Fusing of fans to comply with manufacturers recommended instructions

[garaoke]

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

 

[Marcus Vaughan]

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?

 

[GeorgeCooke]

I think you are missing the experience of what actually happens in practice.

 

[Charlie_]

3amp fuse blows (it won’t trip).. and then how many variants can that be replaced with?

 

[westward10]

The 3A fuse serves one purpose to hopefully rupture if the motor seizes and hence prevent fire from overheating windings.

 

[Charlie_]

PCB mounted fuse built into the fan would be the best solution

 

[Wilko]

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.

 

[Marcus Vaughan]

I think you are missing the experience of what actually happens in practice.

Sorry - that's not good enough for me to not follow Manufacturers Instructions. I still don't see why some people think the MCB will disconnect before the fuse.

 

[Marcus Vaughan]

I think you are missing the experience of what actually happens in practice.

Sorry - that's not good enough for me to not follow Manufacturers Instructions. I still don't see why some people think the MCB will disconnect before the fuse.

 

[Marcus Vaughan]

PCB mounted fuse built into the fan would be the best solution

Seems like a plan.

Another plan would be to use manufacturers that do not stipulate the 3amp fuse. I've stopped using Manrose, and am now using Envirovent. I see Greenwood don't ask for a 3 amp fuse either.

 

[GeorgeCooke]

Sorry - that's not good enough for me to not follow Manufacturers Instructions. I still don't see why some people think the MCB will disconnect before the fuse.

As I said what would you do if you were fitting the fan in a country where FCUs are not available nor compliant?

 

[Taylortwocities]

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?

 

[GeorgeCooke]

No I suggest you ask the manufacturer.

 

[freddo]

It would have to be a rather crappy fan for the motor not to have a thermal fuse embedded in the windings.

 

[Michaelwgroves]

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.

 

[sheppertonspark]

AFDD, soon this fuse problem will be irellavent (not sure if I've spelt that correctly).

 

[sheppertonspark]

AFDD will see stalled motor I believe

 

[freddo]

How?

 

[sheppertonspark]

How?

I said "I believe"

 

[wheeto]

I ... tend to use ... MK boards - [which don't have] have 3 amp MCB’s.

What about 3 Amp MK MCB - B Type - https://www.tlc-direct.co.uk/Products/MK5903S.html ?

 

[Marcus Vaughan]

What about 3 Amp MK MCB - B Type - https://www.tlc-direct.co.uk/Products/MK5903S.html ?

Yes. Thanks for that. I’ve already been put right. It’s good to know....

 

[bigspark17]

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 ---. Yes!
Will the fan manufacturer be able to point liability at me if the fan goes up in flames . No!!

 

[Taylortwocities]

3-pole isolator switch with 3A fuse. This covers all the bases

Excel 3 Pole Fused Fan Isolator Switch - White | QVS Direct - https://www.qvsdirect.com/excel-3-pole-fused-fan-isolator-switch-white

 

[Taylortwocities]

3-pole isolator switch with 3A fuse. This covers all the bases

Excel 3 Pole Fused Fan Isolator Switch - White | QVS Direct - https://www.qvsdirect.com/excel-3-pole-fused-fan-isolator-switch-white

 

[Charlie_]

That's nifty! You can also do a similar thing using euromod inserts

 

[Taylortwocities]

Yes, but not for less than £7.