Schneider RM22LG11MR Level Control Relay

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

Interpretação do modelo: RM22 series modular control relay; LG = liquid level single detection; 11 = 1 contato de mudança (C/O); MR = power supply 24~240V AC/DC; MT version for 380~415V AC power supply

✅ Funções principais

Designed for conductive liquids (água, sewage, etc.) for automatic liquid level control. Two operating modes available:

1. Fill Mode (Fornecimento de água) : 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

Tensão de alimentação: 24~240V CA/CC (universal para AC & CC), 50/60Hz; operating range 20.4~264V

Consumo de energia: AC 5VA / DC 1.5W

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

Power-on delay: 0.6é

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

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

Montagem: Trilho DIN, largura 22,5 mm

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

📌 Terminal Definition

Nota de fiação: 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

Fornecimento de água & drainage tanks, piscinas de esgoto, torres de resfriamento, water purification equipment, automatic pump start/stop, DIN rail mounting inside control cabinet.

⚠️ Model Differentiation & Referência de substituição

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

Substituição legada: RM35LM series (descontinuado, replace with RM22LG for new projects)

Princípio Operacional de Schneider RM22LG11MR

Princípio Fundamental: 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), Mínimo (nível baixo), Máx. (high level).

Electrode submerged by liquid → conductive liquid forms path between C and electrode, baixa resistência;

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. Dois modos de operação (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 abre, bomba para.

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

2) Drain Mode (Sump Drainage)

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, bomba para.

3. Single Level Mode (Opcional, 2 eletrodos)

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

4. Internal Signal & Saída
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, unidades 1 contato de mudança (1C/O, 11 comum,12 NC,14 NÃO);
8. Front panel LED indicates output status; built-in test button simulates status for loop commissioning.
9. Key Design Features
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 / wiring fault.

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

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

Causas

1. Loose A1/A2 wiring, mau contato terminal; 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, curto-circuito)

Soluções

1. Desligar, measure voltage at A1/A2, apertar terminais; 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

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

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

Causas

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)

Soluções

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

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

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

Causas

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, interferência eletromagnética
5. Terminal condensation / leakage between electrodes

Soluções

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

Falta 4: Frequent pump start-stop, relay chattering / oscilação

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

Causas

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)

Soluções

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

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

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

Causas

1. Wrong wiring of output contacts (11/12/14 terminals misconnected)
2. Contact load exceeds rated 8A, erosão de contato / soldagem / circuito aberto
3. No power on downstream control circuit

Soluções

1. Power off and verify contact wiring: 11 comum, 12 NC,14 NÃO
2. Press T test button and measure continuity between 11-14; open circuit = contact damaged, substituir relé
3. Check control power supply for pump / contator

Falta 6: Soldagem por contato, pump runs continuously and cannot stop

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

Causas

1. Sobrecarga de longo prazo, electric arc causes contact welding
2. No surge absorption for contactor coil, back EMF damages contacts

Soluções

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

Recommended On-site Troubleshooting Sequence

1. Ligar, 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, substitua diretamente

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 (fornecimento de água) / Ralo (drenagem)

Manutenção 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 (contator) to protect 8A contacts

Schneider RM22 Harmony Modular Monitoring Relay Full Series List

Series common features: Montagem em trilho DIN, largura 22,5 mm (RM22TG20:17.5milímetros); equipped with T test button, status LED, sealable transparent cover; avaliação de contato: 8A@250 VCA; 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 changeover)|24~240V CA/CC|Modelo padrão, your reference unit, sensitivity 5k~100kΩ|

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

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

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

2. RM22T 3-phase Power Monitoring Relay (Sequência de fase / perda de fase / 3-desequilíbrio de fase / sobretensão & subtensão)

Monitor 3-phase power supply for motor, bomba de água, air compressor protection

|RM22TA31|2C/O|Sequência de fase, perda de fase, 3-desequilíbrio de fase|200~240 VCA|

|RM22TA33|2C/O|Sequência de fase, perda de fase, 3-desequilíbrio de fase|380~480VAC|

|RM22TU21|2C/O|Sequência de fase, perda de fase, subtensão|200~240 VCA|

|RM22TU23|2C/O|Sequência de fase, perda de fase, subtensão|380~480VAC|

|RM22TR31|2C/O|Sequência de fase, perda de fase, desequilíbrio, overvoltage/undervoltage with delay|200~240 VCA|

|RM22TR33|2C/O|Sequência de fase, perda de fase, desequilíbrio, overvoltage/undervoltage with delay|380~480VAC|

|RM22TG20|2C/O|Sequência de fase, perda de fase (versão compacta,17.5milímetros)|183~528VAC|

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

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

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

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

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

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

4. RM22J Current Monitoring Relay (AC current monitoring, sobrecarga / corrente subterrânea)

Work with current transformer CT for motor load current monitoring

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

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

5. Regra de codificação do modelo (RM22XXYYZZ)
6. RM22: Series code Harmony modular monitoring relay
7. XX: Function group

LG: Liquid level, single sensitivity

O: Liquid level, multi-range sensitivity

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

UA/UB: Single-phase voltage monitoring

E: Current monitoring

3. AA: Quantidade de contato

11: 1 contato de mudança (1C/O)

32: 2 contatos de mudança (2C/O)

4. ZZ: Power supply code

SENHOR: 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. Tabela de seleção rápida