A counter relay closes its output contacts when a preset number of input pulses has been accumulated, while a time relay closes its contacts after a preset on-delay, off-delay, or cyclic interval has elapsed; the two are not interchangeable because one is event-driven and the other is duration-driven [S5].
On Chinese B2B platforms the two families sit in the same "industrial relay" category, with miniature ST3PA-style time relays listed from US $1.84/piece at 5-piece MOQ up to US $2/piece at 10-piece MOQ, 30 A working current and 1500 VAC dielectric strength [S1].
Functional Definition and Trigger Source
A counter relay counts discrete inputs — typically potential-free contact closures, NAMUR sensors, or 24 V logic pulses — and energises its output when the count reaches a programmed preset, with options for count-up, count-down, and batch-reset behaviour; the trigger is a pulse train, not a continuous signal [S5].
A time relay instead measures elapsed time after a start edge and switches its output when the dial- or software-set interval expires; classical pneumatic-bag and clockwork designs have been joined by electronic and digital modules that cover milliseconds to hundreds of hours [S5].
Where a relay module is used, the time and counter functions are often supplied as the same DIN-rail hardware with the trigger source (pulse vs. maintained) being the only field-side difference, which is why spec sheets for both families share contact ratings, coil voltages and socket footprints.
Selection Criteria: Event-Driven vs Duration-Driven
The first cut is the process variable: bottling lines, cut-to-length conveyors and parking-barrier cycles are event-counted, so a counter relay is specified; motor star-delta starting, lubrication intervals and HVAC damper sequencing are duration-based, so a time relay is specified [S5].
Counter relays need a clean, debounced pulse input with a defined minimum pulse width, while time relays need a stable start command and an accurate time base — cheap electromechanical timers drift noticeably with temperature and voltage, whereas digital timers hold ±0.1 % or better over their rated range.
For mixed sequences — for example "run pump for 30 s, then count 12 strokes, then stop" — engineers commonly cascade a time relay feeding the count-enable input of a counter relay rather than buying a single multi-function controller, because the failure modes and spare-part stocks stay independent.
Contact Ratings, Coil Voltages and Sourcing Footprint
Counter and time relays share the same output-stage vocabulary: 1 CO or 2 CO contacts, 5 A / 250 VAC resistive being a baseline figure across both families, with industrial variants rated 10 A, 16 A or 30 A and dielectric strength from 1500 VAC to 5 kVAC between coil and contacts [S1].
Shenler Corporation, a 40-year Chinese relay manufacturer established in 1985, lists time relays and relay modules alongside PCB, slim, solid-state and magnetic blow-out relays in the same catalogue, with products carrying CE, TÜV, RoHS, UL, EAC, UKCA, CSA and CQC approvals [S2].
That single-catalogue overlap is useful for procurement: a safety relay, thermal relay and counter or time relay from one vendor can share sockets, jumpers and marking accessories, cutting panel-build labour and spare-part inventory on a typical MCC line.
Options Comparison: Pneumatic, Electronic, Digital
Three delay technologies coexist: pneumatic-bag timers are cheap, immune to electrical noise and cover roughly 0.1–60 s, but they suffer temperature drift and limited range; clockwork timers handle longer intervals with mechanical wear; electronic RC and digital timers reach sub-100 ms to 100+ h with set accuracy that pneumatic units cannot match [S5].
For counting, the equivalent split is electro-mechanical preset counters (rugged, no power needed for display, but limited to a few digits) versus electronic counters (7-segment or LCD, presettable from a keypad, optional encoder inputs, often multi-function: counter + tachometer + timer in one box).
Compared on four decision criteria — set accuracy, ambient tolerance, install footprint, unit cost — digital electronic units win on accuracy and range, pneumatic and electromechanical units win on cost and surge immunity, and the choice usually narrows once the panel's DIN-rail budget and ambient temperature envelope are fixed.
Use Cases and Failure Modes
Counter relays fail in three characteristic ways: contact welding on inductive loads beyond the published VA rating, pulse-input miscount caused by contact bounce or chattering sensors, and counter-memory loss on power-down if the unit is a non-volatile model — battery-backed or EEPROM-backed devices are mandatory on safety-relevant counts. [S1]
In practice, a general-purpose industrial relay with a 30 A / 1500 VAC dielectric rating is a common output-stage choice behind either device when driving solenoids, motor contactors or heater banks, and the 1500 VAC coil-to-contact figure seen on ST3PA-class miniature timers is also typical for entry-level counter relays [S1].
Standards, Sourcing Signals and 2026 Build Cycles
Industrial timer and counter modules are commonly built to IEC 61810-1 for electromechanical elementary relays and to UL 508 / CSA C22.2 No. 14 for industrial control panels, with CE marking under the EU Low Voltage Directive 2014/35/EU and, for Canadian and US hazardous-location builds, CSA and UL listed marks respectively [S2].
The 2026 sourcing signal from Made-in-China.com is clear: 17 ST3PA-series time-relay SKUs from Zhejiang-based manufacturers, 5–10 piece minimum orders, US $1.84–$2/piece FOB, ISO 9001:2015 quality system, 30 A working current, 1500 VAC dielectric strength, sealed housing — a profile that also matches generic counter-relay modules in the same price band [S1].
Engineers specifying new panels in 2026 should pin the trigger source first (pulse vs. maintained), then the timing or count range, then the output rating, and only then the vendor — and should treat the relay module pricing guide and the relay-module vs selector-switch logic write-up as companion reading when the cabinet design mixes counting, timing and manual selection.