Cover image: existing Danch catalog photograph of the 421-06-11440 breaker packaging and label. Identification example; the photograph does not establish its rating, fault condition or application on a particular HD255-5.
Direct answer
Do not fit a higher-rated circuit breaker simply to stop repeated tripping. Record the breaker identity, protected circuit and event history, then have the circuit and specified protection reviewed. The replacement must match the approved application; repeated trips alone do not establish that the breaker is defective.
Identify what is tripping before requesting a replacement
Preserve the full machine model and serial. Record the breaker marking and its circuit position only when safely accessible. Keep a reported loss of electrical power separate from a confirmed breaker operation. If an accessory was recently installed or wiring work was performed, include that history without concluding that it caused the event.
What to record before a service or parts decision
| Record | What to include and why |
|---|---|
| Device identity | Readable part number and marking, circuit position and photograph obtained under safe conditions. |
| Event history | When the trip was noticed and which loads were already operating; no deliberate repeat test. |
| Recent changes | Electrical repair or accessory changes with dates and available records. |
| Technical decision | Applicable diagram and protection specification, assessment finding and approved part identity. |
| Order check | Specified number, application, terminals/mounting and quantity; do not select by physical size alone. |
What the observations do—and do not—establish
A breaker is part of the circuit’s protection, so changing its rating is a design decision rather than a troubleshooting shortcut. A qualified person must determine whether the circuit, connected equipment or protective device needs attention. This guide gives no amperage, reset schedule or bypass method for HD255-5. Unknown markings should remain unresolved until the correct documentation is available.
Turn the record into a clear service handoff
The Danch catalog includes 421-06-11440 as a circuit-breaker listing associated with HD255-5. That is a registered inquiry example, not a verified rating or universal application approval. Send the original marking, machine plate and circuit position. Ask for a documented application match and retain the service finding separately from the quotation.
Safe limits for this guide
Do not repeatedly reset, hold closed, bridge or increase the rating of a tripping device. If there is smoke, burning odor or damaged wiring, follow the machine/site emergency procedure and obtain qualified electrical assistance.
Machine and parts context
This is a general service-planning guide. The linked machine pages organize identification information; they do not make the workflow a model-specific repair procedure.
421-06-11440 Circuit Breaker for Komatsu HD255-5. Registered catalog example; verify the exact serial, installation position and order scope before purchase.
Frequently asked questions
Can I install a larger breaker to prevent tripping?
Not as a fault workaround. Use only the protection approved for the circuit after the fault is assessed.
Does the same housing prove compatibility?
No. Electrical protection characteristics and application also matter.
Is 421-06-11440 confirmed for my HD255-5?
Not from this article. The exact machine and circuit need a documented match.
Sources and scope
- Komatsu parts and documentation access — Manufacturer route to machine-specific parts and service documentation. This portal does not supply the individual limits or application approval for this guide.
The observation checklist is Danch Machinery editorial guidance. No customer case, measured result or technician sign-off is claimed. Published or updated 14 September 2026. Obtain the current documentation for the exact machine before any technical procedure.
Request a parts identification check
Send the complete model and serial, component position, exact number or clearly marked uncertainty, quantity and available service findings. Danch Machinery supplies genuine parts; a quotation does not replace a technical diagnosis.
About this guide
Published by Danch Machinery as general parts-identification and service-planning information. It is not a signed technical inspection or a machine-specific repair approval. Refer to the sources and scope stated in the article; confirm service procedures and fitment with the current manufacturer documentation for the exact machine.
Machine configurations and service requirements can differ by model, serial number and market. Confirm procedures and fitment with the current manufacturer documentation for your exact machine.
