C-bus efficiency concerns

Hi I have been doing a bit of research for my new place where I intend to use C-bus extensively. I have a test rig with some gear I scored from the C-bus Basic course dlt, neo, L5504D2U connected to LED and CFL dimmable loads that I have been testing.
to test power consumption I have an Arlec energy cost meter on the power input to the dimmer, the dimmer is supplying power to the cbus network as well.

The total power consumption is 13 watts but the thing that amazed me is if I unplug the loads from the dimmer I loose about 1watt per load even when all the channels are turned off.
so to summarize:
system all lights off is 13 watts or 9 watts with the CFL's and LED downlights unplugged.

Can someone explain this to me, is it because it's trying to sense what sort of load is on each circuit?

Do the fixed leading edge units (L550xD2A) do this as well?

 

There are 2 aspects to the off-state power consumption of dimmer channels:
- The EMC filter circuitry that sits in parallel with the channel
- The power required to operate the dimmer channel itself

Both types of dimmer, the Universal and Leading Edge, have the EMC filter components. This sits in parallel with the solid state switching components of the dimmer channel and is a legal requirement to ensure that when you dim your lights, you still can get TV and radio reception. The power that bleeds through these components is mostly reactive (not much real power) but it may be enough to cause a CFL or an LED load (certainly non-dimmable ones) to glow or flicker. This is why it is important to get LED or CFL's that are designed for dimming - they handle this bleed current elegantly.

The Universal dimmer channels take their power from the load they are connected to. The channel needs at least some power, regardless of whether the channel is on or off, so that they can be started up. That also means that if a channel is not wired up, you're not wasting any power keeping it running. This also enables the channels on the Universal Dimmer to be wired to different phases, if necessary. The Leading Edge dimmers do not work this way. They have a separate power connection (top right of the unit when mounted normally) and this provides power to the dimmer channels, meaning that all dimmer channels are permanently powered, even when they are not used. The advantage however is that there is a lower leakage current flowing through the load, as the separate power connection is powering the dimmer channels, which can reduce issues with devices that don't handle leakage current well.

The reason you do not see any of these issues with regular wiring with dimmers is that when the load is off the circuit is open, by the mechanical switch.

If you are contemplating using any of the energy efficient lighting types, such as CFL or LED, then I'd recommend you stick with the Universal dimmer. Whilst the leading edge dimmer does work with a reasonable amount of these load types using a leading edge dimmer with an electronic-type load does typically place more stress on the load, shortening it's life.

When considering power consumption, don't forget that each of your devices connected to the bus is using power too (provided by the integrated power supply in the dimmer). If your C-Bus voltage is 30V then the DLT and Neo are using 0.66W each.

 

Thanks for that comprehensive reply Newman,
My concern is that I have planned for 20 dimmer channels ironically for efficiency reasons (daylight harvesting and ability to run lights at less than maximum), I had toyed with the idea of using a relay in line on the same group address but the additional cost and the draw of the additional unit works out about the same, makes more sense to buy an adittional solar pannel

One last thing, last night I noticed a glow coming from the test rig, The Brightgreen D900 is slightly lit when the channel is off, so I understand now from your reply that this is an inherent problem with the universal dimmer, I'm wondering if by having 2 or more loads on each channel will fix the problem?

 

Yes, the Brightgreen D900 does not have any in-built ability to handle the leakage current coming from dimmers, so it glows when there's only one on a dimmer channel. Last time I looked I think you need 3x D900's on a C-Bus Universal dimmer channel to guarantee that they don't glow when off.

 

Ahh Geesh! I thought I had found a solution in the bright green D900, I'm happy to use a better unit I just cant find one

I'd love to hear any suggestions but I have started a new thread as this has gone a bit off topic from where I started, the new discussion is here: http://www.cbusforums.com/forums/showthread.php?p=38719#post38719

 

Preventing power bleed

Just a thought on efficiency and economy.

I measured the current used by the dimming control section of an 8 channel, leading edge dimmer and it consumes around 30 watts (0.125A @ 240V), while idling. This equates to around $73 p.a. per dimmer, at $0.28/kWh.

In a residential dwelling there are typically no lights used for 18 hours of the day. Rather than use a relay coupled with every dimming channel, why not route the active feed to the dimming section through a relay channel and use logic to make the relay switch on whenever any channel of the dimmer is in use?

 

I used an ammeter inline to determine the current draw as I felt a current clamp wasn't accurate enough. Remember that some of that 30W is being dissipated into the load on every connected channel, not just the dimming circuitry, so the lights are never quite "off".

 

Sorry Nick, I didn't realise who I was responding to. It was just a multimeter, my watt meter is only rated for 60V.

 

From my time in Tech support I remember measuring the old c-bus training boards (which contained an 8ch dimmer, 12 channel relay both with onboard power a PCI and few input units) with the Clipsal EZAudit power meter. This training board consumed about 8 watts. The dimmer itself disconnected from C-Bus was less than 4 watts.
Colin