Letter and current
B, C or D before the figure is the tripping characteristic, the figure the rated current. The instantaneous band: B 3 to 5 times the rated current, C 5 to 10, D 10 to 20. A C16 trips instantly between 80 and 160 A.
Reference tool — not a selection
Read a circuit breaker marking before it goes in an RFQ.
IEC 60898-1 breaker
Letter, current, breaking capacity.
Type the marking as on the breaker. Below the examples, an offered breaker can be checked against it: the current, the letter, the poles and the breaking capacity. The bands, the rows and the RFQ line update with every change.
Examples:
Replacement check
On the markings alone: choosing a breaker for the cable and the load stays with the panel design.
All 130 engineering tools
Miniature circuit breakers in lighting, galley and workshop panels carry an IEC 60898-1 marking on the front: C16, 6000 in a rectangle, 3 in a square. The letter is the tripping characteristic, the figure the rated current, 6000 the rated short-circuit capacity in amps and 3 the energy limiting class. Type the marking, and the reader gives the instantaneous tripping band in amps, checks an offered breaker and writes the RFQ line.
The overload (thermal) range is not given here, nor are the K and Z characteristics of IEC 60947-2 breakers: their limits come from the maker.
How a marking is read
Letter, rectangle, square.
For the load
B for resistive loads and long cables, C the general choice and for inductive loads, D for high inrush currents: motors, transformers.
Rectangle and square
The figure in the rectangle is the rated short-circuit capacity in amps (6000 is 6 kA). The digit in the square beside it is the energy limiting class, 1 to 3; class 3 lets the least energy through.
| Letter | Band | 6 A | 10 A | 16 A | 20 A | 32 A | 63 A |
|---|---|---|---|---|---|---|---|
| B | 3–5 × In | 18–30 A | 30–50 A | 48–80 A | 60–100 A | 96–160 A | 189–315 A |
| C | 5–10 × In | 30–60 A | 50–100 A | 80–160 A | 100–200 A | 160–320 A | 315–630 A |
| D | 10–20 × In | 60–120 A | 100–200 A | 160–320 A | 200–400 A | 320–640 A | 630–1260 A |
The overload range and the K and Z characteristics are left out, and so is a list of preferred breaking capacities: the sources give it differently, and the figure on the breaker reads as it stands.
Sources
B, C and D bands: a Schneider-style MCB catalogue and an IMO MCB data sheet, with the NEN 3140 guide’s account of the letters; uses: the IS/IEC 60898-1 summary and the Queensland electrical licence study guide. The rectangle with the breaking capacity and the square with the energy limiting class: IPD’s MCB catalogue pages, the IS 12640 summary and Building’s “As simple as 1, 2, 3”.
Before you send the request
Questions about breaker markings in an RFQ
What does C16 mean on a breaker?
A C tripping characteristic and a 16 A rated current. The C letter sets the instantaneous (magnetic) band at 5 to 10 times the rated current, 80 to 160 A here; B is 3 to 5 times and D 10 to 20 times.
What are 6000 and the 3 beside it?
The figure in the rectangle is the rated short-circuit capacity, 6000 A (6 kA); the 3 in the square is the energy limiting class, and class 3 lets the least energy through.
Can a B breaker replace a C breaker?
Not without a look at the circuit: the letter was chosen for the load. A B breaker trips sooner on an inrush, such as a motor start; a D breaker later, which a long cable may not allow. The reader marks another letter as a point to check.
What should the request include?
The full front marking (for example C16 6000 3), the poles, the maker and type from the side label, the quantity, and a photograph of the breaker in the panel.
Marking read?
Send the line with a photograph of the breaker.
A decoded marking is a cross-check, not a breaker selection. Attach photographs of the front and the side label, and Vessel Core checks them before an offer goes back.
Buyer tools
