RCCB/MCCB with Arduino to protect

Hi Team,

So I recently purchased my arduino for a garden automation project. The only worry I have is, well, honestly, is arduino(electronics), water(nutrient solution is ionic) and stray wires might lead to some kind of short-circuit or some damage, and worst case lead to electrocution.
So I was wondering if anyone has ever used an RCCB with connection from main outlet to the DIY project power supply? This is on top of what ever protection my house already has with the MCCB/RCCB used at a home level.
Idea is simple as below:

Power Socket/Plug (Output 220V, max 6A) -> Connected to RCCB -> Output connected to extension cord or direct adapter -> Connected to Arduino board/other motor supplies etc./

What are your two cents on this? Already someone has used this in their home automation or gardening projects?

If all that's plugged in is an adapter to power an Arduino an extra RCCB is useless. The power supplies isolates main completely so only protection you have is for the socket with the power supply in it.

If you want to have good protection and not worry about the rest of the house you use a separate breaker and RCCB for the socket(s) outside. Done :slight_smile:

septillion:
If all that's plugged in is an adapter to power an Arduino an extra RCCB is useless. The power supplies isolates main completely so only protection you have is for the socket with the power supply in it.

If you want to have good protection and not worry about the rest of the house you use a separate breaker and RCCB for the socket(s) outside. Done :slight_smile:

Sure. Obviously there are a few other high power devices via relay module, like water pump, mixer and all these need 220V. But yes, will be using RCCB. But we need a breaker and RCCB together?

Regards,
ROBOAJAY

Thing is, I would not like to share a breaker nor a RCCB of a outdoor circuit with one indoors. Simply because there is a higher change of water getting in tripping the breaker and/or RCCB and then the light inside is also out which sucks even more.

Same applies if you add a second RCCB or breaker outside. Breakers and RCCB's in series are likely to trip both inside and outside when a fault occurs.

If you plan the protection you can have the downstream RCCB more sensitive than the one at the fusebox. So a fault outside won't black out your fridge.

Perhaps consult a licensed electrician who can design the appropriate levels for you. That is a big part of the electrician's job.

Even if the RCCB down stream is more sensitive, my experience is that if the fault is hard enough (for example water between L and PE) both RCCB's will act. So I would not like to share a RCCB under any circumstances between a indoor (more critical) group and outdoor one. Same for a breaker, if a fault is hard enough both will trip.

But we need a breaker and RCCB together?

No, because an RCCB provides both over-current and unbalanced current protection. The only place the RCCB is needed is where 220v mains can come in contact with water. If you have devices, such as the Arduino, connected through a power supply, there is no need for the RCCB unless the power supply itself can become wet.

The MCCB upstream of the RCCB should be of a higher amp rating so that the breakers are said to be coordinated, which prevents the upstream breaker (MCCB) from nuisance tripping when the downstream breaker (RCCB) detects a fault.

In the US, RCCB's are called GFCI's (Ground Fault Circuit Interrupters) and are required anywhere there is a permanent outlet within 6 feet of water. These devices function by running both the hot and neutral connections through a current transformer and they trip the breaker when the differential current exceeds 1 milliamp. This current is actually the amount of unbalanced current, meaning that the current is going out one lead but it is not being retuned in the other. The assumption is that this current is going to ground, hence the name GFCI.

https://www.nema.org/Products/Documents/NEMA-GFCI-2012-Field-Representative-Presentation.pdf

avr_fred:
because an RCCB provides both over-current and unbalanced current protection.

Absolutely NOT! You have combined RCCB and breakers called RCBO (residual-current circuit breaker with overload protection) or GFCI breaker but a normal RCCB is only interested in unbalance.

avr_fred:
The only place the RCCB is needed is where 220v mains can come in contact with water.

That also depends on the local regulations. here in the Netherlands a RCCB is mandatory for all new installations for normal circuits. A single RCCB may be shared between multiple circuits so that's the most common. But like I said, don't like sharing a RCCB between a indoor group and an outdoor one just for the case there is water and I can't turn it on again. Although if the oudoor group has a breaker that also disconnects the N it's less of a problem. But still, fault outside mustt not interfere with inside in my opinion because outside it's more likely.

avr_fred:
The MCCB upstream of the RCCB should be of a higher amp rating so that the breakers are said to be coordinated, which prevents the upstream breaker (MCCB) from nuisance tripping when the downstream breaker (RCCB) detects a fault.

Even if the down stream breaker is of a lower rating, with a hard fault the up steam breaker is still likely to trip.

avr_fred:
In the US, RCCB's are called GFCI's (Ground Fault Circuit Interrupters)

Yeah, you just have to give them a name. Here we call them "aardlekschakelaar". If it's a combined RCCB and RCCB aka a RCBO we call it an "aardlekautomaat". But or neighbors call them "Fehlerstrom-Schutzschalter" and RCBO respectively.

avr_fred:
when the differential current exceeds 1 milliamp.

Really just 1mA? Not saying you are wrong, but here 20mA is more common or 10mA when not shared.[/quote]