CBus power usage?

(EDIT: Attention moderator, please move this post - I accidentally posted to the wrong forum)

Hi all,

I've recently been making a bit more of an effort to reduce my energy bills, and as a result have been making some enquiries about installing solar panels. One of the companies I spoke to suggested that just having the Cbus equipment draws a huge amount of power, so I'd like to get a feel from Those In The Know..

I realise that since I have dimmers just about everywhere that the actual lighting using incandescent and halogen is more expensive that it could be with LED or CFL, but that's a different, much discussed topic. What I'm talking about here is just the power consumption of the keypads and the DIN mount kit.

It's been a while since I've fired toolkit up, and forgot to check it again before heading out this morning, but from memory my system draws about 1200mA according to the calculation in Toolkit. Is this 1200mA @240V, or at the Cbus line voltage (~27v).

If its at 240V, that's power consumption of over 250W, and closing on 7kWh/day. Where as if its at the line voltage, that's only around 30W and under 1kWh per day.

My system consists of:
20 x series 2000 keypads
8 x PIR sensors
3 x L5508 dimmers
2 x L5512 relays (incl PS, I think)
1 x CNI
1 x PAC
1 x PCI
1 x Power supply
1 x Wireless gateway

 

I don't think it matters too much really.

Hmmm Define huge...
Actually, probably worth getting some perspective here

I too was interested in working out how much power my C-Bus system is using. On the surface, it seemed a little bit (definitely not huge as was suggested to you). A good rule of thumb is to take the c-bus current of each unit, total it up and multiply by 0.035 to give the power in watts.

My network uses 1125mA x 0.035 = 39.37W

Now, here's the perspective.

My alarm panel uses 13W
My ADSL modem router/access point etc uses 11W
My Foxtel box uses 18W (on or off!)
Each PC uses 4-5W ... in the 'off' state (I have 4x)
PC speakers (standby) 7W
Irrigation transformer (3x) @ 5.8W each in standby = 17.4W

This is stuff that's on all of the time and mostly cannot be switched off

Total = 82.4W .. Most of this is standby power that cannot be saved as i can't switch the devices completely off economically.

Compare this with the 40 odd watts for my C-Bus system (I have about 60 units on the network) and this will give some perspective.

There is about another 100W of similar bits of power use in my home.

If you use the calculation I suggested above, this gives you...

1200mA x 0.035 = 42W or 1000W/h per day.. about 25c (similar to flag-fall on a mobile phone call)




I use C-Bus to save me power

I use C-Bus to control my pool pump. The temperature of the pool determines how long the pump (chlorinator) runs. I won't go into the detail but the calculations include the amount of time to generate 0.0089mL/litre of chlorine at a given temperature to generate the ppm of chlorine etc.. etc

It saves me about 1280 hours per year of pump run time or 1,840kWh which equates to $460 (based on 25c per kw/h)

I also use C-Bus to regulate on-time of floor heating and a/c in the morning based on outside temp. and room temperatures. Again, much more in the way of savings than my C-Bus could ever hope to use.

Even if it didn't save me money, I would still have it as I like the convenience of a control system. It's still only about $22 per quarter which I'm happy to spend.




If you are using solar panels and are feeding back to the grid, i imagine you want to minimise the amount of power you are using in your home, when the sun is shining. There is no reason you can't use C-Bus to feedback your consumption and control loads that may impact on your ability to maximise your outgoing power. You can even take information from many inverters and feed into C-Bus to show what you are producing.

 

Thanks for your feedback. Your calcs are very much in line with mine.

The guy I spoke to said that he has seen Cbus using 10kWh per day!! That just didn't sound right. I can only assume that the person doing the measuring *thought* he was measuring only the Cbus equipment, but was also measuring the consumption from the lights connected to it.

I pulled out my plug in power meter last night and discovered a few gotchas.
1. My laser printer, even when in "power save" mode still uses 40W.
2. My home theatre amp had multi-room enabled even though I'm not using it, which meant that it was still using 50W when in standby. Turning off multi-room drops standby usage to a negligible amount.
3. My AV distribution had one unconnected zone still turned on, which meant the amp stayed on 24x7 at 22W usage
4. My server LCD doesn't actually standby properly, and uses 22W continuously.

So there's 2.4kWh per day saved right there.

Interested to know about any inverters that I can get this information out of!

 

To add a little to the above comments, there's really 2 areas you need to consider when determining the power consumption of your C-Bus system:
1. The power used from the bus.
2. The power used to externally power devices.

1. Calculating the power used by the devices connected to the C-Bus network is easy, as it's just network voltage x network current. Toolkit will give you the current consumption for a network and you can get the network voltage from most unit UI's. If your network voltage is 30V and you're drawing 1000mA then the power being used by the bus network is 30V x 1000mA = 30,000mW, or in other words 30W.

2. Some devices have external power connections, such as dimmers and relays, and the power these devices use is in addition to the power used by the bus. Things get a little bit grey here as some DIN units also power the bus but a good rule of thumb is about 5W for each DIN dimmer or relay. Things like a Colour C-Touch or an MRA also have external power connections.

One final caution is that connecting a current transformer, e.g. a clamp-on meter, to your C-Bus network supply cable will not give you an accurate figure of it's power consumption. You really need to use a proper power meter if you are going to make a measurement of the consumption of the system. This is because the dimmer channels have EMC bypass capacitors sitting across them which result in a reactive current flowing that adds almost nothing to the real power consumed. These EMC bypass capacitors increase the current reading from a CT without actually having much impact on the real power. The switch-mode power supplies used in C-Bus products, combined with the EMC bypass capacitors, results in the DIN units having quite a low power factor, which has a similar effect, so a real power meter is the only way to be sure.

 

Good point about the AC. My AC system draws a constant 55W even when it's off. Occasionally it kicks up to over 100W as it decides to heat the unit internals on chilly nights.

 

I have a Xantrex unit with CQC working fine. Protocol is in the manual.

I also have a Fronius Inverted working with CQC. It requires an add-on board. Protocol is published on their web site

I have a request to look at a Sunnyboy inverter. I believe they have a serial port, but I have not found the protocol yet (have not looked hard)

Power One inverters have a serial poirt (RS485 from memory), but the company wont release the protocol for some stupid reason. They do have software and it will have to be reversed engineered to use with third party systems.

Thats about the extent of my knowledge with inverters and their comms

Mick

 

I've since been speaking to another guy at the same company who seems to be a lot more knowledgeable about solar. He's quoted me a SMA Sunnyboy, and has indicated that it comes with a bluetooth interface and PC software. The website also says you can wire it rs485. He's getting me a technical contact at SMA so hopefully I'll be able to make an educated decision on whether I can make it play nice with CQC.

He can and has sold Xantrex before, but recommends SMA over Xantrex.

 

I've just received two updated quotes for a 3kW system; one with a SMA 3000HR 3kW inverter, and one with a Xantrex GT 5kW inverter. Both quotes are identical.

The Xantrex (I keep going to type Xantech ) has built-in rs232 with known protocol (znelbok, I'll need you to send me your CQC driver!).

The SMA has built-in bluetooth (which I assume is access as a virtual com port on the PC), but the protocol is not released. Alternatively, I can fork out an extra $300 for an RS485 interface (plus an rs485 to rs232 converter) and use the published protocol for that interface (apparently the two protocols are different)

Mick, what data do you get from the Xantrex?

(Apologies for going off topic so quickly!)


What information

 

Hi,

I just recently went thru the process of measuring how much power it uses.

I currently have the following

1 x Minder
2 x Power supplies
1 x PAC
1 x CNI
2 x Relay 5504RDP 4 channel
3 x Dimmer 5104D750 4 channel
1 x Dimmer 5508D1A 8 channel
1 x Dimmer 5504D2A 4 channel
1 x Relay 5504RVF 4 channel
3 x 1 button wall switch
7 x 2 button wall switch
12 x 4 button wall switch
1 x Wireless gateway

I measured the following
Minder for 1809 minutes, average running watts 8.18, total cost per year $13.50
I monitored 1 of the power supplies for 1238 minutes, average running watts 11.57, total cost per year $19.09

Your electricity price may vary from mine.

I ued one of those things from Jaycar where you plug it into the wall and then plug the unit you want to measure into that.

Marty

 

Conformist,

I am interested in your method of calculating how long to run your pool pump depending on the temperature and chlorine generation. Is it possible for you to contact me by private message with details.

Thanks

Chris

 

There's probably a few here that are interested - I know I am.

Mick

 

AC standby power

Gentlemen, the standby power consumption from your split system air conditioners is usually the crank case heater, IME this is ~50W. This keeps the oil warm and viscous so the compressor can start as designed. If you don't plan to use your AC over a period you can turn your AC off at the circuit breaker, however you need to turn it on for 4-6hours Before you use it again next season/time. Good Energy Saving Measure for cooling only units over winter.

Froop, Both SMA & Xantrex are quality units, Your decision will be based on the features you want. Xantrex are a Schneider product which may be why some of the senior members have them... ;-)

Conformist, I too am interested in your pool control.