Regarding the installation and electrical connection of cbus dimmer units, do you wire a circuit breaker between the cbus unit and the lights to be controled, i.e. one circuit breaker per cbus channel. like this mains power -------- CBUS dimer unit------Circuit breaker------Lights to protect the cbus gear or what is the standard practice of doing this ?
Good practice is a circuit breaker (matching the dimmer channel Amps) per channel. The disadvantages are : You will need a bigger DB Box and you will end up with a lot of circuit breakers
Good practice would be. RCDMCB - Dimmer - Light to be controlled. This will provide sufficient protection, for cost of install. Cheers
the wiring rules in australia don't require a mcb for each circuit you don't have one for each switched circuit for normal lights why should it be different for c-bus my understanding is that i can connect the c-bus dimmer to a standard lighting circuit and use the mcb at the switch board as the protection
You are quite correct, if I understand your term "circuit" as switched cbus channel. Circuit breaker - cbus unit - load on an existing installation in Australia is fine. "Best practice" however would include the use of an RCDMCB rather than just an MCB. The rules in Australia now require the use of an RCD on all lighting circuits. My original point was that "greater" protection is offered to the cbus dimmer with the use of an RCD. Nothing more, nothing less. The use of additional circuit protection on the load side of the dimmer is expensive, unnecessary and would offer questionable "additional" protection. Hope that makes some sense. cheers
The way that i set out all of my boards is RCDMCB | | | | / \ / \ MCB (Control Power) ----- Cbus Module ----- MCB (Load Power on input) | | | | | | MCB (Control Power) ----- Cbus Module ----- MCB (Load Power on input) | | | | | | MCB (Control Power) ----- Cbus Module ----- MCB (Load Power on input)For each board i find the advantage being that ALL lighting circuits are being feed from an RCDMCB, but also i have individual control over each module. The load MCB is on the input side of the module (8A for 5508D1A) etc The Control MCB is usually about 1A (smallest i could find without having to go to a din mount terminal fuse) If all of the 8 channels combined exceed 8A then (in theory) the load MCB should trip (in theory) Second advantage is that if i do drop a module (and i did recently) i can isolate the individual module by sropping BOTH MCB's, therfore not losing my entire board (and half the C-bus network / house) Thats my thoughts *** I am not an Electrician, this is just my set up, but i find it works well ***
I just use an MCB/RCD for each module. Gives the same effect as your diagram. I am using a three phase setup though with the load spread across each phase, so I need a minimum of three MCB/RCD's. Unfortunately the setup in the shed has the control for both the dimmer and relay on the same phase (the relay is switching all three phases) and last week we had a brown-out on that phase for a couple of hours, preventing the c-bus control side from starting up. TV still worked though on that same phase, so I had a little light at least. Suffice it to say that control will also be spread across the three phases from now on. Mick
Load side circuit protection In regards to load side cct protection, as many have rightfully pointed out, it is not an australian standard. However, there is ongoing debate as to whether it should be fitted to protect the dimmer channel from "frying" if the lamp filament fails and momentarily shorts out within the lamp. In my experience, this very rarely occurs, and is generally only possible in lamps installed inverted (lamp holder on bottom) Due to additional cost in materials and labour to wire load side breakers, i personally dont believe it is all that necessary, but thats my opinion.
If you read the installation manual that comes with the unit, you will find that at a minimum, an 8Amp circuit breaker must be installed on the supply to the dimmer (4x2Amp and 8x1Amp). Then to meet IEC60669-2-1 safety requirements an additional breaker on each output can be installed. As I know nothing about this standard I can only guess that it isn't compulsary in Australia. The circuit breaker protecting the supply of the unit is specified as standard wiring practice and should be observed to protect EACH UNIT. It is something that lots of people are not doing and could void a waranty if something happened (to the discresion of CIS of course!).