Schneider RM22LG11MR Level Control Relay

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

Interprétation du modèle: RM22 series modular control relay; LG = liquid level single detection; 11 = 1 contact inverseur (CO); MR = power supply 24~240V AC/DC; MT version for 380~415V AC power supply

✅ Core Functions

Designed for conductive liquids (eau, eaux usées, etc.) for automatic liquid level control. Two operating modes available:

1. Fill Mode (Approvisionnement en eau) : 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

Tension d'alimentation: 24~240 V CA/CC (universel pour AC & CC), 50/60Hz; operating range 20.4~264V

Consommation d'énergie: AC 5VA / DC 1.5W

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

Power-on delay: 0.6s

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

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

Montage: Rail DIN, width 22.5mm

Protection: 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

Approvisionnement en eau & drainage tanks, sewage pools, tours de refroidissement, water purification equipment, automatic pump start/stop, DIN rail mounting inside control cabinet.

⚠️ Model Differentiation & Référence de remplacement

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

Remplacement hérité: RM35LM series (abandonné, replace with RM22LG for new projects)

Principe de fonctionnement de Schneider RM22LG11MR

Principe fondamental: 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), Min. (niveau bas), Max. (high level).

Electrode submerged by liquid → conductive liquid forms path between C and electrode, faible résistance;

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 closes, 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 ouvre, la pompe s'arrête.

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

2) Drain Mode (Drainage du puisard)

Liquid level reaches Max electrode: C-Max conductive → relay energizes, 11-14 NO closes, 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 pompe s'arrête.

3. Single Level Mode (Facultatif, 2 électrodes)

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

4. Internal Signal & Sortir
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, lecteurs 1 contact inverseur (1CO, 11 commun,12 Caroline du Nord,14 NON);
8. Front panel LED indicates output status; built-in test button simulates status for loop commissioning.
9. Principales caractéristiques de conception
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 / défaut de câblage.

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

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

Causes

1. Câblage A1/A2 lâche, 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, court-circuit)

Solutions

1. Éteindre, measure voltage at A1/A2, serrer les bornes; 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

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

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

Causes

1. Electrode covered by scaling / sludge, liquid equivalent resistance exceeds sensitivity threshold
2. Poor contact of C common electrode (le plus fréquent), 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)

Solutions

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

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

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

Causes

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, interférence électromagnétique
5. Terminal condensation / leakage between electrodes

Solutions

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

Faute 4: Frequent pump start-stop, relay chattering / oscillation

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

Causes

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)

Solutions

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

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

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

Causes

1. Wrong wiring of output contacts (11/12/14 terminals misconnected)
2. Contact load exceeds rated 8A, érosion de contact / soudage / circuit ouvert
3. No power on downstream control circuit

Solutions

1. Power off and verify contact wiring: 11 commun, 12 Caroline du Nord,14 NON
2. Press T test button and measure continuity between 11-14; open circuit = contact damaged, replace relay
3. Check control power supply for pump / contacteur

Faute 6: Soudage par contact, pump runs continuously and cannot stop

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

Causes

1. Surcharge à long terme, electric arc causes contact welding
2. No surge absorption for contactor coil, back EMF damages contacts

Solutions

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

Recommended On-site Troubleshooting Sequence

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

Output toggles by T: Unit healthy, fault in electrode, cable or liquid medium

No response by T: Relay unit damaged, remplacer directement

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 (approvisionnement en eau) / Vidange (drainage)

Entretien préventif

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 (contacteur) to protect 8A contacts

Schneider RM22 Harmony Modular Monitoring Relay Full Series List

Series common features: Montage sur rail DIN, width 22.5mm (RM22TG20:17.5mm); equipped with T test button, status LED, sealable transparent cover; note de contact: 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|1CO (1 changeover)|24~240 V CA/CC|Modèle standard, your reference unit, sensitivity 5k~100kΩ|

|RM22LG11MT|1CO|380~415 V CA|High voltage supply level relay|

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

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

2. RM22T 3-phase Power Monitoring Relay (Séquence de phases / perte de phase / 3-déséquilibre de phase / surtension & sous-tension)

Monitor 3-phase power supply for motor, pompe à eau, air compressor protection

|RM22TA31|2CO|Séquence de phases, perte de phase, 3-déséquilibre de phase|200~240 VCA|

|RM22TA33|2CO|Séquence de phases, perte de phase, 3-déséquilibre de phase|380~480VAC|

|RM22TU21|2CO|Séquence de phases, perte de phase, sous-tension|200~240 VCA|

|RM22TU23|2CO|Séquence de phases, perte de phase, sous-tension|380~480VAC|

|RM22TR31|2CO|Séquence de phases, perte de phase, déséquilibrer, overvoltage/undervoltage with delay|200~240 VCA|

|RM22TR33|2CO|Séquence de phases, perte de phase, déséquilibrer, overvoltage/undervoltage with delay|380~480VAC|

|RM22TG20|2CO|Séquence de phases, perte de phase (version compacte,17.5mm)|183~528VAC|

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

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

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

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

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

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

4. RM22J Current Monitoring Relay (AC current monitoring, surcharge / undercurrent)

Work with current transformer CT for motor load current monitoring

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

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

5. Règle de codage du modèle (RM22XXYYZZ)
6. RM22: Series code Harmony modular monitoring relay
7. XX: Function group

LG: Liquid level, single sensitivity

LE: Liquid level, multi-range sensitivity

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

UA/UB: Single-phase voltage monitoring

ET: Current monitoring

3. AA: Quantité à contacter

11: 1 contact inverseur (1CO)

32: 2 contacts inverseurs (2CO)

4. ZZ: Power supply code

MR: 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

7. Tableau de sélection rapide