Questions about my planned system - and the power supplies

[ergo14]

Hello, sorry for the post in English but the KNX forum for my country seems dead so I'm trying my luck here.

I'm planning a KNX system in my home (~160m), it will soon be wired. The installers originally planned a Beckhoff PLC with mix of some KNX bus buttons + mixed standard 230V + DALI lightning. But after I did my calculations and weighted on the options I decided full KNX system will be the best option for me.

The house is 11m x 11m roughly and has 2 floors.

This is what I planned for my home:

GIRA 504000 KNX Secure switching / blind actuator 24-fold / 12-fold x 2 - controlling venetian blinds and roof window blinds 21 items in total
GIRA 504000 KNX Secure switching / blind actuator 24-fold / 12-fold x 2 - controlling 48 on/off circuits/lights
WEINZIERL 777 KNX IP BAOS x 1 - Programming - and interface for Home Assistant (I plan to do my own visualisations as I am a programmer by trade)
MDT KNX SCN-WS3HW.01 x 1 Weather station with wind measurment
GIRA 210800 KNX DALI gateway Tunable White Plus x 1
GIRA 212900 KNX heating actuator 6-gang with controller x 2 - controlling around 24 heating valves
GIRA 212600 KNX binary input 6-fold 10 - 230 V AC / DC x 1 or more than one for checking states of some devices
Buttons Gira Sensor 4 (5004 003) x 23
Buttons BE-TA55P8.G1 or BE-TAS86.01 x 5
Ceiling mounted presence detectors x 8 - Not sure what brand to pick here (BEG/Steinel?other?) - I will need at least 1 microwave one for the bathroom (something that works through glass), and it would be good if it could help with HCL light controlling.

Seems all the devices are KNX TP1-256 compatible, I also plan IPad for central interface (Home Assistant)/doorbell answering.

The installers do not have experience with wiring/assembling full KNX cabinets without Beckhoff PLC (they installed/wired some other systems but not KNX).

I could get another 3rd party installer if needed, but since I'm a programmer I plan to buy ETS license this month and try to program everything myself just for fun (Already did the KNX Virtual programming) - my electrical knowledge is limited though.

Bus will have around 49 devices in total - some draw more current than others like heating actuators - so I'm thinking one 640mA power supply might be not enough for the system to be stable. So I'm wondering what happens when PSU fails, I don't want to have whole home in the dark.

My current installers are experienced and capable of wiring everything and they had experience with other low-voltage home automaton systems - but they have some doubts on how the system should be powered to be reliable/best practice since they never did 100% KNX system. I have some questions:

1. I saw that Gira/Jung has 1280mA PSU's but one can't have multiple ones on same bus.
Can I just power whole system from one PSU (what about voltage drops?) and have another one somewhere on the shelve on standby in case this one fails and just drop the circuit breaker, replace broken PSU and voila, system is back up (not sure if I have to program it first for the bus to get powered properly?). This seems like cheapest/easiest solution.

2. Should I split my bus line into two with line coupler (is that what its called?) or ip router and put one or two 640maA enertex/GIRA PSU on every line - it seems a lot more expensive but possibly most stable system, also bus gets more complicated for a small home project.

3. How often do PSU's fail in the first place - after how many years I need to replace them because of capactor swelling, element wear?

4. Are there other factors I should consider for powering the KNX bus?

5. Finally - how many bus loops I should have for my house to be safe in case something gets damaged, what makes most sense? One per room, one per floor, one per house?

[gbglace]

1)
MDT STR 640 with redundancy, other wise only one PSU per linie segment, and for each line a separate PSU

in case this one fails and just drop the circuit breaker, replace broken PSU and voila, system is back up

That's how KNX works

2)
several lines in KNX topology not necessary because you don't have so much devices
an extra line and extra cable for weather station (including devices outside the house, motion sensors etc.) is recommended.

3)
10/15+ years or directly or after thunder strike and bad installation

4)

5)
1 loop (but not closed) per floor, depending of complexity of the floor perhaps 2

GIRA 212600 KNX binary input 6-fold

don't miss read contacts for windows or do you plan a separate alarm system where you can get the status from? It's increasing the functionality and comfort of blind controlls.

Ceiling mounted presence detectors x 8 - Not sure what brand to pick here (BEG/Steinel?other?)

depends on the floor plan we don't know
plan for every room a detector, no automatism without sensor data.

and it would be good if it could help with HCL light controlling.

that is a feature in LED controllers and/or external logic. The detectors can controll the brightness but they don't controll the light temperature

GIRA 504000 KNX Secure switching / blind actuator 24-fold / 12-fold x 2 - controlling 48 on/off circuits/lights

for more automatism I prefer actuators able to measure the power consumption (MDT-Series AMS / AMI / AZI)

The installers do not have experience with wiring/assembling full KNX cabinets without Beckhoff PLC (they installed/wired some other systems but not KNX).

But he should know the polish regulations.

RCD >> MCB >> KNX-Actuator >> terminal blocks (Wago 2003 series or Phoenix PTI)
RCBO >> KNX Actuator >> terminal blocks (Wago 2003 series or Phoenix PTI)
a lot of excamples and comments on quality (german regulations) you can find here

[ergo14]

don't miss read contacts for windows or do you plan a separate alarm system where you can get the status from? It's increasing the functionality and comfort of blind controlls.

Yeah there will be ~50 reed contacts connected to a Satel alarm system with INT-KNX board to bridge alarm to KNX installation.

So to sum things up:
I should probably have 1 line per floor, should I use line coupler or IP router? IP router seems cheaper because otherwise I need
1xPSU for the backbone line
and then 2XPSU per line - and line between segments is slower
VS
2 IP routers - each with one PSU
I also should consider having another PSU for just weather station for safety.

Doing this correctly seems to add a lot of cost to the overall system.

[Gast1961]

should I use line coupler or IP router? IP router seems cheaper because otherwise I need 1xPSU for the backbone line
and then 2XPSU per line

This is a misunderstanding. You need one supply for each TP line segment, no matter if the coupler is TP-TP (normal line coupler) or TP-IP (IP router).

So if you use an IP backbone, you only save one power supply in the backbone.

[ergo14]

Yeah I know I need one PSU per line, sorry maybe I was unclear

So I have following charts - which one makes the most sense, I'm thinking option 2, not sure how much of a price difference that would be but they both seem similar.
I wonder if this system would be harder to program somehow if there are more routers ( option 3 would be just having 2 line couplers instead of IP routers, I'm not sure if there would be issues with bus having many telegrams)

Option 1

KNX topology.png

Option 2:
KNX topology alt.png

[Klaus Gütter]

Is there really a need to have floor 1 and floor 2 on separate lines? The only reason I can think of is a separate apartment.

[ergo14]

Is there really a need to have floor 1 and floor 2 on separate lines? The only reason I can think of is a separate apartment.

I was thinking that There are two reasons - the devices in total might exceed 640mA, also in case of damage of the bus itself - smaller part of the house would be affected. But I also wondered if a single line with 1280mA PSU would not be enough for me - that would be the ideal situation (+ weather station on the coupler).

I would like to keep the installation as simple as possible - this is a single family house.

[ergo14]

Option 3 - Wouldnt that make most sense? - Maybe there is some other approach to create galvanic separatation between the weather station and the rest of the house? I think the proper name I should be using would be Line Extender/Repeater?

KNX topology 3.png

[gbglace]

I should probably have 1 line per floor, should I use line coupler or IP router?

one cable not one KNX-line per floor.


Option 3 makes sense.

You don't planned al lot of devices with display like MDT GT2, so with an 960 PSU you can use round about 100 devices. Some peolpe are using 70 devices with an 640 PSU.

[tsb2001]

My configuration:
40 Devices on one KNX-Line measured by the PSU with 640mA
measured current: between 170 and 190mA...

Runs before many years on a 320mA PSU without problems...

[ergo14]

My configuration:
40 Devices on one KNX-Line measured by the PSU with 640mA
measured current: between 170 and 190mA...

Do you have any redundancy setup in your installation?
I tried to do some math on the devices in my setup and its something like this (unless i did it incorrectly):

switching/blinds actuator up 24mA x4
Weinzierl baos up 24mA x 1
weather stattion up 100mA x1
Dali controller up 24mA x1
heating actuator up 160mA x2
presence deterctors up 10mA x 8
buttons up 10mA x 28

That sums up to ~900mA in worst case scenario - I know most of time the system will not draw that much at same time, but maybe I'm counting this incorrectly in the first place.

[tsb2001]

No, my only redundancy is a new packed up PSU in my garage.
All devices in my configuration added up with 10mA or more per device (40). In this case, i have to use a power supply at minimum 640mA.
But the real current from all devices was lower than the specified current in the manual or calculated in the ETS.
My opinion:
buy a PSU with 640mA and current measurement, connect some / all KNX-devices for a test on the table, program all components and take a look at the measured current from the PSU. Than you can make the choise for buying the other PSUs for any other lines.

[gbglace]

A good indication is to make a busreset, that is the moment a lot of devices needs "extra" power. And during programming, but this is one device at once only.

[ergo14]

Right, but when I do that and it turns out its not enough I already bought the PSU ;-)

Anyways to sum things up:

1 line with few branches per floor - and the attic/weather station, blinds actuators for outside engines should be ideally separated via line repeater and their own PSU?

[gbglace]

blinds actuators for outside engines should be ideally separated

not necessary, the BUS divece is the relavant part which should be save.

via line repeater and their own PSU?

in mode line coupler, yes