Key Takeaway
To choose a time delay relay, evaluate 6 criteria: the timing function type (on-delay, off-delay, cyclic, or interval), the timing range (milliseconds to hours), supply voltage (12 V to 240 V AC/DC), contact load capacity (current rating and load type), mounting format (DIN rail modular or plug-in), and environmental conditions (temperature, IP rating). A time delay relay controls circuit operation based on time — lighting, motor starting, automated sequences, or heating cycles.
What is a time delay relay?
A time delay relay is an electromechanical or electronic device that opens or closes a circuit after a programmed delay. Unlike a standard relay that switches instantly, a time delay relay introduces a controlled delay between the command and the action.
It is used in all situations requiring a delay, interval, or timing sequence:
- Lighting: staircase timers, automatic switch-off after a delay.
- Motors: star-delta starting delay, start sequencing to avoid simultaneous inrush currents.
- Heating and ventilation: operating cycles, delayed start-up after power cut.
- Industrial automation: process sequences, safety delays, washing or dosing cycles.
Types of timing functions
| Function | Principle | Typical application |
|---|---|---|
| On-delay | Output activates after a preset delay from power-on | Delayed motor start, start sequencing, preheating |
| Off-delay | Output remains active for a preset delay after command removal | Post-stop ventilation, extended lighting, motor cooling |
| Interval (Pulse) | Output activates for a preset duration then deactivates | Staircase timer, dosing, command pulse |
| Cyclic (Flasher) | Output alternates between on and off at regular intervals | Warning flasher, pump cycling, intermittent ventilation |
| Star-delta | Motor starting sequence: star → delay → delta | High-power three-phase motor starting |
⚠️ Important note
Some time delay relays are multifunction: they integrate multiple selectable timing modes via switch or programming. This is advantageous for maintenance (one model covers multiple needs) but ensure the correct function is configured during installation.
6 selection criteria for a time delay relay
1Timing function type
Precisely identify the required timing behavior: on-delay, off-delay, pulse, cyclic, or star-delta sequence. This is the most important criterion — selecting the wrong function makes the relay unusable for the intended application.
2Timing range
The timing range defines the minimum and maximum adjustable durations, from a few milliseconds to several hours depending on the model.
| Range | Application |
|---|---|
| 0.05 s – 1 s | Fast pulses, debouncing, process sequences |
| 1 s – 60 s | Motor starting, short timers |
| 1 min – 60 min | Staircase timers, ventilation cycles |
| 1 h – 100 h | Long delays, maintenance cycles |
3Supply voltage
The relay must be powered at the voltage available in the panel or enclosure:
- 24 V DC: standard in industrial automation and control systems.
- 24 V AC: common in HVAC systems and certain automation setups.
- 110-120 V AC: specific applications, North American standard.
- 230 V AC: residential and commercial standard in Europe.
- Multi-voltage (24-240 V AC/DC): universal relays, maximum flexibility.
4Contact load capacity
Relay contacts must handle the current of the controlled load. Key parameters:
- Rated current: typically 5 A, 8 A, 10 A, or 16 A depending on model.
- Load type: resistive (heating), inductive (motor, contactor), capacitive (capacitors), or lamp. Inductive load inrush current can reach 6 to 10 times rated current.
- Number of contacts: SPDT (1 changeover), DPDT (2 changeover), 4PDT — depending on circuit complexity.
5Mounting format
- Modular (DIN rail): installs in an electrical panel or enclosure, width in modules (1 to 3 modules). Ideal for staircase timers and distribution board timing functions.
- Plug-in on socket: miniature relay pluggable into a terminal socket (Finder series 55, Omron MY type). Standard in industrial automation for easy replacement.
- PCB mount: soldered directly onto circuit board. Used in equipment design.
6Environmental conditions
- Operating temperature: most relays operate from -20°C to +55°C. In hot environments (unventilated enclosures), verify the limits.
- Protection rating: IP20 standard in enclosures, IP65+ if exposed to dust or humidity.
- Vibration: in vibrating industrial environments (near machinery), prefer solid-state relays (SSR) with no mechanical contacts.
Main brands and ranges
| Brand | Range | Feature | Format |
|---|---|---|---|
| Finder | Series 38 | Modular EMR/SSR interfaces for automation | DIN rail modular |
| Finder | Series 39 | Modular interfaces for industrial enclosures | DIN rail modular |
| Finder | Series 46 / 55 | Industrial power relays / miniature relays | Plug-in |
| Phoenix Contact | Plug-in relays | Manual configuration, flexible control systems | Plug-in |
| Omron | G2R / MY | Plug-in / miniature high-performance relays | Plug-in |
Discover our time delay relays
Frequently asked questions — Time delay relays
Need help choosing the right time delay relay?
Our technical team will help you select the relay suited to your application.
Contact our technical teamBy phone: +33 1 43 44 60 00 · By email: [email protected]
Key takeaways
- First identify the required timing function: on-delay, off-delay, interval, cyclic, or star-delta.
- The timing range must cover the durations needed for your application (ms to hours).
- Supply voltage must match what is available (24 V DC in industry, 230 V AC in commercial).
- Size contact load capacity accounting for load type (resistive, inductive, capacitive).
- Multifunction relays simplify stock management by covering multiple timing modes.
- In vibrating environments or for very frequent switching, prefer solid-state relays (SSR).
- Finder, Phoenix Contact, and Omron cover most industrial and commercial needs.
