Choosing a power cable for a smart home – 2x0.75mm or 2x1mm?

Hello

I want to design my own smart home. As you know, I’ll need to run cables to do this. I want to run a bus system through the rooms, consisting of a power cable (2x0.75mm) and a data transmission cable (4x0.5mm – YTDYekw). This bus will be about 30m long with short branches (up to 2m); for the time being, there will only be about 5 of them. My question is: which ‘power’ cable is best to choose? As I’ve already mentioned, I’m considering 2x0.75mm, but will that be sufficient?? The bus will be connected (via these branches) to various controllers, actuators, sensors, etc., so it won’t draw that much current, but I’m also thinking of connecting three CCTV cameras to this bus – or rather, just to the power cable – at some point (they’ll be powered from this installation). So should I use a thicker cable, e.g. 2x1mm, or will this 0.75 be enough (bearing in mind that I might need to power some other electronics in the future??

As for the voltage, I’ll probably run 12V there so that it’s suitable for future cameras.

Or should I run two power cables?? One would power the cameras (12V) and the other the rest of the electronics (5V). Because I’m not sure whether it’s better value to run two power cables or to use a single 12V cable and fit 5V voltage regulators to each module, controller, etc.??

But my main concern is whether this 2x0.75mm cable will be able to handle it all??
Best regards

Hello.
I was going to write something a bit longer, but I realised that since you’re designing a smart home, you should already know these things – the basics.

Have a read: Link

Here are some formulas you can use. As you can see, a 0.75mm² cross-section can carry a current of 16A continuously under normal conditions. Ideally, you should add up the current drawn by the installed appliances and see if that cross-section is sufficient for you. If your calculated current-carrying capacity is close to the threshold for changing the cross-section, install a larger one.

Franek, why do you want to run power cables all over the house to the cameras? After all, there’s a 240V supply in every room, so when you install a camera, you just run the power to it from the nearest junction box, using a power supply designed for that camera

Just a quick correction – it’s 230V. Thanks for pointing that out, otherwise I’d have been misleading people.

240 V ??? <wow> Either I wasn’t paying attention at school or something’s not right
And secondly, my friend Franek… a smart home costs a fair bit of money, so you need to think carefully first about whether you’ll be able to afford it? Not to mention the computer that would manage the whole house, which has to run 24 hours a day, 7 days a week – which, of course, means high electricity consumption.A smart home is a great idea, but you’ve got to have the cash – and the cash Best regards, ŁP

For beginners in the field of smart home installation and programming, I’d recommend the Integra, just as Bronek did. It offers plenty of features for a reasonable price [just over 1000PLN].

Typical installations, such as KNX, cost in the region of 50,000 PLN for equipment and cabling, plus the cost of installation and commissioning.

If you don’t want to go to such lengths, buy the Integra

Bronek22 wrote:

JohnySpZOO wrote:

Hello.
I was going to write something longer, but I realised that since you’re designing a smart home, you should know these things – the basics.
Here are some formulas you can use. As you can see, a 0.75mm² cross-section can carry a current of 16A continuously under normal conditions.

That’s not true. Because then a 1.5 mm² wire would be able to handle 32 A.
I reckon it’ll be considerably less; I can’t be bothered to look it up right now.
It’s not just temperature that plays a role here. For 12 V, you need to factor in voltage drops.
0.75 mm² is approx. 0.05Ω/m. 10 m is 0.5 Ω, which gives a voltage drop of 8 V at 16 A.
No comment for 12 V.
Bronek

16A is a catalogue specification; this value is given both in H. Markiewicz’s book – Electrical Installations (Chapter 5: ‘Power Cables and Wires’) and in the TFKable catalogue (I found the first one I came across, dated August 2004).

The selection of cables should be made taking into account the following parameters and operating conditions (the most important):
- rated voltage, frequency,
- the location and method of cable routing, the number of conductors, the distance between cables, etc.,
- current load (taking into account the increase in load over time),
- permissible voltage drop,


In addition, the following parameters should be considered when selecting a cable:
- current values in the neutral conductor – 3-phase,
- short-circuit current values,
- load asymmetry – 3-phase,
- protection against electric shock,
- mechanical damage,
- fire hazard,
- the lowest and highest expected temperatures in the room and in the cable’s surroundings,
- the presence of liquids, vapours or gases,
- other environmental conditions.

As regards the current-carrying capacity of a given cable, its routing has a significant impact on this capacity; for example, it differs for a cable laid in conduits or insulation ducts (method A2) compared to a cable laid in the ground (method D).
For example, a 3x1.5mm² cable can theoretically carry a continuous current of 25A – with two conductors carrying current:
- for method A2, the current-carrying capacity drops to 14A,
- for method D, the current-carrying capacity drops to 22A.
This difference in the current-carrying capacity of a cable with a given installation method is due to varying degrees of heat dissipation under load. The temperature is different for a cable in a conduit where there is no ventilation, and yet different again for a cable laid in the ground, where the temperature is usually lower and heat dissipation is significantly better.
The situation is similar for installations in rooms with elevated temperatures, where certain correction factors are taken into account, which effectively increase the cross-sectional area.

The current-carrying capacity of a cable is also affected by magnetic fields. In addition, there are factors depending on the number of circuits arranged in a particular way.

When selecting a cable of a given cross-section, in addition to the effects of routing and temperature, voltage drop has a significant (and, in fact, the most significant) influence. The maximum permissible voltage drops between transformers and loads must not exceed:
- for lighting loads: 5%,
- for other loads: 10%.
If the voltage drop at a given load exceeds the values given above, the cross-section must be increased so that the continuous load rating is maintained. Alternatively, two cables of a suitable cross-section laid in parallel may be used.

Another factor to consider is the mechanical strength of a conductor of a given cross-section. Here, both the way the cable is laid and its length have an impact.

When designing a new installation, safety margins are applied, e.g. for the cable load. This margin may be 10, 20 or even 40 per cent, depending on the nature of the load.

It should also be emphasised that the cross-sectional area of a given cable under a given load varies depending on the material used – Cu, Al!!!
And there are requirements here too.

That’s a brief overview of the use of a particular cable cross-section. It all depends on the intended purpose and the profile of the installation in question.

As for INTEGRE, I agree

Furthermore:
Link
Link

And here’s another interesting little thread on elektroda.pl: Link

Thank you very much for all your replies; they’ve given me plenty to think about As for the cameras, someone wrote that there’s no point in running a power cable to them when there’ll be a socket in every room and you can use a power supply unit to power them. Well, yes, but these days most CCTV kits come with not only the cameras and the recorder, but also an additional power supply specifically for those cameras. So, let’s say the recorder with its power supply is located in a room, and we run a coaxial cable with power (this cable is usually included in the kit) to each of the cameras. I wanted to do things a bit differently because, if I’m ever going to have cameras, an alarm system (motion sensors, glass-break detectors, etc.), as well as smart home electronics (such as control panels, actuators like relays, etc.), why run a separate power cable to every electronic device when everything could be powered from a single bus??

From your comments and my own limited experience, I know that, as someone has already pointed out, there will be significant voltage drops along this power supply line. So I’m wondering whether it wouldn’t be better to run a separate power cable to each room, which would power all the electronics (included in this project) in that room? Unfortunately, the costs would rise slightly, as, for example, two separate power cables would need to be run to two rooms situated next to each other. But the price increase shouldn’t be too significant.

As for INTEGRA, I’m thinking of creating my own control unit based on an AVR microcontroller or even an ARM, though I’m only just starting to experiment with the latter For communication, I’d use RS-232 – or, to be precise, RS-485. This means only two wires are needed for communication. I mentioned the YTDY 4x0.5mm cable in my first post because I intend to keep two wires in reserve – they might come in handy for something one day.

But which control unit I’ll use isn’t important for now; what worries me most is the situation with the power cables, as I’ve been thinking about this for some time, and in about three weeks’ time the walls in my newly built house will be being plastered, so I’d like to lay them beforehand. As for how to lay them, they’ll probably go straight under the plaster without any conduit or the like.

So could anyone advise me on how to solve this problem??

Thank you and best regards

As for the cameras, you can use E5 computer twisted-pair cable, but you’d need to buy special transformers – one for the camera and another for the recorder (around 80 zł per pair). You use the twisted-pair cable: one pair carries the video signal and the other supplies power to the camera; you just need to ensure the distance between the camera and the recorder is within 200 metres, if I remember correctly.

Added after 9 [minutes]:


http://sklep.delta.poznan.pl/transmisja-video-i-audio-+-zasilania-po-skretce_c226_cc0.html
http://www.sklep.e-system.com.pl/go/_info/?id=1161

Franek, the problem with powering the cameras from a single power supply is that if it fails, all the cameras will switch off; but if you run a separate power supply to each one, you can be sure that if something happens to one, you’ll still get a picture from the others

Well, but power supplies have already been developed that have several power sockets, each protected by a separate fuse. A power failure on one circuit doesn’t put the rest of the cameras out of action. I recently installed one of these 12V, 15A units with 18 outputs.

Twisted-pair cable is fine, provided you don’t skimp on the transformers [decent ones cost around 30–35 PLN per pair]. Twisted-pair cable is more resistant to interference. I have cameras at several sites connected solely via twisted-pair cable; the longest run is about 140m. It works without any problems. However, over long distances, it’s worth considering whether to run a separate power cable to the most distant cameras.

A central power supply has its critics and supporters. I’m one of the latter. There’s no problem with interference, as all the cameras are powered from a single source and from the same phase as the recorder

I have not yet encountered any instances of equipment shutdowns caused by fluctuations in the supply voltage. The power supplies currently in use are converters that operate across a wide range of input voltages, usually 110–240V, providing a stable 12VDC output. The power supply in the control unit’s enclosure is a standard transformer, but note that each control unit board has a 16–18 VAC power connection and handles voltage rectification and stabilisation itself, whilst the battery acts as a sort of buffer for the control unit.

Well, yes, there are power supplies that have a dozen or so outputs, but the power supply is still connected to a single circuit, so if one phase fails – and that’s exactly where the power supply is – all your cameras will go down.

Gentlemen, when I brought this topic up, I wasn’t asking whether I was missing a phase or not. My problem is how to route the power cables around the house?? I’m sure a dozen or so people (if not more) on this forum have set up their own ‘smart homes’. Could any of them tell me how they solved the problem of supplying power to the rooms?? Is it via a bus system, as I mentioned earlier – a cable run through several rooms with branches off it?? Or perhaps a separate power cable to each room?? Could anyone advise me?? After all, you’re more experienced

Best regards.

I once installed the wiring in a house like this. It looked something like this.A cabinet containing all the RCDs for safety. Actuators from ABB or Merten – various types for blinds, lighting and dimmers – and a power supply unit for EIB devices (if there’s more than one, a coupler is required). Each lighting or roller shutter circuit runs via a cable, e.g. 3x1.5, from the actuator (to the lamp or roller shutter). The control circuit, however, uses a 2x2 0.5 EIB cable. All devices have 4 pairs of Vago-type connectors.
Route the wiring in a star (“Y”) configuration within a single junction box, with no more than 4 terminals.
You programme the devices using the ETSv3 software; download the database for the relevant device from the manufacturer’s website and select the appropriate function. You assign an address to each device. All devices are equivalent.
It’s quite expensive.
As for the cameras, I ran a 2x1.5 cable to each camera separately from a shared power supply.

Bronek22 wrote:

Franek k wrote:

As for INTEGRA, I’m thinking about building my own control unit on an AVR microcontroller or even an ARM, though I’m only just starting to get to grips with the latter For communication, I’d use RS-232 – or, to be precise, RS-485. That way, only two wires are needed for communication. I mentioned YTDY 4x0.5mm in my first post because I intend to keep two wires in reserve – they might come in handy for something one day.
Thank you and best regards

Mate, as you can see, you don’t have the faintest idea about alarms.
Whatever you build on that microcontroller will only be suitable for nursery school children to play with. Because it has to be reliable.
Communication via R-S makes no sense. Because you won’t be able to build that bus. The experts at Satel
are smarter than you, and it’s not without reason that they designed a 4-wire bus.
How are you going to run the power supply via R-S?
You’re not even capable of making an expander using 16A relays. Because it has to be safe and should be certified.
Mate, just try to learn how to use Satel properly.
You’re not even capable of coming up with functional solutions like the ones in Satel.
Mate, progress lies in using what others have invented. It’s not about reinventing the wheel – and that’s exactly what you’re trying to do. Mate, progress lies in using a computer, not in building a (primitive) computer and an (primitive) operating system.
Mate, SATEL consists of a device and several pieces of software. The first is the control panel software, whilst the other software is dloadx – the control panel management programme.
It’s literally as if you wanted to build a computer and then create an operating system for it as well.
Bronek

Mate, mate, mate...

And I’ll reply to my esteemed friend as follows: As you can see (see above the first post in the thread), this thread was started regarding cable load capacity and the issue of routing power cables. However, my friend is going off on a tangent about an INTEGRA 128 alarm control panel, which has absolutely nothing to do with the topic. Who did I ask to recommend an alarm control panel to me?? My dear friend needn’t worry about what I’ll use to control my home, because if I really wanted to, I could even buy a motherboard like a VIA EPIA, and that would do just fine. What I end up using is entirely my own business.

I don’t know if you’re running some sort of advert for this INTEGRA board, and is that why you’re so fixated on it?? Does progress mean just using what others have come up with?? – Well, good luck with that (with all due respect to Satel; I’ve dealt with them before and am happy with their products).

I may not be able to come up with solutions like those used by Satel, but I don’t just rely on off-the-shelf products all the time; I create some things based on my own ideas, and that’s where we differ, mate. Mate, the art isn’t in putting ready-made parts together – the art is in making something yourself.

Added after 20 [minutes]:

Getting back to those wretched cables, I found some information online about the OMYp 2x1.5mm cable. It stated that the resistance is only 13.5Ω/km, meaning that the voltage drop over 10 metres would be 1.35V with a current of 10A flowing through the cable. Do you know of any better cables with lower resistance?? But they mustn’t be thicker than 1.5 mm ;p