Help with a Thermostat installation

Phew, that's a relief

Thanks Ashliegh for the comprehensive replies... (I'm guessing from the times you're not in the UK?)

I think a big part of the problem is caused by lack of information... since I've never had "hands on" with one one of these thermostat units, what little I know is based on the scant details I've picked up here and from some of the CBUS documentation, - but that doesn't go far enough into technical detail of actual operation to answer my very specific queries...

I "get" that the T-stat is a bit more than just a sensor, really I do... I meant to impart that the single zone models (which is all I require) don't also have the time programming functionality, so I'll still need to do that elsewhere..

So if I may, and since you're clearly very familiar with these units, can I just clarify a couple of points?

first a very specific question, - if I change the thermostat unit to use the lighting application does it lose any functionality? - is there anything that I suddenly become unable to do if the stat is set to lighting? (I ask this because it means the difference between using a spare channel I already have on an existing relay module, or forking out much extra wonga for a new relay module to dedicate to the HVAC application; so I need to know exactly what units to order).

Also, just to confirm: it absolutely IS part of the feature set to be able to remotely set the temperature setpoint on the t-stat from other units? - Is this functionality still available if I've changed the stat to the lighting application?

I have a Comfort alarm panel with a CBUS UCM and I do a lot of Comfort-CBUS integration (all lights off when I arm the alarm type stuff). One of the *major* functions I want is to bring the heating into the same regime, so I specifically want to be able to switch the heating on/off in response to alarm panel events. The UCM can only communicate on the lighting aplication (another reason I'd like to change the stat to lighting).

I do also have a Wiser, - I understand this can operate on all the available CBUS applications? - so I'm assuming that if I have to leave well alone & use the HVAC application that I can use Wiser to translate commands between them... so I could for instance have comfort send CBUS a lighting command (since that's all it can do), and the Wiser could use that as a trigger for (say) setting the temperature setpoint to 15 degrees?

I believe that even if the stat is left in the HVAC application, the setback command can still be used from the lighting application yes?, - how far would this go to giving me the the control I need from Comfort? - for instance, is it possible to setback to a specific temperature setpoint, or is it only specified as an offset from the current setpoint? - If I can have comfort send a setback to 2 degrees C (for example) that would probably have the desired effect (making sure the heating is OFF). Similarly, if I have to specify it as an offset, can I use a large offset of (say) 20 degrees - since my setpoint is invariably around the 20-21C level...

The points above re control from Comfort are fairly crucial, since I intend to do my time schedule programming from there - it's the obvious place; - it knows the sunrise/sunset times for my location, it knows if the house is occupied or not, it knows the difference between weekday/weekends, and it even knows about all the public holidays in the UK. (It's also rock-solid reliable, just like CBUS!)

I think I'm a bit happier about going ahead & ordering a t-stat unit now than I was yesterday! (still need to know if I need to order more relays though..)

Today is a classic example of one of the scenarios I want this stuff to improve:

It's Winter here so it's cold! - it's a weekend, so there wouldn't *normally* be anyone up yet, - hence my heating system isn't programmed to come on for about another hour... Yet today I have decided to get up especially early as I have lots to do... - but the house is cold! - I have an 8-way Neo by the side of the bed, - I would dearly love to have been able to reach out from under the duvet & turn the heating on 30 mins before I crawled out...

 

Excellent...

Thanks Ashliegh, that pretty much ticks all my boxes... I'll go ahead & order a thermostat unit...

My only remaining ponderance now is regarding the Wiser HVAC widget... - as you say, it probably has *way* more stuff in it than I need, - plus if it only works on the HVAC application, then most likely it won't be an option for me anyway, since I'm almost certainly going to use Lighting (yes, I'll be vewy vewy careful!) - my installation is quite straightforward anyway...

So, discounting the HVAC widget, are there other options to get similar levels of functionality? - I can see that it should be childs play to get on/off in the Wiser UI by just switching a lighting group as you've described previously. I also assume it's quite trivial to pick up the temperature broadcasts from the t-stat & display that on the Wiser UI, - but what about changing the setpoint? (I could live without that function if I had to TBH, would be nice though!)

Here in the UK, heating systems tend in the main to be quite primitive, "most" houses only have heating and no cooling, and "most" of these heating systems tend to be quite basic. Hence most of our installers also tend to be quite backwards in their attitude to automation... the electrician fitting the supplied controls (thermostat & timer) started doing sharp intakes of breath when I tried to tell him how (& why) I wanted the wiring done in a certain way so that I could get at it later to modify it... (and muttering about voiding the warranty)...

The response in my house is fairly quick, - typically only about 30-60 mins to come up from cold to a comfy 20-ish degrees - depending on how cold it is to start with. The house is also quite old & very "leaky" internally, so zoning is a pointless endeavour.

 

I'm in a similar wanting to implement position to Paul... and have a couple of additional questions if I may...

Is it posssble to get at this 'DEMAND' as an analog value on C-Bus - perhaps as a group level - or via some programming in a touchscreen/Wiser, or is this hidden within the HVAC app ? I could then translate this to a voltage.

My heating is either 'basic' single stage i.e. just a single on/off relay or it can additionally take an analog (0-10V) voltage that the thermostats generate proportional to the demand / temperature shortfall. In a multi thermostat situation these are combinational in some way - maybe the largest just takes precedence. Close to satisfying demand I believe the boiler automatically reduces its flow temperature to maintain status quo. Would these 'smarts' within the boiler that are managing flow temperature reduction be at odds with the internal assesments that the plant controller firmware in the thermostat(s) was making ?

Just to clarify - this is different to another direct 0-10V to my boiler that can be applied to directly modulate it , but I want to stay away from that approach.

I suppose I could just convert the two level demand from the relays into a three step voltage (satisfied | low | high) but that seems rather low tech.


If I did have a C-Bus thermostat with inbuilt relays can I instead abandon those and use external relays , and can this be on a per relay basis , or must I use the non relay model in the first place ?

In a 4 zone arrangement - what is the major difference between having just temp sensors (? is this possible) in the other three zones and a thermostat , aside from the local display and override feature ? Does the main controller separately 'model' each zone within the plant controller or do local thermostats do that - something temp sensors couldn't ?

Can I schedule each zone for temperature and timewise independently such that in the morning I could bring on a bathroom zone before the kitchen ? (Meaning if bathroom was satisfied but kitchen wasn't then boiler wouldn't fire)

Thanks Ashleigh.. I'm going to delve into the Toolkit help too as suggested... a wealth of info seems available for most C-Bus stuff - it's just knowing where to find it as it's not always in the places I think of.

K

 

The info in toolkit is most useful - it would be good to point users there from the thermostat documentation/pages too... I'll update my above post after digesting it with some answers ... but it also raised some more questions , I hope you'll bear with me..

1) There's isn't any ability for optimised start is there ? - the ability to program a time at which you want the room to reach it's setpoint and the thermostat will switch on a calculated x minutes before that time based on an internal calculation of the estimated time needed to heat the room.

2) Is there any ability to use an exterior temp sensor for weather compensation ? Although maybe the boiler implements that itself directly (makes sense).

3) In a stored hot water system (very common in the UK) the boiler is obviously shared between heating/hot water demand . Is there a way of managing this within the thermostats ?

I don't see any input capability for the hot water temperature (or any sensor offerings) , any separate time management for hot water, any settings for hot water prioritisation or a relay/group output for the diverter valve used to move the flow circulation from hot water to heating ?

If there isn't such a capability and because I need to manage the boiler on/off switching only via the thermostat and not directly, do I therefore have to artifically override any timer programs and raise the setpoints such that the heating will fire, and then reinstate them again each time I have a hot water demand ?

K

 

Kevin. Most boilers will sort this for you and schedule the diverter valves appropriately. Either if the hot water cylinder is calling for heat the boiler flow will be divided between the cylinder coil and the radiators, or the cylinder will get priority so that the baths and showers don't go cold.

This is all handled within the boiler's "brain" I wouldn't try to mess with the diverter valve controls directly. Apart from being uneccessary, you'll have trouble with the "overrun function" which is when the pump and diverter valve continues to pump water through the boiler after the burner has been shut down to prevent dangerous overpressures in the boiler's heat exchanger.

If you want to schedule when the boiler heats up the hot water cylinder, you could put a relay in series between the cylinder stat and the boiler. Closing the relay would allow the cylinder stat to call for heat. Opening it would prevent the boiler from firing in response to calls of the cylinder for heat. Set the boiler's hot water time clock to be on continuously. Now, if you close the relay, the boiler brings the hot water store up to temperature; if you open the relay the boiler stops responding to the temperature of the cylinder.

 

Yes - that's kinda the way it works at the moment but there is no thermostat open/closed signalling - it's a water tank temp 'thermistor' sensor that connects into the existing thermostat, rather than the boiler. Within the thermostat I can set the desired water temperature, and both the water and heating times separately. Well actually I don't think you can have heating without hot water (except by lowering the hot water setpoint) but you can do the reverse. The hot water operates intelligently in a way that ensures at any timer period start the water is already up to temperature. It is a HW priority system.

What I'm trying to understand is how much of this I could retain/enhance using the C-Bus controls as I have no easy ability to further automate the controls, or support zone based demand which I would like to have. This is a large property so zoning is desireable - but it's also difficult to replumb in a more co-operative way so I have to use what's here already. My existing thermostat is on a two wire digital bus (BATIbus I believe) - I was original advised I could daisychain further thermostats onto this but now I'm told this isn't possible due to that feature being not implemented within the boiler firmware.

What your suggesting - (which I do understand I think) would involve replacing the analog hot water temperature sensor with a mechanical threshold on/off one and to use this to implement another on/off demand signal onto the boiler that is a series combination of thermostat (+ maybe time clock) and this also handles the mid position valve control. Just seems a retrograde step and I would lose the ability to set water temperature on the thermostat, end up with two timers, plus sacrifice the hot water ready 'on time' feature. Not sure there is an open/closed HW demand signal on the boiler anyway but I suspect there is.

In my setup I don't think from a safety viewpoint overun would be a problem as it's a single mid position valve that can only be HW/CH or mix - so there's always a circulation path. I suppose some heat could be dispersed briefly into the CH during summer. Pump overun is handled by the boiler internally.

Looking at this from the C-Bus side, and as I would then essentially have a water priority system couldn't the C-Bus room thermostat be calling for heat but in actuality the boiler still occupied for some time heating water ? Which would mean the thermostat plant manger would not get appropriate feedback on the heat provision capabilities and room characteristics ?

Ashleigh is also saying (very strongly) don't bypass the boiler on/off control - but always go via the thermostat - yet the hot water demand would be doing exactly this. Maybe because it's not a heating demand it's not an issue but the thermostat would then still not know that the boiler is unavailable whilst it's heating water. I suppose one workaround could be that a combinational heat demand from both HW and CH could place the valve mid position and heat both.

K

 

I hadn't realised that your boiler used a more sophisticated system to sense and schedule the DHW tank than is usual in the UK. You're right- it would be a retrograde step.

 

Hi Ashliegh, been a while, but I've now got my thermostat connected up to CBUS and I'm actually starting to work on the comissioning/programming, as opposed to just theorising about it...

You mention using a (different) lighting control group to control the thermostat, which makes perfect sense... it just isn't completely clear to me yet how to actually set that up... - I've created another group called "Thermostat" in the lighting application - where in toolkit do I link that to the thermostat on/off function? - there are *loads* of groups referred to in the toolkit UI for these units, and in quite a few different places on the various tabs... - It looks like a bunch of them are duplicated in more than dialogue.. - e.g. the "Cool/Heat Groups" button in the "global" area seems to show much the same as the "Heating Groups" button on the Plant tab... - with a few subtle differences...

Also, I see that toolkit created a whole bunch of groups automatically, some in the HVAC Actuator 1 application (4 groups IIRC), and a load more in the lighting application (9 groups I believe).... oh and 1 more in the Air conditioning application... - is it safe/sensible for me to delete any/some of these? - since I have only a single stage furnace type plant, I have no fan or cooling functionality of any kind, and therefore I expect I have no need of any groups to control this plant that I don't have?.... I'll leave well alone if that is recommended, but I do like to keep things "tidy" and not filled up with superfluous guff that I don't need and will never use....

Also, can I just make absolutely certain that I understand the principle of operation correctly...
If I turn the thermostat ON, that is akin to turning the heating system ON - i.e. when I turn the t-stat on it will do it's calculation of the demand, and if heat is called for will operate the assigned relay (via the stage 1 group assignment). If when I turn the t-stat on, the setpoint is already reached, then it will do nothing.. - I have no cooling plant, so there is no option for it to start implemementing a cooling operation... whilst the t-stat is ON, it will continuously perform this demand assessment and fire the boiler to "make heat" as and when necessary, and turn the boiler off as appropriate according the demand?...

Conversely, turning the thermostat OFF is akin to turning off the heating system as well? - regardless of the ambient temperature compared to the setpoint (i.e. the amount of demand), if the t-stat is turned off, it will not fire the boiler. - the only exception to this being if the Guard function kicks in if it gets *really* cold....

So, if I'm in the first condition: the thermostat is ON, there is demand, and thus the boiler is fired and the heating is on... I then turn the thermostat off - either from it's local on/off button, or by switching the appropriate control group off... what happens? - I would expect that the thermostat will flip the plant control relay back OFF, thus switcing the furnace (boiler) OFF, and turning the heating OFF... - so all I need to do when I leave the premises is to make sure I turn the thermostat off, so I don't end up wasting fuel heating an empty house...

Have I understood that correctly?

Cheers.

Paul G.

 

Conflicting information?

Hi, that seems fairly unequivocal that a LIGHTING group can turn the t-stat on or off... BUT, having spent a lot of time browsing through everything I could find on this topic in the forums, I came across this post from last year...

Which seems similarly unequivocal that the group used to remotely control the thermostat MUST be in the Air Conditioning App (application 172, or AC hex).. so which is true?... - I guess that with new enough switches it probably doesn't matter that much... - from my NEO's or Saturns I can set the secondary application to Air Conditioning and then set keys to switch Communication group 1... - I guess this will perform the desired action? - the 2nd quote above appears to confirm this.... Certainly from my own experience of the options in toolkit, I can't seem to find any way to configure a group in the lighting application to control the t-stat...

Comments?

TIA

Paul G.

 

And some more questions!

Sorry to keep bombarding you with all these questions, - eventually I *will* get this! - and when I do, I'll write it all up & post it up here in case it helps anyone in the same situation as me...
I've noticed a couple of things that I'm not certain if they're "normal" or not...

1: when I installed the t-stat in toolkit, it created a bunch of groups automatically, as I mentioned in another post... - I'm wondering now if I've ended up with too many - possibly caused by duplication of some of them when I changed the primary application to lighting? - see pic1 for a list of the groups I've currently got... - it looks to me like at least a few of them are duplicates across the lighting app & the HVAC 1 app....

2: I've noticed a bunch of group broadcasts every 60 seconds going out on CBUS... - is this normal? - see pic 2 which is a snip of the log from Homeseer (my main HA app) which shows CBUS transmissions on 3 of those automatically created t-stat groups every minute... - it appears that it's not actually *changing* the state of any of those groups, just continuously sending out messages to keep them in their existing state.... - this is occurring whilst the thermostat is *OFF* - is this normal?
In case the screengrab isn't clear enough, the entries are as follows:

13/12/2010 09:31:34 CBUS Group 37 changed, - [CG01] W (heat) Level: 0
13/12/2010 09:31:34 CBUS Group 38 changed, - [CG01] G (heat fan) Level: 0
13/12/2010 09:31:35 CBUS Group 40 changed, - Setback Disable Level: 1
13/12/2010 09:32:35 CBUS Group 37 changed, - [CG01] W (heat) Level: 0
13/12/2010 09:32:36 CBUS Group 38 changed, - [CG01] G (heat fan) Level: 0
13/12/2010 09:32:36 CBUS Group 40 changed, - Setback Disable Level: 1

As you can see here, the same 3 group commands were issued 60 seconds apart... - this goes on continuously....

Thanks in advance for the clarifications guys...

Paul G.

 

When you moved the Thermostat over to the lighting application Toolkit automatically creates the new group addresses necessary for it to live on the lighting application. It leaves groups in the HVAC application alone. There's no harm in them being there, however you can delete them from the HVAC application if you're trying to keep your Toolkit database squeaky clean.

The broadcasts onto C-Bus happen regularly, even when the Thermostat is off, for keeping all the different zones, multiple thermostats and plant controllers in sync. The rate at which messages are sent onto C-Bus for this is defined by the 'Refresh Time' parameter on the C-Bus tab of the UI. It's designed to do this, so it's completely normal.

Based on the log, it looks like the checkbox on the C-Bus tab for 'Enables sending of Thermostat C-Bus messages' is un-ticked. If you tick this box, you'll get not only the C-Bus Group messages but all the inter-thermostat communication messages as well.

 

Excellent answers - thank you!

You are correct, I have the thermostat communication messages checkbox unticked - from what I read, I believed I understood that I don't need that enabled, since I only have a single thermostat.... - does that also include the transmission of the current temperature (as measured by the stat)? - Is there a way to pick up the current temp off the bus & get it into a group level (I have Wiser, so I can do it there if need be)....

I also noticed an error explaining at least in part those messages I was seeing in the logs... - for whatever reason, my thermostat config wasn't set as I thought I'd set it... (I use an offline test install of toolkit on my laptop for reading the help files / taking screenshots etc.) - when I checked my production config, I noticed that the plant group settings were still using some of those default groups rather than my newly created "Boiler Control" group that I'd created for the purpose... also one of those was still enabled for the cooling plant (which I don't have...) Having updated that, I'm now seeing what I believe are more "sensible" messages going onto the bus...

14/12/2010 10:18:27 CBUS Group 35 changed, - Boiler Control Level: 0
14/12/2010 10:18:27 CBUS Group 40 changed, - Setback Disable Level: 1
14/12/2010 10:19:28 CBUS Group 35 changed, - Boiler Control Level: 0
14/12/2010 10:19:29 CBUS Group 40 changed, - Setback Disable Level: 1
14/12/2010 10:20:29 CBUS Group 35 changed, - Boiler Control Level: 0
14/12/2010 10:20:29 CBUS Group 40 changed, - Setback Disable Level: 1

So now the stat is at least sending messages to the lighting control groups that I configured rather than the default ones... - and I now see the point of the earlier warnings about never controlling the plant group directly!!! - if the stat is sending an "off" command to that every 60 seconds, there's not much point in turning it on outside of that control mechanism!

Now that I can see that the stat is at least controlling the correct groups, and thus far appears to be sending the appropriate commands (stat is turned off, so I'd expect to see commands turning the boiler off too...), I'll do a few more tests with various scenarios involving turning the stat on & off locally, changing setpoints etc. and observe the messages I See going out on the bus to confirm everything behaves as I think it should, - following which I think I'll be ready to actually change over the boiler wiring fairly soon and get the plant relay channel actually controlling the heating... - hurrah!

Thanks for all the help getting this far, Hope you'll bear with me a little longer while I continue up this learning curve...

Paul G.

 

If you want to see the current temperature, as measured by the Thermostat, then you need to enable the 'Enables sending of Thermostat C-Bus messages' option. This will make the unit send lots of additional information onto C-Bus, including the current temperature. You could then use logic to map that across to a C-Bus Group Address level if you wanted to.

 

So very nearly there...

Thanks... Now all I need to figure out is the answer to the question a few entries up regarding the group used to remotely turn the t-stat on & off then I reckon I'll be done....

TIA

Paul G.

 

To turn the Thermostat on and off remotely you need to use the HVAC application, not the lighting application. In the HVAC Application, individual zones can be turned on and off.

In your case, where you have fairly simple control of the boiler, you need to turn on and off HVAC Zone 1. To do this from a basic key unit you need to put that key on the HVAC Application, assign a Group Address of 1 to the key and configure the key as On/Off.