Practical Guide to Time Relays — Types, Settings, Wiring & Troubleshooting

1. What a Time Relay Does and where you use it

A time relay is an electromechanical or electronic device that switches output contacts after a preset time or for a preset time. Use time relays for delay-on, delay-off, interval timing, cyclic timing, star-delta motor starting, lighting control, conveyor sequencing, and protection sequences. The device replaces manual timing and adds repeatable, programmable delays to control logic.

2. Common Types of Time Relays

2.1 On-Delay (Delay-on) Relay

On-delay relays begin counting when the coil is energized and close their output contacts only after the set time elapses. Use them to delay motor starting, prevent nuisance starts, or sequence steps where later devices must wait for initial conditions.

2.2 Off-Delay (Delay-off) Relay

Off-delay relays start timing when the coil de-energizes and keep contacts energized for the set duration. Use this for lamp hold-off, ventilation run-down, or keeping pumps running after an event.

2.3 Interval and Pulse Relays

Interval relays energize outputs for a fixed time once triggered. Pulse relays generate a single timed pulse independent of trigger length. Use these for dosing, gating, or short actuation events.

2.4 Cyclic / Repeating Timers

Cyclic timers alternate outputs on and off in repeating sequences. They support symmetrical or asymmetrical ON/OFF ratios and are suited to batching, flashing indicators, or periodic sampling controls.

2.5 Multi-Function Programmable Time Relays

Multi-function modules combine several timing modes, adjustable ranges, and often an LCD or LEDs for feedback. Choose these when you need flexibility in the field without changing hardware.

3. Key Specifications to Check Before Buying

Read datasheets and compare these specifications against your application needs. These items determine compatibility and lifetime performance.

• Timing range: seconds, minutes, hours, or selectable ranges (for example 0.1s–10s, 1s–100s, 1min–100min).
• Timing accuracy and repeatability: important in precision processes.
• Supply voltage: AC or DC ratings (e.g., 24VDC, 110VAC, 230VAC) and tolerance band.
• Contact type and rating: SPDT, DPDT, or solid state outputs, with load current and AC/DC voltage limits.
• Mounting style: DIN-rail, panel, or PCB mount.
• Environmental ratings: operating temperature, humidity, vibration resistance, and IP rating if exposed areas apply.
• User interface: mechanical knobs, DIP switches, rotary selectors, or digital programming and display.

4. How to Select the Right Timing Range and Mode

Start by mapping the required delay values in your process: list minimum, typical, and maximum times. If timing must be adjustable across large spans, select a multi-range or programmable relay. For fine adjustment at short intervals, choose a relay with small step resolution. When safety or regulatory sequences depend on timing, pick a relay with documented accuracy and long-term stability.

5. Basic Wiring Patterns (examples)

Below are simplified wiring patterns. Follow the manufacturer's terminal labe