FH18 Eaton Electrical FH18 Thermal Overload Heater Element

The Eaton FH18 is a replaceable thermal overload heater element used with selected Eaton and Cutler-Hammer motor starters and overload relay assemblies. It is commonly applied in A200 magnetic motor starters and B100 manual motor starters where motor overload protection is provided by a bimetallic thermal overload relay.

During normal motor operation, current flows through the FH18 heater element and produces a controlled amount of heat. This heat acts on the bimetal elements inside the overload relay. If the motor draws excessive current for a sustained period, the increased temperature causes the bimetal mechanism to deflect and open the overload relay’s normally closed control contact. The contactor is then de-energized, disconnecting the motor from the power supply.

FH18 is a calibrated protection component rather than a general-purpose heater. Correct selection must be based on the motor’s actual nameplate full-load current, not only its horsepower rating. Starter configuration, enclosure type, overload relay design, motor service factor and ambient temperature can all affect the applicable current range.

The heater element does not provide short-circuit protection. A suitable branch-circuit fuse or circuit breaker must therefore be installed in accordance with the motor starter instructions and applicable electrical regulations.

Key Features

• Eaton / Cutler-Hammer FH Series heater element
• Designed for A200 and B100 motor starters
• Compatible with Type A and Type B overload relays
• Suitable for NEMA Size 0, 1 and 2 starters
• Class 20 thermal overload relay application
• Calibrated for motor overload protection
• Supports single-phase and three-phase configurations
• Replaceable heater element design
• UPC: 786678629414

Technical Specifications

FH18 Full-Load Current Selection

A200 Type A and Type B Overload Relays

B100 Manual Motor Starters

These ranges must not be combined into one universal FH18 current rating. Always use the selection table that corresponds to the exact starter and overload relay configuration.

Selection Guidelines

Select the FH18 according to the actual full-load amperes printed on the motor nameplate. When the motor and overload relay operate at approximately the same ambient temperature and the motor has a service factor between 1.15 and 1.25, the appropriate heater may normally be selected directly from Eaton’s heater table.

If the motor has a service factor of 1.0 or lower, no service factor is stated, or a maximum protection level of approximately 115% is required, Eaton generally instructs users to select one heater size smaller than the value otherwise indicated.

For non-ambient-compensated overload relays, temperature differences between the motor and controller must also be considered. A control panel located in a hotter or colder environment than the motor can change the required heater selection and may otherwise cause nuisance tripping or insufficient motor protection.

FH17 vs FH18 vs FH19

The adjacent FH heater numbers are different current calibrations, not upgraded versions of one another.

Comparison Note

FH17, FH18 and FH19 share the same general heater family and may fit similar overload relay assemblies, but they are not interchangeable without checking the motor nameplate current and Eaton selection table. Installing an undersized heater can cause nuisance trips, while an oversized heater may reduce the intended level of motor protection.

Applications

The Eaton FH18 may be used in compatible motor control systems for:

• Pumps and circulation systems
• Industrial fans and blowers
• Conveyors and material-handling equipment
• Small compressors
• HVAC motor control panels
• Machine tools
• Packaging machinery
• Process equipment
• General industrial motor starters
• Replacement and maintenance of Eaton A200 or B100 assemblies

Installation and Maintenance Notes

Disconnect and lock out all power before inspecting or replacing the heater element. Confirm that FH18 is the correct heater number for the motor’s full-load current and the exact overload relay configuration.

The heater connecting surfaces should be clean, and the element must be securely attached using the specified hardware. Poor contact, loose mounting or contamination can alter heat transfer and affect overload performance.

For B100 starters, two heater elements are required for single-phase applications and three are required for three-phase applications. For A200 installations, verify whether the assembly uses a three-pole block relay or separate single-pole overload units before ordering the required quantity.

If burnout of a current-carrying element has occurred, Eaton advises replacing the complete overload relay to maintain protection against fire and electric shock rather than replacing only the visibly damaged heater.

Frequently Asked Questions

Is the Eaton FH18 a complete overload relay?

No. FH18 is the calibrated heater element installed in a compatible thermal overload relay. The relay body, trip mechanism and control contacts are separate parts.

What is the current rating of FH18?

The applicable motor full-load current depends on the starter and relay configuration. Common ranges include 1.12–1.22 A, 1.29–1.41 A, 1.04–1.13 A and 1.26–1.38 A for A200 applications. B100 values also differ between single-phase and three-phase starters.

Is FH18 compatible with Eaton A200 starters?

Yes. FH18 appears in Eaton’s heater selection tables for compatible A200 Type A and Type B thermal overload relays used with NEMA Size 0, 1 and 2 starters.

Can FH18 be used with B100 manual motor starters?

Yes. It is part of the FH heater series specified for Eaton B100 manual motor starters. Two heaters are normally required for a single-phase starter and three for a three-phase starter.

Is FH18 a Class 10 fast-trip heater?

For Type A and Type B overload relay applications, Eaton identifies the relay as Class 20. Eaton’s separate Type FT Class 10 overload relay uses directly heated bimetal elements and does not use separate FH calibration heaters.

Can FH18 replace FH17 or FH19?

Not automatically. FH17 and FH19 have different motor-current ranges. Select the heater using the motor nameplate FLA and the appropriate Eaton application table.

Does FH18 protect against a short circuit?

No. FH18 provides thermal overload sensing as part of an overload relay assembly. A suitable fuse or circuit breaker is still required for branch-circuit and short-circuit protection.

Product Summary

The Eaton FH18 is a calibrated overload relay heater element for selected A200 and B100 motor starters. When correctly matched to the motor full-load current and relay configuration, it enables the Type A or Type B thermal overload relay to respond to sustained overcurrent conditions and disconnect the motor before excessive heating causes damage.

Accurate application requires confirmation of the starter series, phase arrangement, enclosure, overload relay type, motor service factor and ambient conditions. FH18 should not be selected solely by physical appearance or treated as interchangeable with adjacent FH heater numbers.

Sourcing Tip

Before ordering Eaton FH18, confirm the complete starter model, motor nameplate FLA, single-phase or three-phase configuration, enclosure type, overload relay type and required quantity. For maintenance replacements, request unused Eaton-marked parts with traceable packaging and verify whether heat damage requires replacement of the complete overload relay.