2.5kW Sauna Heater - fused spur or consumer unit?

[Deuxbiers]

I have a 2.5kW sauna heater for an indoor sauna. The heater pulls 11A. Should it be hardwired to the consumer unit or can I run it from a 13A fused spur?

 

[EFLImpudence]

It depends what else is on the circuit.

Is it just a normal socket circuit?

 

[Murdochcat]

What do the MIs say?

 

[Deuxbiers]

It depends what else is on the circuit.

Is it just a normal socket circuit?

Yes, it’s the downstairs ring main serving part of the downstairs (living room and diner).

 

[Deuxbiers]

What do the MIs say?

The manufacturer installation manual only states it needs a single phase RCD isolated connection. Nothing about a dedicated circuit.

 

[EFLImpudence]

Yes, it’s the downstairs ring main serving part of the downstairs (living room and diner).

Then it would probably be better not on that circuit although it would likely not be a problem if there is no other heavy loads.

 

[ericmark]

The manufacturer installation manual only states it needs a single phase RCD isolated connection. Nothing about a dedicated circuit.

The load current in any part of the circuit should be unlikely to exceed for long periods the current-carrying capacity of the cable (Regulation 433.1.5 refers). This can generally be achieved by:
(ii) not supplying immersion heaters, comprehensive electric space heating or loads of a similar profile from the ring circuit
(iii) connecting cookers, ovens and hobs with a rated power exceeding 2 kW on their own dedicated radial circuit

This is from the appendix, not the main body of the regulations, and it is all about the problem taking a heavy load near the origin. If a heavy load is taken from the centre of a ring final the load will go down both legs reasonably equal. But 2.5 mm² cable use with a ring final needs to be rated 20 amps, but it has an overload of 32 amps, so if the load is near the origin you can get over 20 amps being drawn for an extended time on a cable rated for 20 amps.

So it is up to the electrician to decide if there is a problem or not, he will be making out the minor works certificate, or installation certificate, so he has to ensure it complies.