Terasaki Circuit
Breaker Spare Parts

In the first TemBreak range the type opens with an X and the letter after it is the series: XE is the economical series, XS the standard series and XH the high fault series. The number that follows is the ampere frame. The letter on the end is the trip: S a fixed thermal trip, J an adjustable thermal trip, E an electronic trip, and D a special DC application. Three fields, and only the middle one is a number, which is why a request quoting the number alone leaves out both the series and the trip.

TemBreak 2 keeps the same idea and moves the letters about. The catalogue number is built as a model letter, the frame rating in amperes, and a two-letter type. The model letter separates the economical, standard, high, limiting and earth leakage classes; the first letter of the type is the breaking capacity class; and the second letter is the protection actually fitted — F fixed thermal and fixed magnetic, J adjustable thermal and adjustable magnetic, E electronic, and N no protection at all, which makes the device a switch-disconnector rather than a breaker. That second letter carries the whole thermal-magnetic against electronic question, it decides whether a current sensor and a control supply sit behind the device, and it is printed on the plate.

Neither string is the full ordering description. After the type come an optional-function code, the pole count, the rated current fitted and the connection type — front connection, extension bar, cable clamp, rear connection, plug-in or DIN rail mounting — and on the air circuit breakers the overcurrent relay is written out separately again. Read the whole string off the equipment rather than decoding a prefix from memory. The letters have not been used consistently between generations or between regional catalogues: a Z prefix means one thing in the European TemBreak 2 range and something else in the Australian one, and a page like this cannot publish a key that survives both.

The clearest example is a switch nobody looks at. On a draw-out air circuit breaker the standard auxiliary switch operates in the CONNECTED and TEST positions; on an ACB conforming to classification society rules it operates in the CONNECTED position only. The order form states it from the other direction as well: select a mechanical interlock and a marine type auxiliary switch is what gets supplied with it. The second difference can at least be seen — the red breaker fixing bolt, which locks the body in the CONNECTED position even under strong vibration, is standard equipment on ACBs that conform to ship classification society rules, and the inspection procedure adds a check of the moving arcing contact mounting nut for looseness where those rules apply. None of these differences alters the type designation on the front of the machine, which is why they have to be stated in a request rather than looked up from it.

The maintenance schedule makes the same point about wear. The TemPower 2 manual sorts the working environment into standard and harsh: its standard column names an engine room with air conditioning, and its harsh column an engine room without air conditioning, together with heavy dust, corrosive gases, high ambient temperature and humidity, and constant exposure to vibration. In that category the inspection interval falls to every year, and to every six months once the installation is two years old, against every one or two years in normal service. The moulded case manual shortens its own intervals again for atmospheres carrying sulphurous acid, hydrogen sulphide or salt, and the air circuit breaker order form offers tropicalisation, anti-corrosion and cold climate treatment as options taken at order time. A treated breaker and an untreated one share a type designation, so the treatment is one more thing the plate will not tell you and the switchboard file will.

On the air circuit breakers Terasaki publishes field replacement procedures for the arc chambers, the stationary and moving contacts, the latch release coil, the shunt trip device, the control relay, the magnet hold trigger and the auxiliary switches, and its inspection table gives the criteria that generate those orders: polish discoloured or roughened tips, renew both contacts when one is damaged or has worn past the limit, replace an arc chamber that will not clean up, replace an undervoltage trip whose coil resistance or plunger stroke is out of range. An ACB enquiry is therefore component-level, and it usually arrives as a list rather than as a line. The manual also draws two boundaries the enquiry has to respect: thorough inspection and overhaul are reserved to the manufacturer's own works, and a breaker that has performed three tripping operations near its rated breaking current is at the end of its safe service life and should be replaced rather than worked on again.

The moulded case side runs the other way. In the maker's own periodic inspection table the remedy for worn contacts, a cracked cover or base, a stiff handle, terminals discoloured by overheating and an insulation resistance below the stated limit is, in every case, replace; and after a short circuit, a breaker whose operating handle and arc gas vents are heavily contaminated with soot and molten metal particles is to be replaced without delay. An MCCB enquiry is consequently the device plus its accessories — the field-installable auxiliary and alarm switches, shunt trips, undervoltage trips, motor operators, handles, terminal covers and insulation parts. That split also decides where a verified alternative is worth reviewing: hardware, terminal covers, insulation parts and interlock fittings are ordinary supply questions, while the breaker itself, the trip unit and anything inside a class-surveyed panel stay on the OEM route, because a type approval certificate names type designations and states on its face that a significant change in design or construction may render it invalid. Type approval does not certify the equipment as installed either, so where a replacement has to satisfy a surveyor, the approval status for the specific breaker is confirmed against the certificates held with the vessel's own documentation before the line is ordered.