A correctly selected time relay in 2026 starts with four numeric matches: delay function (on-delay, off-delay, interval, pulse, bistable, flashing), time range, contact rating, and supply voltage; the rest of the spec sheet is filler until those four are pinned down [S7][S8].
Off-the-shelf DIN-rail multifunction units now cover 0.1s to 120h of adjustable delay with a typical repetitive error of ≤1% on ranges ≥1s, and ≤50ms drift on sub-second ranges [S2]. For pump rundown after a heating shutdown, for example, the time relay is the device that actually counts down after the contactor drops, and a wrong range there means either a dry-run or a flooded seal pot.
Delay Function vs. Application Match
On-delay (T-on) is the workhorse: the relay starts timing only after the coil is energised, and the output transfers once the set time elapses, which makes it the right pick for star-delta starters, sequential conveyor staging, and motor soft-start bypass timers [S8][S10]. Off-delay (T-off) holds the output on for a fixed period after coil power is removed, so it suits cooling-fan run-on, lamp after-glow, and capacitor-discharge sequencing where a controlled power-down matters more than a controlled power-up [S6][S8].
Interval, pulse, and star-delta variants each carry a fixed behavioural profile: interval timing energises the output only for the set period, pulse gives a fixed-length output regardless of input duration, and the star-delta preset builds in the 30-100ms transfer gap used in motor starters [S8]. Bistable (latching) and flashing (symmetrical or asymmetrical cycling) functions are the right answer when a flip-flop or a square-wave output is what the circuit needs, not a one-shot [S8]. A buyer who defaults to "multifunction" without checking the actual function list on the data sheet will sometimes find that the function they need (asymmetrical flashing, for example) is only available on a higher-cost variant.
Time Range, Resolution, and Repeatability
Standard commercial ranges start at 0.1s and step in decades: 0.1-9.9s / 1-99s / 0.1-9.9min / 1-99min / 0.1-9.9h / 1-99h, and several DIN-rail families also expose 0.1-99.9s, 1-999s, 0.1-99.9min, 1-999min for finer resolution on long-cycle processes [S1]. The deep-end 0.1s-10 days range is now common on single-function delay-off DIN modules aimed at irrigation, pump, and HVAC applications [S6], and the popular Xinling 81x18x72mm DPDT panel-mount family covers 0.1s-120h continuously adjustable [S2].
Repeatability is the spec engineers under-check: on ranges ≥1s the error budget is typically ≤1% (Er ≤1%), while on ranges <1s drift is reported in milliseconds (Dr ≤50ms) rather than percent, because a 1% spec on a 0.5s range would be meaningless at 5ms [S2]. Reset time ≤1s is the standard recovery window between cycles on most industrial electronic units [S1]. When a process calls for, say, a 14-second window, pick a range that brackets 14s in its mid-third; ranges that sit at the end-stop of a 1-99s dial lose linearity and accuracy because trimmer tolerance stacks with end-of-travel backlash.
Contact Rating, Use Category, and Electrical Life
Two contact ratings dominate the 2026 catalog: AC250V 5A at cosφ=1 (≈1250VA resistive) on the higher-capacity Anhonor family [S1], and AC220V 3A resistive on the compact Xinling DPDT [S2]. Both are quoted for use categories AC-15 (inductive AC loads, solenoid/contactor coils) and DC-13 (inductive DC loads, brake coils, small DC contactors) [S1], which is the language of IEC 60947-5-1 for control-circuit contactors and a critical reference for inductive loads.
Electrical life on these electronic relays is typically ≥10×10^4 operations (100,000 cycles), while mechanical life is ≥100×10^4 (1,000,000 cycles) [S1]; the 10:1 ratio reflects contact wear, not coil wear, so a high-cycle application like a packaging-machine reject gate will eat contact life faster than coil life. For DC inductive loads, derate aggressively: a 24V DC solenoid at 0.5A on a relay rated 250V AC 5A will still see its contacts abused by the lack of a natural current zero, and a snubber (RC for AC, flyback diode for DC) belongs across the coil, not the relay contacts. Power consumption on these units is ≤1.5W, with the higher-power DH11S variant ≤3W [S1], which matters when many timers share one 24V DC rail.
Supply Voltage, Voltage Tolerance, and Form Factor
Universal-voltage supply is now standard: DC 24V plus AC 24V/36V/110V/220V/380V at 50Hz, with operating tolerance 85-110% of nominal [S1][S2]. That 85% lower bound is the figure to remember for genset-fed or long-cable installations where brownout is the real failure mode, not overvoltage. Mounting divides into three buckets: 35mm DIN-rail multifunction (FCT18 family and equivalents) for control panels [S8]; 81x18x72mm panel-mount DPDT with one delayed and one instantaneous changeover for OEM machine builds [S2]; and miniature 0.1kg PCB-style modules like the ZHRT1-D for inside-equipment integration [S4].
Plug-in 8-pin or 11-pin octal bases remain the retrofit favourite because they swap out in seconds without re-wiring, while the bare PCB module (HK1601, 1-50s trimmer-adjustable delay-off) is the format for low-cost OEM volume [S3]. For an in-depth walkthrough of the function-plus-spec-plus-form-factor decision path, the time relay selection guide maps the same three-axis logic to buyer shortlist steps. If the relay is part of a wider control panel build, the selector switch and indicator stack is the next-neighbour component, and its 16/22/30mm form-factor and current-band logic follows a similar catalog-map pattern.
Who a Generic Multifunction Timer Is NOT For
A standard electronic time relay is the wrong pick when any of four conditions show up in the spec: the load exceeds AC250V 5A (≈1250VA resistive), the timing function must survive coil power loss with continued accuracy (true power-off delay with on-board memory), the environment is explosive atmosphere requiring ATEX/IECEx-certified apparatus, or the cycle count exceeds 10^5 electrical operations in a year (high-cycle packaging, automatic test). [S3]
In those cases, the right move is a true power-off-delay relay with internal supercapacitor or battery backup (e.g. the ZHRT1-D power-off-delay family) [S4], an explosion-proof enclosure housing rated for the zone, or a pneumatic / motor-driven timer with mechanical life ≥10^7 cycles. Substituting a standard on-delay relay on a true power-off-delay duty is a common spec error: most "delay-off" units in the catalog actually time after the next power-up, not after power removal, and the difference is a fried contactor coil inrush on every cycle.
Standards, Sourcing Signals, and Shortlist Logic
For any industrial control panel, the time relay must be specced to a recognised use category (AC-15 / DC-13 per IEC 60947-5-1) and the contact rating must be quoted in VA, not just amps, because inductive derating differs by an order of magnitude between categories [S1]. When the relay is mounted alongside lighting control gear on a construction site temporary board, the 85-110% voltage tolerance band is the same on both devices, which simplifies generator sizing.
Shortlist logic in three lines: (1) write down the required function and the required time range with margin; (2) match supply voltage to the control rail, with 85% brownout tolerance as the gate; (3) pick a contact rating ≥2× the inrush VA of the load, with a snubber across any DC inductive coil. The Anhonor-style AC250V 5A units [S1] cover 80% of general industrial control work, the Xinling-style AC220V 3A DPDT modules [S2] cover 15% (smaller panel builds with both delayed and instantaneous contacts), and the bare PCB HK1601 [S3] plus miniature ZHRT1-D [S4] cover the remaining 5% (high-volume OEM and power-off-delay duties). Trackable signals to watch through the rest of 2026: published updates to the FCT18 family and equivalents adding native Modbus or IO-Link read-back of remaining-time, and any extension of the 0.1s-10 days single-function range into the multifunction DIN-rail segment.