefly draw several times more. That welds the contact. For such a load the relay should drive a contactor coil, not the floodlights themselves.

Relay, contactor or SSR?

Task	Best solution	Where to look
Signals, contactor coils, pilot lamps	Interface relay	In this group – by coil voltage
Resistive load up to 16 A (heating)	16 A AC1 interface relay or contactor	GEYA modular 3CO 16 A · Mini contactors
Motor, pump, three-phase load	Contactor + thermal relay or motor protection	Contactors · Thermal overload relays
Frequent switching, temperature control	Solid-state relay (SSR) – no moving contacts	SSR relays
Lighting controlled by push buttons from several places	Impulse relay	Impulse relays

Scheme: PLC → interface relay → contactor → motor

PLC / timer
24 V DC or 230 V AC output

→

Interface relay
coil A1–A2, contacts 11-14 (NO)

→

Contactor
coil A1–A2, power contacts

→

Motor / load
via protection (MCB, thermal relay)

Contact numbering: 11/21/31/41 – common (COM); 12/22/32/42 – normally closed (NC); 14/24/34/44 – normally open (NO). Coil – A1 and A2 (on the dual-coil relay 24 V – A1–A3). Drive the contactor coil through NO contact 11–14 and return the status signal to the PLC through the second contact group.

⚠ What to check before buying

KibirkštisBefore ordering a relay I always check these things – otherwise it means a second trip.

Parameter	What to check	Why it matters
Coil voltage	Value and type: 12 V, 24 V, 230 V; AC, DC or AC/DC	A wrong coil will not pull in or will burn out
Number of contacts	1CO, 2CO, 3CO or 4CO – count the functions + 1 spare	One contact for two unrelated functions is a source of faults
Current and load type	Resistive, inductive, LED, DC	The current on the card applies to resistive load
DC switching limit	Up to what DC voltage the contacts can break current	A DC arc is harder to extinguish
Mounting	Plug-in (needs socket) or modular DIN	A plug-in relay cannot be connected without a socket
Indication and test	LED, manual test button	Faster diagnostics during commissioning
Space in the panel	Width and height under the cover	Not all relays fit under the cover of modular devices

✗ Most common mistakes

⚡ Safe installation – Fazė’s tip

AC and DC coil or 12 V and 24 V coil mixed up.
230 V connected to the 24 V terminals (A1–A3) of a dual-coil relay.
A motor or LED group switched directly through an interface relay, without a contactor.
No suppression diode across a valve or DC coil – the PLC output and contacts fail earlier.
A plug-in relay ordered without a matching socket.
NC (11–12) and NO (11–14) contacts mixed up.
The interface relay treated as protection – circuit left without a circuit breaker or fuse.
Working in the panel without disconnecting and verifying absence of voltage.

KibirkštisI connected a 24 V relay to the PLC and it chatters and does not pull in fully. What is wrong?

FazėFirst check that the coil is DC, not AC – an AC coil on DC behaves exactly like that. Second – that the PLC output can supply the coil current. And if the relay drives a valve or contactor, put a suppression circuit across the load.

Frequently asked questions

KibirkštisHow does an interface relay differ from a contactor?

FazėAn interface relay is for signals and smaller loads, a contactor for power circuits and motors. Usually they work together: the relay drives the contactor coil.

KibirkštisCan a 24 V DC relay be supplied from 24 V AC?

FazėNo, unless the coil is marked AC/DC. For 24 V AC control choose a relay with a 24 V AC coil.

KibirkštisWhat do 1CO, 2CO, 4CO mean?

FazėHow many changeover contact groups the relay has. Each group has a common, a normally closed and a normally open contact.

KibirkštisDo all relays need a socket?

FazėPlug-in ones – yes. GEYA modular relays mount directly on the DIN rail and need no socket.

KibirkštisHow many contacts should I choose?

FazėCount all functions (control, status signal, interlock) and add one spare – an extra contact is often needed later.

KibirkštisDo you help choose a relay for a project?

FazėYes. Send the scheme or a list of devices with control voltage and loads – we will select relays, sockets, contactors and protection and send an offer. Contact us.

Sources

Manufacturer data used in this guide. Checked 2026-11-05.

GEYA – technical parameters of GR8 series interface relays (manufacturer datasheet)
Other relays – according to product cards and manufacturer marking on the product

Disclaimer. This guide is for orientation when choosing products. Final selection must be confirmed by a qualified electrician based on the specific scheme and manufacturer documentation. UAB „Elektrotechnikos sprendimai“ is not responsible for product selection or installation carried out solely on the basis of this guide.

Published: 2026-11-05 · Data verified against manufacturer datasheets: 2026-11-05

Intermediate relays for automation | for PLC and electrical control panels

Control relays | universal automation relays | for PLC and electrical panels

DPDT intermediate relays | 2CO (2 changeover contacts) | control relays for automation

4PDT intermediate relays | 4CO (4 changeover contacts) | industrial control relays

SPDT intermediate relays | 1CO (1 changeover contact) | compact control relays

Relay sockets | for connecting relays to the control system

Relay modules | for the safe operation of electrical equipment

1 - 24 of 27

Code: LY2N 24VDC

OMRON LY2N 24 V DC – interface relay with 2CO contacts (10 A) and 24 V DC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 6.05 € VAT incl.

( 5.00 € VAT excl. )

Code: 40.52.9.024.0000

Finder 40.52.9.024.0000 – interface relay with 2CO contacts (8 A) and 24 V DC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 2.96 € VAT incl.

( 2.45 € VAT excl. )

Code: 40.52.8.024.0000

Finder 40.52.8.024.0000 – interface relay with 2CO contacts (8 A) and 24 V AC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 6.29 € VAT incl.

( 5.20 € VAT excl. )

Code: 40.52.8.230.0000

Finder 40.52.8.230.0000 – interface relay with 2CO contacts (8 A) and 230 V AC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 3.91 € VAT incl.

( 3.23 € VAT excl. )

Code: 55.34.8.024.0040

Finder 55.34.8.024.0040 – interface relay with 4CO contacts (7 A) and 24 V AC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 4.33 € VAT incl.

( 3.58 € VAT excl. )

Code: 55.34.8.230.0040

Finder 55.34.8.230.0040 – interface relay with 4CO contacts (7 A) and 230 V AC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 4.77 € VAT incl.

( 3.94 € VAT excl. )

Interface relay | 2CO | 5 A | coil 24 V DC | plug-in | OMRON MY2N 24 V DC

Code: MY2N 24VDC

OMRON MY2N 24 V DC – interface relay with 2CO contacts (5 A) and 24 V DC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 6.05 € VAT incl.

( 5.00 € VAT excl. )

Code: RSB 2A080BD

Schneider Electric RSB2A080BD – interface relay with 2CO contacts (8 A) and 24 V DC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 2.94 € VAT incl.

( 2.43 € VAT excl. )

Code: RCI424T30

Weidmüller RCI424T30 – interface relay with 2CO contacts (8 A) and 230 V AC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 5.82 € VAT incl.

( 4.81 € VAT excl. )

Safety relay with force-guided contacts | 2CO | 6 A | coil 24 V DC | PCB | ELESTA SGR 282 Z 24 V DC

Code: SGR282Z

ELESTA SGR 282 Z 24 V DC – safety relay with force-guided 2CO contacts (EN 50205, type B), 6 A, 24 V DC coil. Solder-mounted on PCB; for safety circuits where contact status must be reliably monitored.

Price 7.00 € VAT incl.

( 5.79 € VAT excl. )

Code: C7-A20

Releco C7-A20 24 V DC – interface relay with 2CO contacts (10 A) and 24 V DC coil. For control signal isolation, contact multiplication and control of contactor and valve coils in automation panels.

Price 12.00 € VAT incl.

( 9.92 € VAT excl. )

Ultra-slim relay | 24 V DC coil | 1CO (SPDT) | 6 A | 250 V AC | 5 mm | PCB | Finder 34.51 | 34.51.7.024.0010

Code: 34.51.7.024.0010

Finder 34.51.7.024.0010: ultra-slim 5 mm relay, sensitive 24 V DC coil 170 mW, 1CO AgNi 6 A 250 V AC, PCB or 93 series socket mounting.

Price 8.64 € VAT incl.

( 7.14 € VAT excl. )

Code: 2961105

Phoenix Contact REL-MR-24DC/21 (2961105): plug-in miniature relay, 24 V DC coil, 1CO AgSnO 6 A, up to 250 V AC/DC.

Price 5.24 € VAT incl.

( 4.33 € VAT excl. )

Modular interface relay | 3×SPDT | 16 A AC1 | 230 V AC coil | LED | DIN 18 mm | GEYA GR8-316

Code: ESGR8-316

Modular GEYA GR8-316 interface relay with 3 changeover contacts (16 A AC1) and 230 V AC coil. One 18 mm DIN module with LED status indication – for isolating control signals, multiplying contacts and driving contactor coils in panels.

Price 22.14 € VAT incl.

( 18.30 € VAT excl. )

Code: ESGR8-3161

Modular GEYA GR8-308 interface relay with 3 changeover contacts (8 A AC1) and 12 V AC/DC coil. One 18 mm DIN module with LED status indication – for isolating control signals, multiplying contacts and driving contactor coils in panels.

Price 19.78 € VAT incl.

( 16.35 € VAT excl. )

Code: ESGR8-3162

Modular GEYA GR8-208 interface relay with 2 changeover contacts (8 A AC1) and 230 V AC / 24 V AC/DC coil. One 18 mm DIN module with LED status indication – for isolating control signals, multiplying contacts and driving contactor coils in panels.

Price 19.78 € VAT incl.

( 16.35 € VAT excl. )

Code: ESGR8-208

Price 13.61 € VAT incl.

( 11.25 € VAT excl. )

Interposing relay | 12 V DC coil | 1CO (SPDT) | 8 A | plug-in | LANBOO J13A | ES-J13A

Code: ES-J13A

LANBOO J13A plug-in interposing relay: 12 V DC coil, 1CO (NO + NC) 8 A. Mounts in a socket.

Price 4.10 € VAT incl.

( 3.39 € VAT excl. )

Interposing relay | 24 V DC coil | 1CO (SPDT) | 8 A | plug-in | LANBOO J13A | ES-J13A24

Code: ES-J13A24

LANBOO J13A plug-in interposing relay: 24 V DC coil, 1CO (NO + NC) 8 A. Mounts in a socket.

Price 4.10 € VAT incl.

( 3.39 € VAT excl. )

Interposing relay | 12 V DC coil | 1CO (SPDT) | 8 A | with test button | plug-in | LANBOO J13A | ES-J13A1

Code: ES-J13A1

LANBOO J13A plug-in interposing relay: 12 V DC coil, 1CO (NO + NC) 8 A, manual test button. Mounts in a socket.

Price 4.10 € VAT incl.

( 3.39 € VAT excl. )

Interposing relay | 24 V DC coil | 1CO (SPDT) | 8 A | with test button | plug-in | LANBOO J13A | ES-J13A2

Code: ES-J13A2

LANBOO J13A plug-in interposing relay: 24 V DC coil, 1CO (NO + NC) 8 A, manual test button. Mounts in a socket.

Price 4.10 € VAT incl.

( 3.39 € VAT excl. )

Interposing relay with socket | 12 V DC coil | 1CO (SPDT) | 6 A | LED | ultra-slim | DIN | LANBOO | ES-LBJ6A12

Code: ES-LBJ6A12

Ultra-slim interposing relay module with socket for DIN rail: 12 V DC coil, 1CO 6 A 250 V AC, LED indication.

Price 10.38 € VAT incl.

( 8.58 € VAT excl. )

Interposing relay with socket | 24 V DC coil | 1CO (SPDT) | 6 A | LED | ultra-slim | DIN | LANBOO | ES-LBJ6A24

Code: ES-LBJ6A24

Ultra-slim interposing relay module with socket for DIN rail: 24 V DC coil, 1CO 6 A 250 V AC, LED indication.

Price 10.38 € VAT incl.

( 8.58 € VAT excl. )

Code: ES-J13A6

Intermediate relay designed for various control, automation, and protection systems. Due to its miniature size, sealed construction, and silver alloy contacts, this relay ensures stable operation even under demanding operating conditions. It is perfectly suitable for both industrial automation systems and smaller projects or household solutions where reliable signal or load control is required.

Price 5.05 € VAT incl.

( 4.17 € VAT excl. )

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Products catalog

Product Catalog

Intermediate relays for automation | for PLC and electrical control panels

Interface relay guide: how to choose by coil voltage, contacts and load

What do you need? Quick selection

Solution levels: from accessory to industrial solution

Selection matrix: all relays in the group by coil voltage

Coil voltage: how not to get it wrong

Contact load: why 8 A does not always mean 8 A

Relay, contactor or SSR?

Scheme: PLC → interface relay → contactor → motor

⚠ What to check before buying

✗ Most common mistakes

Frequently asked questions

Related guides

Sources

Inform when we have the item on stock