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Transparent bimetallic thermal unit FH55 with clear housing

Eaton

Eaton FH55 Thermal Unit 30.90-33.30 Amps

SKU CH-MSWJ-7A9BZ

Bimetallic thermal overload unit rated 30.90 to 33.30 amps with transparent housing for visual inspection

  • TypeBimetallic
  • ColorTransparent
  • Bimetallic design reacts quickly to overload conditions
  • Transparent housing allows instant visual status checks
  • Trip Class 20 rating suits motor protection needs
  • Compatible with Series A200 and B100 controllers
  • Fits NEMA Size 2 starters for standard installations

Eaton FH55 Thermal Unit

The Eaton FH55 is a bimetallic thermal overload unit designed for NEMA Size 2 motor starters. It provides Trip Class 20 protection for full-load currents between 0.25 and 0.27 amps or 0.29 and 0.31 amps. The transparent housing allows visual inspection of the internal mechanism. It suits maintenance teams replacing worn units in compatible Series A200 or B100 starters.

Replaces original thermal units

This unit directly replaces the original thermal elements in Eaton Series A200 and B100 starters when the trip rating matches the motor full-load current. The jump is worth it when the existing element has tripped repeatedly, shows discoloration, or no longer holds the correct calibration. It restores the intended overload protection without changing the starter enclosure or wiring.

Check starter model and current rating

Verify the starter nameplate lists a compatible model such as B100J0B, B100M1C, or B100W0C before ordering. Confirm the motor full-load current falls within either the 0.25 to 0.27 A or 0.29 to 0.31 A range marked on the unit. Installing a unit with the wrong trip range will cause nuisance tripping or leave the motor unprotected.

Highlights

  • Bimetallic design reacts quickly to overload conditions
  • Transparent housing allows instant visual status checks
  • Trip Class 20 rating suits motor protection needs
  • Compatible with Series A200 and B100 controllers
  • Fits NEMA Size 2 starters for standard installations

Specifications

BrandEaton
ModelFH55
TypeBimetallic
ColorTransparent

Questions about this item

What amperage range does the FH55 thermal unit cover for NEMA Size 2 overload protection?

The FH55 covers 30.90 to 33.30 amps and is rated for NEMA Size 2 starters with Trip Class 20 thermal overload protection.

Which starter series does the FH55 snap into, and what is the common mistake during installation?

It fits Eaton Series A200 and B100 starters; the common mistake is forcing the unit into an incompatible heater slot instead of verifying the exact model number first.

When should the FH55 thermal unit be replaced after a trip event?

Replace the bimetallic FH55 after any overload trip because the thermal element fatigues and will not reset to its original 30.90–33.30 A calibration.

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