Good morning, i'm currently trying to put together a heating control system using siemens logo, i have a heating system with different zones for hot water and heating with twin pumps etc, most of this i have under control, however i'm looking at the heating and I have been asked can we do weather compenstaion. 

I was planning on using the RTD module for external weather temperature and another for the return temperature from the return heating pipe there is also an existing 240V open and close mixing valve, its not a modulating valve. 

Has anyone done anyting like this before i have had a look about at a few ideas and wondered if anyone has written such a thing or a combination of both. 

The plan is to control the on off times on the existing controller like normal so there is no need for night time set back and they want just standard on off, on the internal thermostat as it is at the moment.

Any help on this would be very much appriciated. 

Any questions please ask!

Hello,

Did you see this POST I think it will help you to start

So I got to bench test this today and it works like a dream many thanks for this i really appriciated this.

Best Regards

Neil