Power usage?

Just wondering what the average power consumption is for c-bus. I've read that each node will draw around 180mA, and should be run at 36V giving 6 watts per node. Is this the case, or do they actually draw less than that?

Also how much power do the components you are likely to use in the switch board/panel draw?

 

Where did you read that? It's not even close. The amount of current drawn by a unit will vary from type to type. Most units draw from 18 to 32mA. A good rule of thumb is 0.035W per mA.

I have about 60 units on my network and my total power is about 40W. This is bugger all compared with things like standby on a PC (about 4.5W), alarm panel (about 8W), DSL modem/router a whopping 11W.

 

Not sure where I got that figure from - I thought I read it in the specs somewhere, but I can't find it after re-reading. Presumably a brain fart.

Good to know that the power requirements are low though, thanks!

 

After installing my CBUS Current Measurement on the cbus circuit. My cbus install draws 1.67A or 409w with everyting off. I have 106 units and 1950ma (tool kit says my install requires 1925ma) of cbus power supplies.

cbus voltage is 28.5v * 1.95A = 55w

the Dimmer losses can not be the rest can they ?? All dimmers are connected to IRON core transformers.

I have 8 x 8 channel dimmers.

I think I need to get the current clamp out and see where is it going as turning 1 dimmer off is enough to bring down the cbus network and stop the cbus current measurement from working !

Charles

 

Getting a current clamp out might not help you that much.

The C-Bus Current Measurement Unit is just that - it measure current, not power. It cannot know anything about power factor or direction of current flow.

The power factor of the C-Bus Power supplies is not very high. The EMC bypass capacitors in the dimmer channels also contribute to the low power factor.

If you want evidence of this, try monitoring the power of the system (with everything off) and then turn on something that is highly inductive, such as an exhaust fan. In my house, turning on my toilet exhaust fan makes the power for my whole house go up, but the power for the C-Bus network go down by a few watts. Another way of doing this is to turn on a known unity power factor load, such as a 100W incandescent bulb, when all other loads are off, and when all other loads are on. If the power factor was near 1, you would see the power consumption increase by almost exactly 100W when you turn that load on in both cases. If the power factor is low when everything is off, then the increase in power will be less than 100W.

So, the moral of the story is that a simple current clamp is not the most accurate way to measure power consumption when the power factor is low, like it is on a C-Bus circuit. Your C-Bus network, large though it may be, isn't really costing you 409W worth of power.