Power Supply Issues

I don't know how familiar you are with CBus so I will just mention some basics.
Software burden needs to be enabled on unit address 01 which according to your pictures is USB PCI.
I don't think that is your problem.
If you were having trouble scanning the network and all the unit LED's were normal then that would be something to look at.

As far as I can tell when you disconnect part of the network it is taking out the CBus indicator?

Keep in mind if you split the CBus network and remove all the clocks the perfectly healthy unit's CBus LED will go out.
One clock minimum three recommended for redundancy.
Since the network is down you can't scan it to see a list of all the clocks so you need to note all that down from all the output units in the database or whatever scans you were able to do.

I think the problem is going to be a faulty unit or a short in the pink cable.
Of course knowing the wiring route would be handy at this stage.
Split the CBus network up and you will be able to narrow it down.

If there is just one distribution board you could disconnect any CBus pink cable going out from there and give that a go for a start.

 

I don't think that is your interface.

 

thanks for the feedback,

Your right my interface is 5500PCU not 5100 so that's not it.

I am reasonably familiar with CBUS as have in my own house for last 11 years but have not touched it in id say at least 5 years which is a testament to the reliability of the system.

This system with the fault was not setup by me but the electrician who worked on it unfortunately passed away to serious illness last year. It had being completely stable up until about a year ago when intermittent problems started and became more frequent to the point the network goes down daily but recovers itself. Reducing the size of the network eliminating about 7 input devices seems to have restored stability.


The CBUS units are all in one cabinet and there are about 7 cbus network tails. If I connect up all tails sometimes immediately sometimes within 2-3 hours the cbus light will go off on all units and the system stops working overrides still fine. If I reduce the network by it seems any 2 tails it recovers and works fine.


There are 3 clocks enabled - one on the relay is showing as the active one in toolkit. I might try disabling it as a clock so that one of the other ones takes up the roll. However when the network is down the cbus light on all output units including ones with clocks and power supplies is off and when I measured the voltage it was only 9 volts.

I guess next step is to remove the power supplies from the network one by one when its in failure mode to see if I can narrow it down as there will be plenty of power with only 4 power units connected.

It doesn't appear to be a wiring fault in building as I say because I can change the tails that are connected disconnected and get the same behaviour.


Thanks again appreciate your patience and feedback.

 

Something must be presenting a very low impedance when the voltage drops to 9V.
So if this turns out to be an intermittent faulty power supply I am interested how to diagnose it for my own benefit.

I just made a RJ45 CBus cable with a 5W 82 ohm load resistor.
Plugged that into a single dimmer unit with 200mA power supply.
The dimmer has clock enabled so both LEDs were on solid.
The load was enough to drop the voltage across the resistor to 17V and made the CBus unit LED flash as expected.
I didn't measure the open circuit voltage but according to Toolkit my network runs around 30V normally.
I think that might be worth trying to load up all your power supply units individually and see if you can isolate a problem.

 

Brilliant idea, hope to get back to the site this weekend and will try that. As it is have left them working by removing sensors so they can control with switches and seems ok so far

 

Quick question which light flashes the one labelled unit or the one labelled cbus? I presume the latter?

 

The CBus LED.
Below 20V it flashes
If one of the units has a faulty power supply I imagine it wii show up at full load quite quickly just from the voltage.

Don?t burn fingers resistor gets hot.
Use electrician.

 

well spent some time at it yesterday evening and one big surprise I cant believe I hadn't noticed the last day is that the wiring was done wrong so instead of putting + on blue and orange it was on blue and blue white while - was on orange and orange white! It was fixed of course coming off the cbus units. I don't think that was the problem but I have started changing over the switch anyway. Of course I couldn't get it to fail while I was there last night so I added the hardware burden anyway and well see how it goes. I didn't try the resistor test as I didn't have a 5w to hand I might just parallel up a bunch of 1k resistors 0.5w

 

That's a shame
I would have liked to see that load resistor work.

Even the crossed wiring, burden none of that is going to pull 5 x 200mA power supplies down to 9V with out a serious fault in the hardware or wiring.

 

I still intend to try it also I read the front of the units only 3 supplies. The part number in toolkit was wrong or doesn't indicate the p for non power units so power is right on the edge but is staying up in the high 20's but might explain why if one unit is failing it's dropping right down

 

Yeah I was pretty sure Toolkit can't tell.
And that changes things a bit.

 

so cbus thinks we have 5 but we only have 3 and 602 ma is requirement so we are right on the margin.

 

so as expected it just failed again.

I had them disconnect the switches and ran a scan and noticed one of the 3 relays which is also power supply is slightly lower than the other 2 - all three are side by side and daisy-chained together. Could this be a tell tale sign.

Will try the relay load test this week. Also the 2 dimmers come after the relays in the chain and they are at 33.3v?

 

I don’t think you can trust the voltage readings to be that accurate.

When it is all connected and working what voltages are showing?
I’m going to test max voltage at 200mA here, maybe 150 ohms.
I now think the 82 ohm load just proved the power supply limits the current to 200mA.
Will let you know.
10W resistors would be better.

edit with 156 ohm resistive load the voltage was about 29V ie 190mA

 

This is a bit of a guess.
Going back to what Nick said about multiple power supplies missing being likely.
Since you only have 3.
If 2 went out and you saw 9V on the CBus.
Then the impedance at 200mA would be 45 ohms.
45 ohms with 3 power supplies and 600mA total should show about 27V.
Which is about what I would expect.

I doubt 2 power supplies have failed and would be getting someone to take a close look at the 240V supply to the output units with power supplies.
And maybe grab a din rail power supply.
For my jobs I like to see a bit more available than the minimum.
Since there is 7 CBus cables going out of the board couldn't hurt to take a close look at where they all join too if there is any chance you could drop 2 units that way.

 

I've 3 units dropped at the minute when it failed.
Voltage was about 26.5

 

So 26.5V when 3 units lost their CBus LED?
Or did it drop to 9V.
If it was low CBus voltage on the whole network every unit's CBus LED would be out.
Does that point you to maybe a break in the pink cabling?

 

Hi towbar
I was wondering how you got on?
I looked back to your original power calculation.
You are over the power supply limit so adding a power supply would be a good place to start.