Bathroom light switch and fan conundrum

[houseofrabbits]

We have a problem which we didn't know was a problem until an electrician came round a few days ago. In our upstairs bathrooms the light switches trigger the fans in both bathrooms e.g. if we turn the light on in the en-suite the fans in both the en-suite and the family bathroom come on. Both fans also come on when we switch the light on in the family bathroom.

Our electrician thinks this is against regulations but will get back to us. I've tried googling but can't find anything about light switches triggering fans in different bathrooms. We live in a new-build we've had since new 6 years ago. Also we are selling our house and need to get this sorted ASAP if it is a problem. Has anyone encountered this before?

Even if it against regs I can't see how it could be thought of as being dangerous.

Doubt if it's dangerous in itself but a) it would be annoying and b) it shows that someone has botched up the wiring to the fans, so you wonder what else they have cocked up that you don't know about

@PaulaSmith1 we've lived with it for 6 years as we didn't realise it was a problem so I don't think it's dangerous necessarily, just annoying.

@BruceAndNosh that is now our concern, what else has been botched.

To complicate matters we are selling the house to my parents who are renting the house out, so they have to get an electrical condition report which will fail if this lights/fan malarkey is against regs. The only good thing if it is against regs is we could ask the developer to foot the cost rather than having to pay for it ourselves (my parents want it sorted whether it's against regs or not!)

Are you sure they are separate fans, and not one fan ducted to several rooms?

we had this in an ensuite, but it was just one light and the fan, so when the light was on the fan was too....I managed to sweet talk the electrician into putting a spur in with a switch so I could have light but no fan

(like when you have the washer plugged in under the worktop with just a switch above to turn it on and off)

Have you anything like that outside either of the bathrooms?

We had that when we got the extractor put in the bathroom at our old house. Apparently it was easier to wire in that way. We sold 2 years ago and it was never mentioned.

Why not put a call/email in to the house builders and ask them to rectify the situation? You've nothing to lose by asking them nicely initially and if they are difficult a solicitors letter might help

So yes it turns out that yes it is just one fan in the loft with separate ducts so each switch turns the fan on. My husband explained to me that I actually have the wrong end of the stick and that isn't what the problem is 😂 The problem is when you take each switch off the wall they have 2 wires (light and fan) and if you just turn lights off at the fuse box the fan wire is still live, and apparently the labelling on the fuse box is unclear.

So do you mean there is no isolator switch for the fan? It's usually near the light switch but often higher or lower iyswim so you could turn it off if you didn't want it to come on with the light - if so I'd say that's not right and you should contact the builders to come and sort it (no idea about regulations but it does sound dubious) might be worth mentioning that they would be liable if someone were to be electrocuted! Also I'd discuss with your neighbours to see if they have the same as if so you'd have a better argument with the builders to come and rectify all the houses.

if the fan is working with the lights then it must surely belong to the light circuit , if it doesn't go off with the light fuse then it must have its own fuse/circuit

Isolator switches should definitely have been installed for the fans. contact the builders and see what they have to say about the matter. I would also hunt hiGh and low for the actual isolator switches because you never know sometimes they do put them in the most strange place that you would never think of looking. But yes for a safety point of view I think isolators even six years ago would’ve needed to have been part of the overall electrical compliance certificate for sign off on a new build. My House is 10 years old that has isolator switches.

There exactly the problem, there are no isolator switches on the upstairs bathrooms (there is downstairs). The fuse box is also labelled poorly so it's difficult to know when the fans are turned off.

I don't believe there is a regulation requiring fans to have local isolation. Though it is good practice to have one for maintenance.

It would be normal to have the bathroom fans supplied from the lighting circuit, especially if they are operated by the light switch, and I think it improbable that they would be on a different circuit and not isolated by turning off the lighting circuit MCB. Are you sure they aren't?

P.S.

If somebody tells you there us a requirement for a fan isolator, ask them where it is.

If they "Part P," it isn't.

If say say "BS7671" ask them which section. If they say "701" it isn't, though it does say, IF you have one, where it can't be.

@PigletJohn we are 100% sure they are not on the same circuit. There are 2 separate wires coming from the light switches for the upstairs bathrooms (one for lights and one for fan) and when you turn the 'upstairs lights' fuse box switch off the fans still run.

You mean turning off the MCB means the lights go dead and the fan doesn't? That's very unusual.

It sounds like your fan is in the loft. Since the purpose of a fan isolator is to facilitate safe maintenance of the fan, an isolator, if present, might be placed close to the fan so that somebody working on it can see nobody turns it on.

Sounds like a 5 minute job to replace the single switch with a double switch. It will fit onto the same backing plate and will keep the circuits separate. If you want both fan and light on, turn on both switches. It's exactly what we have.

@PigletJohn yes that's correct!

If the isolator switch is in the loft next to the fan, will turning that off mean that the wire in the actual switch for the lights is also no longer live? We think at the moment the wire is on the same circuit as the central heating, as when we turn that switch in the fuse box for the central heating off that turns the fan off.

[quote houseofrabbits]@PigletJohn we are 100% sure they are not on the same circuit. There are 2 separate wires coming from the light switches for the upstairs bathrooms (one for lights and one for fan) and when you turn the 'upstairs lights' fuse box switch off the fans still run.[/quote]
Are you sure the wires are still live though? The fan may still run because of stored power (capacitor) rather than the wires to it still being live. Does it stop after a few minutes with the fuse box switch turned off or does it run forever?

"If the isolator switch is in the loft next to the fan, will turning that off mean that the wire in the actual switch for the lights is also no longer live? "

No, the purpose of the fan isolator is to isolate the fan. Depending how it is wired, it might possibly isolate some other wires and switches, but I wouldn't depend on it.

I find it curious that the fan is not supplied from the lighting circuit as is usual.

It's not forbidden to have two circuits in one switch. Consider the hall/landing light switch, which operates both the upstairs and the downstairs lighting circuits.

It's just a whimsical novelty to wire a bathroom fan the way you describe.

@user1497207191 absolutely sure it's still live, the fan doesn't turn off.

@PigletJohn thanks for clarifying re the isolator switch that may or may not be in the loft. My DH is sure there isn't one (he turned the electrics for the whole house off when he did some fan maintenance) but we are going to go into the loft to check tomorrow.

It's just strange as the fan for the downstairs loo has an isolator switch and when you take the light switch off the wall it only has one wire coming off it. It's odd they didn't do the same upstairs.

Yes.

Very unusual.