Temperature controller

Hi I was hoping you might be able to help?

Firstly a question about ABA0 is this unit still current? and can i connect the RTD modules to it OBA2?

I am looking to use a OBA0 Logo PLC with 3 off RTD expansion modules to monitor 5 areas to look after our heating control, But i have a couple of problems.

If i use the PT100/1000 control Analogue threshold trigger it works based on the setpoints low and high if the temp goes below the low setpoint it ignores it? i cant seem to use a lower than symbol i have looked to see what others do but i cant see an easy fix?

With each of these i would like to display the temperature using the basic HMI.

And i would like to use the time clock to give me a frost protection mode when the workshop is empty

But i would also like to be able to raise and lower the setpoint on each of the areas as well as the frost protection, it gets cold here in scotland..

thanks very much, I believe that you are correct thanks for the advice I am away from my pc at the moment so I can't look at what you have put up. So thanks in advance any other advice gladly taken.

Have a great new year

Can i ask how you negate an output i didn't pick up on that? could you let me know i have potentially to move from pt100 to Analogue 0-10v for the control as the sensors will be to far away from the PLC, so i have to convert this to 0-10v control instead of pt100.

 wrote a similar program but cant seem to invert the output?

I found the extra part of your drawing which has the dot n it i couldnt see it in the begining.

I dont need it to be 100% accurate but if i use pt100 the increased resistance will give me large issues, were as if i use the 0-10V scale it should be easier are my thoughts, i was going to use a pt100 to 0-10v transmitter to try an lower the error.

The only other way i could do it is place a Logo on each transmitter but the costs would go up significantly, i have a dual purpose which is to control the heating better in our large wharehouse and stop the heating when the large delivery trucks are at the doors.

I cant seem to quiet get all of this to work together at the moment but im working through it.. any advice as i previously wrote greatfully accepted