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Manufacturers want there fans fused to 3a on the permanent feed but the switch wire is still on the 6a MCB doing an eicr is a c2 if there is no RCD protection
 
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T

Toneyz

I assume you mean as it in a bathroom or because the cable is buried in the wall? C3 for both if to a previous edition of the regs ie full supplementary bonding was in place if not C2.
 
D

Deleted member 9648

Manufacturers want there fans fused to 3a on the permanent feed but the switch wire is still on the 6a MCB doing an eicr is a c2 if there is no RCD protection
IMO if there is a 3a fuse on the permanent line then it complies with manufacturers instruction. The switched live is only a trigger, the fan uses the permanent line to operate so a fuse on that line will serve the purpose intended.
 
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IMO if there is a 3a fuse on the permanent line then it complies with manufacturers instruction. The switched live is only a trigger, the fan uses the permanent line to operate so a fuse on that line will serve the purpose intended.
Switch left on is a supply to the timer at a higher rating than the feed
 
Why not just wire the bathroom with a 3 amp fuse to the lighting and fan then wire everything downstream off the fused spur, problem solved
 

Richard Burns

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The manufacturers want both permanent and switch line fused by a single fuse and since this involves the wiring outside the fan they cannot install a fuse in the fan.
If they only wanted the permanent line fused they could do this, but do not because that is not their intention.
From a fusing point of view the fuse is there to prevent cables being overloaded and causing fire.
From a protective point of view the fuse should disconnect the power to a piece of equipment.
Fusing the permanent line only will do the former but not the latter.
Someone removing the fuse or finding the fuse had blown might work on the fan not realising there was still a live supply to the fan (if the switch was on), though they should check for dead at the equipment and not just at the supply.
For coding this is down to the inspector, the lack of RCD protection would be a situation where in case of a fault it could give rise to danger, the lack of a 3A fuse on the switched line would be a far lower risk and almost minimal if a 3P isolator were fitted, so the coding would apply to the lack of RCD protection.
 

Taylortwocities

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I’m sure this has been said before but
I’ll do it again…

A 3amp fuse on a (usually lighting) circuit that is protected by a 6amp MCB is pointless. The MCB will trip a long time before a 3A fuse will pop.

I’ve a feeling the 3A thing originally came from when the fan may be powered from something like a ring final which has a much higher current rating.
 
A lot of electricians forget that the wiring regulations stipulate that a manufacturers instructions supersedes the wiring regulations, so if a manufacturer states they require a 3 amp fuse on that product you have to install a fuse on the circuit like I mentioned previously the best way to cover this point is to install a 3amp fused spur at the loop then everything from that point onwards is protected by that fuse on both permanent and switched conductors, the idea of the 3amp fuse is to cover every eventuality on an installation from a BS 3036 fuse through to BS60898 MCB or BS61009 RCBO, I agree the MCB/RCBO would trip quicker than the fuse but at least the installation would comply with the manufacturers instructions.
 
D

Deleted member 9648

I’m sure this has been said before but
I’ll do it again…

A 3amp fuse on a (usually lighting) circuit that is protected by a 6amp MCB is pointless. The MCB will trip a long time before a 3A fuse will pop.

I’ve a feeling the 3A thing originally came from when the fan may be powered from something like a ring final which has a much higher current rating.
Some time back there was an instance of one of these fans causing a fire, presumably it seized. It ended up in court and the manufacturers gettout was that a 3a fuse had not been fitted as per instructions. This despite the fact that we all know a 3a fuse would make no difference.
 
Some time back there was an instance of one of these fans causing a fire, presumably it seized. It ended up in court and the manufacturers gettout was that a 3a fuse had not been fitted as per instructions. This despite the fact that we all know a 3a fuse would make no difference.
Completely agree I remember reading the same article in one of the trade magazines, the blame was put back onto the installer
 
c3 if no RCD on bathroom lights but check IP ratings & zones also. Seen several installs with a split load board where the bathroom light and fan were wired off the ring via a 3a fused spur, thus providing the RCD protection.
 

Wilko

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Hi - sorry to be a party pooper, but a BS1363 3A fuse is more sensitive to overload than a BS60898 6A mcb. For example, the 3A fuse will always melt at 6A but the mcb will never trip.

IMG_0416.jpg
 

Charlie_

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Arms
Manufacturers instructions are usually nonsensical, inappropriate and unattainable; a bit like the serving suggestions on food packaging
 
Manufacturers instructions are usually nonsensical, inappropriate and unattainable; a bit like the serving suggestions on food packaging


Might be nonsensical but as per The Wiring Regulations which in the UK we have to follow the manufacturers instructions supersede the Regulations and the greatest knowledge of all the electrician
 

Andy78

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Might be nonsensical but as per The Wiring Regulations which in the UK we have to follow the manufacturers instructions supersede the Regulations and the greatest knowledge of all the electrician
This is not the case. The regulations ask us to "take account of" manufacturer's instructions. This has recently been changed from the previous wording of "must be followed"

The reason for this is the proliferation of less than useful or appropriate info that is included in some products. Some would ask us to install to lesser standards than BS7671 asks.
 
Might be nonsensical but as per The Wiring Regulations which in the UK we have to follow the manufacturers instructions supersede the Regulations and the greatest knowledge of all the electrician
Rubbish. Manufacturers instructions are for guidance only and yes we have to take account of them. But we do not have to follow them, especially when they are wrong.

In this case,
1. FCUs are not needed or used on lighting circuits which are already adequately protected.
2. A 3a FCU offers no discrimination against a 6a MCB in spite of 'Contacts' post above.
3. The fuse is to protect the cable, not the device on the end of it. It would be non compliant for a manufacturer to fit a cable so small it required 3a protection.
4. How would the manufacturers instructions be complied with in all the other countries where FCUs are neither available nor compliant?
 
2. A 3a FCU offers no discrimination against a 6a MCB in spite of 'Contacts' post above.

Why are so many people saying this? If you look at the time/current trip curves - then the 3amp fuse will trip first?

Am I missing something?
 

Wilko

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Hi - Out of curiosity I have asked manufacturers what this is all about but they've been tight lipped. I have seen fans that don't spec 3A fuses and they seem to have a fuse on the control board and/or claim they've a thermal overload for the motor.

IMG_1441.JPG
 

Taylortwocities

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I’m not sure. Shall I ask Winston1 on diynot.com? He keeps banging on about exactly this, in the same way that you do.

He also has a thing about transformers, and not having 13A sockets on lighting circuits too.

Exactly the same bees that you have in your bonnet. Hmm, makes you wonder, do you have a long-lost identical twin?
 

freddo

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It would have to be a rather crappy fan for the motor not to have a thermal fuse embedded in the windings.
 
Assuming you bring all wiring back to bathroom light, how about an inline fuse here, space permitting?
It wouldn't work in my bathroom as I have spots, but the vast majority of installs I do, I use Polo lights.
 

bigspark17

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Arms
Why not just wire the bathroom with a 3 amp fuse to the lighting and fan then wire everything downstream off the fused spur, problem solved
Shouldnt be a sfcu doing the whole bathroom as the ideal of a local isolator is to isolate the fan itself without interrupting other supplies ie.. lights.
I always put a 3a module fuse holder in a click mini 3 apparatus faceplate along side the 3pole isolator. On 1st fix i always mark the loop in loop out cable and they get paired into the top of fuseholder, thus making perm live & sw live 3A protected.

Do i think its OTT. Yes!
Do i do it to cover my own ass. Yes!
Will the fan manufacturer be able to point liability at me if the fan goes up in flames . No!!
 
D

Deleted member 26818

Ask a grown-up to explain ;);):)
Are you grown up?
Can you explain what difference the permanent feed being fused at 3A would make to the requirement for RCD protection?
Can you further explain what the discussion regarding fusing both the permanent feed and the switched feed has in relation to the requirement for RCD protection?
 

DPG

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Are you grown up?
Can you explain what difference the permanent feed being fused at 3A would make to the requirement for RCD protection?
Can you further explain what the discussion regarding fusing both the permanent feed and the switched feed has in relation to the requirement for RCD protection?
Whoops, touched a nerve! I did put smilies to indicate it was a joke.
 
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