C-Bus thermostats

I have just installed three thermostats (one master, 2 slaves) each controlling their own zones, and after some initial setup pains (mainly me not understanding all the options) it's working great. One operational issue I have however is that when a person wishes to turn off their zone, they have a habit of just pressing the on/off button on their thermostat assuming it will just turn off their zone, but of course it shuts the entire system off. Getting them to just lower the temperature is fraught with dangers because if the thermostat is in auto mode it can start cycling between heating and cooling modes which is a problem. As the thermostats don't have an OFF mode, is there user friendly way around this issue?

Also, when a thermostat is put in slave mode it disables all the on-board relays which makes them unavailable for zone/damper control. Is there anyway around this, or is it a good excuse to try the new ELV relay module

 

It's a carrier ducted reverse cycle system using simple RWG 24VAC control. I just moved the connections from the existing thermostat to the C-Bus unit, checked it a few thousand times, crossed my fingers, turned it on, and it worked

To be fair I did actually set the thermostats up on a bench with some leds to make sure I had the programming correct and get the multiple zones working before I installed it.

 

Taking the relay issue first, the RWG control takes 3 relays, and 4 zones giving a total of 7. I have 5 relays in one thermostat so i need 2 more which physically exist in another thermostat but are disabled in software. The thermostat damper dialog tells me that setting any zone group to unused will issue standard lighting commands but I can't figure out how to do this as it only lists the HVAC application (or is it just implying lighting type commands?). It also gives me the option of calling up existing relays, but these are already dedicated to the lighting application and I can see no way of using them. Am I missing something here or is the dialog misleading? I can use a L5108 but once I set it up for the HVAC application I end up with 6 spare channels which again I can see no way of using on other applications. At present I am using logic to convert HVAC damper commands to lighting commands which works fine but seems an odd thing to have to do.

On the first point the 3 thermostats are set up to individually control their own zones, so while 2 might be set up a slaves in toolkit they are operating independently and are not just mimicing the master (that is an option but not how I am using it). The master can only control it's zone and not affect the others. Previously each zone had a simple switch to open and close it's damper and a single centrally located thermostat. When a person left that zone could just hit the switch to close the damper. The 3 thermostats now give independent temperature control for each zone which everyone that sees it wants (Clipsal needs to advertise this more!), but what I can't figure out is the switch that just turns off that zone. As you state the power switch is global and shuts off the whole system. Just turning down the temperature is not very user friendly and doesn't work if the thermostat is in auto mode, and the mode selection doesn't give me an off option. I'm sure this must have been thought of during the design, but I just can't figure out how to do it. Any help would be gratefully appreciated.

Ashley

 

Hi Ashley,

I know it has been a long time since you posted this problem, but have you managed to solve it.
As I am about to install a very similar setup also with Carrier Ducted A/C system.

 

After much experimenting:

1/ I run the system in either Heating or Cooling mode, never Auto. This way you can shut a zone off just by winding down (for heating, up for cooling) the temperature to disable a zone.

2/ I also programmed a nearby switch to turn the zone on and off manually although everyone just uses the temperature control.

3/ All the thermostats are duplicated on a color touch screen (and wiser) which does give you independent zone control and allows centralized operation.

As for the relay problem I bought an 8 channel ELV relay to control the zones.

I'm currently running 4 zones which unfortunately is the limit of the system. My next problem is to figure out how to add 3 more zones for the remaining rooms.

 

Thanks for your prompt reply. I too have a seven zone system.
I am wondering, if it is at all possible, to have four zones managed by C-Bus thermostat up to its stated limit (i.e. master / slave configuration). Then have the other four zones dampers independently controlled by the thermostat/relay to simply open/close as it reaches set temperature.
I.e. to switch on the system, you must have at least one of the four C-Bus zones on, then manually switch on any of the additional four zones.

As for switching zones on/off, if you have a four zone programmable Thermostat configured as a slave with the User Interface configured to display a particular zone, can you use the Zone button to switch the zone on/off? I assume this can be achieved, by setting the thermostat to only display/control one zone (from the User Interface Tab - User Controlled Zone).
Unfortunately, I have not installed the thermostats yet, so I cannot test it. But I have been playing around in the Toolkit.

 

You can have a thermostat control a zone but not the plant by setting it up as a master on an independent Communication Group and just assigning the damper zone output. If you were keen you could also write logic to turn the real plant on whenever a thermostat on a different communications group was enabled. Turning the plant off is a bit more complex as you have to test if its the only thermostat calling for heating/cooling. Theoretically you could have 1024 zones (4 zones on each of 256 communications groups). I sort of had this running on the bench but have never got around to installing it (it's on the to do list but I was hoping Clipsal would get around to expanding the zone count for me).

You can turn zones on and off from the 4 zone thermostat but its kind of long winded as you have to press the zone button, rotate the knob to select the zone you want to control then press the button. I found it much easier to use a local switch or touchscreen (or wiser).