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Transparent thermal unit with bimetallic element

Eaton

Eaton MSH4-5A Thermal Unit 3.60 to 3.99A

SKU CH-J8MZ-10S29

Bimetallic thermal overload unit rated 3.60 to 3.99 A, Trip Class 20, compatible with NEMA sizes 1, 3, 4, 5 and Series MS starters

  • TypeBimetallic
  • ColorTransparent
  • Thermal overload protection for 3.60 to 3.99 A motors
  • Trip Class 20 ensures reliable overload response
  • Bimetallic 2.000 design provides consistent thermal operation
  • Compatible with NEMA Size 1, 3, 4, 5 starters
  • Fits Series MS and multiple MST model variants

Product identity

The Eaton MSH4-5A is a bimetallic thermal unit designed for overload protection in motor control circuits. It covers a full-load current range of 3.60 to 3.99 amperes and carries a Trip Class 20 rating. The transparent housing allows visual inspection of the element. Compatible with NEMA Size 1 through 5 starters and the Series MS family.

Fit and limits

This unit suits maintenance teams replacing a tripped heater element in an existing Eaton or Cutler-Hammer starter. It also fits panel builders assembling new motor starters that require the 3.6 to 3.99 A range. Buyers needing a different current band, a solid-state overload relay or a Trip Class other than 20 should select another part.

Deciding specification

The critical figure is the 3.60 to 3.99 A full-load current window; the starter’s nameplate current must fall inside this band for correct protection. Cross-reference lists include Grainger numbers 1H385, 1H396 and 1H397 plus numerous MST model variants. Verify the exact model before ordering.

Highlights

  • Thermal overload protection for 3.60 to 3.99 A motors
  • Trip Class 20 ensures reliable overload response
  • Bimetallic 2.000 design provides consistent thermal operation
  • Compatible with NEMA Size 1, 3, 4, 5 starters
  • Fits Series MS and multiple MST model variants

Specifications

BrandEaton
ModelMSH4-5A
TypeBimetallic
ColorTransparent

Questions about this item

What comes with the Eaton MSH4-5A thermal unit and what else is needed?

The package contains the bimetallic thermal unit itself. A compatible Series MS overload relay (such as MST01 or MST02 models) must be purchased separately to complete the installation.

Which current rating should I select for my motor?

Choose the MSH4-5A when the motor full-load current is between 3.6 and 3.99 A. This unit is rated for Trip Class 20 and fits NEMA Size 1, 3, 4 or 5 starters.

What does the 3.6 to 3.99 A range mean once the unit is installed?

The thermal unit will trip to protect the motor if the current exceeds approximately 3.99 A for the Trip Class 20 time curve, providing overload protection matched to that current window.

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