Amount of RCDs in a single family home

[Jeecha]

Hello,

Electrician has planned over 20 RCD and RCBO devices in the distribution box for my home and I wanted to verify if what he proposes is reasonable, as here in the "Show your distribution" thread, there are usually significantly fewer of them, even for large distributions.

Briefly about the home - it's a one family two story home with 3 bathrooms, underfloor heating using gas, air conditioning with multi-split heat pumps (2 outdoor units), photovoltaics on roof. Home will use KNX as the integration backbone with mix of DALI (CC and phase dimming) and KNX (CV) for light control.

The power lines, which have individual separate RCD/RCBO on them are currently following:
1) sliding outdoor gate;
2) territory lighting - in pavement, on fence, on gate etc;
3) wall sockets on balcony and terrace;
4) functional outdoor lighting at entrance, on balcony and terrace;
5) decorative outdoor lighting on facades;
6) heating and hot water (gas heater, circulation pumps, distribution valves);
7) water pump in well;
8) sockets in garden;
9) sockets+towel rails for each bathroom separately (so 3 RCBO there);
10) light in bathrooms (1 RCBO for all 3);
11) kitchen - fridge;
12) kitchen - induction surface;
13) kitchen - dishwasher/faucet boiler/sink;
14) kitchen - general sockets;
15) laundry - 3 separate RCBOs for washing machine, dryer and sockets;
16) 2 separate RCBOs for each outdoor AC unit, because each of them has a maximum of 20A, so they need to be on different phases to spread the load;
17) ceiling IR heaters on terrace;
19) sprinkler system;
20) ventilation system with heat/humidity recovery.

So that's 26 in total and I have probably forgot something. I can understand his argument, that having these on a separate RCD devices will reduce the problems and chance of them tripping if there is a fault, and developing fault in one of them will not have severe effect on rest of the home. However having so many increase cost because of RCDs themselves, because of larger distribution needed to accommodate all of them and man hours needed to assemble it all.

Is the above separation reasonable, or would the common practice be to group the lines to reduce the amount of RCDs needed?

Also, the country code does not require ALL sockets protected by RCD, so currently indoor wall sockets only have MCBs. However it looks like in Germany it is mandatory, so all the distributions shown here always have RCD on all lines. I assume from safety perspective, it would be better to do that too, even though it is not required by the code just yet?

P.S. Sorry for writing in English

[Lennox]

was ich so in den letzten 3-5 Jahren gesehen habe, sind bei uns in OÖ/AT ca. 3-5 Stk. RCD´s und nochmals so viele RCBO´s
in der Regel in einem "normalen" Einfamilienhaus verbaut.

Dies kann und sollte ja länderspez. überall anders geregelt sein...

[gbglace]

It are a lot but for me it seems OK because there are a lot of functional groups which I dont't like having connected in case of failure. In outdoor area a RCD/RCBO makes mor sence compared to a MCB.

I have no outdoor stuff connected to my main cabinet so I count 13 RCBO and 5 RCD followed by several MCB's.

[Crashman]

In comparison:

In my home (house, 2 floors, 190 square meters) I used:

3 RCD with 6 MCB each (different devices like KNX, oven, microwave and kitchen wall sockets)
12 RCBO (per Room mainly for general wall sockets and shutters)
1 AFDD for 230V lights


I would advice you to use RCBOs/RCDs for all walk sockets.

[FrankMaier]

I don't understand how many RCBOs you really have, because you mix RCD and RCBO.

For example: If your kitchen is protected by one single RCD and the fridge, induction surface, dishwasher, sockets are protected by indiviual circuit breakers behind this RCD, that's fine and makes sense. However if he used for fridge, induction surface, dishwasher, sockets a separate RCBO each, then that might be overkill.

Your installation sounds luxury, but so do the devices you have. I mean, you might be able to reduce a few MCB in the outdoor area, but in the end, you should ask yourself if it's worth it.

And yes, it's wise to have RCD on all lines, especially wall sockets.

[Jeecha]

The list was each a separate residual current device. For example for the kitchen area there are currently 4 individual RCBOs - one 1P+N for dishwasher and other under the sink equipment, one for sockets, one for fridge+freezer and 3P+N one for induction surface.

So it's close to 30 individual residual current devices (RCBO or RCD) in total.

That's the reason I asked - it looks like a bit of an overkill to me too, but electrician insists that having this many is needed so if some equipment fails, it does not affect others. Cost wise it is also quite expensive - the RCBOs and RCDs cost close to half of the KNX equipment I have in distribution...

[FrankMaier]

I agree with you. One should also ask, how likely or how often will a RCD trigger, so how relevant is this "comfort"? In the best case the RCD will trigger never.
Or one could ask: What would be so bad about a single RCD for the kitchen, followed by several MCBs for the socket, dishwasher, ...? The dishwasher triggers the RCD, fine, then you can't cook any longer. Who cares? Is this a drawback for you? I doubt it.

One RCD for Territory lightning, Wall socket on balcony, functional outdoor lightning, decorative outdoor lightning, sockets in garden, sprinkler system. That's all outdoor stuff, and if everything turns off if one of them malfunctions (and also only malfunctions in such a way, that the RCD triggers and NOT the MCB), who cares? None of them is vital.
The same could be done with the IR Heater and the AC units: One RCD, followed by several MCBs. That way you also don't need expensive 20A RCBOs.
The same for laundry, but here, you might gain nothing, because a separate RCD and MCB needs more space than 3 RCBOs and the cost might be similar.

But I also want to state, that some here in the forum also tend to such an installation your electrician suggests. So it's not wrong but also not mandatory.

So maybe you make whish list and calculate the savings. If the savings are worth the trouble, then present it your electrician.

[gbglace]

A defect in dishwasher could switch off the freezer and not only during time you are at home. So for me I set for each device with water contact a RCBO.

[Jeecha]

Thanks everyone for the response. It seems that this is more of trade-off between fault tolerance and convenience against cost.

I will keep the separate RCDs/RCBOs for the critical systems, which need to function while I am away, like heating or fridges, so they are completely independent from each other. Perhaps some of the non-critical appliances, which are operated when present, or do not impact comfort much, like outdoor lights and sockets/IR heaters, can be grouped more to reduce amount of RCD/RCBO devices in distribution slightly.