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Discuss Fusing of fans to comply with manufacturers recommended instructions in the Electrical Forum area at ElectriciansForums.net

garaoke

EF Member
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
 

anthonybragg

Electrician's Arms
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.
 

wirepuller

Forum Mentor
Electrician's Arms
Trainee Access
DIY
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.
 

garaoke

EF Member
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
 

Richard Burns

Respected Member
Forum Mentor
Electrician's Arms
Trainee Access
DIY
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

Electrician's Arms
CCTV / Alarms
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.
 

leebut

Regular EF Member
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.
 

wirepuller

Forum Mentor
Electrician's Arms
Trainee Access
DIY
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.
 

leebut

Regular EF Member
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
 

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