Schneider Electric LRD10 — TeSys Thermal Overload Relay Guide

By Abdullah Zahid
14 min read
Schneider Electric LRD10 TeSys Deca thermal overload relay 4 to 6A Class 10 for three-phase motor protection

Schneider Electric LRD10 TeSys Deca Thermal Overload Relay — Specifications, Price and Selection Guide

If you are specifying or replacing a thermal overload relay for a small to medium three-phase motor circuit built around TeSys D contactors, the Schneider Electric LRD10 is the part most controls engineers reach for first. It covers a 4 to 6A thermal setting range, carries a 690VAC voltage rating, delivers built-in phase loss detection, and mounts directly to LC1D09 through LC1D32 contactors without adapters. The decision comes down to one critical check: does your motor's full-load amperage fall within that 4 to 6A window, and do you have a TeSys D series contactor on-site?

If you have already confirmed this is the right part, check current pricing and availability at LeadTime.ca — ships worldwide.

Who Should Buy the LRD10 — and Who Shouldn't

The Schneider Electric LRD10 is the correct choice for engineers and technicians who meet all of the following criteria:

  • Motor nameplate full-load amperage falls within the 4 to 6A thermal setting range
  • Site electrical system operates at 600VAC or 690VAC — not above
  • Existing or planned contactor is TeSys D series: LC1D09, LC1D12, LC1D18, LC1D25, or LC1D32
  • Circuit requires a 1NO + 1NC auxiliary contact output for PLC signaling or panel indication
  • Application is a three-phase motor — not a single-phase load
  • IEC standard compliance is acceptable or required for the installation

If your motor FLA exceeds 6A, the LRD12 (5.5 to 8A range) is the correct next step. If your site runs NEMA-style starters from any other manufacturer, the LRD10 will not physically fit — do not order it without verifying the contactor brand and model first.

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What the LRD10 Does in a Motor Protection Circuit

The Schneider Electric LRD10 is a bimetallic thermal overload relay in the TeSys Deca family. Its job is to monitor the current drawn by a three-phase AC motor and interrupt the control circuit before sustained overcurrent causes insulation breakdown or winding damage. Unlike a fuse or breaker, which trips almost instantaneously on short-circuit, a thermal overload relay is calibrated to tolerate the brief inrush current a motor draws at startup — typically 3 to 7 times full-load amperage — while still tripping reliably under sustained overload conditions. The LRD10's Class 10 designation means it will trip within 10 seconds when current exceeds the relay's thermal setting at the rated overcurrent threshold.

The bimetallic element inside the LRD10 responds to heat generated by current flow. As the element bends under sustained thermal stress, it eventually trips the mechanism, opening the NC auxiliary contact and signaling a fault to the control circuit. Ambient compensation is built into this design: the bimetallic strip self-corrects for changes in surrounding air temperature across the full −20 to +60°C operating range, which means a relay calibrated for a 5A motor on a cold morning will not nuisance-trip when the panel warms to 45°C in the afternoon. This matters on production floors where enclosure temperatures shift with shifts.

Phase loss detection is integral to the LRD10's thermal design. If one of the three supply phases is lost — a common failure mode in industrial motor circuits — the relay detects the resulting current imbalance and trips before the motor draws destructively high current on the remaining two phases. This protection is passive and automatic; it requires no separate relay, no additional wiring, and no configuration. For critical motors driving compressed air, HVAC fans, or process pumps, this single feature justifies the LRD10 over cheaper alternatives that omit it.

Typical System Architecture for TeSys Motor Starters

The LRD10 sits at the load side of the contactor in a standard IEC motor starter assembly, between the contactor output terminals and the motor terminals. It occupies no additional DIN rail space when direct-mounted.

  • Upstream: Three-phase supply enters through branch circuit protection (fuses or motor circuit protector)
  • Control layer: PLC or relay logic energizes the TeSys D contactor coil (LC1D09 through LC1D32) via the control circuit
  • Protection layer: LRD10 clips directly onto the contactor load-side terminals — no separate mounting bracket or adapter required
  • Signal output: The LRD10's NC auxiliary contact feeds back to the PLC input or control relay, signaling trip status; the NO contact can drive an indicator lamp or alarm
  • Downstream: Motor terminals connect directly to the LRD10 power terminals (T1, T2, T3), completing the three-phase circuit to the motor

Typical Applications and Deployment Scenarios

The LRD10's 4 to 6A range and Class 10 trip characteristic make it most at home protecting small to medium three-phase motors rated up to 2.2 kW at 400V. In water treatment and irrigation systems, it protects three-phase pump motors where single-phase loss from a damaged supply cable would otherwise go undetected until the motor windings fail. The built-in phase loss detection addresses exactly this failure mode without requiring additional instrumentation.

In HVAC and refrigeration systems, fan and blower motors run continuously for long hours under variable load. The LRD10's ambient compensation prevents false trips when enclosure temperatures climb during summer operation, while still responding correctly to genuine locked-rotor or sustained overload events. Facilities managers who have dealt with midnight nuisance trips on HVAC circuits — and the service calls that follow — recognize the value of ambient-compensated bimetallic protection immediately.

Conveyor lines and light production equipment benefit from the manual reset option. When a motor overloads and trips the LRD10, an operator must physically press the reset button, which forces acknowledgment of the fault before restart. This prevents automatic re-energization of a jammed or overloaded conveyor, which is both a safety requirement and a mechanical protection measure. The reset type is field-adjustable via a dial on the relay face — no tools required to switch between manual and automatic.

For OEM panel builders and system integrators, the LRD10 is a standard bill-of-materials item for compact motor starter assemblies. The direct-mount design eliminates auxiliary wiring between the contactor and overload relay, reduces panel width, and simplifies field replacement — a technician can swap a failed relay in minutes without touching the power wiring.

Application Typical Deployment
Three-phase pump motor protection LRD10 direct-mounted on LC1D12 or LC1D18; NC contact wired to PLC fault input; manual reset
HVAC fan or blower motor LRD10 on LC1D09 or LC1D12; ambient compensation critical in rooftop enclosures; automatic reset acceptable
Conveyor or light production machine LRD10 on LC1D18 or LC1D25; manual reset for operator intervention; NC contact to E-stop circuit
Retrofit replacement on existing TeSys starter Direct swap — verify existing contactor model and motor FLA before ordering LRD10
OEM compact motor starter panel LRD10 paired with LC1D09 or LC1D12 in standard IEC starter assembly; reduces panel footprint
Laboratory or machine tool motor circuit LRD10 standalone or contactor-mounted; low-current motor protection in controlled environment

Purchase-Decision Specifications and Variant Comparison

Parameter Value Notes
Thermal Setting Range 4 to 6 A Adjustable via front-face dial; covers small to medium motors
Trip Class Class 10 (10A) Trips within 10 seconds at rated overcurrent threshold
Voltage Rating 600VAC / 690VAC Do not exceed 690VAC
Frequency Range 0 to 400 Hz Supports 50/60 Hz and variable frequency drives up to 400 Hz
Contact Configuration 1NO + 1NC One normally open, one normally closed auxiliary contact
Contact Rating 10 A Nominal auxiliary contact rating
Number of Poles 3 Three-phase motor protection only — not for single-phase loads
Phase Loss Detection Yes Built-in; automatic; no additional wiring required
Operating Temperature −20 to +60°C Ambient-compensated bimetallic design
Enclosure Rating IP20 Use inside enclosed panel or contactor housing

Full technical specifications are available on the product page at LeadTime.ca.

Feature LRD10 (4–6A) LRD12 (5.5–8A) LRF Electronic (90–150A) Soft-Starter (Integrated)
Amperage Range 4 to 6 A 5.5 to 8 A 90 to 150 A Varies by model
Technology Bimetallic thermal Bimetallic thermal Solid-state electronic Electronic + contactor
Trip Class 10 10 or 20 Configurable Configurable
Phase Loss Detection Yes Yes Yes Yes
Manual / Auto Reset Both (field-adjustable) Both (field-adjustable) Configurable Configurable
Diagnostics None None Yes — fault codes Yes — network capable
Installation Complexity Simple; direct mount Simple; direct mount Requires power supply Moderate
Right For Motors up to 2.2 kW at 400V Medium motors 3 to 4 kW Large motors 90+ kW New systems requiring ramp control

If your motor FLA exceeds 6A, the LRD12 is the correct selection — check the full TeSys relay range and current availability at LeadTime.ca.

Expert Verdict: Is the LRD10 Right for Your Application?

The Schneider Electric LRD10 earns its place on the standard bill of materials for any IEC-standard motor starter panel where the motor nameplate FLA sits between 4 and 6A. The bimetallic design with ambient compensation is genuinely well-suited to industrial floor conditions — dusty, thermally variable environments where electronic relays can be finicky and where simplicity is a maintenance advantage. Phase loss detection is automatic and requires no configuration; for pump and fan motors where a lost phase causes silent winding damage, this built-in protection is not optional. The direct-mount compatibility with the full LC1D09 through LC1D32 contactor range means field replacement takes minutes, not hours, and the 0 to 400 Hz frequency rating covers installations paired with variable frequency drives without needing a separate overload device.

There are real limits to acknowledge honestly. The LRD10 has no diagnostics — when it trips, the relay tells you nothing about the magnitude or duration of the overcurrent event. For facilities moving toward predictive maintenance or remote monitoring, an electronic overload relay with fault codes and network connectivity is the better long-term investment. Motor FLA headroom is also narrow: at 4 to 6A, there is no buffer for motors whose FLA is close to 6A and whose starting conditions produce extended inrush. If your motor FLA is 6A or above, the LRD12 (5.5 to 8A) is the safer choice — its range overlaps and provides meaningful margin. For motors above the 4 kW continuous range, move to the LRD21 (9 to 13A) or LRD32 (16 to 24A). And if your facility runs NEMA-style starters, the LRD10 simply will not fit — this is the single most common ordering error and it results in a return shipment, a production delay, and a frustrated technician.

From a procurement standpoint, the LRD10 is a widely stocked part with typically short lead times from authorized Schneider Electric distributors. That said, stock levels can vary by region and distributor tier, and verifying availability before committing to a build schedule is always worth the five-minute call. Ordering through a specialist distributor matters here because a knowledgeable team can cross-check your contactor model, confirm motor FLA alignment, and flag reset-type requirements before the order ships — eliminating the return cycle that costs more in technician time than the relay itself. Check current pricing and stock for the LRD10 at LeadTime.ca — available to buyers worldwide.

For volume pricing or to confirm lead time before committing to a build, contact the LeadTime.ca team directly — we ship worldwide.

What Engineers Need to Know Before Ordering the LRD10

Because community discussion specific to the LRD10 is sparse in public forums, the most actionable pre-order intelligence comes from the pattern of ordering mistakes that surface at the distributor level — the wrong-size relays that arrive on site, the IEC parts ordered for NEMA panels, and the manual-reset units installed on unattended equipment. These are not hypothetical scenarios; they represent the most common reasons the LRD10 gets returned or misapplied, and understanding them before ordering saves real time and money.

The first category of mistakes involves amperage range mismatch. The LRD10's 4 to 6A thermal setting range sounds straightforward, but buyers regularly order it for motors whose nameplate FLA is 6.5A or 7A — just outside the window. At that point, the LRD12 (5.5 to 8A) is the correct part, and the overlap between the two models makes the decision less obvious than it appears. The fix is simple: pull the motor nameplate FLA before placing the order, not after. If the FLA is anywhere near 6A, consider whether the LRD12's wider range provides better margin for your specific motor and load profile.

The second category involves contactor compatibility. The LRD10 is an IEC-standard device designed exclusively for the TeSys D series. It will not mount on NEMA-style contactors from other manufacturers. Buyers who inherited a panel or are replacing a failed relay without checking the contactor brand on-site frequently discover this incompatibility after the part arrives. If there is any uncertainty about what contactor is installed, the model number is printed on the contactor housing — confirming it starts with LC1D is the only check that matters. When you need fast answers on compatibility for a specific site configuration, the LeadTime.ca team can work through the verification with you before the order is placed, which is precisely the kind of support a specialist distributor provides that a generic online channel cannot.

Wiring and Installation Overview

The LRD10 is designed for straightforward installation by qualified electrical personnel. The following points cover the key requirements and verifications — refer to the Schneider Electric installation manual for full wiring diagrams and torque specifications before proceeding.

  • De-energize the contactor fully and verify zero voltage on all three phases using a calibrated meter before handling the relay or terminals
  • Align the relay onto the contactor load-side mounting pins and slide until fully seated with no visible gap between relay and contactor body
  • Connect three power terminals (one per phase) to the contactor load terminals; tighten screw clamp terminals hand-tight, then add one-quarter turn with a wrench — do not over-torque
  • Connect the NC auxiliary contact terminal to the control circuit fault input (PLC, relay, or alarm); connect the NO contact to an indicator lamp or secondary signal as required by the control design
  • Set the thermal dial to the motor nameplate FLA within the 4 to 6A range, and confirm the reset-type selection (manual or automatic) before applying power

Compatible TeSys D Contactors

The LRD10 mounts directly — without adapters or auxiliary brackets — onto the following TeSys D series contactors. Verify the exact model number on the contactor housing before ordering.

Contactor Model Pole Count Typical Motor Size LRD10 Compatible
LC1D09 3-pole Up to 4 kW at 400V Yes
LC1D12 3-pole Up to 5.5 kW at 400V Yes
LC1D18 3-pole Up to 7.5 kW at 400V Yes
LC1D25 3-pole Up to 11 kW at 400V Yes
LC1D32 3-pole Up to 15 kW at 400V Yes

Note: While the LRD10 mounts on all five contactor models above, its 4 to 6A thermal range is appropriate only for motors whose FLA falls within that window. Larger contactors in this list paired with larger motors will require LRD12, LRD21, or LRD32 for adequate protection.

Wrong-Part Prevention Checklist

Before placing your order for the Schneider Electric LRD10, run through every item on this checklist. Skipping even one step is how incorrect parts end up on site.

  1. Verify motor FLA from nameplate and confirm LRD10's 4 to 6A range covers it
  2. Confirm site voltage is 600V or 690VAC (do not use on higher-voltage systems)
  3. Check contactor model on-site to ensure LC1D09, LC1D12, LC1D18, LC1D25, or LC1D32 compatibility
  4. Specify manual or automatic reset requirement (dial adjustment available on unit)
  5. Verify facility electrical standard (IEC vs. North American) — LRD10 is IEC standard
  6. Check if phase loss sensitivity is required — LRD10 provides it; verify circuit design expects it
  7. Confirm three-pole configuration matches three-phase motor (not single-phase load)

If any item on this list raises a question before you order, contact the LeadTime.ca team — confirming these details before the order ships is faster and cheaper than returning an incorrect part after the fact.

Frequently Asked Questions

Can the LRD10 be used with a variable frequency drive, and does the 0 to 400 Hz frequency rating cover standard VFD outputs?

The LRD10 carries a frequency rating of 0 to 400 Hz, which covers standard 50 Hz and 60 Hz installations as well as variable frequency drive outputs within that range. However, VFD applications introduce current waveform distortion that can affect bimetallic thermal elements differently than sinusoidal current. Always verify the specific VFD output characteristics and consult Schneider Electric's application guidance before deploying the LRD10 in a VFD-driven motor circuit.

What is the difference between manual reset and automatic reset, and which is safer for an unattended pump station?

Manual reset requires an operator to press the reset button on the relay face after a trip event, preventing automatic restart without human acknowledgment. Automatic reset allows the relay to re-energize after the bimetallic element cools, which can cause repeated motor starts without fault investigation. For unattended equipment, automatic reset carries real risk: a motor that repeatedly restarts into a fault condition can sustain winding damage or create a safety hazard. Manual reset is the standard recommendation for unattended sites unless the control system provides remote fault acknowledgment logic.

Is the LRD10 a direct swap for an older TeSys D overload relay, or does the terminal layout differ?

The LRD10 is part of the TeSys Deca series and is designed for direct mechanical and electrical compatibility with the LC1D09 through LC1D32 contactor range. For retrofit applications, verify the existing relay model number and confirm it is from the TeSys D family before assuming a direct swap. If the existing relay is from an older TeSys series or a different product line, terminal positions and mounting clip geometry may differ. When in doubt, bring the existing relay model number to your distributor for cross-reference before ordering.

What does the LRD10 trip indicator show, and how do I distinguish a phase loss trip from a thermal overload trip?

The LRD10 is a bimetallic thermal relay with no electronic diagnostics or fault code display. A trip event opens the NC auxiliary contact and, depending on configuration, may illuminate a trip indicator on the relay face. The relay does not differentiate between a thermal overload trip and a phase loss trip through any visual or electrical output — both conditions open the same NC contact. Determining the root cause requires investigating the supply voltage on all three phases and reviewing motor current data from external instrumentation. If fault differentiation is a requirement, consider an electronic overload relay with diagnostic output capabilities.

Does the LRD10 comply with Canadian electrical standards, and is it suitable for CSA-regulated installations?

The LRD10 carries CSA C22.2 No. 14 certification in addition to UL 508, IEC 60947-4-1, IEC 60947-5-1, CE marking, ATEX certification, and RoHS compliance. It is suitable for CSA-regulated installations in Canada. Note that the LRD10 is an IEC-standard device; if your Canadian facility uses North American NEMA-style starters rather than TeSys D series IEC contactors, the physical mounting compatibility issue takes precedence over the certification question.

Why Order the LRD10 From LeadTime.ca

  • Ships worldwide — not restricted to any single country or region; international orders handled directly
  • Specialist knowledge on TeSys contactor and relay compatibility — the team can verify LC1D contactor match and motor FLA alignment before your order ships
  • Commonly paired components (LRD10 with LC1D25 or LC1D18) can be sourced together, reducing procurement cycles and shipping events
  • Volume pricing available — contact directly for project quantities or recurring OEM orders
  • Response time from a team that understands industrial controls — not a general-purpose online retail platform

LRD10 At-a-Glance Summary

  • Thermal setting range: 4 to 6A — suitable for three-phase motors up to 2.2 kW at 400V
  • Trip class: Class 10 — trips within 10 seconds at rated overcurrent threshold
  • Voltage rating: 600VAC / 690VAC — do not exceed 690VAC
  • Frequency range: 0 to 400 Hz — covers 50/60 Hz and VFD outputs within range
  • Auxiliary contacts: 1NO + 1NC — direct PLC or panel wiring without additional relay
  • Phase loss detection: built-in and automatic — no additional wiring required
  • Direct-mount compatible: LC1D09, LC1D12, LC1D18, LC1D25, LC1D32 — no adapter required
  • Reset type: manual or automatic — field-adjustable via dial on relay face
  • Operating temperature: −20 to +60°C with ambient compensation
  • Certifications: UL 508, IEC 60947-4-1, CSA C22.2 No. 14, CE, ATEX, RoHS
  • Enclosure rating: IP20 — install inside enclosed panel or contactor housing
  • Dimensions: 70 mm L × 45 mm W — compact direct-mount footprint

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