A landlord in Leeds rang asking why his new boiler spur had no visible switch. Nobody had asked him whether he wanted switched or unswitched before it was fitted.

What Does a Fused Connection Unit Actually Do?

A normal 13A socket assumes you'll plug and unplug something. A fused connection unit assumes the opposite: a fridge, a washing machine, a boiler, an extractor fan, or anything else that's meant to stay wired in place permanently. Instead of a socket and plug, you get a fused, hardwired connection point with its own BS 1362 fuse, sized to protect that specific appliance rather than sharing a fuse rating with everything else on the circuit.

This matters because a fixed appliance drawing a specific current gets a specific fuse rated for it, rather than relying on the ring main's general protection. A landlord converting a kitchen and needing to hardwire a dishwasher or a washing machine under a worktop is the classic use case.

Switched vs Unswitched: Which One Do You Actually Need?

Our honest take: default to switched unless there is a specific reason not to. The one case where unswitched genuinely matters is where someone flicking a switch by accident would cause a real problem, such as an alarm system or a boiler that a well-meaning guest or contractor might otherwise turn off without realising what it does.

Do You Need a Flex Outlet Version?

Standard fused connection units expect a fixed cable entry, wired directly into the back of the unit. A flex outlet version adds a cable gland on the front or side of the plate, letting a flexible cord run from the FCU to the appliance itself. This is the version to specify for a boiler or water heater where the appliance itself has a flex tail rather than a fixed cable, and it is the detail most likely to get missed on a first-fix electrical schedule.

Fitting a Fused Connection Unit: What to Check First

Minimum backbox depth on the BG Nexus range runs around 29mm to 35mm depending on the exact model, generally shallower than a standard double socket, which usually makes retrofitting straightforward. Confirm the fuse rating matches the appliance's actual current draw before fitting, rather than assuming every FCU takes the same 13A fuse as a plug top.

This is notifiable electrical work under Part P of the Building Regulations if it involves a new circuit, particularly relevant in a kitchen, which counts as a special location. A price reality check: a single BG Nexus fused spur typically runs £8 to £15 depending on finish and features, a minor cost against getting the switched vs unswitched decision wrong and having to swap it after first fix.