Basic dimming question

Hi all.

I'm new here, this is my first post, please be gentle.

I just bought a house which needs a lot of work. I have been reading a lot about home automation and would like to try and install a basic C-Bus setup, just dimming lights for now.

I can't seem to find the information I need. I have seen 8 channel dimmers for sale, but rated at only 1A per channel. Can I use this to control lights in 8 rooms, using low power LED lights in each room, with each room as a separate channel?

1A seems really low. I have been reading about trailing edge dimming, but it doesn't make much sense to me. How could I set this up, and what would I need?

Any help would be greatly appreciated!

 

Hi Tension,

Ill answer your questions as simply as I can, and I'm sure others will chip in as well.

Retrofitting C-Bus to an existing house is a lot more work, but very doable. I have done a few of my own over the years, so don't be put off by the extra work.

Lots of information is here of course, but also on the CIS website http://www2.clipsal.com/cis/technical/

A 1A dimmer is 1A per channel which at 240V is approx. 240W. Therefore with an 8 channel dimmer you can individually switch 8 different loads (light(s)) up to 240W each.

As for universal dimmers, these are the (relatively) new kid on the block. To give you an over simplified explanation;
In the old days (before LED lights and electronic transformers) almost all standard lighting could be dimmed by leading edge dimmers. These are what the standard C-Bus dimmers are. however LED's and electronic transformers tend to work better on trailing edge dimmers. So Clipsal brought out a universal dimmer that does both leading and trailing edge, and switches between them automatically. So to be the most universal, choosing universal dimmers is the safest way forward (but at an extra cost of course).

The last thing you should know is what constitutes a C-Bus minimum system.
You will need at least one of the following units;

1. Switch
2. Relay or Dimmer
3. Power Supply (may be separate or included in the relay/dimmer)
4. PC interface for programming (Serial, USB or Ethernet)

I have oversimplified some aspects of what I have said, but this should get you a little further on.

Cheers

Rohan

 

Dont be put off by the low amperage you read for each channel.

If you find you need more than 1A for a set of lights (say four lights for a total of 1.2A), you can slit them up across two channels and then through the configuration of the dimmer, have two channels (or more) come on at the same time acting as if they were one channel.

But as Rohan indicated, go the universal dimmer over the leading edge dimmer. Especially if you are looking at LED's.

The best way to learn is to read, read and play. If you are starting off small you can put it together on the bench and try it all out before you commit it to the house. You wont be disappointed though (apart from price) - its the bees knees.

Mick

 

Thanks for the replies guys! Really appreciate it!!

I was only thinking of LEDs because I thought the 1A rating meant I couldn't use normal cheap halogens. So you think I could run 4 60w halogens per channel then? If so, that is the route I would like to go down.

Also, does this mean I can use a leading edge dimming unit? Preferably one with a power supply built in.

Could you maybe post links to what I would need to buy?
I think one 8 channel dimmer box should be fine if I can run 4x 60w halogens per channel..

Thanks in advance.

 

It depends on what you call "normal halogens"

A simplefied rule of thumb is;

Leading edge is suitable for
240v Incandescent globes
240v halogens
12v halogens if driven by an iron core transformer.
12v LED if driven by an iron core transformer

Trailing edge is suitable for
240v LED assuming they are dimmer capable
12v halogens if driven by an electronic transformer
12v LED if driven by an electronic transformer.

Some electronic transformers CLAIM to work with both LE and TE dimmers.

These are only rules of thumb, and especially when it comes to LED's results will vary considerably with different manufacturers units.

Be very wary of cheap Chinese units, even if they claim to be dimmable as often they are just rubbish and won't dim properly, or even at all.

So my advice is to get a sample of the combination you want to use, set it up and see how it performs, before buying a house full.

Cheers

Rohan

 

Leading Edge can also do 12v halogens if driven by an electronic transformer - you just need to select the correct transformer so as not to exceed the capacitance limits of the dimmer. There is a data sheet outlining the transformers that can be used, their specs and how many you can use per channel on the different relays

As for the number (on watts only), A 1A channel can handle 240W (@240V), so in theory, 4 x 60W = 240W and should be OK. I would run 50W though just to leave a little wiggle room. This is of course all on electronic transformers that are suitable as well (I have 4 halogens using electronic transformers on a 1A channel currently)

 

If you are new to this remember to put a 1amp mcb on the output of each channel. If you need any help email me @ [email protected]

 

Thanks for the replys guys.

I started this thread a year and a half ago but still haven't got my head round exactly what I need. Been doing some essential work on the house and C-bus is next on the list. I will be completely rewiring the lights from scratch (thankfully its a bungalow!).

I have decided on universal dimmers and LED lights (cheaper running costs I think). How many LED lights can I use per channel then?

Also, am I right in thinking that I can run LEDs straight from a universal dimmer box without any transformers?

Thanks.

 

This is not a C-Bus requirement, I believe it is a UK wiring rules requirement

 

Hey,

Just to answer a couple of your questions, for the number of LEDs per channel, it really does depend on the LEDs you use. But from most you can happily do 6-8 per channel.

The C-Bus dimmers aren't LED drivers, so you will most definitely still need a transformer for them.

 

As for running LED's directly from the dimmer - that depends on the LED unit.

LEDs are ELV, but the fitting may have a driver build in.

I just removed some MR16 halogens and replaced then with GU10 LED's. The MR1's had a transformer but the GU10 LED's are 240V so the transformer comes out.

Basically, it all depends on what you are putting in, but the dimmer works on 240VAC only (230VAC if you want to be technically correct to the standards)