isolation switch

Should an extractor fan in a kitchen be fitted with an isolation switch? I've come across one which seems to be wired dirwetly from the power ring main. I'm unhappy.
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On Wed, 17 Dec 2014 22:48:00 +0000, charles wrote:

I presume there's a switch of _some_ kind...?
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On 17/12/2014 22:48, charles wrote:

Most fans stipulate they should be fed from a fused outlet of typically no more than 5A. So a switched fused connection unit is normally the obvious choice.
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On Wed, 17 Dec 2014 22:49:20 +0000 (UTC), Adrian

Xpelair with an integral pull cord perhaps?
I'd be far more concerned about the lack of a fuse than an isolator.
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Graham.

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my concern about an isolator was that the switch stuck ON when the pull cord link snapped off. I traced the supply to the ring main, which I had to turn off. But yes, the wiring that I saw certainly should have been protected by something less than a 32A MCB
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Anything connected to a final ring - other than sockets - should be via an FCU.
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Dave Plowman snipped-for-privacy@davenoise.co.uk London SW
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That's what I thought, but can you quote the regulation number?
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On Thursday, December 18, 2014 11:40:56 AM UTC, charles wrote:

an

14th Edition (1970 Amendment)
A.48 Apparatus permanently connected (i.e. not through a plug and socket-ou tlet) to a radial or ring final sub-circuit of the type described in Regula tion A.43 or A.44 shall be protected locally by a fuse of rating not exceed ing 15 amperes and controlled by a switch conforming with the requirements of Regulations A.58-61, or by a circuit-breaker of rating not exceeding 15 amperes.
I don't have any more recent edition of the Regs to hand.
Owain
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Unfortunately I can't quote regulations that were superceded in 1981 to a contractor who did the work in 2014. But, thanks
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On 18/12/2014 12:14, charles wrote:

Are you absolutely sure that there isn't an FCU hidden inside a cupboard somewhere?
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On Thursday, December 18, 2014 12:16:16 PM UTC, charles wrote:

My flat was built in 1968, so I'm still okay working to the 14th ? ;-)
Owain
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It is possible that he's hung a cupboard over the top of it, but it isn't visible from inside the cupboards.
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charles wrote:
Snip - fan directly fed from 32A circuit.

What do the Fan Instructions say? They are what will determine whether you need a fused spur, or fed via the 32A circuit. You already have an isolator - the circuit breaker. The fan is unlikely to need overload protection, unless called for by the Manufacturers Instructions.
Of course, it would be good practice to locally switch/fuse it for maintenance purposes, but it is not required if the Manufacturers Instructions do not require it - most do BTW.
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On Thu, 18 Dec 2014 18:30:50 +0000 (UTC), "A.Lee"

Good grief Alan, it's a kitchen fan, not a wind-tunnel at BAE. No way can he rely just on a 32A MCB.
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On 18/12/2014 20:41, Graham. wrote:

To be fair, it depends on the circumstance. If you can argue there is no way for the fan to cause an overload of its supply cable, then you can dispense with overload protection altogether. Then the remaining requirement is for fault protection. Say it were connected via 1.5mm^2 T&E, then that would be adequately fault protected by a B32 MCB.
(however its likely that a fan will stipulate overload protection via a fuse).
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On Thu, 18 Dec 2014 16:32:32 +0000 (GMT), charles

Is it twin & earth cable that's connected to the fan, or is it flex. If it's flex that's a good indication that there is some sort of connection nearby.
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Graham. wrote:

Could you please explain why you think that? I've got a 3 watt (0.0125A) lamp here running on a 10 A circuit breaker.
Why is that safe, when a 0.625A (~150w) fan would not be OK running on a 32A breaker?
The typical 3A fuse used to 'protect' typical fans does not protect the fan at all, and in most cases would be pretty useless. The fan is a fixed load (typically), so would not draw more power than it is rated for, except in fault conditions. Then, you would expect the circuit breaker to open, as short term loading wil be far more than 32 amps.
The big uncertaintly here, is what make the fan is, and what the Manufacturer stipulates, as I said above. If they say it should have a fuse and DP switch, then it should have one. But dont confuse the fuse as protecting the fan, all it is doing is protecting the supply cable, even then, it is prety useless.
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No idea never seen them

the internal wiring in the fan wouldn't support 32A/

Not in my book

I've found the relevant reg: 4.33,2.1. "A device for the protection of overload shall be installed at the point where a reduction in the value of the current-carrying capacity of the conductors of the installation.
There's also quite a bit in 537.
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I'm sure there's a connetcion, but I suspect it's under the plaster.
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charles wrote:

Google the Make and Model, and you'll be pretty likely to get the instructions. If it says "Must be supplied by a double switch and fuse", then he has no comeback at all, and should change the wiring to suit.

No, but it wont need to, it'll only be carrying whatever the motor draws.

But BS7671 says your Circuit Breaker / Fuse can be the Isolator.

But take into account 433.3.1 (ii)
Anyhow, the point is moot, as you do not know how it is connected. Ring him to find out?
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