Schneider RM22LG11MR Level Control Relay

Harmony RM22-L Level Control Relay (Conductive Electrode Liquid Level Monitoring)

Interpretazione del modello: RM22 series modular control relay; LG = liquid level single detection; 11 = 1 contatto di scambio (C/O); MR = power supply 24~240V AC/DC; MT version for 380~415V AC power supply

✅ Funzioni principali

Designed for conductive liquids (acqua, liquami, ecc.) for automatic liquid level control. Two operating modes available:

1. Fill Mode (Fornitura d'acqua) : When liquid level falls below Min electrode → relay energizes, starts fill pump; when liquid level reaches Max electrode → relay de-energizes, stops pump.
2. Drain Mode (Sump Pumping) : When liquid level reaches Max electrode → relay energizes, starts drain pump; when liquid level drops below Min electrode → relay de-energizes, stops pump.

It adopts resistance probe detection, judging liquid level based on liquid conductivity, not float switch. Adjustable detection sensitivity.

📋 Electrical Specifications

Tensione di alimentazione: 24~240 V CA/CC (universal for AC & DC), 50/60Hz; operating range 20.4~264V

Consumo energetico: AC 5VA / DC 1.5W

Output contact: 1 changeover contact 1C/O (11-12 normalmente chiuso, 11-14 normalmente aperto), AC-15/DC-13, 8A@250VAC

Power-on delay: 0.6S

Probe circuit: Massimo. 12V AC at electrodes, electrode current ≤1mA; maximum probe cable length 1000m

Sensibilità: St standard sensitivity 5kΩ～100kΩ, continuously adjustable via potentiometer

Montaggio: Guida DIN, width 22.5mm

Protezione: Sealing transparent protective cover to prevent on-site misadjustment; built-in diagnostic test button + status LED indicator

📌 Terminal Definition

Wiring note: 3 electrodes inside tank: C common pole, Min minimum liquid level, Max maximum liquid level. Only applicable to conductive liquids; not for insulating oil and other non-conductive media.

🛠️ Typical Applications

Approvvigionamento idrico & drainage tanks, pozze di liquami, torri di raffreddamento, water purification equipment, automatic pump start/stop, DIN rail mounting inside control cabinet.

⚠️ Model Differentiation & Riferimento sostitutivo

1. RM22LG11MR: 24~240 V CA/CC, single changeover contact
2. RM22LG11MT: 380~415V AC power supply version
3. RM22LA32MR: Dual-contact version, two-channel output

Legacy replacement: RM35LM series (interrotto, replace with RM22LG for new projects)

Principio di funzionamento di Schneider RM22LG11MR

Principio fondamentale: AC resistive conductive liquid level detection (Conductivity type)

A low-voltage AC sensing signal is applied between electrodes. The device measures liquid resistance between two electrodes and compares it with the sensitivity threshold set on the front panel. The internal circuit drives output relay action.

Low voltage AC signal on probe side to avoid electrolytic corrosion of electrodes caused by DC.

1. Detection Circuit

The relay outputs low voltage AC sensing signal (approx.12V AC, current＜1mA) between C (common electrode), minimo (basso livello), Massimo (high level).

Electrode submerged by liquid → conductive liquid forms path between C and electrode, bassa resistenza;

Electrode exposed above liquid → circuit open, extremely high resistance;

Potentiometer sets sensitivity threshold (5kΩ~100kΩ) : Measured resistance ＜ threshold → liquid detected; resistance＞threshold → no liquid detected.

👉 Only valid for conductive liquids. Not applicable for oil, ultra-pure water (very low conductivity) and insulating liquids.

2. Two Operating Modes (3-point liquid level control with hysteresis memory logic)

1) Fill Mode (Water Make-up)

Liquid level below Min electrode: C-Min circuit open → internal relay energizes, 11-14 NO chiude, starts fill pump.

Liquid level rises, submerges Min but not reaching Max: C-Min conductive, internal memory holds status, pump keeps running.

Liquid level reaches Max electrode: C-Max conductive → relay resets, 11-14 si apre, la pompa si ferma.

If liquid level drops but remains above Min, pump will not start. Two-point start/stop prevents frequent pump cycling.

2) Drain Mode (Drenaggio della coppa)

Liquid level reaches Max electrode: C-Max conductive → relay energizes, 11-14 NO chiude, starts drain pump.

Liquid level falls, leaves Max but still higher than Min: memory holds status, pump keeps draining.

Liquid level below Min electrode: C-Min open → relay resets, la pompa si ferma.

3. Single Level Mode (Opzionale, 2 elettrodi)

Use only C+Max or C+Min for single-point alarm / controllare. Small delay can be enabled to suppress false triggering caused by liquid wave and foam.

4. Internal Signal & Produzione
5. A1/A2 supplies power to relay (24~240V AC/DC wide range), power circuit is electrically isolated from probe measurement circuit;
6. Measurement circuit continuously acquires resistance between electrodes;
7. Logic unit judges status based on mode and electrode signals, unità 1 contatto di scambio (1C/O, 11 comune,12 NC,14 NO);
8. Front panel LED indicates output status; built-in test button simulates status for loop commissioning.
9. Caratteristiche principali del progetto
10. AC sensing: No DC voltage applied to electrodes, prevents electrolysis, bubble generation, electrode corrosion and accelerated scaling.
11. Adjustable resistance threshold: Adapt to sewage / clean water with different conductivity via sensitivity knob.
12. Hysteresis memory logic: Requires recognition of high & low level points, avoids frequent relay switching caused by minor liquid fluctuation.
13. Max electrode cable length up to 1000m. Beware of stray capacitance interference for long cables; false triggering tends to occur under high sensitivity setting.
14. Fault Correspondence Based on Principle

Electrode scaling → equivalent liquid resistance rises above threshold → liquid present but device reports no liquid;

Conductive foam layer → electrode not touching actual liquid level but circuit conducts → false liquid level detection;

Poor contact of C electrode → measurement reference lost, all liquid level detection invalid.

Troubleshooting for Schneider RM22LG11MR

Pre-diagnosis method: T test button on front panel. Press T when powered on to toggle relay output status, to distinguish unit failure or external electrode / guasto al cablaggio.

Colpa 1: No response after power on, power LED off

Sintomo: A1/A2 supply voltage normal, no LED light, relay no action

Cause

1. Loose A1/A2 wiring, poor terminal contact; wrong polarity for DC supply
2. Input voltage out of 24~240V AC/DC operating range
3. Internal power circuit damaged (lightning surge, transient overvoltage, cortocircuito)

Soluzioni

1. Spegnimento, measure voltage at A1/A2, tighten terminals; check polarity for DC supply
2. Verify supply within rated range; check upstream MCB and fuse
3. Replace unit if LED still off with correct supply voltage

Colpa 2: Relay does not act when electrode submerged (liquid detected but no response)

Sintomo: Liquid covers Max/Min electrode, relay status unchanged, pump does not start/stop

Cause

1. Electrode covered by scaling / sludge, liquid equivalent resistance exceeds sensitivity threshold
2. Poor contact of C common electrode (most frequent), measurement reference lost
3. Broken electrode cable, loose wiring at Min/Max/C terminals
4. Sensitivity set too low (resistance threshold too small for sewage to conduct)
5. Medium conductivity too low (ultra-pure water, insulating liquid, not suitable for this model)

Soluzioni

1. Remove electrodes, pulito / polish scale and sludge; regular electrode maintenance
2. Priority check C electrode: ensure C is immersed in liquid and wiring secure
3. Spegnimento, test cable continuity, tighten Min/Max/C terminals
4. Increase sensitivity appropriately (raise resistance threshold, adjustable from 5kΩ~100kΩ)
5. For low-conductivity water / olio, use float level switch instead

Colpa 3: Relay false action when liquid level below electrode (detects liquid with no actual liquid), pump starts unexpectedly

Sintomo: Liquid level below electrodes, relay reports liquid present, pump starts mistakenly

Cause

1. Conductive foam / scum on liquid surface closes electrode circuit (common in sewage tank)
2. Long electrode cable, stray capacitance causes false trigger (>300m is high risk)
3. Sensitivity set too high, minor leakage triggers detection
4. Electrode cable routed in parallel with power cable, electromagnetic interference
5. Terminal condensation / leakage between electrodes

Soluzioni

1. Raise electrode mounting position to avoid foam; install foam baffle
2. Reduce sensitivity; use shielded cable for long signal wire, shield single-end grounded; separate from power cables
3. Clean terminal condensation, improve cabinet moisture resistance

Colpa 4: Frequent pump start-stop, relay chattering / oscillazione

Sintomo: Liquid level stable within range, relay repeatedly energizes and de-energizes, pump cycles rapidly

Cause

1. Severe liquid turbulence, liquid surface sweeps electrodes repeatedly; intermittent conduction by foam
2. Dirty electrodes, unstable electrode resistance
3. Wrong operation mode, hysteresis logic disabled (only single electrode wired)

Soluzioni

1. Extend electrodes, install anti-surge sleeve; mount electrodes in still zone of tank
2. Clean electrodes, fine-tune sensitivity and avoid critical setting
3. Standard 3-electrode wiring (C+Min+Max), enable built-in hysteresis memory logic, avoid single-point control

Colpa 5: Relay LED normal but output contact no action, pump fails to start

Sintomo: Level indicator LED correct, but downstream contactor / pump does not work

Cause

1. Wrong wiring of output contacts (11/12/14 terminals misconnected)
2. Contact load exceeds rated 8A, erosione da contatto / welding / circuito aperto
3. No power on downstream control circuit

Soluzioni

1. Power off and verify contact wiring: 11 comune, 12 NC,14 NO
2. Press T test button and measure continuity between 11-14; open circuit = contact damaged, sostituire il relè
3. Check control power supply for pump / contattore

Colpa 6: Saldatura dei contatti, pump runs continuously and cannot stop

Sintomo: Liquid level reaches stop position, output remains closed, pump cannot shut down

Cause

1. Sovraccarico a lungo termine, electric arc causes contact welding
2. No surge absorption for contactor coil, back EMF damages contacts

Soluzioni

1. Replace RM22LG11MR immediately if contacts welded
2. Add RC snubber or freewheeling diode for inductive load (bobina del contattore) to protect 8A internal contacts

Recommended On-site Troubleshooting Sequence

1. Accendere, check power LED; LED off → inspect A1/A2 power supply
2. Press T test button and observe output toggle

Output toggles by T: Unità sana, fault in electrode, cable or liquid medium

No response by T: Relay unit damaged, replace directly

3. Verify C common electrode fully immersed and wiring tightened
4. Clean electrodes and adjust sensitivity knob
5. Check if signal cable runs together with power cable; use shielded cable for long distance
6. Confirm mode selection: Fill (fornitura d'acqua) / Drenare (drenaggio)

Manutenzione preventiva

1. Sewage application: Clean electrodes every 3~6 months to prevent scaling
2. Keep electrode cable length within 500m where possible; reduce sensitivity and adopt shielded cable if longer
3. Ensure cabinet moisture-proof to avoid terminal condensation leakage
4. Install surge absorption device for inductive load (contattore) to protect 8A contacts

Schneider RM22 Harmony Modular Monitoring Relay Full Series List

Series common features: Montaggio su guida DIN, width 22.5mm (RM22TG20:17.5mm); equipped with T test button, status LED, sealable transparent cover; valutazione dei contatti: 8A@250VAC; suffix MR=24~240V AC/DC universal supply; MT=380~415V AC supply

1. RM22L Conductivity Level Monitoring Relay (series of your model)

Conductive electrode liquid level detection for high/low level control of water tank and sewage sump

|RM22LG11MR|1C/O (1 cambio)|24~240 V CA/CC|Modello standard, your reference unit, sensitivity 5k~100kΩ|

|RM22LG11MT|1C/O|380~415 V CA|High voltage supply level relay|

|RM22LA32MR|2C/O (2 cambio)|24~240 V CA/CC|Dual-channel output, 3 sensitivity levels: LS/St/HS|

|RM22LA32MT|2C/O|380~415 V CA|Dual-contact high voltage supply level relay|

2. RM22T 3-phase Power Monitoring Relay (Sequenza di fasi / perdita di fase / 3-squilibrio di fase / sovratensione & sottotensione)

Monitor 3-phase power supply for motor, pompa dell'acqua, air compressor protection

|RM22TA31|2C/O|Sequenza di fasi, perdita di fase, 3-squilibrio di fase|200~240 VCA|

|RM22TA33|2C/O|Sequenza di fasi, perdita di fase, 3-squilibrio di fase|380~480 VCA|

|RM22TU21|2C/O|Sequenza di fasi, perdita di fase, sottotensione|200~240 VCA|

|RM22TU23|2C/O|Sequenza di fasi, perdita di fase, sottotensione|380~480 VCA|

|RM22TR31|2C/O|Sequenza di fasi, perdita di fase, sbilanciare, overvoltage/undervoltage with delay|200~240 VCA|

|RM22TR33|2C/O|Sequenza di fasi, perdita di fase, sbilanciare, overvoltage/undervoltage with delay|380~480 VCA|

|RM22TG20|2C/O|Sequenza di fasi, perdita di fase (versione compatta,17.5mm)|183~528VAC|

3. RM22U Single-phase / DC Voltage Monitoring Relay (Sovratensione & Undervoltage monitoring)

AC/DC single-phase voltage monitoring for DC panel and single-phase power protection

|RM22UA32MR|2C/O|1~100V AC/DC|24~240 V CA/CC|

|RM22UA33MR|2C/O|15~500V AC/DC|24~240 V CA/CC|

|RM22UA33MT|2C/O|15~500V AC/DC|380~415 V CA|

|RM22UB34MR|2C/O|Wide range single phase voltage|24~240 V CA/CC|

4. RM22J Current Monitoring Relay (AC current monitoring, sovraccarico / sottocorrente)

Work with current transformer CT for motor load current monitoring

|RM22JA21MR|1C/O|0.1~5A AC|24~240 V CA/CC|

|RM22JA32MR|2C/O|0.1~5A AC|24~240 V CA/CC|

5. Regola di codifica del modello (RM22XXYYZZ)
6. RM22: Series code Harmony modular monitoring relay
7. XX: Function group

LG: Livello del liquido, single sensitivity

IL: Livello del liquido, multi-range sensitivity

TA/TU/TR/TG: 3-phase power monitoring

UA/UB: Single-phase voltage monitoring

E: Current monitoring

3. AA: Contact quantity

11: 1 contatto di scambio (1C/O)

32: 2 contatti di scambio (2C/O)

4. Z.Z: Power supply code

SIG: 24~240V AC/DC universal (most widely used in engineering)

MT: 380~415V AC 3-phase high voltage supply

6. Legacy Model Replacement (RM35 → RM22)

RM35LM old level relay → RM22LG / RM22LA

RM35TA/TU old 3-phase protection relay → RM22TA/TR/TU

RM35 series discontinued, select RM22 for new projects

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