Can CBus handle HVAC?

Hi All,

We know it can, but it seems we are facing a market perception here in New Zealand that CBus is traditionally a lighting control system.

It seems that there is not a lot of history on CBus handling HVAC ( heating, ventilation and air conditioning ), other than a hundred or so of our own clients sites.

If anyone has any comments on their own experience of handling HVAC control with CBus equipment, or is aware of case studies where this has been done, we would be greatful for your comments.

Our position is that CBus is quite capable of handling digital and analogue inputs and outputs, that there has always been a heating application reserved within toolkit, and that there are products such as the temperature sensor which have embedded heating control algorithms in them.

Also, with the PAC, touchscreen and schedule plus logic engines, we can write any form of algorithm we wish into a CBus application.

We are confident CBus is up to the job, but it would be nice to be able to point out that we are not the only ones!

Any info appreciated.

Regards

Stephen Laidler
ECOsystems, New Zealand

 

This is a common misunderstanding. Over the last few years, more and more non-lighting C-Bus Applications have been made available, greatly increasing the scope of what is possible using C-Bus.

The recent release of PICED V4 and C-Touch/PAC firmware V3 has made control of devices via the C-Bus HVAC, Security, Telephony and Measurement Applications very easy. This has opened up endless possibilities for the integration of all sorts of systems with C-Bus.

 

C-Bus IS traditionally a lighting control system no doubt about that, however, once people get involved with the technology it doesn't take long nor much imagination to start thinking of all the other things it can control, irrigation, doors - pretty much anything that goes up or down, left or right, on or off.

The main reason that you don't see many instances of C-Bus controlling HVAC (completely) is the old re-inventing the wheel. If you know a bit about HVAC systems you will know that other than a remote on/off and maybe a remote zone selection, using a basic control system arrangement like C-Bus would be a real pain in the ar$e to actually control the various components of a an AC system. There are many AC system arrangements, but taking the most common (especially for domestic) the external fan/compressor unit and the internal fan/coil unit there are several circuits that have to be sequenced properly for the unit to work without self destructing. The big ones are running the compressor without fans and trying to restart the compressor a very short time after previously stopping (high head pressures). Then of course there is the temp sensing, compressor cycling, and PI / PID loop control so you don't get overrun and oscilate between heat and cool cycles etc.

So all of this is taken care of (bullet proof style) in the very inexpensive application specific control modules, temps and keypads that come with the AC units or as standard control packages. So there you have it - why reinvent the wheel - its already there. Not sure there is a way to make a wheel any more round ???

For 80-90% of cases having a remote start/stop from C-Bus to an AC system and maybe remote zone control, you will achieve all the really useful benefits of having some control of an AC system from C-Bus. Tie the on off status to the home / away mode. Dial in to start the system up on the way home. Touch screen or key inputs in individual rooms to open close dampers - thats the practical stuff.

You don't change setpoint like you might dim the lights a few times during an evening so why go to all the trouble to have setpoint everywhere at your fingertips.

If you have the time and the patience go ahead and re-invent the wheel. If you see smoke coming out of the compressor you got the sequence wrong or maybe you got the sequence right but for some reason one of the CBus channels didn't get the message or is faulty but the rest is working - now you have to muck around to get the smoke back into the compressor

It would be very interesting to know why the C-Bus temprature controllers are continually delayed. When they are released I wonder how many they will sell - traditionally sparkies don't do AC and Fridgies don't do C-Bus

 

Hi Lucky 555

I think you may have answered your own question as to why the C-Bus Thermostats are delayed in your points about the complexity.... These devices have to work perfectly and have so many different modes and options. I can say for sure, they are very close and the demand for them is very strong. I agree that (generally), sparkies don't do HVAC and Fridgies don't do C-Bus but..... Systems Integrators need to do everything (or at least work with the various trades and have a good understanding of how they gel together).

The themostats have many residentual and commercial applications and coupled with devices such as the recently released B&W MKII touchscreen, will give the opportunity to have well integrated products at a fraction of the price of current touchscreen-type systems.

Having worked in this industry for over 14 years, the gear coming though is very exciting.

Cheers

 

Hi Conformist,

I just had a scan through the installation instructions for the C-Bus thermostats, I didn't have a headache at the start but I do now. Wow there are lots of options there and the programming looks - well that's where the headache kicked in.

I appreciate what you say in relation to how handy a C-Bus thermostat would be and there are people lining up to get them, however, I remember how handy the telephone interface sounded, and how often the telephone interface capabilities would be mentioned in the automation speel - hell I even referred to it in my original post where I mentioned dialing in to start the AC on the way home.... But (I know you should not start a sentance with But) how many telephone interface units get sold each month ?

I think you will get a handfull of people with the necessary skills (C-Bus and HVAC) who will offer these units to the market. In terms of a mainstream product, not sure. When the units do hit the streets and you identify a few clever integrators who can use them send one over to my place with a field trial unit to put on my ducted system. The AC is the only thing I don't have tied in at my place, I'll be happy to provide feedback

 

Hi again Lucky 555 (and the rest of interested 'C-Bussers')

The thermostats (as I'm sure you have read) are perfect for certain installation types, but not all! I can completely appreciate what you have said with the telephone interfaces, but they only really offer limited functionality and not a lot of bang for your buck... but...... thermostats are a little different. When you use a thermostat with the soon to be revised temperature sensor (actually, you'll be able to use the temperature sensor with a logic engine say in the new B&W MKII touchscreen), you can get some great functionality for a fair price. Of course, not all air conditioners will be compatable but there are (now) a number of systems which have serial control. These can be coupled to a PAC or B&W T/Screen (logic model with RS232) and you have very good control.

Again, thanks for your patience with regard to the thermostats. As Lucky555 has said, they are a powerful little beast and there is a need to get these absolutely right.

Cheers

 

This is the way I believe it is best achieved. Leave the control up to the AC guys and just get C-bus to press the buttons for you.

I personally have an AdvantageAir system which has serial control. I believe that AdvantageAir are developing a C-bus module at the moment - hopefully soon there will be something to talk about.

For those that have a simpler system that they must have integrated, the C-bus thermostat is the solution, but anyone starting from scratch should look at a solution that is talked about above.

Mick

 

Thanks guys

Thanks for your comments, which seem to confirm our own understanding of the current C-Bus and HVAC market, - that yes C-Bus can do it, and in many ways, shapes and forms, but that it goes against the grain to supercede a traditional HVAC PID based controller with C-Bus.

We have found that it is worth re-inventing the wheel. The wheel in this case is the traditional conventional building management system, which is associated with a typical 30% excess energy consumption. The conventional approach has a fundamental flaw which will almost always lead to heating and cooling systems fighting with each other.

We converted one such traditional system to our new approach using the CBus platform, and achieved up to 80% equipment run time reductions, according to our load monitor.

What we have found is that it is very easy to control behaviour with the CBus style of programming. We have renamed scenes to 'events' and can use these as a basis for our new approach of fuzzy logic adaptive thermal comfort control.

We have also blown a lot of traditional HVAC myths out of the water. HVAC control can get very complex, as per our own conventional systems which take into account enthalpy and all manner of quantified conditions. We have shown it does not need to be that complex, and in fact it is more effective the more simple you can make it, simple systems are easy to tune and adjust, meaning that it is far more likely the building occupant can get the system to behave in the desired way, without heating and cooling fighting.

Regards

Steve
ECOsystems NZ

 

Advantage Air

I too spoke with Advantage Air in Brisbane and they referred me to Melbourne. Whilst they were full on with supporting my installation concept, when it came down to the crunch of providing the support and pricing purchases they fell to pieces.

 

Disabling PID during ramp up....

Hi CIS..

I'm reopening this thread, because it is of relevance to me now in using the cbus thermostat to control a domestic hydronic system.

My point one installer ("Cleverhome") in Melb and I are fine tuning our solution for domestic hydronic control.

We have set the toolkit plant to "Basic Hydronic"

My question is: is it posssible to disable the PID control within the cbus thermostat to stop "cycling" during the heating systems recovery from a very low ambient temperature? Yes I know this sot of thing is subject to patents and many a PhD !!

We definitely don't want to fiddle with the PID settings, until we know what we are doing! My problem is the t-stat keeps turning off my heating during this initial ramp up phase...

Also just how accurate is the "PID" of your t-stat? Is it similar to other t-stats that are know to be good controllers of hydronic...or is "copying" the logic in these subject to copyright problems? Would it be for example, possible to have a couple of "choices" based on certain t-stat brands within toolkit?...or is this legally impossible?

 

Thanks. Very well understood!

Thanks Ashleigh.

I have a hydronic system. The boilers heat radiant heat panels. ie case 1.

I takes around 45min-to 1 hr to reach say an ambient of 21 degrees from a cold start of say 17 degrees...

I thoroughly understand why tweeking is a highly sensitive thing to do..that's why i asked before I tweeked !!

It's also why I asked if there were some t-stat "templates" (for want of a better expresssion) that could be copied. I know from speaking to the hydronic installers that certain tstats are "ideal" for a domestic hydronic panel enviroment. Others are useless. For example: if I sent over the Honeywell and L&G t-stats I was using before...could the PID in these be "mirrored"...?
...sort of like what you do with some difficult IR codes???
Once you had these, they could be put into toolkit as "ready made" plants suited for domestic hydronic panels ...and tweeking wouldn't be necessary...and the next guy would be tickety boo...

You see tweeking as you rightly describe is fiddly...and involves multiple toolkit adjustments...and assumes the customer has a desire to muck around with toolkit (see my other posts on what I think of this interface). Otherwise I have to get out my installer every time (at huge expense)...and of course they don't actaully live with you!!! (or he sometimes feels he does!)...isn't there an easier way or some suitable templates ready to go?

If this can't be done, I'd much rather ramp up the setpoint to say 25 degrees, when getting up in the cold mornings and be done with it. This approach seems to be cheating, but at least it appears to work and stop the "cycling"...

P.S this sort of heating is very common in more upmarket homes in Melb. (the sort that may have/be contemplating cbus) We live in a rather European climate down here after all! It would also help the folk in UK...

 

Ok!

Thanks Ashleigh. Understood...

At least with my set up I can visually see when the relays are activated
On a cold weekend, when I've got some spare time and nothing else to do...I'll (gently) tweek away