High efficient central 24V and 12V power supply what shall supply all devices in a house of 7 flats

Hello,
I live in a house with 7 other parties and we decided to make it smart-home ready by connecting flats by common network, which includes multiple MikroTik APs. In addition, we are going to install a 2N intercom, as the first smart-home system.
All devices shall be either powered by PoE or a central 12 V or 24 V power supply that is installed in the server room in the basement. We have to pull fibre optic to connect anything with each other as the cable conduit is not always big enough to allow a cooper-only installation. At least, we can pull a tow -pair-wire to pull power supply in parallel to the fibre, to power the switches / APs (which in turn supply downstream devices by PoE) by a central power supply

So, I am currently looking for highly efficient power supply units with each

  • 12 V, 100 W to 200 W
  • 24 V, 200 to 500 W

a DC/DC converter from one voltage level to the other instead of the second power supply is also an option.

It looks like only the MEAN WELL Switching Power Supply Manufacturer UHP series is the proper choice (price-wise and in regard to efficiency).
A DC/DC converter doesn’t cost much less than an AC/DC converter, plus it is less efficient.
It’s quite late right now, but I’m quite right, don’t I?

The only remaining concern is their partial load and idle consumption, as there are some loads that are not on all the time (I dropped MW an email).

Anyone around who is using these power supplies or may have a better option in mind?

Many thanks

Stefan

Maybe Balluff have something that fits your needs? Industrial spec power supplies.

checked them but I do find only 24 V. In addition they state typical 90%efficiency which is not that accurate as I could choose between 92 %, 94%, … at other vendors.

Are there any proper power supply providing 24V AND 12 V as that would things make easier in regard of power supply sizing

just found that
Combine two 12V power supplies for 24V | All About Circuits

that could also work :), any thoughts?

For 12V consider using a PC power supply, they all have efficiency ratings.

12 V are currently off and on loads, wondering what is a good one for which operates efficiently far off rated power

I have considered a similar setup for my far off plan to have a solar system and battery backup. If you plan to run 12/24VDC through a building big enough to have 7 flats, power supply efficiency is far from your biggest power loss. You will see far greater transmission losses.

Since, like you, my plan is to have small voltage regulators at/in each device, I decided that running 24VAC would actually be best. I believe 24V is considered “low voltage” so regulations are more lax, and 24V to 12/5/3.3V regulators are compact and readily available. If regulators that accept 24VAC are not available, diode bridges that can handle a few amps are that can be put in front of the regulator.

As for supplying the 24VAC, I plan to get a 24V transformer. These are fairly common as they are used to power HVAC equipment (at least here in Canada). No regulation will be needed since each device will have its own AC/DC converter and regulator.

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24VAC is also common for CCTV, powering remote cameras over long cable runs.

48VDC is a century old telecom standard for power over long runs, still used in ethernet PoE standards today. 48VDC equipment isn’t very available to home users though, outside of the power-limited PoE usage.

I tried running some stuff on long cables from a 12V supply but the devices could not cope with the voltage at the far end. Nothing was using a lot of power and the theoretical voltage drop should not have been that great. I suspect moisture got into the cable. Worth checking if what you want to run has a bit of tolerance on the voltage.

In the end I put some SWA cable in and ran 240V to the location rather than trying even larger copper on 24V

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but a part of it :slight_smile: , as even some percentage could make a difference in the electricity bill it is at least worth considering >90%. I do my math to see when break-even is expected.

are not a concern

but didn’t find a proper one what is properly to the case that 12V is currently only backup power in case the PoE fails to power the intercom.


may I post my current consumers:

12 VDC

24 VDC

cable lengths range from 10 m to 30 m depending on voltage and consumer

a simple wiring exits as well:
image

Poor attitude. The regulations are primarily concerned with stopping you setting fire to the house with your friends inside. At least understand what they are, and why they are.
You can start a good fire with a carpet nail through a cable connected to a 24V 500W supply.
That might be “safe voltage” but it is high energy.

Wrong thinking. Your cabling must deal with peak demands, the voltage drop along the cable doesn’t care if this infrequent or not.
You can’t afford to drop much from 12V and are going to need thick fat cables to carry 100W over 30m.
16mm2 for a 5% drop at 8A, that’s about 10mm diameter. As thick as your little finger, with insulation. And you need a pair. This gets costly.

devices are located in a concrete room in the basement. The power supply shall come with overcurrent protection etc.
It is considered to put fuses like this here
image
inline where power lines branch off to the flats.

cable sizing is done based on maximum power consumption with a safety factor of two.
Cable sizing is done based on based on DIN VDE 0298-4 and DIN VDE 0891-1

Does this sounds better :slight_smile: ?

And how do your cable sizes come out? Voltage drop is an issue for you, the low-voltage consumer, and is not part of the safety ratings about cable overload. It’s perfectly safe to drop 25% of your voltage, but your end device won’t like that.

you almost got me, I have just doubled checked and done a worst case calculation
minimum is Ø 0.80 mm
I’m in the range of ~6% voltage drop in the worst case