Home DIY

Does the new fan have a timer option? If yes, it might be wrong to assume you can wire it with just your two wires. I recently installed a timered vent axia fan in place of a non timer fan, thinking I could wire it without a permanent live and it would operate like a non timered fan.

I was wrong, the circuitry in the vent axia timer fan required the permanent live to be there in order to work, so what was supposed to be a 30 minute job turned into an all day one digging up my floor boards to find a suitable location to wire off.

It's a VASF100B which doesn't seem to have a timer and should come on with the lights, apparently

Check the wires you've connected to it (with a proper voltage tester, safety first). Are they live? Do they go on and off when the lights go on and off?

An electrician did check it before I replaced the fan and said it was all live, but I don't have a voltmeter to check myself

Worth getting one of these to help you troubleshoot

https://www.screwfix.com/p/lap-mas830b-digital-multimeter-600v/75337

Is there a transformer involved with either the old fan or the new fan?

No idea, sorry. I'm totally clueless with DIY.

I'm thinking it might be easier just to get the same model as before, at least I know the old one worked and it won't mean any rewiring

No worries, everyone starts clueless. You posted 3 images, I gather the first one is the new fan, the 3rd one is the old extractor fan, what's the second one? It looks like a transformer, was it already there or did it come with the new extractor?

Transformers convert voltage from your mains (240V) down to some other voltage. What I'm thinking is your electrcian was right, your cables are indeed live, but perhaps they are at the wrong voltage for what your new fan needs.

Yep, it was already there and supplying the old fan - the new fan didn't come with anything, just the fan unit

Think that might be your culprit, have a look at the sides of it to see if there is any printed text that suggests it is a transformer (something like input voltage 240V, output voltage 5V as an example). Assuming it is a transformer, and your old fan was wired to it, then your old fan was a lower power unit running off low voltage. Your new one probably wants full mains voltage, but instead is getting a reduced one and hence won't run.

I suggest looking in the manual of your new fan to see what voltage input it requires. If it's 240V you'll want to ditch the transformer and wire it in directly to the mains.

A multi meter should also be able to confirm if what I'm saying is correct.

That's it, the new fan wants mains, the old fan wants 12v and the transformer is doing that, thanks for the help!

The cost of buying another fan is gonna be far less than getting someone to rewire it (probably) so I'll just do that

We're gonna redo the bathroom next year anyway, so I'll get that done at the same time and use this fancy new fan then

Anyone got a recommendation for someone who can fit rooflights? Co we'd like to buy from is supply only, but their stuff comes recommended by others in the business

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Can I remove an RCD from a consumer unit myself or do I need to get someone in?

One of our two RCDs keeps tripping. It has five fuses linked to it: the sockets at the front of the house, the front lights, our oven, doorbell and a separate single socket. So every time it trips these all go off. It's one of these and 63A seems plenty even with an oven on the circuit - the rest is LED lights, the odd phone charger and a hi-fi:
https://www.screwfix.com/p/mk-sentry-63a-30ma-dp-type-ac-rcd/86634

I originally thought there was a problem with the sockets, but last night with just the lights fuse on (and no lights on, as we were out) it tripped. This morning I managed to get it working with just the sockets, but then it tripped very quickly. This was when I was using something, but all previous trips have been when we're not really using stuff, just a few LED lights on etc. and we weren't switching anything on/off.

As it seems to trip regardless of which fuses are switched on, I suspect the RCD. Although our builder reckons it's unusual for them to fail and a quick Google supports this.

Therefore I'd like to swap the two RCDs we have to see if the problem is with the RCD or the wider circuit - especially as I just checked and a new RCD is £40 at Screwfix - but I don't know how to do that. It seems to involve taking the consumer unit apart to some degree which I don't fancy. Do I need to get someone in?

I'd ask our builder but when I spoke to him yesterday he was home sick so I don't want to bother him...

Swapping RCD is quite straight forward. Your fuseboard should be a din railed system. Turn power off to the board and take the front cover off and swap the RCD over.

If you have built your own computer, you'll be fine.

If it were me, I'd unplug everything I take the led lights out and put them back in one by one. Leaving them on for a bit, to warm up and see if there is an issue with current returning to earth or a neutral and positive in balance.

EDIT - Stupid question, did a sparky check the system and sign it off? Did by chance he leave any paperwork giving any electrical values for the system?

Thanks, that's pretty much what I thought. I have got one of those pens which tell you when stuff is live so I can use that and be careful. It does use a DIN rail. Will have to be tomorrow morning now it's dark.

At the moment the RCD is tripping no matter which fuse is on. I've tried various individually and it trips almost straight away or straight away. But if I can swap the RCDs I'll know whether it's a faulty RCD or not as we never have problems with the other one which covers the back of the flat.

Sparky did check it and sign it off but that was a few years ago. We pretty much had the place rewired and the tripping issue didn't happen for along time, but has recently started happening more regularly, so something seems to have changed. Don't think I've got anything like that.

Thought about a humidistat fan? Keeps running till the humidity drops?

Be careful if you're only armed with a voltage detector. It would make sense to get the CU looked at. An electrician would probably remove the CU cover and tighten/check the connections, it's not unusual for a connection to be loose.

You need to work safely and diagnosis further than loose wires in the fuses is beyond the scope of a voltage detector.

Thanks, my builder basically said don't touch it. I agree it makes sense to get someone to look at it, it seems a bit ridiculous that the 'fuses' (I know they're not actually fuses) in modern consumer units aren't actually consumer replaceable. What an ironic moniker.

It's health and safety, there's no problem taking the cover off if you have a bit of training and some tools. No one is going to encourage you to do it, especially not some random on the internet!

If I had the time I could describe a few ways that the process can go wrong but there are quite a few checks you should be making after the work which it sounds like you are not equipped for.

If you have any exterior fittings on your installation I would disconnect those. Switching off the breaker doesn't necessarily solve the problem of a line/neutral fault which is what the RCD is supposed to pick up because of the way the neutrals are joined in some cases.

Just as a bit of added info. One reason consumers are not encouraged to replace breakers or 'allowed' to create new circuits is the breaker is chosen based on the type of cable, where the cable is located and the overall resistance of the circuit. It's a relatively complicated process to calculate and test although it generally leads to the same configuration in domestic installations.

If a consumer changes a breaker for a different rating there is a chance that the circuit won't be adequately protected in the case of a fault. So fire or injury could be the result.

If you're in West London, I've got a builder I would recommend who's done loads at our place. I know he's comfortable with Velux windows, you'd have to ask / assess whether you want him to go ahead with these.

Thanks, it looks like our builder can do it after all