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
On Thursday, December 18, 2014 11:40:56 AM UTC, charles wrote:
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
I don't have any more recent edition of the Regs to hand.
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.
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
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
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
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.
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.
Google the Make and Model, and you'll be pretty likely to get the
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
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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