24 volt DC FELV equipment installed in a location containing a bath or a shower.

(FELV) is a catch-all term to describe any extra-low-voltage circuit that does not meet the requirements to be considered to be   SELV  (in effect double insulation or reinforced between the mains and the ELV side) or PELV (you may have single insulation between mains and ELV, so long as you earth one pole or the transformer centre of the ELV side ).


Although the FELV part of a circuit uses an extra-low voltage, it need not be  protected from accidental contact with higher voltages in other parts of the circuit in a way that operates ADS - so autotransformers and thyristor based voltage reduction would be  acceptable ways to derive 12V from 240 for example.  Older transformers that were not split-bobbin, and rely purely on grease proofed paper between primary and secondary, with no earth on the secondary side, would also count as FELV,  pre-war bell transformers are like this, and are better converted to PELV.


Therefore the protection requirements for the higher voltage  apply to the FELV side of the wiring as well...


But is it really FELV ?


If it is, yes treat as if it was all at mains voltage, because a condition that  makes it so will not always operate ADS.  So it needs an RCD.

But do be sure it really is only FELV, almost nothing is these days.

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I have emailed the manufacturer to ask them.


There is no doubt that if the 230 V supply is taken into the shower room a RCD is required, but if that is outside of the shower room and all the cables are 24 Vdc supplied by the FELV transformer I think it still needs 30 mA RCD protection, so I install it. 


I am just checking I am not going over the top and gold plating jobs.


Andy Betteridge