Controlling central heating (HVAC) through X-10

Post by **MindBender** » Wed Aug 23, 2006 5:07 pm

Hello Guys,

The reason I started my X-10 project is to control my heating remotely. The Honeywell Chronotherm is a nice device, but my day isn't divided in four parts and the times I arrive at home are never the same. So it would be nice to have the possibility to turn on the heating before I leave the office. Most thermostats can only be programmed to follow a temperature curve throughout the day (or week), but I don’t' want that: I only want to turn off the heating automatically after 0 o'clock, I don't want the heating to switch on automatically.

So what I need is simple: A X-10 device that acts like two analog devices. The first should be a thermometer, capable of requesting the current room temperature. The second should be the set point of my heating system and should be both requestable as settable.

Currently I'm overhauling my complete heating system; The boiler is being replaced, pipes are rerouted, etc. Modern boilers use 'modulating burners' (We techies just call that a proportional actuator, like we have been doing since long before boiler manufacturers even existed). These boilers can be controlled using a simple on/off thermostat as well, but in order to achieve their maximum efficiency (of 109%, muwhahahaha) a proportional control loop is required. Somehow every manufacturer has thought of his own proprietary solution for boiler/thermostat communication, probably to protect their market. A few manufacturers have decided to embrace the OpenTherm standard for this (kudos guys!)

Many manufacturers have hear about the need of remote controlling heating systems, but all of them have their own system, varying from sending SMS messages to logging onto their website or sending email to their server. Even though the problem is simple, they keep the solution complex to make sure they maintain in the loop so they can charge a yearly fee for theirs services. Techies like us see right through that and immediately see that their ‘services’ don’t add any value to the system. We also don’t want to pay for sending an SMS message each time we want to turn the heating on or off.

I thought it wouldn’t be too difficult to find an OpenTherm compatible thermostat which can be controller through X-10, but after a long search I turned out to be wrong.
So far I have found the following devices, no of them are proportional:
http://www.resconsys.com/products/stats/x10.htm
http://www.marmitek.com/nl/catalogus/pr ... roduct=232

Then there are the people who talk about building they are own thermostat. Well, controlling a central heating system is far more complex than it seems, even if you're only turning the boiler on and off. Let alone when youre trying to achieve maximum efficiency and if you want to use the OpenTherm protocol.

I have seen the digital input modifications of the Chronotherm IV OpenTherm thermostat at Leike's forum, but I think thats a bit minimalistic

Does anybody know about a better OpenTherm solution?

Post by **Bwired** » Wed Aug 23, 2006 7:37 pm

As I told before I'm busy building a interface right now. If it works you can get all the opentherm HVAC information on the rs232 port. I have build the interface but I'm not able to get some data good data on the rs232. I asked Heino Peter also member of this board to help me on this and he agreed! At the end of the year I hope to have a fully operational opentherm interface.
The interface is placed between the thermostat and the HVAC and is powered also by the HVAC. A good thing about it is that all the data you recieve on your thermostat (and more) is in the opentherm protocol. It's data like Bar pressure, temp water, temp heating, set temp, outside temp, status on and off, burning on etc.
No I already have a SAX15 installed in my HVAC and I can swith the heating on. Nice about opentherm is when I switch the heating on with the SAX15 I see it directly on my opentherm thermostat (heating On). Once you have the above interface you also have a fully operational HVAC domotica solution which can be controlled by computer and your thermostat without limitations! Perhaps it's even possible to send on and off commands over this interface? [img]="/uploaded/bwired/200694174613_opentherm.jpg"[/img]
I think this is the only solution all the other things I saw I did not like much!
See also topic http://www.domoticaforum.eu/topic.asp?T ... =opentherm

I had the same experiance as mindbinder and the 2 thermostats he found are not opentherm. Here is the schematics of the opentherm interface, Perhaps there are more Domoticans who wants to build it!
What do you think Mindbender?

Download Attachment: [img]images/icon_paperclip.gif[/img] OpentThermostat

Regards Pieter

Post by **Han** » Thu Aug 24, 2006 11:21 am

Hi there,
I have reported about my exercices with X10 sensor data at some other places in this forum. The X10 temperature sensors (thermostats)that are available on the market all misuse dim and bright commands as a means to transmit analog data to the controlling program; long transmission times and strange translation tables. In my opinion not a good solution.

My second thought is that the decission to put on or off the heating system should be taken by the home controll software and not by the (X10) device itself (thresholds values should be set in the controlling program). This gives much more flexibility as you can use time of day, season, absence etc to control the heating system.

I have build the temperature sensor based on the extended X10 code format (ftp://ftp.x10.com/pub/manuals/xtc798.doc).
Specification of the device: Download Attachment: [img]images/icon_paperclip.gif[/img] TL01.zip 100.13 KB

I have some spare PCB's for this device. If somebody wants to give it a try let me know.
Opentherm looks very promissing. I'm not sure, but I don't think my heating system is supporting this type of interface.[:(]

Han Alink

Post by **Henk** » Mon Aug 28, 2006 10:41 am

In case hacking the electricity meter is no problem – consider the following modification on your thermostat and having full control on your heating application.

Most thermostat will have an option for a continue temperature setting – the desired temperature will be set by two buttons up and down ….. so open the thermostat – find the two buttons and solder 3-4 wires and connect them to two relays both controlled by X10……
In case you have a Chronotherm IV and selecting the continue temperature mode , if you keep pressing down it will stop at 7C …or pushing up it will stop at 31C… so in this way you can reset and know the starting point and synchronise both your controller and thermostat …..and then click up to the desired temperature –.each click is a half a degree. Of course you have to set the thermostat in the CONTINUE mode and don’t use manually the up/down buttons anymore – use X10 control / RF to do the up/downs to control the temperature in your living room …. Only look at the display unit the read the selected temperature setting.
No need to do every time a total reset (back to 7C) just keep track of up/downs and see how reliable it will work – may be a weekly/nightly reset ….. so first going down – take it safe 20x2 = 40 clicks and going up from 7 to 20 degree it will be 2x13=26 clicks –

If those up/down buttons are pushed too long (more than one second) the temperature may jump several degrees. Only if you are sure your X10 signals can be precisely time- controlled (don't bet on it) you will need an small electronic circuits with a the right "push-time" so the X10 on time has no influence.

In case you don’t want two X10 devices you may go for one ….. in case the X10 output is on between 5-10 sec. it will put the output in up mode – turning on for 10-15 sec it will be down – and sending pulse between 0-2 sec. the temperature will jump by half a degree …. This kind of circuit shouldn’t be a hard job ….. I asked on internet already for some ideas …

Post by **Henk** » Thu Aug 31, 2006 12:49 pm

A Chronotherm III thermostat can be easily modified to control the set-point temperature as described in the previous entry ... the panel is connected by a flat cable and just sticking stripped thin wires together with the cable will do the trick - of course you can also solder those connections .... (see picture)

the wire lay-out is 2+5 cold 2+6 = warm , be aware you need a precise time to close those contacts - so make a RCcontrolled transistor circuit so the contact closure will be about 1/3 of sec.
In case you need other controls 1+7=start programm , 2+7 = continue
so in case you have enough X10 outputs you may even switch from manual operation to X10 controlled ....
The Chronotherm III has a range of 7-31 degree and only increments of one degree are possible. (Chronotherm IV will do 1/2 degree steps)

You may use a dimmer-module so the dimming range of 100-50% will increase temperature and going from 50%-0% will lower the temperature ... but you need an additional electronic circuit to filter those levels and producing the right and time controlled pulses - think this is a nicer solution at the time length coded pulses in the previous reply......

Place a low voltage transformer and rectify it so full range will be 10Volt and check the linearity of the volt output with dim level - Feeding this singal to a two level amplifier - one will switch at 2.5V (cold) and the other at 7.5V (warm) .. the output will be timed controlled and switch off after 1/3 sec.
So starting with dim level 0% - so decreasing temperature with 2 degree ... one command up to 50% (1Cup) - then 0% then 50% (1Cup) then 0% ...
Increasing temp by two degree .... start at 0% - 50% (1Cdown) - 100% (1C up) - 50% - 100% (1Cup) - 50% - 100% (1Cup) - 0% - increasing the temperature you will always need one extra pulse to compensate the cold pulse .....

I didn't care to have a look at the inside of my Chronotherm IV and check if the same construction has been used .... likely you can use a similar technique - so at least this is a benefit of using classic button thermostat instead of the new generation touch screen ....
[img]images/icon_paperclip.gif[/img] Thermostat.jpg

Post by **MindBender** » Mon Nov 06, 2006 1:10 am

Good News: I have purchased a Remeha OpenTherm gateway and installed it into my heating system. It connects to the Openthem bus als shown in Pieter's diagram above and it offers an RS232 interface with which the OpenTherm bus can both be observed and manipulated. Remeha didn't want to disclose anything about the protocol on the RS232 port, but they do have a little Windows program with which the setpoint can be set. This program also is able to show the room temperature, the outside temperature, water temperatures, the status of heater and tapwater and a whole lot of other things. I'm sure it can be tied to X10 fairly easy, but it would be even nicer to ty it up to a serial port of a computer running your domitica software.

I'm pretty sure this gateway works with the Remeha Celcia 20 OpenTherm thermostat only, but a similarly looking thermostat is sold under different brand names too, so I guess it's pretty generic and these other brands may sell their version of the gateway too.

The Celcia 20 has a standard digital input, which can be programmed for many different functions, so I guess it's a pretty good domotica thermostat even without the gateway.

Post by **Bwired** » Mon Nov 06, 2006 9:31 am

Thats really good News Mindbender, just like me you keep on digging:-)
I think with this solution you are very close to even control your heating system, So actually control it with your HA system as well with the thermostat and both getting and displaying the same status etc. I can help you some what with the software I think, I have the complete opentherm protocol, so if you want you can have it. Then you need to hack the protocol for the rs232. Some questions: Do you have a Remeha heating system or like I think is the interface working on all opentherm systems which have a opentherm connector (like my Nefit opentherm heating system)
Again good News.Pieter

Post by **Han** » Mon Nov 06, 2006 12:20 pm

Hi,
I'm still trying to get there in the simple way. The main reason I'm trying to control my heating system is to get a higher confort and less costs.
- Less cots by switching it to a lower temperature automatically at night time and during absence.
- More confort by switching the system on by remote command (xda), before I'm comming home.
In both cases the precission of the temperature control is not that important.
So this is what I have, and what I'm going to do:
- I have an X10 temperature transducer
- I have a version of Zeus (control software) that is able to set thresholds for temperature and use the received temperature in "If/then/else" cases and scenes.
- I started designing/building a simple X10 receiver which contains 2 relays; one for switching between my conventional thermostat and the other for switching on and off the heating system (when it is enabled by the first relay).
It's simple, but I think I can acheive my goals in this way.
Once I have to install a new heating system (in a few years) I will dive into the world of Opentherm.

Han Alink

Post by **MindBender** » Mon Nov 06, 2006 2:03 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Han
 So this is what I have, and what I'm going to do:
- I have an X10 temperature transducer
- I have a version of Zeus (control software) that is able to set thresholds for temperature and use the received temperature in "If/then/else" cases and scenes.
- I started designing/building a simple X10 receiver which contains 2 relays; one for switching between my conventional thermostat and the other for switching on and off the heating system (when it is enabled by the first relay).
It's simple, but I think I can acheive my goals in this way.
Once I have to install a new heating system (in a few years) I will dive into the world of Opentherm.<hr height="1" noshade id="quote"></blockquote id="quote">I have said it before and I will say it again: Regulating a room's temperature is one of the most underestimated controlling task. It seems very simple, but in order to do it right it's utterly difficult. It's not very difficult to get a controller regulating the temperature. Preventing overshoot is slightly more difficult, but still feasible. But do make the system work in the most energy efficient way is far more complex than meets the eye. Even if you use a standard thermostat and put in a relay to open the circuit you're disturbing the regulation because a modern boiler uses an anticipation resistor heater inside the thermostat. Breaking the circuit would sabotage this system. And not using this system leads to degradation of efficiency.

If you want to control the tempurature with your domotica system, the only way to go is by controlling your thermostat. Really. If you don't care about flexible temperatur settings, you can very well use the digital input of a Honeywell or Celcia 20 thermostat. I would (and did) choose for the latter one because it's digital input can be programmed for different functions.

The Remeha gateway doesn't control the boiler, but the thermostat. It's and OpenTherm system, so the combination of Celcia 20 and GateWay should be able to work with other OpenTherm boilers as well. The Celcia 20 goes for about 140 Euro (half of that on Marktplaats.nl) and the GateWay without modem goes for about 114 Euro. I will publish the results of my protocol reverse enginering on my website soon. I'm trying to get a deal from HomeSeer out of this: I'll make them a plugin, they'll give me a life-time license. I wonder if they're interested.

Post by **Han** » Mon Nov 06, 2006 2:42 pm

Hello Mindbender,
I know that it's not easy to control temperature.
What I'm trying to say is that at the 2 moments that I want my home automation system to control the temperature, I do not care too much about accuracy. The temperature may very plus/minus 1 to 2 degrees C.
When I'm home my existing thermostat will do the job.
Does that make sence?
Regards,
Han

Han Alink

Post by **MindBender** » Mon Nov 06, 2006 3:58 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Han
 When I'm home my existing thermostat will do the job.
Does that make sence?<hr height="1" noshade id="quote"></blockquote id="quote">Yes, totally! I'm sorry; I misunderstood your earlier explanation.

Post by **Bwired** » Sun Nov 12, 2006 9:31 pm

Hi Robert,
I think you forget my humble questions 5 levels above:-)
thanks Pieter

Post by **MindBender** » Sun Nov 12, 2006 10:34 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Bwired
 I think with this solution you are very close to even control your heating system, So actually control it with your HA system as well with the thermostat and both getting and displaying the same status etc. I can help you some what with the software I think, I have the complete opentherm protocol, so if you want you can have it. Then you need to hack the protocol for the rs232. Some questions: Do you have a Remeha heating system or like I think is the interface working on all opentherm systems which have a opentherm connector (like my Nefit opentherm heating system)<hr height="1" noshade id="quote"></blockquote id="quote">The GateWay doesn't directly control the boiler; It controls the thermostat. So you need to have at least a Remeha Celcia 20 thermostat and a Remeha Gateway. I'm fairly sure those two will work in conjuction with your Nefit boiler, perhaps with a few features less. In logging mode the Gateway give me more than enough information for my domotica system. Even the water temperatures, outside temperature, room temperature and the percentage of the burner is showing. A downside is that if you set the setpoint, the program is interrupted and the setpoint is active until another setpoint is set or until somebody presses a button on the thermostat. It's not possible to send a command that will resume the program. Also, the setpoint reported by the thermostat is the manual setpoint, not the setpoint sent remotely.

Post by **Bwired** » Sun Nov 12, 2006 10:57 pm

OK thanks, That's a lot of useful information. With the interrupt you mean the program which comes with the opentherm controller? Can't you create your own program then I think there will be no limitations at all

. I know thats not easy!! As I told before I hope to start a project regarding this with Heino Peters so your info is very useful. Good luck with hacking the protocol and keep us posted.
Pieter

Pieter Knuvers
www.bwired.nl Online House in the netherlands. Domotica, Home Automation.

Post by **MindBender** » Sun Nov 12, 2006 11:42 pm

<blockquote id="quote">quote:<hr height="1" noshade id="quote">Originally posted by Bwired
 With the interrupt you mean the program which comes with the opentherm controller? Can't you create your own program then I think there will be no limitations at all

.<hr height="1" noshade id="quote"></blockquote id="quote">When you set a setpoint remotely, it will interrupt the day/week program in the thermostat and there's now way to re-engage this program through rs232, so you must have your computer execute a self programmed day/week program. Unfortunately you cannot enable/disable warm water, like the thermostat's program can, so you will loose some functionality. Or efficiency, if you enable warm water 24/7.