Potentially having new fusebox (UK) fitted with RCCBs, problems with 2 wire dimmers?

I’m considering having our old fusebox replaced with a fusebox that meets the current (haha!) UK building regulations. The new fusebox would have residual current circuit breakers which I believe would break the circuit when a difference of 30ma is detected.

I have a few Fibaro Dimmer 2 units fitted behind light switches around the house. The wiring in the house only has earth, live and switched live at the switch and these Fibaro dimmers cleverly leach a small amount of current to earth to power themselves. Does anyone know if these dimmers would cause the RCCBs to cut off?

Rewiring the lighting circuits to bring neutral down to the switches really isn’t an option, the wiring is plastered into the walls. If the dimmers are going to cause a problem then I’d rather no only find out after the fusebox has been replaced. :slight_smile:

Disclaimer I am not a electrician and not in your country.

I believe you are mixed up. It will not be earth but what is called neutral, active and switched active. If you don’t understand the differences please do not do any wiring and get a pro in.

The RCD’s will not trip as they only detect any current that does not return down the neutral because the current travels through a body into the ground. They do not stop people from getting killed so don’t think u r safe to do the work because u have them.

The switches that leak a bit of current through the light globe to still get power are then fussy on the type of globes you use. Some globes will block the leakage. Don’t buy your globes in bulk until you test one works.

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There’s no neutral at the switch, there’s live, switched live and earth. The neutral wire goes from light fitting to light fitting and never down to the light switch.

There’s a good explanation of the 2-wire system here:

You can not leak to the earth or you will trip the Breaker. Perhaps your device does this in a very small amount and you will find the install guide will go into this. The leakage may be through the load aka the globe and hence the info in my last post.
Each country is different and in mine there is only two wires and metal pipe that is earthed in old homes. Best to get local advice.

I am getting local advice, I’ve had an electrician look at and give me a quote for replacing the fusebox. I’d like to get people’s experience of using Fibaro dimmers with RCCBs too.

I looked at the link you gave and it is very clear to me that it is referring to the cable type and the earth is not connected to earth. Very confusing to use the word earth, they should have used the term 3 core cable. The diagram is clear that it uses neutral which stays in the roof, and your device uses the active and switched active lines. It gains the power by leaking power through the globe when the globe is turned off.

So in short no it won’t flip a RCD device as it does not leak to earth but though the load. If it is working now it will keep working after your box is upgraded. Just be aware that some globe types will not work with that system.

I had to rewire our house from the system you described and we used rcbo devices everywhere. My background is electronic design and repair.

Depends on the breaker. Different ratings are available as well as different delays.
Get a sparky and get advice.

I’ve got an electrician and have received a quote for the work. What I’m interested in but I don’t think I explained very well in the OP is to hear people’s experience of dimmers with modern fuseboxes.

@matt1, I think answered your question very well in post#2

I have used Fibaro and Aeon dimmers in modern RCB setups, without a problem. They do not “trip” the RCB when wired correctly.

Where I have had some issues is where your light bulb can “flicker” with these devices. Can’t recall exactly what the cause was but I believe it’s discussed over on Vesternet in their docs so you may have read about this already.

That’s good info, thanks.

When you say “wired correctly” do you mean when wired using a 2 wire or a 3 wire system? I installed most of my Fibaro dimmers behind the wall switch using the 2 wire system but I’ve remembered that I have one dimmer fitted in the ceiling rose of a light fitting which, since we have a neutral up there, uses the 3 wire system. I may be able to move at least one other dimmer up to the ceiling rose of one of the lights off I needed to.

I just meant, logically wired in a correct fashion. I wasn’t referring to either a 2 or 3 wire setup. Same would apply to both.

Wherever you can physically put the unit is grand. I happen to have enough space behind my physical switches, so I put them there