High Current MCBs 63A–125A for Sub-Mains & Heavy-Load Circuits
High current MCBs from 63A to 125A are used where a circuit carries more load than a standard final circuit breaker is designed for. They are commonly specified for sub-mains, plant equipment, HVAC systems, distribution board feeds, and other installations where higher current capacity is needed.
This range is built for electricians and contractors working on heavier-duty circuits, with options covering different current ratings, pole formats, and trip characteristics depending on the load and supply arrangement.
Quick answer: A high current MCB is typically a breaker rated from 63A to 125A, used for larger loads, sub-main feeds, and distribution circuits where standard lower-rated MCBs are not suitable.
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Compared with standard domestic MCB ratings, these devices are chosen where the installation design calls for a breaker that can handle a higher continuous current and protect larger cables, feeders, or more demanding equipment. That makes them a common choice on commercial boards, industrial systems, and larger specialist installations.
- 63A–125A current range – for larger loads and feeder circuits
- Single, 2 pole, 3 pole and 4 pole formats – to suit different supply arrangements
- B and C curve options – depending on circuit behaviour and inrush current
- Suitable for sub-mains and heavy-load circuits – including plant and building services
- Used in commercial and industrial boards – where stronger-duty circuit protection is required
Need related protection products? Browse our full MCB range, 3 pole MCBs, 4 pole MCBs, and three phase boards & accessories. For delivery and returns, see our delivery information and returns policy.
6kA MCB – 63A 1 Pole C Curve (WMC163C)
£2.08
£2.99
The WMC163C is a 63 A single-pole 6 kA Miniature Circuit Breaker (MCB) designed for large feed and distribution circuits where inrush currents from motors, welders or transformers demand higher tolerance. Its C-curve tripping profile (5–10 × In) provides robust inrush immunity while ensuring rapid...
6kA MCB – 63A 1 Pole B Curve (WMC163B)
£2.08
£2.99
The WMC163B is a 63 A single-pole 6 kA Miniature Circuit Breaker (MCB) built for high-load distribution circuits, feed boards and plant equipment. It delivers accurate overcurrent and short-circuit protection using a B-curve tripping profile (3–5 × In), providing fast disconnection on faults without nuisance...
63A 4 Pole 10kA MCB C Curve – WKC463C
£15.05
The WKC463C is a 63A 4 pole 10kA Miniature Circuit Breaker (MCB) engineered for three-phase + neutral protection. With its C Curve trip characteristic, it is designed for heavier inductive loads such as motors, pumps, HVAC systems, EV charger circuits, and commercial sub-distribution boards in...
63A 4 Pole 10kA MCB B Curve – WKC463B
£15.05
The WKC463B is a 63A 4 pole 10kA Miniature Circuit Breaker (MCB) designed for three-phase + neutral protection. With its B Curve trip characteristic, it is best suited to resistive load applications such as large socket outlet groups, small power distribution panels, and lighting circuits...
1 Pole 10kA MCB 63A C Curve WKC163C
£5.00
The WCED WKC Series 10kA Miniature Circuit Breakers (MCBs) are high-performance devices designed for precise overcurrent detection and short-circuit protection. Built to handle demanding applications, they provide reliable protection for domestic, commercial, and industrial distribution systems – including solar PV with SPD and EV charging...
Where High Current MCBs Are Used
High current MCBs are used on circuits that sit above standard final circuit ratings, especially where a breaker is protecting a sub-main, a larger item of equipment, or a distribution feed supplying downstream loads. In these cases, 63A, 80A, 100A, or 125A protection may be needed depending on the design current and cable arrangement.
Typical Applications
- Sub-mains feeding secondary consumer units or distribution boards
- Plant and building services such as pumps, air handling, and HVAC equipment
- Commercial and industrial machinery with sustained higher current demand
- Workshop and facility supplies where multiple downstream circuits are being fed
- Larger single-phase or three-phase loads depending on the pole configuration
Choosing Between 63A, 80A, 100A and 125A MCBs
The correct rating depends on the design current, cable capacity, installation method, and the characteristics of the load being protected. A 63A MCB may suit a smaller feeder or plant circuit, while 100A or 125A devices are more likely to be used on larger sub-main or higher-demand installations.
B Curve vs C Curve High Current MCBs
B curve high current MCBs are generally used on heavier circuits with lower inrush current and more predictable load behaviour. C curve high current MCBs are often selected where motors, compressors, or other inductive equipment create a higher start-up current.
- B curve – for lower inrush, steadier load profiles
- C curve – for equipment with higher start-up or inrush current
Single, 2 Pole, 3 Pole & 4 Pole Options
High current MCBs are available in different pole formats to match the supply arrangement and switching requirement of the circuit:
- Single pole – for larger single-phase loads
- 2 pole – where a line and neutral switching arrangement is needed
- 3 pole – for three-phase circuits without neutral switching
- 4 pole – for three-phase plus neutral circuits
High Current MCBs vs Standard MCBs
The main difference is current rating and intended application. Standard MCBs are commonly used on final circuits such as lighting and sockets, while 63A–125A MCBs are used on larger feeder circuits, heavier loads, and upstream board protection where a lower-rated device would be undersized.
Used Alongside Distribution Boards & Three Phase Protection
High current MCBs are often specified alongside general MCBs, 3 pole MCBs, 4 pole MCBs, and wider three phase boards & accessories where the installation includes larger loads or multi-pole protection requirements.
FAQs on High Current MCBs
What is a high current MCB used for?
A high current MCB is used to protect larger circuits such as sub-mains, feeder circuits, plant supplies, and other heavy-load electrical installations.
When would I use a 63A or 125A MCB?
These ratings are used when the circuit design requires a breaker above standard final circuit sizes, typically on larger loads or distribution circuits.
Should I choose B curve or C curve?
B curve is generally used where the load has lower inrush current, while C curve is chosen where the connected equipment has a higher start-up current.
Are high current MCBs only for three-phase systems?
No. They are often used on three-phase systems, but they can also be used on larger single-phase circuits depending on the application and pole format required.
Why Buy High Current MCBs from Power & Data UK?
Power & Data UK supplies trade-focused circuit protection products with dependable UK stock, practical product choice, and fast dispatch. Orders over £30 qualify for free UK mainland next-day delivery, and products are backed by a 2-year manufacturer warranty. For unwanted items, see our returns policy.