DIY Doctor

Extractor Fan

Postby dunaldo » Mon Oct 17, 2011 12:01 pm

The extractor fan i have currently is connected with a standard plug, but the new extractor fan requires to be connected using an omni-polar switch. It also says to use a double pole switched fused spur outlet. Can i just replace the current socket with the double pole switched fused spur outlet?

Regards Paul
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Simply Build It

Postby ericmark » Thu Oct 20, 2011 4:46 am

The question is "Can I" but there is nothing to say what skills the "I" referred to has. Or the location of the fan.

Normally a single socket and fuse connection unit will fit into the same back box and to swap from one to the other is not a problem. But the question is why would any fan say it has to be a FCU rather than plugged in and the only thing I can think of is the earth arrangement. Why any fan should have a high earth leakage I don't know but I would assume it is some industrial unit?

This raises a question as to RCD protection and double earth connections and one would want to ensure the earth is good so likely one would want to measure the loop impedance.

In other words without knowing why the manufacturer has stipulated using a FCU one can't really answer the question. I can't think of any fan I have fitted in a domestic premises which could not be powered from a plug. There are some areas where you can't use a plug and socket for example in bathrooms but that's all to do with where fitted not to do with the fan.

It is common with bathroom fans to have two line feeds one switched with light the other non switched and there are a number of ways to wire these in. The two common methods are a three pole switch taking feed from lights or a FCU and a double pole light switch possibly also a push button. If this is the case then it is not a simple swap one has to decide what is required.

In a bathroom Part P and Part F have to be complied with and the rules as how fans can be switched does get complex. It is all to do with windows. It does make sense if there is a non opening window then using the lights as only way to start the fan is not really going to work as one can't switch on fan without also switching on lights.

For a fan with "run on" one could connect both line feeds together and still run it from a plug so it's not the fan but the location that determines how it is to be wired.

The big question with small fans is fuse size with most lights being 5/6A and the preferred sizes for a fuse in a plug being 3A or 13A some manufactures stipulate 3A fuse and one has to use some common sense to work out if one needs to really fuse down from 6A to 3A or if they were just stating the preferred size.

I know this does not directly answer your question and I admit I hung back on this one as was not sure how to answer but I hope it has either helped or given you the prompt required for you to ask the question with more information as to what you are trying to do.
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