How to Read an MCB Nameplate: Markings, Symbols, Ratings, and Trip Curve Explained

The Short Answer: What Do MCB Nameplate Markings Mean?

An MCB nameplate tells you the miniature circuit breaker’s rated current, trip curve, voltage rating, breaking capacity, pole configuration, application standard, wiring symbol, and AC or DC suitability. The most common marking format is something like C16 6000 230/400V~ IEC 60898-1, which means a C-curve 16A AC MCB with 6kA rated short-circuit capacity under the stated standard.

Read the markings in this order:

1. Trip curve and current rating: B16, C20, D32.
2. Rated voltage and AC/DC symbol.
3. Breaking capacity: 6000, 6kA, 10000, or 10kA.
4. Standard: IEC 60898-1, IEC 60947-2, UL 489, or other regional marking.
5. Pole configuration: 1P, 1P+N, 2P, 3P, 4P.
6. Wiring diagram, line/load direction, and polarity if marked.
7. Manufacturer, model number, certification marks, and accessory markings.

If you are using the nameplate to select a new breaker, also read MCB Selection Guide: How to Choose the Right Miniature Circuit Breaker. This article focuses on decoding the markings.

MCB Nameplate Markings at a Glance

Marking	Example	Meaning	Selection risk
Trip curve + rated current	C16, B20, D32	Curve letter plus rated current in amperes	Wrong curve may cause nuisance trips or poor fault protection
Rated current	16A, 32A, 63A	Current the MCB is designed to carry continuously under specified conditions	Oversizing may fail to protect the cable
Trip curve	B, C, D	Instantaneous magnetic trip characteristic	Must match load inrush behavior
Breaking capacity	6000, 6kA, 10000, 10kA	Maximum short-circuit current the MCB can interrupt under rated conditions	Must exceed available fault current
Rated voltage	230/400V~	AC operating voltage rating	Must match system voltage and pole use
Standard	IEC 60898-1, IEC 60947-2	Product test/application standard	Household/similar vs industrial application context
Pole marking	1P, 1P+N, 2P, 3P, 4P	Number and arrangement of switched/protected poles	Wrong pole count can create wiring and isolation problems
AC/DC symbol	~, DC mark, + / –	Current type and sometimes polarity	AC MCB cannot be assumed suitable for DC
Wiring diagram	line/load or internal contact diagram	How terminals and poles are arranged	Miswiring can defeat protection or indication
Certification mark	CE, UL, TUV, CCC, etc.	Market or certification indication	Must match the exact model and project requirement

For a broader MCB definition page, see What Is a Miniature Circuit Breaker (MCB)?.

What Does C16, B20, or D32 Mean on an MCB?

The marking C16 combines two pieces of information:

• C = trip curve
• 16 = rated current in amperes

So C16 means a C-curve MCB with a rated current of 16A.

Other examples:

Marking	Curve	Rated current	Typical interpretation
B10	B curve	10A	Sensitive instantaneous trip, often used for low-inrush circuits
C16	C curve	16A	General-purpose circuit with moderate inrush
C32	C curve	32A	Higher branch circuit current, still C-curve behavior
D32	D curve	32A	Higher inrush tolerance, only where suitable for the circuit

Do not read C16 as “16kA” or “curve C plus 16kA.” The number after the curve letter is the rated current, not the breaking capacity.

For a deeper curve explanation, see Understanding Trip Curves.

B, C, and D Trip Curves on the Nameplate

The trip curve letter tells you the instantaneous magnetic trip range. For common IEC-style MCBs:

Curve	Typical instantaneous trip range	Common use
B curve	3-5 x In	Low-inrush loads, long cable runs where fault current is limited
C curve	5-10 x In	General loads, small motors, lighting groups, mixed circuits
D curve	10-20 x In	High-inrush loads such as transformers or larger motor starting circuits

In means rated current.

Example: a C16 MCB has a rated current of 16A. Its instantaneous trip range is typically around 5-10 times rated current, so roughly 80-160A under the relevant test conditions.

The curve should be selected based on inrush current and fault-loop conditions. Choosing a D-curve breaker simply to stop nuisance tripping can be unsafe if the available fault current is too low to trip it quickly.

Rated Current vs Breaking Capacity

Two markings are often confused:

• Rated current: the normal current rating, such as 16A or 32A.
• Breaking capacity: the short-circuit interruption rating, such as 6000A or 10kA.

Example:

C16 6000

This means:

• C16 = C-curve, 16A rated current
• 6000 = 6000A short-circuit capacity, commonly read as 6kA

The MCB does not carry 6000A continuously. It is rated to interrupt that level of short-circuit current under its specified test conditions.

For more detail, see 6kA vs 10kA MCB Breaking Capacity.

What Does 6000, 6kA, 10000, or 10kA Mean?

MCBs may show breaking capacity as:

• 6000
• 6000A
• 6kA
• 10000
• 10kA

These refer to rated short-circuit breaking capacity under the marked standard and voltage.

Marking	Meaning
3000 or 3kA	3,000A short-circuit capacity
4500 or 4.5kA	4,500A short-circuit capacity
6000 or 6kA	6,000A short-circuit capacity
10000 or 10kA	10,000A short-circuit capacity

The correct rating depends on the prospective short-circuit current at the installation point. A panel close to a transformer may require a higher breaking capacity than a circuit far downstream.

For calculation context, see How to Calculate Short Circuit Current for MCB.

Icn vs Icu vs Ics on MCB Nameplates

Some MCBs show Icn, while others show Icu and Ics. These terms come from different standard contexts.

Marking	Common standard context	Meaning
Icn	IEC 60898-1	Rated short-circuit capacity for household and similar MCB applications
Icu	IEC 60947-2	Ultimate short-circuit breaking capacity
Ics	IEC 60947-2	Service short-circuit breaking capacity

Do not treat these as identical markings. An MCB intended for household and similar final circuits may mainly show IEC 60898-1 data such as Icn. An industrial DIN-rail MCB may also carry IEC 60947-2 ratings such as Icu and Ics.

The practical rule is simple: read the breaking-capacity value together with the standard, voltage, and application context. A “10kA” marking without the applicable standard and voltage is incomplete.

For a deeper standard comparison, see IEC 60898-1 vs IEC 60947-2 for MCBs. For breaker rating terms, see Icu vs Ics vs Icw vs Icm.

How to Read Rated Voltage and AC/DC Symbols

Voltage markings tell you where the MCB can be used.

Common examples:

Marking	Meaning
230V~	AC single-phase voltage rating
230/400V~	AC rating for phase-neutral / phase-phase use depending on pole arrangement
400V~	AC three-phase line-to-line use, depending on product and pole type
DC, VDC, +, -	Direct current rating or polarity information

The tilde symbol ~ means alternating current (AC). It does not imply DC suitability.

An AC MCB should not be used in a DC circuit unless the nameplate and datasheet explicitly provide a DC rating and wiring method. DC arc interruption is different from AC interruption, and some DC breakers are polarity-sensitive.

For DC-specific issues, see DC Circuit Breaker Polarity: Polarized vs Non-Polarized DC MCB Guide.

How to Read Pole Markings: 1P, 1P+N, 2P, 3P, 4P

Pole markings tell you how many conductors the MCB switches or protects.

Marking	Meaning	Typical use
1P	One protected pole	Single-phase live conductor in many systems
1P+N	One protected pole plus neutral switching, depending on design	Single-phase circuits where neutral isolation is needed
2P	Two poles	Single-phase two-pole isolation, some DC circuits if rated
3P	Three poles	Three-phase circuits without neutral switching
4P	Four poles	Three-phase plus neutral switching

Do not assume 1P+N is the same as 2P. In many 1P+N devices, only the phase pole has overcurrent protection, while the neutral pole is switched but not protected. Always check the wiring diagram.

IEC 60898-1 vs IEC 60947-2 on MCB Nameplates

The standard marking helps you understand the intended application context.

Standard	Typical context	What to check
IEC 60898-1	Household and similar AC MCB applications, often operated by ordinary persons	Icn, B/C/D curves, final circuit suitability
IEC 60947-2	Low-voltage circuit breakers for industrial switchgear and controlgear, typically selected by skilled persons	Icu, Ics, utilization context, industrial data
UL 489	North American branch circuit breaker standard	UL listing, voltage system, interrupting rating, panel compatibility

Some industrial DIN-rail MCBs may carry both IEC 60898-1 and IEC 60947-2 data, but you must verify the exact model and datasheet. Do not assume dual-standard certification from appearance alone.

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Real Example: Decode a Typical MCB Marking

Example marking:

C16 6000 230/400V~ IEC 60898-1 1P

How to read it:

Part	Meaning
C	C trip curve
16	16A rated current
6000	6000A, or 6kA, rated short-circuit capacity under the stated conditions
230/400V~	AC voltage rating
IEC 60898-1	Standard/application context
1P	One-pole MCB

This example does not by itself prove suitability. You still need to check:

• load current
• cable size and installation method
• prospective short-circuit current
• AC or DC system type
• trip curve and inrush current
• pole arrangement
• local code or project specification
• manufacturer datasheet

For full selection workflow, see How to Choose the Right Miniature Circuit Breaker.

Common Mistakes When Reading MCB Nameplates

Mistake 1: Confusing rated current with breaking capacity

C16 and 6000 are not the same type of rating. C16 describes curve and rated current. 6000 describes short-circuit capacity.

Mistake 2: Using the 125% rule everywhere

Some codes and continuous-load applications require specific sizing margins, but this is not a universal global rule for every MCB installation. MCB selection must also consider conductor ampacity, load type, installation method, ambient temperature, and local regulations.

Mistake 3: Assuming all 6kA MCBs are equivalent

Breaking capacity must be read with voltage, standard, pole arrangement, and product family. Two breakers marked 6kA may not be interchangeable.

Mistake 4: Ignoring trip curve

A C16 and a B16 have the same rated current, but different instantaneous trip behavior. The wrong curve can cause nuisance tripping or delayed fault clearing.

Mistake 5: Using an AC MCB in a DC circuit

The ~ symbol means AC. DC circuits require explicit DC voltage and breaking ratings, plus correct wiring and polarity if specified.

Mistake 6: Treating 1P+N as the same as 2P

Pole construction affects protection, neutral switching, and wiring. Always read the internal diagram.

Mistake 7: Replacing by front label only

For replacements, check mounting system, busbar compatibility, terminal size, pole arrangement, certification, and manufacturer documentation, not only current rating and curve.

MCB Nameplate Checklist Before Selection

Before approving or replacing an MCB, record:

Check	Question
Current rating	Does In match the load and cable protection requirement?
Trip curve	Does B/C/D curve match inrush and fault-loop conditions?
Breaking capacity	Is Icn/Icu/Ics high enough for the available fault current?
Voltage	Does the rating match the AC or DC system voltage?
Standard	Does IEC 60898-1, IEC 60947-2, UL 489, or other marking match the project?
Poles	Is 1P, 1P+N, 2P, 3P, or 4P correct for the circuit?
Wiring	Does the diagram match line/load direction and neutral arrangement?
DC suitability	If DC, is the device explicitly DC-rated and wired correctly?
Accessories	Are auxiliary contacts, shunt trips, or busbars compatible?
Model number	Does the replacement match the exact product family and datasheet?

For procurement and supplier selection, see MCB Manufacturer and the VIOX MCB product page.

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FAQ

What does C16 mean on an MCB?

C16 means the MCB has a C trip curve and a rated current of 16A. The letter is the trip curve; the number is the current rating.

What does 6000 mean on an MCB?

6000 usually means 6000A, or 6kA, rated short-circuit breaking capacity under the stated standard and voltage conditions.

What does 10kA mean on an MCB?

10kA means the breaker is rated to interrupt a prospective short-circuit current of 10,000A under specified test conditions. It does not mean the breaker can carry 10,000A continuously.

What does the tilde symbol mean on an MCB?

The tilde symbol ~ means AC. It indicates alternating-current rating. DC suitability must be marked separately or confirmed from the datasheet.

What is the difference between B curve and C curve MCB?

B curve MCBs typically trip magnetically at 3-5 times rated current. C curve MCBs typically trip at 5-10 times rated current. C curve is more tolerant of moderate inrush current.

What is the difference between C16 and C32?

Both are C-curve MCBs, but C16 is rated 16A and C32 is rated 32A. The higher current rating does not automatically make it safer; it must match the cable and load.

What is Icn on an MCB?

Icn is the rated short-circuit capacity commonly associated with IEC 60898-1 MCBs. It tells you the fault current the breaker is rated to interrupt under that standard’s test conditions.

Is Icu the same as Icn?

No. Icu is an IEC 60947-2 ultimate breaking capacity rating. Icn is used in IEC 60898-1 contexts. Read each value with its standard and voltage conditions.

Can I replace an MCB with another brand if the markings match?

Not automatically. Electrical ratings may match, but mounting, busbar compatibility, terminal size, certification, accessories, and panel approval may differ.

Can I use an AC MCB for DC?

Only if the MCB is explicitly rated for DC and installed according to its DC wiring diagram. AC ratings alone are not enough for DC circuits.

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Summary

An MCB nameplate is a compact technical specification. To read it correctly, decode the curve and current rating first, then check breaking capacity, voltage, standard, pole configuration, AC/DC symbol, wiring diagram, and model data.

The essential distinction is simple:

• C16 tells you curve and rated current.
• 6000 or 6kA tells you short-circuit capacity.
• 230/400V~ tells you AC voltage suitability.
• IEC 60898-1 or IEC 60947-2 tells you the standard context.
• 1P, 1P+N, 2P, 3P, or 4P tells you pole arrangement.

For safe selection, do not read one marking in isolation. Use the nameplate together with the datasheet, cable sizing, available fault current, load type, and applicable project standard.

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Sources Used

• Current VIOX page: How to Read the Nameplate of Miniature Circuit Breaker
• Circuit breaker overview and common MCB curve ranges
• VIOX: IEC 60898-1 vs IEC 60947-2
• VIOX: MCB Breaking Capacity 6kA vs 10kA