ᐅ Is an Additional Circuit Breaker / RCD Really Necessary for a Home Office?

kati1337 schrieb:

Can you give me a somewhat layman-friendly explanation of why this is actually possible/useful? Maybe I can convince him to run the CAT cables through a conduit in the wall after all...

There’s no need for a detailed explanation. It’s written in his “bible.” Does installing the conduit take just as long as running the cable? You can simply unroll the conduit in a long straight run and then push the cable through it. Afterwards, lay both the cable and conduit neatly on the floor and cut them to length accordingly. It does take a bit longer, yes, but not twice as long. Still, that’s not your problem. That’s just how it’s stated.

The issue with bends is partly true. But it’s not a big problem. We pulled cables through three 90-degree bends in our setup. We threaded a piece of Styrofoam onto a string, sucked it from one end with a vacuum cleaner, then pulled a fish tape through and pushed or pulled the cable at both ends.

kati1337 schrieb:


The electrician says:

• We need a separate circuit for the office: $150
• a separate residual current device (RCD): $115
• and because we are getting an additional circuit and RCD, also a bigger distribution board: $490

The reasoning behind the “extra circuit” is questionable, but that can be discussed. Let him have that one. The joke is that this extra circuit is billed at $150. At least in our case, that includes installation, devices like the RCD and circuit breakers, etc. Here, it means running a separate cable to that one room. The ceiling breakthrough has to be done anyway for other cables. Also, channels have to be cut into the wall in that room even without the extra circuit.
Please let that sink in. Technically, $150 is charged just to wire an additional cable in the distribution box, pull it through the existing ceiling opening to the door. A trained electrician can do that in 5 minutes, max 10.
The extra RCD — Google “RCD + MCB” (Residual Current Device plus Miniature Circuit Breaker). The device costs about $30. Sometimes more depending on the supplier. If he wants to make a $50 profit, then you may be looking at $100 total. The device is the same size as a circuit breaker but takes up much less space. The catch? It combines both functions, so you don’t have to sacrifice an entire DIN rail slot for an RCD plus circuit breaker. So the need for a bigger distribution board is eliminated entirely.

For the entire work, a price of $150 would be reasonable. If the distribution board is actually undersized and an RCD+MCB must be installed, $200 is still acceptable.
Talk to the general contractor about what they’re charging. Saying “Chamber of Crafts” (Handwerkskammer) often helps as well.

When I read things like this, it always annoys me that I’m not self-employed. You can turn rubbish into gold like that.

The CAT cables should be installed as required by the current DIN standards, meaning they should be replaceable within the installation conduit. The explanation is far-fetched.

kati1337 schrieb:

I don’t understand why a separate RCD for the computer would be necessary, but he insists on it strongly.

I don’t see the problem. My system is secured not only with additional RCDs (yes, I know they are primarily for personal protection, not the equipment). All tech outlets also have additional local surge protection. I don’t know how you handle this, but my technology—especially sensitive devices with data storage like PCs—is important to me. I would never dream of connecting them to the same circuit as the rest of the house, especially when all options are still available.

kati1337 schrieb:

I also find the socket situation strange. That would mean the distribution board was fully planned in advance, which doesn’t seem quite right. But I’m not an expert. :/

There can be many reasons why a larger board is needed. We don’t know exactly what he is installing or what else you have. The board usually contains more than just circuit breakers and the two RCDs.

kati1337 schrieb:

At this point, I’m out of ideas. Can we still run both our computers on one circuit while also running the fridge, freezer, and so on?

To answer that, you’d need to know what wiring you have in the walls and what the board contains. Without background information, it’s just guesswork.

kati1337 schrieb:

and everything always works perfectly here.

In the past, there were no RCDs (or they were not mandatory), and everything "worked perfectly" then, too. Nowadays, two RCDs are mandatory, and in wooden houses, even fire protection switches are required. You learn from mistakes.

teh_M schrieb:

but another 3-phase RCD in addition to the other two? That doesn’t make much sense if that is the case.

It doesn’t necessarily have to be three-phase.

Mycraft schrieb:

The CAT cables should be installed according to the current DIN standard, meaning they have to be replaceable inside the conduit. The explanation given is far-fetched.

I’ll try to push this through the general contractor. We would also prefer it that way.

Mycraft schrieb:

I don’t really see the problem. My system is not only protected by additional residual current devices (RCDs) (yes, I know these are actually for personal protection, not for protecting the equipment). All technical sockets also have additional local surge protection. I don’t know how you handle this, but my equipment, especially sensitive devices with data storage like PCs, are important to me. I would never even consider connecting them to the same circuit as the rest of the house, especially when all options are open.

I basically have no objection to a second circuit. But the extra RCD doesn’t make sense to me (shouldn’t the RCD trip regardless where in the house the device causes the fault? What’s the advantage of having the computers on a separate RCD? That they won’t be disconnected if another device elsewhere in the house trips the RCD? Or that the house won’t lose power if a PC trips the RCD? What’s the idea behind it? I already asked the electrician twice, but all I got was “you need that for the PCs.”

Mycraft schrieb:

There can be many reasons why a bigger distribution board is necessary. We don’t really know what he’s building there or what else you have. The board usually consists of more than just circuit breakers and the two RCDs.
You would have to know what’s installed in the walls and what’s inside the board. Without background info this is just guesswork.

I haven’t been able to find out which circuits he’s planning for the house. I already asked but got no answer. Otherwise, he wants to install 3 RCDs (2 as required by code (??)) and one for the office. I also can’t find out what other breakers he plans to install. As far as I know, each room gets its own circuit breaker (I assume those are MCBs?), and some rooms with lots of electronics, like the kitchen, may have several. In our kitchen in the old house, for example, the electric stove has its own breaker but not its own RCD.

Mycraft schrieb:

It doesn’t necessarily have to be three-phase.

All the RCDs in the offer say: "RCD - 40/0.03"

kati1337 schrieb:

That they are not disconnected from the power if another device somewhere in the house trips the RCD? Or that the house doesn’t lose power if a computer trips it? What’s the idea behind this?

Yes, that’s the idea: the more RCDs, the less you lose power. Possibly they want to be extra safe and completely isolate the room from the rest. Which is actually not a bad idea for higher-end technical equipment (this was already suggested earlier).

I might even go as far as using 2.5mm² (approximately 8 AWG) NYM cable for the supply line to the gaming room. (You never know, maybe that’s their plan too.)

kati1337 schrieb:

Otherwise, they want to install 3 RCDs (2 according to regulations (??)), one for the office. I can’t find out what other circuit breakers they plan to use.

Yeah, it’s definitely frustrating when they don’t communicate clearly. Then just insist through the general contractor to provide you with a plan.

kati1337 schrieb:

I know it so that each room has its own circuit breaker (those are MCBs, I assume?), and some rooms with a lot of electronics, like the kitchen, have even more.

Yes, MCB means Miniature Circuit Breaker. In everyday speech: a fuse or breaker.

kati1337 schrieb:

In our old house’s kitchen, for example, the electric stove has its own circuit breaker. But not its own RCD.

Like I said, that was how it used to be. It’s like how cars used to not have seat belts.

kati1337 schrieb:

For all RCDs listed in the offer, it says: "RCD - 40/0.03"

That doesn’t say much besides what’s already known: 40A rated current and 30mA residual current trip sensitivity. Pole number or type is unknown.

They could also be double-pole devices; I have installed those myself. Just that I use significantly more than the minimum requirements.

teh_M schrieb:

I’m not sure exactly what he wants to install, but adding another three-phase RCD to the existing two doesn’t make much sense, if that’s the case.

As far as I remember, DIN 18015 Table 2007 requires more than one RCD.

In our construction, the electrician insisted on a separate RCD for the external cables, which was number 3.

Otherwise, depending on the rating factor, it may also be necessary to have a separate protection either with its own RCD or a higher-rated RCD because the nominal current is exceeded.

teh_M schrieb:

I would look for a combination of RCD and MCB if you really need an RCD, since it only takes up 2 slots in the panel instead of 5.

My combined RCD+MCBs only require one module space, but they are a bit more expensive.

Mycraft schrieb:

All technical sockets also have additional local surge protection.

Which surge protection device do you specifically use? I’m still searching.

The advantage of multiple RCDs is: if one RCD trips, the other separate RCD circuits continue to function. For example, it can be useful to protect the refrigerator separately, so that if the RCD trips while you’re away, the fridge does not remain without power for a long time.