Extractors & fuses

[Octopus]

All

I attended the Elecsa update in Woking last night - useful as it was there was one "thing" that stood out was their emphasis on extractor fans being fused down to the "manufacturers instructions".

So given that 90%+ of fans suggest fusing down to 3A, and given that most will need live and switched live, and (as far as I know) there is no such thing as a fan isolator switch with 2 fuses in it, how do other members deal with this?

Most cowboy installs seem to ignore the requirement for an isolation switch anyway.

 

[malcolmsanford]

Did they say why they felt the need to protect the fan with a 3amp BS 1362 fuse, and why the 6amp (normal) protection device on the light circuit was not adequate.

 

[Octopus]

Did they say why they felt the need to protect the fan with a 3amp BS 1362 fuse, and why the 6amp (normal) protection device on the light circuit was not adequate.

They emphasised that installation of fans (and any other product) should ALWAYS be to the manufacturers instructions so if it says fuse down to 3A, then that's what we should do. Not always practical or possible.!

 

[malcolmsanford]

I know our regs say we must follow the manufacters instructions, but I would lay my pension on a 6amp MCB tripping before a 3amp BS 1362 fuse even thinks about it .......................just seems that the schemes are following everything parrot fashion.

 

[Amp David]

Time for someone to invent a 2 gang switch FCU then! as most fan have a run on.

Or do they just want the perm line fusing down?

 

[Des 56]

Unless you wire the fan off the light using the switch wire of the light to trigger the fan,I see little problem with the means to fuse down the fan, as per the silly manufacturers instructions

Given I never use the level of light to determine the need for ventilation,I have never had this problem (independent operation of the fan in my case by a seperate pull cord or such)


If a system was required to be triggered by the light,then a switched fused spur before the light supply would seem to be the means to do so,if it isn't then a switched fused spur to feed the fan + controls

 

[i=p/u]

well its the perm live that is always fused..... just get the job done and go home and ratlle your hobbies, lifes to short for numbskulls to dictate it and complicate it as the part p doctor says electrics aint difficult but he doesnt mention the regs as being a piece of pis

 

[telectrix]

if everybody employed a punkah wallah, the dole queue would be nil.

 

[Silly Sausage]

But how would you determine their litres/sec airflow in order to comply with Part F?

 

[Des 56]

if everybody employed a punkah wallah, the dole queue would be nil.

and the talked about required ventilation test instruments could definitely be replaced by the standard fart extraction rate type of standard,the punkah wallah would speed up to suit

 

[malcolmsanford]

But how would you determine their litres/sec airflow in order to comply with Part F?

A swift kick in the go's I always found was an adequate Variable Speed Drive

 

[Octopus]

Time for someone to invent a 2 gang switch FCU then! as most fan have a run on.

Or do they just want the perm line fusing down?

Either I wasn't listening too hard or they didn't say whether it was perm live, sw live or both but it did come across as both.

Interestingly I've been out today installing a fan and new lights in a "no RCD" house, so what I did was drop the feed from the loop through a RCD FCU (where I'd normally put a fan isolation switch) and put a 3A fuse in the holder. A success for abiding by the rules!

 

[SirKit Breaker]

Sounds like a bum covering exercise if you ask me. The manufacturers instructions always take precedence over BS7671, but i am with Malcolm on this a 6a 60689 will trip long before a 3a 1361 has even had time to think about blowing. I will carry on doing as i do. If the manufacturers want 3a fusing on both L and S/L then let them fit internal fuses.

Cheers..........Howard

 

[Marvo]

A bathroom extract fan is so low current, plus it's normally double insulated, plus it's out of customers reach, plus it's IP 65/66 construction, it's also operated by a pull cord switch/ light switch from outside the bathroom. I could understand if the people in the house were actually coming into contact with the fan but they wouldn't under normal circumstances. So my question is why are there so many specific regs about extract fans in the UK?

 

[Doomed]

I always fit a fuse on the permant live as well as the 3 pole isolator.

Boss always moans at me.

On a similar vain alot of boilers want fusing to 3A and a two pole isolating switch, so a standard switched fuse spur is no good. (I still fit the switched fuse spur).

 

[pushrod]

I always fit a fuse on the permant live as well as the 3 pole isolator.

Boss always moans at me.

On a similar vain alot of boilers want fusing to 3A and a two pole isolating switch, so a standard switched fuse spur is no good. (I still fit the switched fuse spur).

MK do a DP switched FCU :smile5:

 

[D Skelton]

Most cowboy installs seem to ignore the requirement for an isolation switch anyway.

What requirement for an isolation switch?

Edit: By that I mean a local 3 pole isolation switch, not isolation in general.

 

[Sickmick]

The story I heard (could have been scare tactic) from 2 different NIC assessors, was that this issue had already been before a court. A fault had developed that lead to a fire on a fan unit, which had been wired via the traditional 3 pole fan isolator from the 6 amp lighting circuit. Manufacturer said it wouldn't have happened if their instructions had been followed, and the court agreed and since BS7671 says follow manufacturers instructions the electrician was found to be at fault. Since hearing that I've always followed the wiring diagram in the instructions, there's a couple of configurations they suggest, either fuse the light or install seperate pull switch for the fan.

 

[D Skelton]

I would bet money on that being a scare tactic. If the fan was wired in on a 6A lighting circuit a reasonable assumtion can be made that the circuit was protected by a 60898. I fail to see what type of fault could occur that could cause a fire if the circuit was protected by a 6A MCB unless it was the wiring at fault. Also, if the manufacurers instructions are saying to fuse down to 3A, I fail to see the logic as a 6A 60898 would trip long before a 3A 1362 even begins to think about blowing.

 

[Johnny-G]

The story I heard (could have been scare tactic) from 2 different NIC assessors, was that this issue had already been before a court. A fault had developed that lead to a fire on a fan unit, which had been wired via the traditional 3 pole fan isolator from the 6 amp lighting circuit. Manufacturer said it wouldn't have happened if their instructions had been followed, and the court agreed and since BS7671 says follow manufacturers instructions the electrician was found to be at fault. Since hearing that I've always followed the wiring diagram in the instructions, there's a couple of configurations they suggest, either fuse the light or install seperate pull switch for the fan.

My Elecsa assessor told me the same story on my last assessment a couple of weeks ago, it's obviously an area they feel needs drumming home.
Funnily enough, I'm currently looking at a job which requires an IPX5 fan in zone 1 (water jets are probable) which the customer insists needs a timer & it's a pain to fuse it down to 3a, especially as there's no void above the light fitting and the wiring is going to have to be surface mounted in trunking.
I'm doing my utter best to find some equipment that neglects to mention or doesn't require any further protection.