That was my thought too. Some 3A MCBs do exist but relatively rare.I would have thought the fan would have it's own internal fuse, even a non-replaceable one.
All the faulty mains bathroom fans that I have examined have had a thermal fuse buried in the winding. I have concluded that it's a requirment.
I am fitting a Manrose MF100T ventilation fan in our bathroom. This will have a 3 pole isolator outside the bathroom and the plan is to run it in conjunction with the bathroom light so that the fan comes on when the light is operated typical of many windowless bathrooms and en-suites in many modern houses.
The issue is that the manufacturer specify’s a 3A max. fuse for live and switched live and of course the lighting circuit is 6A.
One option is to fit a fused spur unit into the incoming feed for the bathroom but that means all lights beyond that point would now be protected by a 3A fuse and the issue is that there are at least 3 ceiling fans in the rooms beyond that point.
An alternative is to take 3-core and E cable from the bathroom light as planned and using two FCU’s One for live and the other for switched live before running the rest of the cable to the 3-pole isolator.
The trouble is that I have not seen this arrangement anywhere. My daughters new build has one bathroom, 2 en-suites and a cloakroom/WC all windowless and all with ventilators activated by the light switch and I know all the lighting circuits are 6A.
So what to do?
I have a link to a similar fan which unlike the instructions for the MF100T has a wiring diagram
Or do you need a pull cord isolator?
Theo
I may be missing something but why not /one/ FCU protecting a branch from the light circuit to /only/ the light and fan?
for the fan and one for the light, rather than having the fan always come on with the light. This means you don't have the fan noise at night time and you can leave the fan on for a while in the morning after a vindaloo supper the night before.
Thanks Robin that idea came to mind shortly after I posted. So thanks for the link to the earlier thread and I think that will be the way to go. I have used the 3-plate method but because of the 22deg pitch of our roof I rewired the lighting circuit with a series of Wago boxes in the area where there was a bit of headroom with single cable feeds going to the various light fittings. So if I feed the existing feed and the ongoing feed to the next light to the input side of the FCU I can then take the output into the existing Wago box for the bathroom light and make all my connections there.
Thanks again
Richard
3x40w = 120w, half an amp 3x60w = 180w, 0.75A. no problem
Just do what 95% of sparkies do, and dont bother with the fused spur. There really is no need for it. Or, buy a Greenwood fan, they dont require a 3 amp fuse.
What happens next time work is done at the same premises? I thought there was a 'last man out' rule making each successive electrician responsible for the entire system - or is responsibility restricted to the work done by each individual electrician? I have never been sure.
You have to ensure your own work is to regs, but you don't have to update the work done by anyone else in the past. eg it's fine to add an extra socket on a circuit with rewireable fuses, even though the latter is not up to current regs. If you were adding a new way in the consumer unit you couldn't install that with a rewireable fuse, but you could put it behind an RCBO if that would fit in the old CU - if not you'd need to change the board.
Practically speaking you couldn't do it any other way, since J. Random Electrician has no idea what could be lurking in the parts they can't access. Otherwise you'd have to tear the house apart every time you changed a light fitting.
Theo
Unfortunately not. All new work must comply with current standards. So an extra socket added onto a rewireable fused circuit would have to be a RCD socket, or fed from a RCD spur, and, the cable must be surface mounted, or run in mechanically proteted cable/containment,as any cable less than 50mm from the surface must be RCD protected. Also, the earthing and bonding must be acceptable, no bonding, then the job cannot be done (legitimately).
Back to the 3 amp fused fan, it used to be (in BS7671) that you have to follow manufacturers instructions, but that was changed, in either Amd 3 of the 17th, or 18th, I cant remember which. Now, you need to 'take account' of the manufacturers instructions. Putting in a 3 amp fuse on a RCD and 6A CB protected circuit is not going to protect anything, so it can be ignored.
Nobody will GAF. There is a good argument that the 3amp fuse is spurious, so is ignored, as, really, it does nothing, other than allow a way of local isolation (which is not a requirement of the wiring regs.)
If you go to a house to do work, you are only responsible for the work you have done, thats why all of the electrical certificates have an 'extent of installation covered by this certificate' box, which you fill in to show what you have done, e.g. "added fused spur from existing circuit 2 to supply single socket in hallway". Fill that in, then you cannot be blamed for the socket falling off with exposed wires in the bedroom.
When your house burns down because of a short in the fan leading to a fire, which would have blown a 3A fuse, you will have to convince your insurance company that the absent fuse would have made no difference when they refuse to pay out. Good luck with that.
Thanks for clarifying that. I genuinely did not know. My guy was installing a new consumer unit, so I suppose that creates a wider set of responsibilities. He said he had to check the condition of the existing wiring.
A short would trip the 6A breaker anyway. An overload would be different, but a ventilation fan, even if stalled, would not overload a
3A fuse.Sensibly, with such fans being connected to the lighting circuit to be able to operate with the lights, the requirements should specify that the fans should be suitable to be on a 6A circuit without additional protection.
I'm not talking about stalling, I'm talking about a short somewhere - whether it's in the motor winding or any control circuitry (timer, PIR, humidity sensor, etc) doesn't matter.
You're missing the point. Insurance companies will use /any/ excuse, no matter how unlikely, to avoid paying out. I agree the 6A breaker should trip, but if it doesn't and you haven't got the 3A fuse as a backup, that's what the insurance company will focus on.
When I had a ceiling fan and light installed in a new conservatory, the instructions stated that a 3A fused switched spur was required. The electrician who installed the fan said I didn't need it. I told him to put it in, and it actually proved quite useful when I had to disconnect the power to the fan to install a new remote control receiver in it.
Do you think a technical non-compliance is enough? Don't you think the insurers would need to show (on the balance of probabilities) that the method of installation materially contributed to the insured event?
On what grounds wouldn't they pay out? They'd surely have to prove you *intended* the house to burn down as a result of not fitting the fuse. Otherwise all accidental damage policies would be pointless.
Even if they did prove this I don't see how it invalidates the insurance. One's insurance is against one's house burning down, not against a 'random event' causing one's house to burn down. If I drop a cigarette on the floor (not that I have ever smoked) and as a result the house burns down then (following the same sort of logic as about the fuse) then it's "my fault" for dropping the cigarette and for having an inflammable carpet and for not having sprinklers installed, etc. etc.
I think gross negligence would suffice. If you leave the keys in your car, you could hardly argue that you did not intend someone to steal it.
HomeOwnersHub website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.