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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.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?