What is a multifunction timing relay? A multifunction (multi-range) timing relay is a single DIN-rail or plug-in device that selects between several timing functions — on-delay, off-delay, star-delta, flasher — and several time ranges, typically spanning 0.1 s to 100 h, via rotary switches or DIP selectors, instead of shipping as separate fixed-function parts. That consolidation cuts the number of distinct timer part numbers a panel builder has to stock, at the cost of a larger front-panel control set and one extra configuration step per unit. This article covers how function selection works, how range selection interacts with setting accuracy, multi-voltage supply handling, panel-stock economics, what Schneider and ABB actually cover under "multifunction," and when a fixed-function timer is still the better choice.
How Function Selection Works
On a modular multifunction timer — Schneider Zelio Time RE22, ABB CT-MFD — a rotary switch on the front face picks the operating mode: on-delay, off-delay, one-shot/interval, symmetrical or asymmetrical flasher, and on two-output variants, star-delta. A second rotary switch or DIP bank selects the time-range band, and a potentiometer or thumbwheel sets the exact value inside that band. The terminal layout stays the same across modes — start/reset input, auxiliary supply, change-over output — the mode selector changes the internal logic, not the wiring.
What Actually Changes Between Modes
Selecting on-delay starts the count the instant supply is applied and transfers the output once the count reaches the set value, holding it there. Selecting off-delay transfers the output immediately on trigger and reverts it the set time after the trigger is removed. Selecting star-delta activates a second output and exposes a dedicated transition-time potentiometer that the on-delay and off-delay modes do not use at all.
How Range Selection Works, and Why Range Count Matters
Range selection sets the ceiling for the timing dial. Choosing the "1 s" range lets the potentiometer set 0.1-1 s in fine steps; choosing the "10 h" range reaches hours of delay with the same physical dial travel. A timer offering eight ranges from 0.1 s to 100 h spans four decades of adjustment in one device, where covering that same span with fixed-range timers would take four or five separate part numbers.
More ranges give finer resolution near the low end of a wide overall span. They also give more ways to select the wrong band and set an unintended value by a factor of ten.
What we see in the field: a delta contactor pulling in a fraction of a second early because a technician left the range switch on "1 s" after a spare-parts swap instead of the intended "10 s." The fix is a five-second range check at commissioning, not a different relay.
Setting Accuracy Across Multiple Ranges
IEC 61812 accuracy of operation is stated per range, as a percentage of the set value, not as a fixed number of seconds across the whole part. A repeat accuracy of ±0.5% on a 10 h range still permits several minutes of cycle-to-cycle drift; the same ±0.5% figure on a 1 s range is a few milliseconds. Picking the finest range that still covers the required setpoint improves absolute accuracy at no extra cost — a 30 s delay set near the top of a "1 min" range repeats tighter than the same 30 s set near the bottom of a "10 min" range.
Formula: Repeat Accuracy Error — Source: IEC 61812, accuracy-of-operation clause
Δt = ± (a% × tset)
| Symbol | Description | Unit |
|---|---|---|
| Δt | Maximum deviation between successive timing cycles at the same setting and conditions | s |
| a | Repeat accuracy class of the selected range, typically ±0.5% to ±1% | % |
| tset | Set time value on the active range | s |
Multi-Voltage Supply Handling
Many multifunction timers accept a wide AC/DC supply band on one part number — commonly 24-240V AC/DC — so the same catalog item sits behind a 24V DC control transformer on one job and a 230V AC control circuit on the next, without a dedicated low-voltage variant.
What Multi-Voltage Does Not Change
Function and range selection are independent of the supply-voltage input. Multi-voltage only widens which control transformer or supply the timer can be wired behind; it does not add functions, and it does not change the timing-range table printed on the front of the unit.
Panel Stock Economics: One Part Number vs Several
A panel builder running on-delay, off-delay, and occasional star-delta jobs across different orders can stock one multifunction timer in bulk instead of three fixed-function parts in smaller lots — fewer bins, fewer reorder points, one datasheet to train technicians on. The trade-off is a higher per-unit price than the cheapest fixed-function equivalent bought at volume, and more front-panel setup to verify at each install.
Some panel builders still standardize on a fixed-function timer for their single highest-volume application, typically on-delay for motor and conveyor sequencing, and keep the multifunction part on the shelf for spares and low-volume jobs. See how to select a timing relay for the volume-versus-flexibility trade-off in more detail.
Schneider RE22 and ABB CT-MFD: What "Multifunction" Covers in Practice
Schneider's Zelio Time RE22 series covers several functions and ranges in a 22.5 mm modular housing, with rotary function and range selectors, and a two-output star-delta variant designated RE22R. ABB's CT-MFD range covers a comparable function and range set in a 17.5 mm modular housing, also DIP- and rotary-set. Both mount on DIN rail next to the rest of the control gear — see timing and control relays and contactors for the parts they typically sit beside in a star-delta or sequencing circuit.
Neither brand's public documentation is worth quoting at the exact-figure level here — confirm the specific function list, range table, and contact rating on the selected part number before specifying it into a design.
When a Fixed-Function Timer Is the Better Choice
A dedicated on-delay-only timer has fewer front-panel controls, one function to verify at commissioning, and a lower per-unit cost at volume. See on-delay timing relay and off-delay timing relay for the single-function versions of the same logic covered above.
Fixed-function star-delta timers put the safety-critical transition-time setting on its own dedicated potentiometer instead of sharing panel space with a mode selector, which some specifications prefer for that application specifically. See star-delta timing relay for motor starting for the transition-time logic and why it matters on a two-output timer. For the full function taxonomy this article assumes, see types of timing relays, and for the broader device category, the timing relay engineering guide.
Frequently Asked Questions
What does "multifunction" mean on a timing relay?
It means one physical device can be set, via a front-panel rotary switch, to operate as an on-delay, off-delay, one-shot, flasher, or in some models a two-output star-delta timer, instead of being built for only one of those functions.
How many time ranges does a multifunction timer typically offer?
Common parts offer several ranges spanning roughly 0.1 s to 100 h in decade bands, selected on a second rotary switch or DIP bank, separate from the function selector.
Does a multifunction timer lose accuracy compared to a single-function timer?
Not inherently. Repeat accuracy is a percentage of the set value on the selected range, and multifunction parts publish the same class of figure, typically ±0.5% to ±1%, as fixed-function equivalents on a comparable range.
Can one multifunction timer replace both an on-delay and a star-delta timer?
Only if the specific part number includes a two-output star-delta mode in its function list — not every multifunction timer does. Check the mode table on the datasheet rather than assuming star-delta is included.
What is multi-voltage supply on a multifunction timing relay?
It is an auxiliary power input rated across a stated AC and/or DC band, commonly 24-240V, so the same part accepts several standard control voltages without a dedicated variant per voltage. It does not affect which functions or ranges are available.
Why would a panel builder still choose a fixed-function timer over a multifunction one?
Fewer front-panel controls, one function to verify at commissioning, and lower per-unit cost at high volume on a single repeated application, such as on-delay sequencing on every unit of a conveyor line.
Conclusion
A multifunction timing relay trades a slightly larger control set and one extra configuration step for fewer distinct part numbers on the shelf. Function and range selectors are independent of each other and of the supply-voltage rating, and accuracy is specified per range as a percentage of the set value, not as a flat figure across the whole device. Where a job runs one function at high volume, a fixed-function timer still wins on cost and on the number of settings a technician has to check at commissioning; where a job mixes on-delay, off-delay, and occasional star-delta duty across different orders, one multifunction part covers all three.