I'm thinking of getting an extractor fitted (Part P - bah!) in a bathroom in a rented ground floor flat. I assume there will be power available in the ceiling rose so am expecting to just run some surface trunking from the rose to the fan.
Questions: Do the regs require that the light has to be on an RCD? (There's only one lighting circuit so this would mean that all the lights will be on the RCD). Are there any recommendations for trunking that is "nicer" than others?
Run a feed from the light to an RCD outside the bathroom. Then rewire the 'enclosed' light fitting.
Fit a 3 pole isolation switch outside the bathroom wired from the light to a timed extractor fan fitted in a suitable position.
Drop and fit a 'plastic type' ceiling - this will hide all the cables.
Since the wiring you propose will be surface mounted, there is no direct requirement for a RCD for cable protection. So long as the bathroom has supplementary equipotential bonding, and the main equipotential bonding in the property is also to current standards. Then your change will be fine.
Note that you will also need a fan isolator switch to allow for maintenance of the fan. This does not necessarily need to be in the same room, but should be close enough that someone cleaning or replacing the fan can see if anyone it about to fiddle with it! If you fit the typical light switch activated with run on timer type fan, then the switch will need to be a three pole device.
If the EQ bonding is not to current standards then you would need to bring that up to scratch.
Under the 17th edition you can also avoid the need for supplementary bonding in the bathroom so long as the main bonding in the property is correct, and *all* circuits that enter the bathroom are protected by RCD(s) with trip thresholds of 30mA or less.
D line trunking.
E.g.
17th Ed does, but it's not retrospective. As for adding a fan to a 16th Ed installation, some BCOs will be happy providing it all still conforms to 16th Ed, others will require you to upgrade to 17th Ed.
That's subjective. Smallest size mini trunking which will take the cable, with clip on lid, is probably least obtrusive. Clipped cable may be even less obtrusive, being smaller still.
Do those in the 'know' here avoid RCBO's ? If the property in question has a modern CU with MCB's then one of the solutions is to fit an RCBO on the appropriate lighting circuit in place of the 6A MCB.
I've done that on both my lighting circuits, but then I'm an amateur - what do I know?
Rob.
That's fine if there's an RCBO available which can substitute your MCB.
RCBOs are fine, but there can be practical problems like finding a single module one that will fit the CU in use (assuming there is not space for a two module wide one).
Surface trunking across half the ceiling is surely going to look bad. It is possible to bury it even if you dont have any access to the joists. Just cut a notch in the plaster that extends each side of each joist, so the cable sits mostly above the ceiling, but dips down and is shallowly buried at each joist.
NT
If you're lucky, the joists will run the other way. A couple of holes and a fish wire (e.g. from a wire coat-hanger, provided you're sure you won't push it into something live inside the ceiling), and use it to pull through the real cable.
A length of 1mm T&E can even work as a fish wire, and also an expanding tape measure, or one of the clock-spring type drain unblockers, or the lid from mini trunking.
Plastic-coated wire hangers are safer.
;-)
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