Merlin Gerin M08H1 TF786220404/05 Masterpact Air Circuit Breaker Product Description

Overview

Merlin Gerin M08H1 TF786220404/05 is an air circuit breaker of the Merlin Gerin Masterpact series (legacy brand, later acquired by Schneider Electric). This Merlin Gerin air circuit breaker has an 800 A frame size, H breaking capacity grade, and the part suffix TF786220404/05 is the factory drawing / reference number for this specific unit fitted with LSI trip function. M08H1 is widely used for main incoming, bus tie and heavy feeder protection in industrial and marine low‑voltage switchgear, and it is a common spare for renovation and replacement of old Masterpact panels.

Features

Merlin Gerin M08H1 TF786220404/05 air circuit breaker adopts a high‑performance arc quenching chamber for reliable short‑circuit interruption. This Merlin Gerin air circuit breaker is equipped with LSI protection (long‑time overload, short‑time delay, instantaneous short‑circuit), with adjustable setting values. M08H1 supports built‑in current transformers to supply signals for the trip unit. The Merlin Gerin air circuit breaker reserves mounting positions for motor operator, shunt release, undervoltage release, auxiliary contacts and alarm contacts for remote control and status feedback. This breaker complies with IEC 60947‑2 standards and is validated for stable operation in industrial and marine switchboard environments.

Specs

Merlin Gerin M08H1 TF786220404/05 air circuit breaker

• Brand: Merlin Gerin (Schneider legacy Masterpact)

• Model: M08H1

• Reference drawing number: TF786220404/05

• Frame rated current: 800 A

• Breaking grade: H

• Rated operational voltage: 380–690 V AC

• Protection type: LSI (Long time / Short time / Instantaneous)

• Mounting: Fixed / Withdrawable

• Poles: 3P / 4P

• Standard: IEC 60947‑2

Principle

Merlin Gerin M08H1 TF786220404/05 air circuit breaker uses the LSI trip unit to continuously sample secondary current signals from internal CTs. Under overload conditions, the long‑time protection curve triggers delayed tripping. For moderate short‑circuit faults, short‑time delay protection acts selectively to coordinate with downstream protective devices. When severe short‑circuit current occurs, instantaneous protection releases the contact mechanism immediately. The arc chamber splits and cools the arc generated during contact separation to safely isolate the fault circuit.

Applications

Merlin Gerin M08H1 TF786220404/05 air circuit breaker is widely deployed in factory main distribution rooms, marine switchboards, water treatment plants and MCC cabinets. This Merlin Gerin air circuit breaker serves as transformer secondary incoming protection, bus coupler protection and large motor feeder protection. M08H1 fits switchgear overhaul and spare replacement of legacy Merlin Gerin Masterpact breaker systems. It protects cables, transformers and loads from overload and short‑circuit damage.

Installation & Maintenance Notes

Follow official Merlin Gerin Masterpact service manuals during installation of Merlin Gerin M08H1 TF786220404/05 air circuit breaker. Apply the specified torque for main busbar terminals to avoid overheating. Back up LSI protection parameters before replacing the breaker or trip unit. Conduct periodic inspection of operating mechanism, contact condition and auxiliary wiring, especially in high‑humidity marine environments. Confirm exact model M08H1 and reference number TF786220404/05 before spare‑part swap‑out to verify breaking capacity, frame size and trip function compatibility. Maintain cabinet ventilation to prevent high ambient temperature affecting trip accuracy.