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Borrowing a pemanent live


MalcyB

Question

Hi All

Could someone just confirm that I am alright to do this.

I am fitting a timer fan tomorrow and how the wiring has been done I will get the sw/l & N from a junction box, but am I ok to get my permanent live from the light switch that will be switching it on?

Thanks

Malc

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9 answers to this question

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IMO - A fan being a fixed item will draw a fixed amount of current and wont overload the cable - therefore no need to fuse down in theory as the only time it will pull more than Ib is in fault i.e. short which will draw zillions of amps for a very short time and trip the 6A MCB, not allowing the cable to overheat.

With all fixed equipment you can select cable size with Ib as the defining criteria (Other factors grouping etc may have to bre taken into account)

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Its asked for by the manufactures if you choose not to obey they note it as a deviation, when i asked a few people about the need for a 3A fuse elecsa (when i was with them) told me fan manufactures have blamed no 3A fuse on fires caused by failed or blocked fans. Poor excuse or not its in the instructions of every fan I can remember fitting so I shall continue to provide one all be it a pain in the arse.

The fuse isnt there to protect the cable to it, its to protect the fan itself, I know people will argue the fusing characteristics of a B6 and a 3A fuse it doesnt change the instructions.

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Yes that sounds OK , Malcy, you also need to be able to isolate the fan , for cleaning etc. Do this either with a 3 pole switch in the 3 core to the fan ( L/N/ SW) or a switched spur in the feed to the light.

Deke

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Malc - you'll have to take the perm live from before the switch tho............

or you'll have 2 switched lives :D

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the fan will probably have to be fused down to three amps are previously mentioned by use of a swtiched fused spur, so a fan isolator isnt always enough.

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If its coming from a lighting cct on a 5A fuse / 6A MCB, why would it need derating to 3A?

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If its coming from a lighting cct on a 5A fuse / 6A MCB, why would it need derating to 3A?

Manufacturers instructions usually state this but I never do. As far as I am concerned a fan switch should be enough, if the things gone faulty you would bin it anyway.

Batty

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and make sure also that you dont take the perm live from one circuit and the neutral from another ;)

---------- Post Auto-Merged at 17:10 ---------- Previous post was made at 17:09 ----------

oops just looked at the date, admins not going to be happy ive been looking down the cellar again :slap

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