Monitoring Relay Price List: ABB and Schneider Compared

What sets the price of a monitoring relay? A monitoring relay's price tracks the number of functions it measures in one housing, the module width (17.5-22.5 mm DIN rail), and whether it needs an auxiliary supply or draws power from the measured line itself, per IEC 60255 and IEC 60947-5-1 construction classes. Buy on function count without checking hysteresis, delay, and output contact rating, and the "cheaper" unit ends up needing a second device to do the job the first one should have covered. This article compares ABB CM range and Schneider Electric Zelio Control pricing structure, covers what pushes a unit up a price tier, and gives a working method for matching relay to budget across single-phase voltage, three-phase supply, current, level, and temperature monitoring.

What Determines Monitoring Relay Pricing

Four variables move the price needle. Function count is the biggest one: a single-function relay (voltage only, or current only) sits at the bottom of the range; a combined phase-sequence-plus-voltage-plus-asymmetry unit sits well above it. Measurement method is second — average-sensing is cheaper than true-RMS, and true-RMS matters once the load has harmonic content from VFDs or switch-mode supplies on the same bus. Output configuration is third: one change-over contact costs less than two, and a higher contact rating (enough to drive a contactor coil directly, versus needing an interposing relay) adds to the bill. Auxiliary supply requirement is the fourth: relays that self-power from the monitored three-phase line (like ABB's CM-MPS) remove a separate power supply from the panel bill of materials, which is a real installed-cost saving even if the relay's own list price is similar to an aux-powered equivalent.

What Pushes a Unit Into a Higher Price Tier

Four line items do most of the work. Auxiliary-supply-free operation removes a power supply from the BOM but can sit at a similar or higher relay price than an aux-powered equivalent — the saving shows up elsewhere on the panel, not on the relay's own line item. Selectable fault memory (latching output that requires manual reset after a trip, versus automatic reset) is a feature that top-tier models add and entry models skip. True-RMS measurement, needed once VFDs or switch-mode loads distort the waveform, adds cost over average-sensing designs. And a second change-over output contact, which lets one relay drive both a contactor coil and a PLC alarm input without an interposing relay, costs more than a single-contact version. None of these are optional on some jobs — a hospital IT system needs latching output on its temperature monitoring relay or IMD regardless of what it adds to the unit price.

Schneider Zelio Control Price Tiers: RM17, RM22, RM35

Schneider's Zelio Control range splits into three tiers by module width and function count, and the price follows that split closely. RM17 is the entry tier — single-function devices such as RM17TE (three-phase supply: sequence, loss, over/undervoltage in one unit) or RM17UB (single-phase voltage). RM22 sits in the middle: a 22.5 mm compact range covering three-phase (RM22TR) and level (RM22LG/RM22LA) at a similar function count to RM17 but in a narrower, newer housing. RM35 is the top tier — multifunction devices like RM35TF (three-phase multifunction: sequence, loss, asymmetry, over/undervoltage combined), RM35UA (voltage with wider setting range), RM35JA (current), and RM35ATR (temperature/thermistor). RM35 units carry the highest list price in the range because one part replaces what would otherwise need two RM17 units, and RM35 typically adds selectable fault memory the lower tiers skip. When a spec calls out the monitoring and control relays category on Stoklink, RM17 and RM35 both show up, and the price gap between them is the function-count gap, not a quality gap.

ABB CM Range Price Tiers

ABB's CM range follows the same logic under different model codes. CM-MPS and CM-MPN cover three-phase monitoring (sequence, failure, asymmetry, over/undervoltage); MPS needs no auxiliary supply, which trims panel wiring cost even where the relay's own price is comparable to MPN. CM-ESS and CM-SRS handle single-phase current (over/under); CM-EFS extends current monitoring. CM-ENS and CM-ENE cover liquid level via conductive sensing. CM-TCS, CM-MSS, and CM-MSN cover temperature and PTC thermistor inputs. CM-UFD and CM-UFS combine voltage and frequency in one part. Across the CM range, the price step-up pattern mirrors Schneider's: single-function models are the cheapest entry point, and models adding a second measured quantity, selectable fault memory, or true-RMS sensing sit above them. All CM units are 22.5 mm DIN and carry one or two change-over outputs — the contact count is itself a line-item cost difference within the same functional family.

Cost-Per-Function: A Fair Way to Compare List Price Across Models

Comparing a single-function RM17UB against a five-function RM35TF on list price alone favors the RM17UB every time, because it always will be cheaper — that is not a useful comparison. Divide list price by the number of monitored functions and the multifunction units usually come out ahead once you would otherwise need two or three single-function relays to match the same coverage.

ABB CM vs Schneider Zelio Control: What the Price Difference Buys

Neither brand is consistently cheaper across the board — the price gap between ABB and Schneider on a given function is usually smaller than the gap between that same brand's entry and top tier. Pick the tier the application needs first, then compare list prices within that tier.

When the Cheaper Relay Costs More Overall

What we see in the field: a panel builder specs the lowest-price single-function voltage relay, then discovers the job also needs phase-sequence checking on the same feeder. Now it is two relays, two DIN rail slots, two sets of terminal wiring, and two devices to commission and document — against one multifunction relay that would have covered both from the start. The single-function part wins on its own line item and loses on installed cost. The same pattern shows up with output contacts: a single-contact relay driving both a contactor and a remote alarm needs an interposing relay added on, which is another part number, another wiring point, and another failure mode.

How to Buy: Matching Function Count to Budget

Start from the fault the relay needs to catch, not from the lowest price on the list. A motor circuit that only needs phase-sequence blocking at startup does not need a five-function relay — an entry-tier device is the correct spec, not a compromise. A feeder that needs sequence, loss, asymmetry, and voltage window in one enclosure justifies the RM35 or CM-MPN price step, because the alternative is stacking two or three cheaper relays into the same panel space. Cross-check the function list against what is already covered elsewhere in the circuit: a motor already protected by a motor protection circuit breaker for overload does not need overcurrent duplicated in the monitoring relay, and a circuit already using thermal overload relays for thermal protection is often better served by a monitoring relay focused on phase and voltage faults instead. For the full breakdown of relay types and what each one is built to catch, see the types of monitoring relays guide and the how to select a phase and voltage monitoring relay walkthrough.

Conclusion

Monitoring relay pricing is not arbitrary — it tracks function count, measurement method, output configuration, and auxiliary supply need, and both ABB CM and Schneider Zelio Control follow the same tiering logic under different model codes. Spec to the fault the circuit needs to catch, compare cost-per-function within a tier rather than list price across tiers, and count installed cost (panel space, wiring, interposing relays) before defaulting to the lowest sticker price. For the underlying engineering behind these functions, the monitoring relay engineering guide covers threshold, hysteresis, and trip delay in more depth.