Power Supply Issues

Have been asked to look at some issues another electrician is having on a site
Have identified power as the major issue, although technically the system appears to be a good balance of powered & un-powered units
Voltages at units in the vicinity of the DB are good (>27vDC)
However as I get to the furthest devices, the voltages drops off (<23vDC)
To solve the issues short term, I have removed blind & fan control relays of the network as these are not being used right now, this has brought the above back up to around 25-26vDC
I suspect the issue may just be losses through the connections as he has looped around every switch & sensor. I cannot find any other issues, his work is excellent & neat & he is well within the capacity range (reckons he used just under 2 boxes of cable, & has only 60 devices on the network)
My question is, is it ok to simply add 2 power supplies (there's 4 levels to this house) remotely to raise the voltage levels. I can easily access the bus cable & connect the power supplies. In theory I know it should be fine, but is it acceptable practice?
Cheers

 

CBus manual says 15V min, recommended 20V
What is the problem which leads you to think 23V is not enough?

If you want to install more power supplies then just consider 2000mA max.
Check the actual units to make sure they have power supplies and don't just rely on what Toolkit says in the database.

Distributing the power supply units will obviously help with voltage drop in large premises.

 

Thank you for your reply
The 1st thing I noticed on site was the C-Bus lights flashing which indicates low voltage. When I removed the blind & fan control units,the network stablised & I was able to scan
I tested voltage physically from + & - to earth (balanced)on all powered output units & also at random inputs around the place
I have always tried to maintain network voltage at a min of 26-27v to ensure stability
This is a large house, but the way he has cabled it while extremely neat may contribute to Vd, as he has 1 cable looping around all the inputs over 4 floors

 

If the install was done within CBus specs then it is hard to see how there could be any problems.
Did you check the actual units to see if they have CBus power supplies?
Burden requirements for the network?

 

not the system voltage

What was the issue he could not fix, that he called you in for?

From what you describe it sounds more like a Burden issue.
Having all the power supplies in one DB is not ideal but is common practice.
I don't have a problem with remote PS mounting, but also doubt this is your issue.
A site I looked at this week showed 17V on the touch screen that was about furthermost from the power supplies, yet the system is working fine. (The issue I was there turned out to be DALi ballasts). This had 10 powered relays and about 80 devices.

 

The system would not respond to any inputs. Not a burden issue as unit 1 is correctly set and i use a hard burden on my pc interface.
Strange how removing some units of ths network stabilised all and let me scan with no issues.
Just checked with the owner and all is working fine since. All powered units are providing power.
I would normally cable each floor as a separate bus cable back to the DB. Easy to narrow down faults. In this case its 1 bus cable looping around 60 units

 

For 60 CBus units you should try no burden.

http://www2.clipsal.com/cis/techtrain/__data/page/1940/Network_burden.PDF

 

A drop of 6 volts over potentially 600 metres of cable and 50 plus devices seems very normal. Anything over 20 volts should give very reliable communication.
You could have removed the fault by disconnecting those units, either its termination or device itself.

 

Result

Adding 2 power supplies has stabilised the system.
Min voltage is 26 volts.

 

Just remember 2000mA max.
How many mA total on the network now?
Did you distribute them a bit better?
I'm surprised if that was the only problem because 23V is within specs.

 

I am just under the 2000mA
The 2 additional power supplies are located 1 on each level , the original power supplies are located in the MDB in the basement
I was always been under the impression that we should be maintaining voltages around 25v, not sure where I got that from but I've worked with it for 15years !!

 

I have always been under the same impression Ray, and often if the voltage is getting around 22v mark I can start having issues. It wouldn't surprise me that some older units need a bit more voltage to keep running propperly.

 

Having a similar power supply problem on a network at a relatives house. It has being stable for 5 years but recently started becoming unstable occasionally now daily. CBUS light goes out and switch lights just flash.
I took a look this evening while failing and had only 9v on the bus between + and -. Removed about 6 devices and it recovered. Tried to narrow it down but adding any device brought the network down. Reconnected that chain and disconnected a different chain and again it worked fine so problem seems to be with one of the power supplies shorting the bus when the load exceeds a certain level. Any ideas how I find out which one as all 5 outputs have inbuilt power supplies? Its using a software burden on the network no hardware one present. Device list attached

EDIT: The 5508rvf are really L5508D1A dimmers - for some reason they were not in the list on calculator

 

Voltage list when stable with 8 units removed

 

It should be written on the front of the output units.
Otherwise you need to read the part number from the unit.

That might not be the problem.
Any other work going on around the home?
Are all the units with power supplies powered up?

Don't forget you can use the LED indicators on the CBus units for some diagnostics.

 

Thanks Daryl

They added Solar PV but that was a few years ago but I see in another thread that caused a problem with the units cycling however that doesn't happen in this case. The network just goes down, lights remain in their same state and you operate correctly through the override buttons.

All power supply units are powered on all the time. Interestingly cycling the mains on the cbus side of the output/ps units does not resolve the issue I have to reduce the number of items on the network.

I am going to source a hardware burden just in case.

Can you point me to some details on the led diagnostics please?

 

You can download the CBus unit installation instructions from CIS website.
Looking at the CBus unit LED indicators is always a good place to start when there is some problem.
http://www2.clipsal.com/cis/technical/product_groups/cbus/output_units

Sometimes a breaker supplying power to one of the CBus output units with power supply can get overlooked.
It happens, especially if there is multiple distribution boards.
CBus unit LED indicators will show that sort of thing right away and more.
Just mentioned recent work in case someone damaged some cabling.

 

All output units are on same breaker and unit led stays on solid but cbus light goes out.

 

Chart from "CBus basic training manual volume 2 v2".
It has lots of tips for fault finding.
Google it and download.

 

just spotted this which could be a problem?

"Important Note: Always disable all 5100PC Interface Network Burdens before installing C-Bus DIN range products, which include a power supply (non ?P? suffix versions). If a burden is required, use the built-in burden on the DIN Rail unit only"

As this network is configured with the pc interface at address 1 with burden on.