3A Fuse for fan

[LewisM]

Hello, I have to replace a fan with a timer for a client who has already purchased a fan, the new fan requires a 3A fuse as per manufactures instructions, currently only an isolator is in place, am I right in thinking that the switch live on a timed fan only acts a trigger so if I swap the 3 pole isolator for a click one wich is a 3pole isolator with fuse carrier in it and place a 3A fuse on the load side of the permanent live that this would be sufficient?

 

[radiohead]

That's exactly what I do. The fan runs on the permanent live so as long as that is fused I feel it's covered the manufacturers requirement. If I'm installing from scratch though I'll run the supply to the room through a 3a FCU

 

[LewisM]

Yeah same if installing from new a bit tricky in a finished house with no loft access etc to add a fcu before.

 

[Taylortwocities]

Never saw the need for the 3A fuse requirement.
Most fans run from a 6A MCB protected lighting circuit.
A 6A MCB will always trip before a 3A fuse can blow.
So a 3A fuse is a pointless requirement.

 

[westward10]

A 3A fuse is for fire protection, the assumption being a locked fan motor will rupture a 3A fuse quicker than the protective device at the consumer unit. A university study came to the conclusion this was inconclusive based on manufacturer variation.

 

[Pretty Mouth]

Never saw the need for the 3A fuse requirement.
Most fans run from a 6A MCB protected lighting circuit.
A 6A MCB will always trip before a 3A fuse can blow.
So a 3A fuse is a pointless requirement.

Time/current curves show that the 3A fuse should operate first:

 

[Midwest]

I used the Scholmore SFCU grid switch, to take into account manufacturers instructions for insurance purposes.

However, to put it into prospective, I replaced a fan once that birds had nested it. The fan was jammed, and burnt out and the local 3A hadn’t gone, and the owner was unaware if the 6A mcb had tripped. Greenwood Airvac installation instructions say ‘Fuse: 3 amp normally required (when fan is supplied from a 6A lighting circuit no local fuse is required)’.

 

[pc1966]

I used the Scholmore SFCU grid switch, to take into account manufacturers instructions for insurance purposes.

Presumably using the FCU and the 3-pole switch?

Obvious question on the "must be 3A fused" guidance is whether that implies both permanent live and switch live have to be from a 3A fused supply as then you would need 2 FCUs.

However, to put it into prospective, I replaced a fan once that birds had nested it. The fan was jammed, and burnt out and the local 3A hadn’t gone, and the owner was unaware if the 6A mcb had tripped. Greenwood Airvac installation instructions say ‘Fuse: 3 amp normally required (when fan is supplied from a 6A lighting circuit no local fuse is required)’.

I would imagine that the motors have (or should have) a thermal fuse to prevent overheating anyway as a motor rated as taking 0.1A or so is going to burn out long before a 3A fuse goes. More so if the bearings get tired and high friction so it is on permanent overload (but not locked).

 

[Midwest]

Presumably using the FCU and the 3-pole switch?

Obvious question on the "must be 3A fused" guidance is whether that implies both permanent live and switch live have to be from a 3A fused supply as then you would need 2 FCUs.


I would imagine that the motors have (or should have) a thermal fuse to prevent overheating anyway as a motor rated as taking 0.1A or so is going to burn out long before a 3A fuse goes. More so if the bearings get tired and high friction so it is on permanent overload (but not locked).

I just used the one fcu, for the permanent live which runs the fan, not the trigger.