Plug it in or wire it in? Two heaters from the same maker can give opposite answers, and the manual is the only place that settles it.

On this page

• What decides it
• What manuals say
• Picking the fuse
• Double pole and 3mm
• Timer trap
• Bathrooms
• Common mistakes
• What to buy
• FAQs

Panel heater fused spur or plug: what decides it?

There is no single answer, because heater makers write the connection method into each manual. Some heaters ship with a plug. Others ship with a bare flex for fixed wiring. Follow the manual for your model, not a general rule.

The wording is blunt. A heater marked "not suitable for connection via a plug top" must go through a fused connection unit. Fitting a plug anyway means the manufacturer's instructions have not been followed.

What do real heater manuals say?

Dimplex publishes its manuals online, so you can compare what one maker asks for across different heaters.

That is one brand and four different instructions. Several manuals also ban placing the heater above or below a fixed socket, so plan the spur position before you settle the heater position.

How do you pick the fuse for a fixed heater?

Dimplex's bathroom heater manual gives a typical split for 230V equipment: 3A up to 700W, and 13A above that. The fuse protects the heater's flex, so the manual's figure beats guesswork. The arithmetic is watts divided by 230.

At 230V, 3A is 690W, so Dimplex's 700W cut-off is a rounded figure. Check the rating plate and the manual rather than relying on the rounding.

Why do manuals ask for double pole and 3mm?

Three of the Dimplex manuals above ask for a double pole isolating switch with at least 3mm of contact separation. A double pole switch breaks live and neutral together, so the heater is properly isolated when it is off.

BG lists its Evolve switched fused connection unit, the PCDBS52W, as double pole on its own product page. BG's Evolve spec sheet gives the box depth and the standard but no contact gap. Ask BG before you rely on it where a manual demands 3mm.

Can you put a timer or smart switch in front of a heater?

Check first. Dimplex's bathroom panel heater manual says it must not be connected through an external switching device such as a timer. A timer spur or smart switch ahead of the heater is exactly that.

The manual explains why: repeated switching could reset the heater's thermal cut-off and create a fire hazard. If you want scheduling, choose a heater with built-in controls.

What changes in a bathroom?

Bathrooms add a layer on top of the manual. Sockets are restricted there, so a plug-in heater is rarely an option. Choose a heater whose manual names the bathroom, as the BPH100M does, and wire it through a fused connection unit.

Zones, IP rating and RCD protection all apply. Have a registered electrician do and certify the work, and place the fused connection unit where the manual and the zones allow.

Where do heater connections go wrong?

• Fitting a plug to a spur-only heater. The manual says not suitable for a plug top. Follow it.
• Mounting the heater under a socket. Several Dimplex manuals say not to, and the storage heaters add above and in front.
• Fusing by habit. Dimplex says to rate the fuse for the appliance's flex, with a typical split of 3A under 700W and 13A over.
• Putting a timer ahead of the heater. Some manuals forbid it outright.
• Boxing an Evolve unit too shallow. BG's minimum for its Evolve fused units is 35mm.

Which fused connection unit should you buy?

For a fixed heater, choose a switched, double pole unit with a flex outlet. TEO's fused connection units collection lists 55 units. The BG Evolve PCDBS52W in Brushed Steel is £7.18. The same unit bundled with a 35mm steel back box is £9.85. For a metal look, see Nexus Metal Brushed Steel.

• Manual checked: plug, spur, or either.
• Unit is switched and double pole where the manual asks for isolation.
• Fuse set from the manual: 3A up to 700W by Dimplex's split, 13A above.
• Back box at least 35mm for Evolve fused units.
• No timer or smart switch ahead of the heater.

Prices checked 31 October 2026.

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