Trying to understand bathroom lighting and fan connection

Puk · Post by **Puk** » Fri Mar 19, 2021 7:36 pm

Good evening all. I found this forum with some googlefu and had a read but I’d quite like some reassurance.

I’m in the process of renovating an old Edwardian semi that was last decorated in 94, omg so much green wallpaper!

The better half has chosen a posh light fitting to go in the bathroom and a new fan, the fan doesn’t require an earth and is ip45 certified, it’s going in a zone 1 area. The light fitting is going into zone 2 which it’s certified for but needs an earth. My consumer unit has a working rcd fitted.

I want to replace the pull switch as it’s a bit naff, somewhat sticky and also covered in old paint. The switch has only two wires into it, red and black and a terminated earth.

I dropped the lighting rose and it’s only got two wires into it, red/black and a taped up earth.

The old fan didn’t function although was burning hot(!) when I removed it, the old fan had a live/neutral/switched-live and a folded back earth.

I’ve tried to understand lighting rings but I’ll be honest I’m more of a chisel and mallet kinda guy.

Would I basically be alright to just do as I wish, swap out the fan, fit a new light fitting (and connect it to the taped up earth) and replace the full cord switch .

Here are some pics attached, the pull switch, old/new fan, old/new light fitting.

Do I need to do anything to prove the earths are connected anywhere for the light fitting? Or is it assumed it’s fitted to a junction box in the roof correctly.

Is there anything I should do before swapping stuff over at all in your eyes? (Other than switching off the power obviously!) I appreciate the input.

Also does anywhere know a producer of a silent pull switch?

Edit I should add. I don’t have an isolator switch fitted for the fan. When I remove the attic floor boarding I might well drop the wiring down and fit one above the bathroom door. But currently there isn’t one fitted.

Someone-Else · Post by **Someone-Else** » Fri Mar 19, 2021 7:53 pm

The earth in the pull cord is supposed to be where it is in your picture. (Nothing wrong with where the earth is connected)

Ideally the earth should be tested as it may be connected to nothing. (It has been known)

Unless you can prove there is a working earth, I would NOT put that light in a bathroom.

I doubt you will find a silent pull cord, since having mounted on the ceiling is like mounting it on an echo chamber. (You can of course mount a normal switch instead in a convenient location)

Oh, and lighting is NOT on a ring, it is a radial. (Daisy chain if you will, from supply to first light to send light etc, and stops at last light)

Does the RCD work?

Puk · Post by **Puk** » Fri Mar 19, 2021 8:13 pm

Hi Someone-else.

The rcd does work. I proved it by accident the other day. I was test fitting a shower pump and it started without any water in it, spun up and threw the rcd. Amazingly it worked fine afterwards, I was expecting it to have turned itself to ash.

I understand the earth is alright in the switch, but as I’ve not seen an earth inside any other light switches in the house it made me curious.

I am more than happy to pay for a sparkie and was planning on it anyhow. But when I started to fit the new fan the light peaked my curiosity whether I could do it and this is what I’ve found.

Someone-Else · Post by **Someone-Else** » Fri Mar 19, 2021 8:33 pm

A pump running is not a reason for an RCD to trip.
I would suggest you carry on as planned and get an electrician to carry out an Electrical Installation Condition Report (EICR) In English, it is a check to see is everything ok, needs attention, or dangerous.

Puk · Post by **Puk** » Fri Mar 19, 2021 8:41 pm

That’s interesting, the shower pump was screaming when the rcd cut it, I’d inadvertently not turned it off when I cut the water to it, when I disconnected the pipe the last bit of cold came out and was enough for it to fire the pump up.

I’ve lived here a year now and never had the rcd go off for any other reason. I’ve tested it routinely with the test switch.

Is there a way to test the earth is indeed earthed as it should be? The junction box for it is in the ceiling under the attic boarding and insulation so not particularly easy to access. Or can only an electrician perform such a test?

Would you suggest I not fit the fan either at this point?

Someone-Else · Post by **Someone-Else** » Sat Mar 20, 2021 1:18 am

As you said, the fan does not require an earth, so that is the least of your problems.

An RCD trips when it detects current going to earth, it is not overload protection. (Something drawing more current than it should)

Who ever tests anything will need access to it, electricians do not have a "magic wand" they still need to have access.

You could do a crude test if you had a multi meter (What does my signature say?)

Puk · Post by **Puk** » Sat Mar 20, 2021 4:53 pm

I do have a multimeter, I generally use the dc side for hobby type electronics. It has AC and shielded probes with only 5mm tips exposed so I wouldn’t be against using it on an ac setup.

What am I looking for, measuring voltage between red wire on light switch and earth and same in the light else?

Someone-Else · Post by **Someone-Else** » Sun Mar 21, 2021 12:58 pm

Ideally you should measure the resistance of the earth at the light, and light switch.

If you check for voltage between live and earth, that just tells you there is a differance between live and earth. You can (and do) get a voltage but no current, it would be a bit late to find that out the hard way.

Puk · Post by **Puk** » Tue Mar 30, 2021 12:23 pm

So I found some time to revisit this.

I used a meter between the terminated earth in the switch and exposed earth above the light fitting, I also did it between the light fitting and the earth in a fused spur box that’s in the bathroom that use to run an electric fan heater. I have little to no resistance between them.

I replaced some other switches around the house the other day and the back boxes were all earthed too.

Would you consider this a safe assumption that I could wire in this light fitting? I’m leaning toward it being fine, obviously I haven’t tested whether the true earth from the consumer unit is satisfactory, the electrics were last inspected and passed in 2013 confirming it’s to the BS7671 standards.

Puk · Post by **Puk** » Wed Mar 31, 2021 7:09 pm

So I went ahead and fitted this light. I used my meter and checked the resistance between the earth wire in the ceiling rose and a radiator, I also did it between the rad and the switch terminated earth, both checked well. After that I fitted as necessary. So this one is closed.