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Overload Relays

With the introduction of overload relays in the mid-1900's, motor protection reached a new level. When a protective relay was added to a standard contactor, it provided a low-cost level of protection saving time and money on replacing the more expensive pieces of machinery that were being operated down stream of this new "starter".


Electronic overload relays come in many different forms and have evolved over the years. Originally there were bi-metal heaters, which were strips of metal that when heated to a certain temperature, would cause a "trip" and shut down power to the contactor and subsequently the motor being operated. This allowed for automatic protection of a motor in an over-amperage state. One heater was needed for each leg of the motor and these bi-metal heaters were used for many years.


Following the use of bi-metal heaters came the introduction of thermal overload relays. These provided greater flexibility in motor protection with phase loss (single phase sensitivity) tripping, different class trips (from 5 to 30 though 10 is the standard), manual or automatic reset and most importantly a wider AMP range per unit.  While bi-metal heaters had a small AMP range, sometimes 1 to 2 AMPS at most, thermal overloads could have AMP ranges ranging 20 to 30 AMP in the higher ratings.  This provides for great convenience and portability should an application change from 460 volt down to 230 volt.


The newest innovation in this category is the advent of electronic or solid state overload relays.  These relays offer every option imaginable from a 4:1 or even a 5:1 AMP adjustment ratio to class selection all in the same unit.  Larger units can have AMP ranges from 20-100 AMP, manual and automatic reset and trip class selections from 5 seconds up to 30 seconds. These electronic overload relays also are now self-powered and no longer require a separate power source for operation.

  • GE RT1U overload relay

    RT1U

    GE Industrial RT1U thermal overload relay that is 3 phase, has 1 normally open (N.O.) and 1 normally closed (N.C.) base mounted auxiliary contacts, automatic or manual reset and is adjustable from 14.5 to 18 AMPS.  This GE overload relay has Class...

    MSRP: $75.00
    $44.32
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  • SPE-22

    SPE-22

    Benshaw Surprotex SPE-22 Electronic Overload relay with selectable trip class from 5-30, AMP ranges from 1 to 22 AMPS (must choose specific AMP range above), screw terminals and an option for direct mount or separate mount.  Direct mount overload...

    MSRP: $210.00
    $129.10
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  • Schneider Electric LRD32 overload relay

    LRD32

    Square D / Telemecanique LRD32 contactor with an AMP range of 23A-32A. For use on Square D / Telemecanique contactors from LC1D25 - LC1D32.Overload RelaysClass 10 or Class 20 bimetallic overload relays are available up to 140 A. They are bimetallic...

    MSRP: $73.00
    $47.45
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  • XTOB057DC1

    XTOB057DC1

    Eaton XTOB057DC1 thermal overload relay adjustable from 40 to 57 AMPS with 1 N.O and 1 N.C. auxiliaries, manual and automatic reset and a reset button. These thermal overloads are directly mounted to any Eaton XTCE040D, XTCE050D or XTCE065D 3 pole...

    MSRP: $174.00
    $61.43
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  • XTOB024DC1

    XTOB024DC1

    Eaton XTOB024DC1 thermal overload relay adjustable from 16 to 24 AMPS with 1 N.O and 1 N.C. auxiliaries, manual and automatic reset and a reset button. These thermal overloads are directly mounted to any Eaton XTCE040D, XTCE050D or XTCE065D 3 pole...

    MSRP: $154.00
    $54.50
    Add to Cart
  • XTOB040DC1

    XTOB040DC1

    Eaton XTOB040DC1 thermal overload relay adjustable from 24 to 40 AMPS with 1 N.O and 1 N.C. auxiliaries, manual and automatic reset and a reset button. These thermal overloads are directly mounted to any Eaton XTCE040D, XTCE050D or XTCE065D 3 pole...

    MSRP: $154.00
    $54.50
    Add to Cart
  • Schneider Electric LRD12 overload relay

    LRD12

    Schneider Electric LRD12 thermal overload relay adjustable from 5.5 to 8 AMPS and directly mounts to any LC1D09 through LC1D32 TeSys contactor. This 3-pole Schneider Electric overload relay has Class 10 protection, phase loss sensitivity and screw...

    MSRP: $62.00
    $40.30
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  • Lovato RF380650 overload relay Lovato RF380650 dimensions

    RF380650

    Lovato Electric RF380650 overload relay adjustable from 4 to 6.5 AMPS and mounts to any BF09, BF12, BF18, BF25 or BF32 3-pole contactor. This overload relay has phase loss protection (single phase sensitivity), manual or automatic reset options and screw...

    MSRP: $59.51
    $39.63
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  • Schneider Electric LRD10 overload relay

    LRD10

    Schneider Electric LRD10 thermal overload relay adjustable from 4 to 6 AMPS and directly mounts to any LC1D09 through LC1D32 TeSys contactor. This 3-pole Schneider Electric overload relay has Class 10 protection, phase loss sensitivity and screw...

    MSRP: $60.00
    $39.00
    Add to Cart
  • GE RT1T overload relay

    RT1T

    GE Industrial RT1T thermal overload relay that is 3 phase, has 1 normally open (N.O.) and 1 normally closed (N.C.) base mounted auxiliary contacts, automatic or manual reset and is adjustable from 17.5 to 22 AMPS.  This GE overload relay has Class...

    MSRP: $75.00
    $44.32
    Add to Cart
  • Siemens 3RU1136-4FB0 thermal overload relay

    3RU1136-4FB0

    Siemens 3RU1136-4FB0 class 10 thermal overload relay for direct mounting on size S2 contactors (3RT1033, 3RT1034, 3RT1035 and 3RT1036), is adjustable from 28A to 40A and has phase loss protection. The manual or automatic reset feature on this...

    MSRP: $107.00
    $62.16
  • GE RT1G overload relay

    RT1G

    GE Industrial RT1G thermal overload relay that is 3 phase, has 1 normally open (N.O.) and 1 normally closed (N.C.) base mounted auxiliary contacts, automatic or manual reset and is adjustable from 1 to 1.5 AMPS.  This GE overload relay has Class 10...

    MSRP: $75.00
    $42.75
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