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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

  • Product typeBimetallic
  • Product 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.

How it compares

Measured against everything we stock in AV Accessories & Components, at today’s prices. Recalculated every night.

Price $37.99
Typical for this category: the median of 3,838 items is $41.99.

Specifications

Product
Brand nameEaton
Model nameMSH4-5A
Product typeBimetallic
Product 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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