installing new cooker hood. some advise please

[EFLImpudence]

I have argued that it may stop the chip-pan fire being sucked up but I realise it doesn't happen often.

It just seems logical.

Even if you don't agree with that, can you think of a reason why it should not be done or an advantage of having it on another circuit?

 

[phatboy]

If you run it from the cooker circuit, then until the point where the FCU is placed the cable should remain sufficient to be connected to a 32amp breaker, which can be a bit of an issue squeezing 2 sets of output cables from the cooker switch.

 

[JohnW2]

If you run it from the cooker circuit, then until the point where the FCU is placed the cable should remain sufficient to be connected to a 32amp breaker, which can be a bit of an issue squeezing 2 sets of output cables from the cooker switch.

See 433.2.2. In situations like this, it is usually permissible to run reduced size cable from the cooker switch to the FCU, the overload protection of the cable being provided by the downstream OPD (the fuse in the FCU).

Kind Regards, John

 

[stillp]

If you run it from the cooker circuit, then until the point where the FCU is placed the cable should remain sufficient to be connected to a 32amp breaker, which can be a bit of an issue squeezing 2 sets of output cables from the cooker switch.

See 433.2.2. In situations like this, it is usually permissible to run reduced size cable from the cooker switch to the FCU, the overload protection of the cable being provided by the downstream OPD (the fuse in the FCU).

Kind Regards, John

As long as the reduced size cable is "installed in such a manner as to reduce the risk of a fault to a minimum".
Mechanical protection?

 

[JohnW2]

See 433.2.2. In situations like this, it is usually permissible to run reduced size cable from the cooker switch to the FCU, the overload protection of the cable being provided by the downstream OPD (the fuse in the FCU).

As long as the reduced size cable is "installed in such a manner as to reduce the risk of a fault to a minimum". Mechanical protection?

Not necessarily. One only has to satisfy (i) or (ii) of 433.2.2. Hence, if there is adequate fault protection [per (i)] the requirements of (ii), including the bit you quote, do not have to be satisfied. Let's face it, this is no different from the situation with an unfused spur from a ring final (or an unfused 'reduced CSA branch' from a radial final), and I've never heard anyone suggesting that they require 'mechanical protection'!

What I don't really understand is when one would ever need to invoke 433.2.2(ii) - since I would have thought that virtually any circuit/cable (with a very few exceptions) would necessarily have to have adequate fault protection, hence satisfying 433.2.2(i). Am I missing something?

Kind Regards, John

 

[stillp]

What I don't really understand is when one would ever need to invoke 433.2.2(ii) - since I would have thought that virtually any circuit/cable (with a very few exceptions) would necessarily have to have adequate fault protection, hence satisfying 433.2.2(i). Am I missing something?

One of us is! That's why I added a question mark.
433.2.2 (i) refers to Section 434, the relevant subclause of which seems to be 434.2.1, which repeats the words "installed in such a manner as to reduce the risk of fault to a minimum".

 

[JohnW2]

What I don't really understand is when one would ever need to invoke 433.2.2(ii) - since I would have thought that virtually any circuit/cable (with a very few exceptions) would necessarily have to have adequate fault protection, hence satisfying 433.2.2(i). Am I missing something?

One of us is! That's why I added a question mark. 433.2.2 (i) refers to Section 434, the relevant subclause of which seems to be 434.2.1, which repeats the words "installed in such a manner as to reduce the risk of fault to a minimum".

True, but one doesn't have to satisfy any of 434.2.1 if 434.2.2 applies - and, as is being discussed (at length ) in another thread, it is quite quite likely (probably very likely if the csa reduction is not extreme) that fault (as opposed to overload) protection of the 'reduced CSA' cable will be adequately provided by the circuit's primary (upstream) OPD.

Kind Regards, John