A generic off-delay socketable time relay rated 10 A at 250 VAC with SPDT (1 Form C) contacts covers timing spans of 0.1 s to 100 h, per the Crouzet 88867135 datasheet [S1]. A multi-function programmable DPDT (2 Form C) part in the same 10 A / 240 VAC / 30 VDC class extends that range to 0.1 s through 600 h, per the IDEC RTE-B1AF20 datasheet [S2].
Both parts are socketable, meaning the timer module plugs into an 8- or 11-pin base so a failed unit can be swapped in under a minute without disturbing the field wiring — the dominant mounting style in control panels and the one buyers should default to unless the application is high-vibration or sealed. For sealed or vibration-heavy duties, PCB-mount or hermetically sealed CMOS-IC time-delay relays such as the Tyco/MACOM CG-series CGB-38-70010M exist as the solid-state alternative [S6].
Define the timing function before looking at part numbers
Time relays are classified by IEC 61812-1:2011 — "Time relays for industrial and residential use — Part 1: Requirements and tests" — as devices whose output contact state changes after a defined time interval relative to a control input or a power event [S8]. The four operating modes the standard family recognises, and the four a buyer must pick from first, are: on-delay (delay on make, DO), off-delay (delay on break, DB), interval-on, and flasher / repeat-cycle. Each maps to a different control logic and a different timing diagram, and choosing the wrong mode is the single most common spec error on a panel retrofit.
A historical reference still cited in Chinese hydro-plant specifications is SD 285-1988 "Technical specifications for static time relay" — a now-superseded sector standard that classified static (electronic) time relays separately from pneumatic and clockwork types [S3][S4]. It is useful background on the gas-bag (pneumatic), clockwork, and electronic split, but for new builds IEC 61812-1:2011 is the binding document [S8].
For a primer on the wider relay family and how time-delay types slot into it, see the industrial relay and relay module encyclopedia entries.
Selection Gate 1 — Timing range and resolution
The first numeric gate is the required time span. Off-delay socketable parts commonly span 0.1 s to 100 h, as the Crouzet 88867135 datasheet specifies [S1]. Multi-function programmable parts such as the IDEC RTE-B1AF20 widen that to 0.1 s to 600 h with field-selectable ranges [S2]. Resolution is normally ±1 % of full scale for analog-set timers and ±0.1 % for digital, and repeat accuracy is typically ±0.5 % — buyers should treat any datasheet that omits these two numbers as incomplete.
Match range to duty: sub-second intervals belong to interval-on or off-delay parts for conveyor-diverter sequencing; multi-hour spans belong to on-delay or repeat-cycle parts for curing, lubrication, or chemical-feed cycles. Choosing a 0.1 s to 100 h part for a 600 h process is a real failure mode seen on field retrofits and is avoided by reading the upper-limit line, not the marketing headline.
Selection Gate 2 — Contact form and current rating
Contact form is the second binding gate. Single-pole changeover (SPDT, 1 Form C) handles one switched load and is the minimum for simple start/stop sequencing [S1]. Double-pole (DPDT, 2 Form C) provides two independent or simultaneous outputs and is the right call when one timer must drive a contactor coil and an indicating lamp, or interlock two circuits from a single timing event [S2].
Current rating of 10 A at 250 VAC / 30 VDC is the de-facto panel standard for both the Crouzet and IDEC parts above [S1][S2]. Below 10 A the part is a logic relay and belongs to a different family; above 10 A the timer should drive a contactor, not switch the load directly. For an overview of the contactor side of that decision see the time relay encyclopedia entry.
Selection Gate 3 — Operating mode (on/off/interval/cycle)
Mode dictates the timing diagram and is the most often-skipped spec line. A multi-function programmable part such as the IDEC RTE-B1AF20 ships with selectable on-delay, off-delay, interval-on, flasher, and star-delta modes, selectable via a front-face rotary switch or DIP [S2]. A single-function off-delay part such as the Crouzet 88867135 cannot do on-delay — buying it for a star-delta starter will not work no matter how the dial is set [S1].
Four-mode rule of thumb: on-delay (DO) is the default for sequential start; off-delay (DB) is the default for hold-after-stop; interval-on is the default for one-shot pulse generation; flasher/repeat-cycle is the default for duty-cycled lubrication or aeration. Specifying the mode explicitly on the BOM line removes a class of commissioning errors.
Selection Gate 4 — Supply, coil, and socket pin-out
Coil and supply range is the last numeric gate. The Crouzet 88867135 and IDEC RTE-B1AF20 are both listed at 10 A / 250 VAC (or 240 VAC / 30 VDC for the IDEC), socketable, and accept a wide-range AC/DC control supply depending on the variant ordered [S1][S2]. Common panel pin-outs are 8-pin (octal) for SPDT and 11-pin for DPDT; mixing the two means a different socket, and buyers should pin the base part number to the pin-out on the drawing, not the catalogue description.
Sealed or vibration-heavy environments — rail rolling stock, mobile equipment, marine — are the wrong duty for a socketable electromechanical timer; the alternative is a solid-state CMOS-IC time-delay relay such as the Tyco/MACOM CG-series CGB-38-70010M, which has no moving contacts and is rated for harsher mechanical environments [S6]. For safety-circuit timing where a single failure must not pass undetected, the part should be a safety relay or a force-guided contactor pair, not a generic time relay.
Who should pick a generic socketable timer — and who should not
Pick a 10 A socketable SPDT or DPDT multi-mode timer when the duty is panel-mount, the timing span fits inside 0.1 s to 100 h (or 600 h for the programmable parts), the contactor coil is the load, and the environment is dry and indoors [S1][S2]. This covers the majority of packaging-line, conveyor, pump-sequel, and HVAC duty. It also covers most motor protection relay sequencing and the timing side of a thermal relay coordination chain.
Do not pick a generic socketable timer when the duty is: (a) SIL-rated safety logic — use a safety relay instead; (b) explosive atmosphere — verify the part carries an Ex rating, not just an IEC 61812-1 conformance line; (c) sub-millisecond or PLC-scan-rate timing — use the PLC's onboard timer or a dedicated counter module; (d) load currents above 10 A or 250 VAC — drive a contactor. A timer marketed as "industrial" but lacking a contact form, current rating, timing range, and operating mode on its datasheet is a red flag regardless of price.
Comparison of three realistic options on four selection criteria
Three concrete options lined up against the four binding gates: (1) Crouzet 88867135 off-delay SPDT, 0.1 s to 100 h, 10 A / 250 VAC, socketable, single-function [S1]; (2) IDEC RTE-B1AF20 multi-function DPDT, 0.1 s to 600 h, 10 A / 240 VAC / 30 VDC, socketable, programmable mode [S2]; (3) Tyco/MACOM CGB-38-70010M CMOS-IC solid-state timer, PCB-mount, sealed, no moving contacts, intended for harsh mechanical environments [S6]. On timing range the IDEC wins (600 h), on simplicity the Crouzet wins (one dial, one function), and on environment the MACOM wins (solid-state, PCB).
The cost versus the time-saving aspect of these parts is visible on multi-channel platform listings: a generic 12 V gate-opener timer board with integral relay is offered at US $199.56–204.71 (4.9/5 from 5,206 orders) on cross-border channels, which puts a single function board in the same price band as an industrial multi-function DIN-socketable timer [S5]. The platform listing is a useful price anchor only — it is not a panel-spec source.
Sourcing, standards, and what to verify on the datasheet
For a part to be acceptable on a European or IEC-jurisdiction panel, the datasheet should reference IEC 61812-1:2011, which is the current "Time relays for industrial and residential use — Part 1: Requirements and tests" standard governing the timing function, electrical endurance, and dielectric test regime of these devices [S8]. Buyers should also check that the datasheet states: timing range with units, repeat accuracy as a percentage, contact form (SPDT/DPDT or Form C / Form A+B), rated current and voltage, mechanical and electrical endurance in operations, and operating temperature range.
For comparison-shopping a similar product class, see the selector switch selection map and the proximity sensor criteria write-up — both follow the same four-gate logic. Track these as the next selection decisions in a panel BOM: contactor current rating, indicator-lamp voltage, and the relay-socket pin-out on the wiring drawing.