Single-pole MCBs are the most common overcurrent devices used in UK domestic and light-commercial boards. They disconnect the live conductor during a fault while leaving the neutral intact - making them ideal for standard final circuits like lighting, sockets and small appliances.
Quick Answer: A single-pole MCB breaks only the live conductor under overload or short-circuit conditions. Use them on standard 230V final circuits such as rings, radials, lighting, boilers and small appliances. They are not suitable for isolation - only fault protection.
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What Single-Pole MCBs Actually Do
A single-pole MCB monitors the current flowing through the live conductor. If overload or short-circuit conditions occur, it disconnects the live only, leaving the neutral connected. This delivers fast fault clearance while keeping wiring simple and compact on final circuits.
Single-pole MCBs provide:
- Overload protection (thermal trip)
- Short-circuit protection (magnetic trip)
- Compact footprint for tight boards
- Standard DIN-rail compatibility
When to Use a Single-Pole MCB
Single-pole devices are the default choice for the majority of 230V final circuits in UK properties. They offer the right level of protection without the extra cost or space of multi-pole alternatives.
Use a single-pole MCB for:
- Socket ring or radial circuits
- Lighting circuits (LED, halogen, CFL)
- Boiler supplies and small heating controls
- Cooker and hob circuits (where single-pole is appropriate)
- Small appliance circuits
They’re the correct choice anywhere the neutral does not need to be disconnected for fault protection.
When Single-Pole MCBs Aren’t Suitable
Because they break only the live conductor, single-pole devices are not isolation switches and shouldn’t be used where full disconnection is required.
Avoid single-pole MCBs for:
- Three-phase circuits (where pole-linked isolation is required)
- Machinery or plant equipment needing full isolation
- Outdoor or exposed circuits where double-pole switching is recommended
- TT systems where full neutral disconnection may be required
In these situations, double-pole or multi-pole MCBs/RCDs are the correct choice under BS 7671.
Installer-Favourite Single-Pole MCBs
These are commonly used across domestic and light commercial final circuits.
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FAQs
Installers often want clarity on when a single-pole device is the correct option. These quick FAQs cover the essentials.
Do single-pole MCBs provide isolation?
No. They disconnect the live only and should not be used as isolation switches.
Are single-pole MCBs compliant for domestic use?
Yes. They are standard for most 230V final circuits in UK properties.
When should I choose double-pole instead?
Use double-pole on circuits requiring neutral disconnection or where BS 7671 mandates full isolation.
Do single-pole MCBs work with RCBOs?
Yes - RCBOs provide combined overcurrent and earth leakage protection, while the MCB provides overcurrent only.
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