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Phone: +86 16626708626Description
Key Technical Specifications
- Rated control voltage: 24 V DC.
- Operating voltage range: 0.9–1.4 × rated voltage (21.6–33.6 V DC).
- Contact configuration: 1 changeover contact (1 CO / SPDT).
- Contact material: AgNi 90/10.
- Contact thermal current: 16 A; application switching capacity depends on load category and operating voltage.
- Coil power consumption: 0.4 W.
- Operating time: 8 ms maximum closing delay; 6 ms maximum opening delay.
- Indicator: Red LED.
- Socket: Included; base with logical isolation.
- Terminals: Screw terminals; tightening torque 0.5–0.7 N·m.
- Dimensions: 15.5 mm W × 77 mm H × 71 mm D.
- Operating temperature: −40 to +70 °C.
- Protection rating: IP20.
- Mechanical life: 30 million operating cycles, typical.
- Weight: 0.064 kg.
Siemens identifies this as a complete SIRIUS LZS coupling relay with a 24 V DC coil, one changeover contact, red LED, logic-isolation socket, and screw terminals.
Product Introduction
The Siemens LZS:RT3B4L24 is a SIRIUS LZS plug-in coupling relay supplied as a complete unit with a 24 V DC relay, one changeover contact, red LED, and logic-isolation socket with screw terminals. It provides galvanic isolation and contact multiplication between control outputs and field loads.
Check the load’s utilization category and switching current before wiring. The 16 A value is the thermal current rating, not a universal switching rating; use the Siemens load-category data to confirm suitability for the actual AC or DC load.
LZS:RT3B4L24
LZS:RT3B4L24
Troubleshooting Quick Reference
| Symptom | Possible Cause | Relevance to This Part | Quick Check Method | Recommendation |
|---|---|---|---|---|
| Red LED is off when commanded on | Missing or low coil voltage, wrong polarity, PLC output fault, or relay fault | High | Measure DC voltage across A1 and A2 while commanded on; verify polarity and that voltage is within 21.6–33.6 V DC | Check the control output and wiring before replacing the relay |
| LED is on, but the load does not operate | Open contact, incorrect terminal wiring, load supply fault, or failed load | High | With the circuit safely isolated, check continuity between 11–14 when energized and 11–12 when de-energized; confirm load power separately | Verify contact numbering and load-side supply; replace only if contact operation fails |
| Relay chatters or drops out | Coil voltage sag, loose terminal, excessive control-circuit impedance, or unstable output | High | Measure voltage directly across A1–A2 during operation; inspect screw-terminal tightness to the specified torque | Correct supply or wiring problems; do not compensate by exceeding the rated coil range |
| PLC output remains on after command is removed | Welded contacts, wiring fault, or downstream backfeed | Medium | Isolate the load circuit and test the relay contacts for continuity in both coil states | Check for overload or inductive-load stress; replace the relay if contacts remain closed |
| Relay runs hot or contacts fail early | Load exceeds the applicable rating, frequent switching, or unsuitable utilization category | Medium | Compare the load type, voltage, current, and switching frequency with Siemens ratings for the relevant utilization category | Select the relay using the load-specific rating; add appropriate suppression for inductive loads |
| Replacement does not fit the existing wiring layout | Different terminal style or relay/socket variant | Medium | Match the complete Siemens part number and inspect the socket terminal arrangement before wiring | Do not substitute another LZS variant based only on coil voltage |
For persistent faults, provide technical support with photos of the part number and wiring, coil voltage readings, load voltage/current, and PLC output diagnostics.
Frequently Asked Questions (FAQ)
What is included with LZS:RT3B4L24?
It is the complete relay unit: plug-in relay, 24 V DC coil, red LED module, and socket base with logical isolation and screw terminals.
What do the contact numbers mean?
The relay has one changeover contact: terminal 11 is common, 12 is normally closed, and 14 is normally open. The Siemens circuit diagram also identifies the coil terminals as A1 and A2. Verify the markings on the actual base before wiring.
Can it switch a 16 A load?
Do not assume that. Siemens specifies 16 A thermal current, but the permissible switching load depends on voltage, AC/DC type, utilization category, and load characteristics. Select using the manufacturer’s load-specific ratings, not the thermal-current figure alone.
What coil voltage does it need, and does polarity matter?
The rated coil voltage is 24 V DC, with an operating range of 21.6–33.6 V DC. The relay drive is polarized, so observe the A1/A2 polarity shown on the product diagram and wiring documentation.
Is it currently discontinued?
Siemens Industry Mall lists LZS:RT3B4L24 as an active product and shows an estimated dispatch time of three working days for its catalog listing. Actual availability and delivery depend on region and seller inventory.
Is the Siemens order quantity one or five?
Siemens lists a minimum order quantity of five in the catalog information retrieved. Some distributors may offer different order quantities, so confirm the seller’s minimum and packaging before purchasing.
Why might a surplus unit cost less than one from Siemens?
Secondary-market pricing may reflect surplus or previously held inventory, but condition varies by seller. Confirm whether the unit is new surplus, factory sealed, or used; also ask for test details, warranty coverage, and return terms.
