Will C-Bus work with existing Fig8 cabling?

Hello all.

I recently had an enquiry from a client who's existing system was wired in Fig8 cable and is now on the verge of complete failure. It's not a C-Bus system. I'd like to recommend a C-Bus replacement option, if we can utilize existing infrastructure and at least save this poor sod the cost of wiring over and beyond the cost of hardware and programming.

Outwardly, one would assume that 2 cores should be enough. However, given the pairs in Cat5 UTP are twisted, would using the Fig8 open up communications to potential noise/interference issues, seeing as the twists aren't there to cancel out any induced noise?

Does anyone have any experience using this type cabling backbone with C-Bus?

 

You should be fine.

The C-Bus protocol is pretty robust and if electrical noise gets into the system the transmitting devices will automatically retry. I know of at least one installation where the wrong wires of cat5 cable were paralleled (resulting in no twist), and to top that off, the C-Bus the cables were run in bundles including mains wiring - against recommended practice, but despite this, the installation worked just fine.

There are a few other subtle differences between wiring but at the frequencies that C-Bus uses for communication, they would not be significant. There is a slight chance that other equipment such as sensitive audio amplifiers, placed near to the wiring could pick up noise more readily from the C-Bus wiring in figure-8 cable, but this can probably be worked around by shifting the relative positions of the equipment and the wires if it does become a problem.

If the other aspects of the installation meet the basic requirements (no runs over 1000m, wire cross-section no less than 2 x 0.5mm squared copper, Both conductors floating, etc.), the installation should be just fine.

 

Thanks Don.

I thought as much, given that I've seen early C-Bus systems run on telephone pairs and work just fine..!!

Appreciate the re-assurance.

 

grasshopper

Unlike a lot of figure 8 cables the pink CBus cable has a mains rated jacket.

I can't think of any good reason to supply a customer with an install which is not done to the manufacturers specifications.

At the very least ring CIS tech support and get it in writing because they are the ones you will be dealing with if you run into any problems.

 

Other than the installation exists with figure 8 already??

 

Ok. So let's assume we're all good with the existing Fig8 infrastructure.
What would the forum's view be of placing 5101R's in ceiling spaces, adjacent
to the lighting group it's meant to control?
It appears this particular installation has been wired with remote relays in the ceiling space, from which the TPS then goes to each fitting in the group.
Can these units alone be placed there or do they need an additional enclosure?
Thanking you all in advance.

 

Here is a picture.
There is always the 5101RC to consider.

 

Thanks Daryl.
I seem to recall that the load side if the 5101R also comes with a cover. If that's the case, do u think its safe to put these units in the ceiling space?

 

I'm not familiar with it only the 5101RVF which is often used in a ceiling space.
I think the 5101R is meant to go in a fluorescent light fitting.
It also has a 0-10V output for dimming fluros.
Looking at the picture I cant imagine how it could be suitable for terminating a few twin and earths without an enclosure.

My thoughts are that you should consider replacing the figure 8 bus wiring if at all possible and look at whether it's worthwhile moving the relays to a board.

It's not your money you are spending but you are the one who will wear any problems that might arise if you choose to install contrary to the manufacturers specifications.
Especially with regard to bringing figure 8 cable into a switchboard.

CBus is a solid product but the whole job is only as reliable as the installation.

 

Thanks again Daryl.

I know your'e trying to be helpful but what you're suggesting will potentially add between $10-20K, if not more, to the job cost.

I've since spoken with C-Bus Tech support and they see no major issue with placing these units in ceiling spaces, provided the temperatures remain within product limits (which in the 5101R's or RC's case is around 50deg C). I can't imagine temperatures in these locations getting even close to temperatures in fittings, given that all lamps in this place will ultimately go LED.

Especially with regard to bringing figure 8 cable into a switchboard.
Not sure what's meant by this as there'll be no central switchboard location if components are wired remotely, in a distributed manner?

It's not your money you are spending but you are the one who will wear any problems that might arise if you choose to install contrary to the manufacturers specifications.
Totally agree, which is why I've also stipulated to the client related caveats pertaining to the integrity of the existing infrastructure.

If money wasn't an issue (i.e. in a perfect world) I would most certainly re-wire. However, the sad reality of this situation is simply that re-wiring is just not an option due to the exorbitant costs.

 

Yeah the 5101 wont be a problem in the ceiling within its temperature rating.

Is there any relays or figure 8 going in the switchboards?
My main concern was that you were going to go against the manufactures wiring specification inside the board.
Also the age and condition of the figure 8 given that the customer is having problems.
If Clipsal is willing to back the product on figure 8 cable there is not much for me to add.

If you don't mind, what was the original system?

 

My guess is hpm icontrol or oscar..

Out of interest, how large of a system is this going to be and how much do you estimate will be on the fig8?

 

How big a job are you talking that it would cost $10-20k to re-wire? If you use the relays you are talking about you only need to rewire the figure 8. So at that cost it must be a massive install.

 

Hi grasshopper
So all the existing relays are in the ceiling and none in the boards?
That would be a major job to move the relays.

 

doesn't need to be massive to rack up 10-20k. Even a small 2 bedroom house with inaccessible wiring (requiring the plastering to be remove, repaired, and repainted) can easily add up to those amounts.

 

5101R needs additional protection on 240V side

the 5101R was designed to be installed in luminaire bodies, hence the shape. Practicality did not take it there.
It can be a very useful device, however you must install it in something as the 240V terminals are not double insulated and require single insulated cables for termination, it does not have a cover for the mains side. SO it makes it awkward and expensive to install it in an adaptable box of some type.
I mounted one on a back board and screwed a large terminal box cover over it in one instance, not pretty but functional.