bathroom extractor fan

[gavin.sibley]

Hello all,

Just a quick one, I think I know the answer anyway but it's one of those I'm doubting myself haha

I wired up a extractor fan In a customers bathroom, taking a feed from the light via a 3 pole isolator and onto the fan.

The fan went faulty so I went back to test and power was still getting to the fan on both live and switched love conductors, and all connections were right, so told customer it was a faulty fan.

At this point we introduce the plumber, who supplied the fan In the first place.

He is now saying that the fan has bed wired up wrong and isn't allowed to be wired in this way.

Just wondering if anyone can tell me whether this is right or wrong, as I said I think I know what's coming but he's making me doubt myself.

Cheers,
Gavin

 

[EastAnglian]

If the fuse pops on the perm live and the fan stops working then our poor homeowner might quite reasonably assume the thing is dead and receive a potentially fatal shock from the switched live which isn't as dead as it appears!

While not disagreeing with the need to fuse the switched line if a home-owner chooses to dismantle a fan without isolating it via the 3 pole switch first then any consequences are on their head. Aside from this, a 3A fuse will not protect a person from a potentially fatal electric shock, as it requires somewhere between 75 and 200mA (yes, mA) to cause the heart muscles to fibrilate if current flows through them. Shock protection is provided by your RCD which of course is designed to pop out at less than 30mA fault current.

If you touch the mains about the lowest resistance you will offer on any path that involves the major organs is 500 ohms, usually a lot higher like 2,000 ohms .... you will need about 38 ohms max to pop a 3A fuse, assuming it ruptures at about 2 x rating.

 

[decolad69]

While not disagreeing with the need to fuse the switched line if a home-owner chooses to dismantle a fan without isolating it via the 3 pole switch first then any consequences are on their head. Aside from this, a 3A fuse will not protect a person from a potentially fatal electric shock, as it requires somewhere between 75 and 200mA (yes, mA) to cause the heart muscles to fibrilate if current flows through them. Shock protection is provided by your RCD which of course is designed to pop out at less than 30mA fault current.

If you touch the mains about the lowest resistance you will offer on any path that involves the major organs is 500 ohms, usually a lot higher like 2,000 ohms .... you will need about 38 ohms max to pop a 3A fuse, assuming it ruptures at about 2 x rating.

Yes, but the isolator was installed......... if they decide not to switch off that's their fault.

Decolad69

 

[EastAnglian]

Yes, but the isolator was installed......... if they decide not to switch off that's their fault.

Decolad69

Isn't that what I just said ? :willy_nilly::dunce2:

 

[davethsparky]

So tell me then, how to YOU install a bathroom fan "to take account manufacturers' instructions" (Regs 134.1.1 & 510.3) when said instructions indicate that both Line & Switched Line inputs must be protected by a 3A fuse?

.

Is the answer not obvious? Either buy a decent fan that doesn't require this nonsense. or a double pole pull switch, one side switches a light as normal other side switches a 3amp supply for the fan, then a perm an sw live are available to the fan both protected by the 3 amp fuse.

 

[davethsparky]

While not disagreeing with the need to fuse the switched line if a home-owner chooses to dismantle a fan without isolating it via the 3 pole switch first then any consequences are on their head. Aside from this, a 3A fuse will not protect a person from a potentially fatal electric shock, as it requires somewhere between 75 and 200mA (yes, mA) to cause the heart muscles to fibrilate if current flows through them. Shock protection is provided by your RCD which of course is designed to pop out at less than 30mA fault current.

If you touch the mains about the lowest resistance you will offer on any path that involves the major organs is 500 ohms, usually a lot higher like 2,000 ohms .... you will need about 38 ohms max to pop a 3A fuse, assuming it ruptures at about 2 x rating.

Nobody said a 3A fuse would prevent a fatal shock!

My point is that the 3A fuse should interrupt all of the lives going to the fan, is it not a fundamental requirement that protective devices interrupt the line conductors of the device they are protecting?

 

[decolad69]

Isn't that what I just said ? :willy_nilly::dunce2:

not sure ?

 

[telectrix]

personally, i can't understand the current fad of wiring the fan into the light. 1. if you are using the bathroom in daytime, you need to switch the light on for the fan to work. 2. you need a pee at 3.00am. switch on the light to see what you're peeing into and the fan kicks in, waking the missus and the sprogs. bloody pointless. feed the fan through a 3A FCU independently of the light. tghen the fan is used when and if you want it. ssssimplessss.

 

[decolad69]

personally, i can't understand the current fad of wiring the fan into the light. 1. if you are using the bathroom in daytime, you need to switch the light on for the fan to work. 2. you need a pee at 3.00am. switch on the light to see what you're peeing into and the fan kicks in, waking the missus and the sprogs. bloody pointless. feed the fan through a 3A FCU independently of the light. tghen the fan is used when and if you want it. ssssimplessss.

Is it not a Buiding Reg ? I thought you had to have a run on facility for use after curries ? No ?

Decolad69:28:

 

[telectrix]

you can still use the timer function. think about it.

 

[decolad69]

So you can .......... :blush5:

 

[Geoffsd]

There's me thinking the purpose of a fuse was to protect a conductor from overload but apparently it is to stop incompetent idiots getting a shock when the fan stops working and they poke about inside without isolating the circuit.

 

[telectrix]

no. the purpose of the fuse is that the manufacturers think it will blow when the fan seizes up because it's cheap crap, and prevent a fire.

 

[davethsparky]

And where on earth did you learn that? I don't see anything in this thread to suggest that. I did say that if the fuse operates but is connected in such a way that the fan remains live despite the operation of the fuse then it may lead to the false assumption that the fan is not live.
As you say a fuse is there to protect the cable, which of course raises the question of how it can be acceptable or the fuse to leave part of the cable live if it is there to protect the cable when all of the conductors in the circuit are part of the same circuit?

And of course you have missed the point of the discussion which is concerned with the use of said fuse to protect the equipment not the cable.

Please do take the time to read the posts and understand the things you have read before posting unhelpful sarcastic comments.

 

[telectrix]

was that aimed at moi?

 

[EastAnglian]

a double pole pull switch, one side switches a light as normal other side switches a 3amp supply for the fan, then a perm an sw live are available to the fan both protected by the 3 amp fuse.

Yep, that certainly works too!