Quick Answer: What Are the Main Types of Time Delay Relays?
A standard control relay switches as soon as its coil or input signal changes. A time delay relay adds one more condition: time. That sounds simple, but it changes the whole control sequence. The wrong timer type can make a compressor restart too soon, a fan stop before purge is complete, or a motor starter transfer at the wrong moment.
The main types of time delay relays are classified by timing function, control method, output design, and mounting style. For search and selection, the most important group is the six functional timer relay types:
- On-delay timer relay: delays output turn-on after input is applied.
- Off-delay timer relay: keeps output active for a preset time after input is removed.
- Interval timer relay: turns output on for a fixed time after a trigger.
- Repeat cycle timer relay: repeatedly alternates output on and off.
- Star-delta timer relay: controls motor starter transition timing.
- Multifunction timer relay: combines several timing functions in one device.
This guide also covers two important selection layers that buyers often confuse with function types: power-off delay behavior แล้ว technology or mounting classifications such as solid-state, electromechanical, DIN-rail, plug-in, panel-mount, and PCB timer relays.
If you are looking for the general working principle, wiring terminals, symbols, and testing method, use VIOX’s Time Delay Relay Guide. This page focuses specifically on timer relay types and when each type should be selected.
Six Time Delay Relay Function Types Comparison Table
| ประเภท | Common aliases | Trigger event | Output during timing | Output after timing | ความเสี่ยงหลักในการเลือกใช้งาน |
|---|---|---|---|---|---|
| ออนดีเลย์รีเลย์ (On-delay relay) | Delay on make, delay on energization, TON | อินพุตทำงาน (ON) | Output remains OFF | Output turns ON | Confusing it with off-delay |
| ออฟดีเลย์รีเลย์ (Off-delay relay) | Delay on break, delay on release, TOF | อินพุตหยุดทำงาน (OFF) | Output remains ON | Output turns OFF | สมมติว่าทำงานได้หลังจากไฟฟ้าดับทั้งหมด |
| Interval timer | One-shot, pulse timer | Trigger or supply is applied | Output turns ON | Output turns OFF | Selecting a sustained-output timer instead |
| Repeat cycle timer | Recycle timer, cyclic timer, flasher | Supply or trigger is applied | Output alternates ON/OFF | Continues cycling until reset | Not checking ON-first vs OFF-first behavior |
| สตาร์-เดลต้าไทม์เมอร์ | Wye-delta timer, star-delta transition timer | Motor start command | Star stage is held | Delta stage is enabled | Using a general timer without correct transition logic |
| ไทม์เมอร์แบบมัลติฟังก์ชัน | Universal timer relay | ขึ้นอยู่กับโหมดที่เลือก | ขึ้นอยู่กับโหมดที่เลือก | ขึ้นอยู่กับโหมดที่เลือก | Wrong mode or range selected during commissioning |
1. On-Delay Time Delay Relay
หนึ่ง on-delay time delay relay delays output activation. It is also called delay on make, delay on energization, หรือ TON in many control diagrams. When the input or coil receives voltage, the timer begins counting. If the input remains present until the preset time expires, the output contact changes state.
Typical sequence:
Input ON -> timing starts -> preset time expires -> output ON
Input OFF -> output resets
Use an on-delay relay when the controlled equipment should not start immediately.
The practical detail is that most on-delay relays need the input to remain present during the timing period. If the signal disappears before the preset delay is reached, the timer usually resets and the output never changes state. Always check the timing diagram for pulse-triggered exceptions.
การใช้งานทั่วไป ได้แก่:
- motor or pump startup sequencing;
- compressor restart delay;
- delayed energizing of a contactor coil;
- alarm filtering to avoid nuisance signals;
- conveyor line startup order.
Where On-Delay Relays Are Often Misused
On-delay relays are sometimes added to “solve” frequent trips or repeated motor starts. That can hide the symptom without solving the root cause. If a motor, compressor, or pump restarts too often, check voltage, overload setting, mechanical load, pressure switch behavior, and control logic before simply increasing the delay.
For a detailed timing diagram, see On Delay vs Off Delay Timer.
2. Off-Delay Time Delay Relay
หนึ่ง off-delay time delay relay keeps the output active after the input signal is removed. It is also called delay on break, delay on release, หรือ TOF. The output energizes immediately when the input is applied, then remains active for the preset delay after input removal.
Typical sequence:
Input ON -> output ON immediately
Input OFF -> timing starts -> preset time expires -> output OFF
Use an off-delay relay when a device should continue running after the command signal stops.
การใช้งานทั่วไป ได้แก่:
- cooling fan post-run after motor shutdown;
- exhaust fan purge after process stop;
- pump run-on after a float switch opens;
- delayed lighting turn-off;
- auxiliary circuit hold-off during shutdown.
Standard Off-Delay vs True Power-Off Delay
This is a critical distinction. Many off-delay relays still require control power while timing. They delay release after a trigger signal changes, but the internal electronics still need a supply.
The reason is simple: in electronic off-delay relays, the timing circuit, output driver, and internal relay coil or semiconductor output still need energy while counting down. If the main supply is removed and there is no separate auxiliary supply or stored energy, the relay cannot continue timing.
เป็ ไทม์เมอร์แบบ Power-Off Delay ที่แท้จริง can hold its output for a limited period after supply removal. Depending on the product design, this may be done with an internal energy-storage circuit, such as a charged capacitor, or a mechanical latch mechanism. Always verify the timing diagram and datasheet before using an off-delay relay in a fan purge, brake release, alarm hold, or safe shutdown circuit.
3. Interval Timer Relay
หนึ่ง interval timer relay produces a fixed-duration output after receiving a supply or trigger input. It is also called a one-shot timer หรือ pulse timer in many control circuits. Instead of waiting before switching, it turns on for a set period and then returns to its normal state.
Typical sequence:
Trigger signal -> output ON -> preset time expires -> output OFF
Interval timers are useful when the control system needs a timed pulse.
This is the key difference from on-delay operation: an on-delay relay creates a delayed sustained output, while an interval timer creates an immediate output pulse with a defined duration.
Internally, the interval function usually starts timing at the same moment the output changes state. When the preset time expires, the timing circuit releases the output even if the input remains present. That is why interval timers are useful for one-shot actions but not for circuits that need the output to remain on continuously after a delay.
การใช้งานทั่วไป ได้แก่:
- dosing pump pulse control;
- buzzer or warning light activation;
- signal extension for a PLC input;
- short ventilation or purge period;
- automatic reset pulse in simple control logic.
Interval Timer Selection Tip
Check whether the interval begins on power-up or only after a separate trigger input. Two interval relays may look similar but behave differently during power recovery.
4. Repeat Cycle Timer Relay
เป็ repeat cycle timer relay alternates the output between ON and OFF states. It is also called a recycle timer, cyclic timer, หรือ flasher timer depending on the application. Some models use one time setting for both states. Others provide independent ON-time and OFF-time adjustment.
Typical sequence:
Output ON for T1 -> output OFF for T2 -> repeat
การใช้งานทั่วไป ได้แก่:
- flashing beacons;
- periodic ventilation;
- lubrication cycles;
- irrigation control;
- intermittent pump or fan operation;
- simple cyclic machine actions.
What to Verify Before Choosing a Repeat Cycle Timer
For repeat cycle applications, verify:
- whether the cycle starts with ON or OFF;
- whether ON and OFF times are independently adjustable;
- whether the output resets or resumes after power interruption;
- whether the contact rating is suitable for the connected load.
The starting state matters in alarms, lubrication, and machine sequence applications.
In procurement, do not assume every repeat cycle relay starts the same way. One model may start with output ON, while another starts with output OFF. That small difference can completely change the behavior of a beacon, lubrication pump, or ventilation damper.
5. Star-Delta Timer Relay
เป็ star-delta timer relay is a specialized time delay relay used in star-delta motor starters. It is also called a wye-delta timer in North American terminology. It controls the timing between the star starting stage and the delta running stage.
Its purpose is not just “delay.” It must coordinate contactor transition logic so that star and delta contactors are not energized at the wrong time.
Typical use:
- three-phase induction motor starting;
- reduced-voltage starting;
- applications where starting current must be reduced;
- pump, fan, compressor, and machine motor starters.
In a typical star-delta starter, the timer coordinates three contactors:
| เวที | Contactor behavior | Timer role |
|---|---|---|
| Start in star | Main contactor and star contactor energize | Timer begins transition delay |
| Transition | Star contactor releases before delta contactor closes | Timer provides the changeover sequence |
| Run in delta | Main contactor and delta contactor remain energized | Timer keeps the starter in run condition |
| Stop or trip | All contactors release | Timer resets |
The exact transition delay and any open-transition dead time must match the motor, starter design, and contactor documentation. Do not copy a timing value from another motor without checking the application.
For open-transition star-delta starters, the timer should provide a controlled changeover gap so the star contactor has released before the delta contactor closes. In many practical starter designs this dead time is specified in the tens to hundreds of milliseconds range, often around 50-150 ms, but the correct value must be verified against the contactor and starter documentation.
Why a General Timer Is Not Always a Star-Delta Timer
A general on-delay relay can provide a delay, but star-delta starting requires the correct transition sequence and interlocking logic. In motor starter panels, always match the timer to the starter design and contactor control circuit.
6. Multifunction Time Delay Relay
เป็ multifunction time delay relay combines several timing modes in one device. Depending on the model, it may include on-delay, off-delay, interval, repeat cycle, signal-on delay, signal-off delay, or other timing functions.
Multifunction types are useful when:
- the exact timing mode may change between projects;
- distributors want to reduce stock variety;
- OEMs build different control panels from the same relay platform;
- maintenance teams need a flexible replacement option;
- panel builders want one DIN-rail component for several timing tasks.
Main Risk with Multifunction Relays
The flexibility is also the risk. A wrong function setting can make a machine start too early, stop too late, or fail to reset correctly. During commissioning, record the selected timing mode, range, and dial setting inside the control panel documentation.
For fixed, high-volume equipment, a single-function timer relay can reduce setting errors. For maintenance stock, small-batch panels, and distributors, a multifunction timer relay often reduces part-number variety and makes emergency replacement easier.
สำหรับการเปรียบเทียบเชิงลึก โปรดดูที่ ไทม์เมอร์รีเลย์แบบมัลติฟังก์ชันเทียบกับไทม์เมอร์รีเลย์แบบฟังก์ชันเดียว.
Additional Function Behavior: Power-Off Delay Timer
เป็ power-off delay timer is used when the output must remain active for a short period after the supply is removed. This is different from many ordinary off-delay relays, which still require control power while timing.
การใช้งานทั่วไป ได้แก่:
- holding an alarm signal briefly after power loss;
- controlled shutdown of an auxiliary circuit;
- brake release timing;
- fan purge after supply interruption;
- preventing an immediate drop-out in sensitive control logic.
Because power-off behavior varies significantly between products, the datasheet timing diagram is mandatory. Do not select this type by name alone.
Technology Types: Solid-State vs Electromechanical Time Delay Relays
Time delay relays can also be classified by internal technology.
| เทคโนโลยี | ความแข็งแรง | ข้อจำกัด | การใช้งานทั่วไป |
|---|---|---|---|
| Electronic / solid-state timing | Compact, adjustable, multifunction options | Sensitive to incorrect voltage or wiring | Modern DIN-rail control panels |
| Electromechanical timing | Familiar relay behavior, visible contact logic | Larger size, mechanical wear | Replacement and legacy control systems |
| การตั้งเวลาแบบลม (Pneumatic timing) | Simple delay mechanism, no complex electronics | Lower precision, environment-sensitive | Older or specialized industrial systems |
| การตั้งเวลาแบบขับเคลื่อนด้วยมอเตอร์ | Suitable for long timing cycles in some legacy systems | Mechanical complexity | Older timing systems and replacements |
For new industrial control panels, electronic DIN-rail timer relays are usually the most common choice. However, replacement projects should match the original function, contact layout, reset behavior, and voltage before changing technology.
Mounting Types: DIN Rail, Plug-In, Panel-Mount, and PCB Timer Relays
Timer relays are also selected by mounting style.
| ประเภทการติดตั้ง | ดีที่สุดสำหรับ | สิ่งที่ต้องตรวจสอบ |
|---|---|---|
| ไทม์เมอร์รีเลย์แบบติดตั้งบนราง DIN | Control cabinets and distribution panels | Module width, terminal layout, wiring diagram |
| Plug-in timer relay | Maintenance replacement and socket-based control panels | Socket pin layout and timing function |
| ไทม์เมอร์แบบติดตั้งบนหน้าตู้ | Front-panel adjustment and operator access | Panel cutout, voltage, output contact |
| PCB timer relay | OEM equipment and compact electronics | Board layout, soldering, enclosure temperature |
For B2B buyers, mounting style affects more than installation. It affects spare parts, panel space, labeling, replacement speed, and wiring safety.
Output Contact Types for Time Delay Relays
The timing function controls when the output changes. The contact configuration controls how the circuit is switched.
| ประเภทการติดต่อ | ความหมาย | การใช้งานทั่วไป |
|---|---|---|
| สป.ด.ที. | หน้าสัมผัสแบบเปลี่ยนทางหนึ่งชุด | Basic control circuit |
| DPDT | หน้าสัมผัสแบบเปลี่ยนทางสองชุด | Two circuits or feedback plus control |
| NO timed contact | Normally open contact with timed action | Delayed energizing |
| NC timed contact | Normally closed contact with timed action | Delayed release or interlock logic |
| เอาท์พุตรีเลย์ | Dry contact output | Contactor coil, signal, PLC input |
| Transistor output | Solid-state output on some models | PLC and electronic control circuits |
When controlling contactor coils, solenoids, or inductive loads, check the contact’s inductive load rating, not only its resistive current rating. Control circuit categories such as AC-15 and DC-13 under IEC 60947-5-1 are commonly used to evaluate electromagnetic load switching.
Typical Ratings to Verify Before Ordering
The correct timer relay type still has to match the electrical rating of the control circuit. The values below are common market examples, not universal specifications. Always verify the exact model datasheet before ordering or replacing a relay.
| พารามิเตอร์ | ตัวอย่างทั่วไป | ทำไมถึงสำคัญ |
|---|---|---|
| แรงดันไฟฟ้าควบคุม | 12 VDC, 24 VDC, 24 VAC/DC, 110/120 VAC, 220/230 VAC, 380/400 VAC | Wrong voltage can prevent operation or damage the relay |
| ช่วงเวลา | Fractional seconds to minutes or hours; multifunction relays may cover wide ranges such as 0.1 s to 100 h | The selected range must include the required delay with adjustment margin |
| ติดต่อเอาท์พุต | SPDT, DPDT, เอาต์พุตรีเลย์, เอาต์พุตทรานซิสเตอร์ | Determines how many circuits can be switched and how the relay interfaces with the panel |
| Contact category | Resistive rating plus inductive control rating such as AC-15 or DC-13 where applicable | Contactor coils and solenoids stress contacts more than resistive loads |
| การติดตั้ง | DIN rail, plug-in socket, panel mount, PCB | Affects panel layout, replacement speed, and wiring method |
| พฤติกรรมการรีเซ็ต | Power reset, trigger reset, true power-off delay, memory or no-memory function | Determines what happens during power interruption or signal loss |
How to Choose the Right Type of Time Delay Relay
Use the application problem to choose the relay type. A useful engineering shortcut is to ask the function question first, then verify the electrical rating.
| คำถามสำหรับการเลือกอุปกรณ์ | Typical scenario | Suitable relay type | สิ่งที่ต้องตรวจสอบ |
|---|---|---|---|
| Should the output wait before turning on? | Motor sequence, compressor restart delay, delayed contactor coil | ออนดีเลย์รีเลย์ (On-delay relay) | Input must stay present during timing unless datasheet says otherwise |
| Should the output stay on after the command stops? | Fan post-run, pump run-on, lighting delay, purge cycle | ออฟดีเลย์รีเลย์ (Off-delay relay) | Whether control power is still required during timing |
| Should the output remain active after supply loss? | Alarm hold, fan purge, brake release, safe shutdown assist | Power-off delay timer | Internal energy storage or latch behavior and maximum hold time |
| Should the output run for one fixed pulse? | Dosing, alarm pulse, signal extension, timed actuation | Interval timer | Whether timing starts from supply input or a separate trigger |
| Should the output repeat ON/OFF cycles? | Flashing beacon, ventilation, lubrication, pump cycling | Repeat cycle timer | ON-first/OFF-first behavior and independent ON/OFF settings |
| Is this a star-delta motor starter? | Three contactors must transition from star to delta | สตาร์-เดลต้าไทม์เมอร์ | Transition sequence and dead time required by the starter design |
| Does one stocked part need to cover several modes? | OEM panels, distributor stock, flexible maintenance replacement | Multifunction timer relay | Mode selector, time range, and commissioning documentation |
| Is the panel already built around a socket or DIN rail? | Retrofit, maintenance, or new control cabinet | Plug-in or DIN-rail timer relay | Mounting style, terminal layout, wiring diagram, and space |
Common Applications by Industry
| Industry or system | Common timer relay types | การใช้งานทั่วไป |
|---|---|---|
| HVAC and refrigeration | On-delay, off-delay, repeat cycle | Compressor restart delay, fan post-run, defrost timing |
| ใช้เครื่องยนต์ควบคุม | On-delay, off-delay, star-delta | Staggered starting, cooling pump run-on, reduced-voltage starting |
| ระบบอัตโนมัติทางอุตสาหกรรม | Interval, repeat cycle, multifunction | Dosing, indexing, signal pulse, flexible machine sequence |
| Lighting and signaling | Off-delay, interval, repeat cycle | Stairwell delay, alarm pulse, flashing beacon |
| ระบบปั๊ม | On-delay, off-delay, repeat cycle | Anti-short-cycle delay, run-on, periodic pumping |
| แผงควบคุม OEM | Multifunction, DIN-rail timer relay | Reducing part variety and adapting timing logic by project |
Field Note: The Wrong Type Can Look Like a Failed Relay
In packaging machines, conveyors, and pump panels, a timing complaint often sounds like “the timer relay is bad.” In practice, the relay may be working exactly as designed, but the wrong timer type was selected.
A common example is replacing an off-delay relay with an on-delay relay because the voltage and pin layout look similar. The machine may still power up, but the fan, pump, or actuator sequence becomes wrong. This is why experienced panel builders compare the timing diagram before comparing price, voltage, or brand.
ข้อผิดพลาดทั่วไปในการจัดซื้อ
Mistake 1: Selecting by Time Range Only
A relay with the correct time range can still be wrong if the timing function, reset behavior, output contact, and voltage do not match the circuit.
Mistake 2: Treating Off-Delay and Power-Off Delay as the Same
Some off-delay relays need power during timing. If the circuit must hold output after supply loss, verify true power-off delay behavior in the datasheet.
Mistake 3: Ignoring the Starting State of Repeat Cycle Timers
Some repeat cycle timers start with output ON. Others start with output OFF. This difference can be critical in alarms, lubrication systems, and machine sequences.
Mistake 4: Using a Timer Relay Contact as a Power Contact
Timer relay outputs are usually control contacts. Use them to control a contactor coil, PLC input, signal lamp, or interface relay. Do not use a small timer contact as the main switching device for motor power.
Mistake 5: Replacing a Timer Relay Without Checking the Diagram
Two timer relays can share the same voltage and pin style but use different timing logic. Always compare the timing diagram, not only the terminal numbers.
คำถามที่พบบ่อย
What are the most common types of time delay relays?
The most common types are on-delay, off-delay, interval, repeat cycle, star-delta, multifunction, and power-off delay timer relays. In industrial panels, on-delay and off-delay are the most frequently used basic functions.
Which type of time delay relay is used for motor starting?
On-delay relays are commonly used for motor startup sequencing. Star-delta motor starters use a dedicated star-delta timer to control the transition between star and delta operation.
What type of timer relay is used for fan post-run?
An off-delay relay is typically used for fan post-run because it keeps the fan running after the stop command is removed. If the fan must run after total supply loss, verify whether a true power-off delay timer is required.
Is a multifunction timer relay better than a single-function timer relay?
Not always. A multifunction timer relay is flexible and useful for OEMs, distributors, and maintenance stock. A single-function timer relay can be simpler for fixed applications where the timing mode should not be changed accidentally.
What is the difference between interval and on-delay timer relays?
An on-delay relay waits before turning the output on. An interval timer turns the output on for a fixed period after a trigger, then turns it off automatically.
What is the difference between repeat cycle and interval timer relays?
An interval timer produces one timed output pulse. A repeat cycle timer continuously alternates between on and off periods until the input or supply condition changes.
Can one timer relay replace another type?
Only if the timing function, voltage, terminal layout, contact rating, reset behavior, and timing diagram match the original application. A relay that physically fits can still perform the wrong timing sequence.
Which timer relay type should distributors stock?
Distributors often stock multifunction DIN-rail timer relays because they cover many common applications. However, high-volume OEM customers may prefer single-function models for simpler commissioning and fewer setting errors.
Buyer Note for OEMs and Distributors
For OEM and distributor projects, the timer relay type should be matched to the control logic before discussing branding, packaging, or stocking quantity. A practical sourcing request should include timing function, control voltage, output contact, mounting style, labeling requirement, wiring diagram, timing diagram, and contact-rating information.
VIOX ELECTRIC can support timer relay selection for control panels, OEM equipment, and distributor stock planning. For technical approval, request the latest datasheet and confirm model-specific ratings rather than relying on product photos alone.
สรุป
Choosing the correct time delay relay type starts with the control problem, not the time range. The six main functional types are หน่วงเวลาเปิด, off-delay, interval, repeat cycle, star-delta, และ มัลติฟังก์ชัน timer relays. Use on-delay for delayed start, off-delay for delayed stop, interval for a timed pulse, repeat cycle for periodic operation, star-delta for motor starter transition, and multifunction models when one relay must cover several applications.
Before replacing or specifying any timer relay, compare the timing diagram, control voltage, time range, contact rating, mounting style, and reset behavior. In control panels, the wrong relay type often looks like a wiring fault or a failed device, even when the relay is working normally.
For buyers, the safest ordering process is to define the required timing logic first, then confirm datasheet details such as 24 VDC or 220/230 VAC control voltage, contact configuration, AC-15/DC-13 inductive load capability where applicable, and the required adjustment range.
