If there was a 13A socket or an equivalent then it might be more of a concern, if as you say there is no evidence of damage from the environment, then it is not really an issue, The locked door thing as I recall it was more about sockets and access to things that might be operated with wet hands or get hot to touch.  From the boiler point of view it may or may not need some ventilated space, but a vent to somewhere other than a wet bathroom may be best.

I'm inclined to agree based on what you describe - no electrical code, but not the best design.

M,

No I don't disagree.

I have a bathroom, which contains an airing cupboard, which in turn contains a boiler and I have never felt threatened by it.

I think that 701.411.3.3 applies - RCD protection required.

Given that there is no obvious reason why a wet and naked person would be operating the boiler, if there is no RCD protection, I would grade C3.

Thanks guys.  There is rcd protection.

Gary

I remember reading about the door should have a lock or at least some way of keeping it shut but don't know where. Is this written into the regs somewhere as i can't see anything in 701. 

You might be thinking of the space under the bath - which can be considered outside zones if it's only accessible by means of a tool (701.32.3). As far as I recall there hasn't been anything similar for doors in general (otherwise half the landing in a typical house could end up in zones) and a plateswitch for the immersion in an airing cupboard has been standard practice for generations).

   - Andy.

An RCD is fine, or supplementary bonding to all exposed and extraneous conductive parts would do it too. No cupboard etc required at all.

There used to be a wide held belief (especially in NICEIC contractors around here) that a cupboard with a lock on it (tool or key required to "unlock it") was required to satisfy boilers, immersion heaters, sockets etc being out of bathroom zones if the proximity alone without such door would render them within the zone.

Now I might be persuaded, to some degree, that a bathroom door has a reasonable expectation of being closed whenever bathroom in use, Therefore items in a hallway/landing might not need such distances.

However, just because a cupboard has a lockable door does not mean it will get locked/unlocked at every use. So relying on this "technicality"  is a red haddock IMHO. 

If a cupboard door had such a latch that it locked when clicked shut but needed a tool/key to re-open, then I suppose that might help but I`ve never seen or heard of that situation for a bathroom cupboard.