Difference between Temperature Constant and Room Setpoint

[hvxl]

Your log contains hardly any data before you set the thermostat to 19.5. So I cannot compare the before and after situation. The log stops before heating is switched off again. So no comparison can be made there either.

[Kytrix]

Hello,

Here is a new test:


my temperature order was 20 but my room was 18.
at 8:19 I tried :
CH=1
then
MH=2
then
RR=0
then
RR=1

nothing happens at each step, the CH stay off.

so at 8:30 I changed the thermostat temperature (was at 18)
and then it works as always.

The only thing I notice (to explain how the thermostat awake the boiler) is that log:

Code: Select all

08:30:25.308952  T00000300  Read-Data   Status (MsgID=0): 00000011 00000000
                               - CH enable: enabled (1)
                               - DHW enable: enabled (1)
                               - Cooling enable: disabled (0)
                               - OTC active: not active (0)
                               - CH2 enable: disabled (0)
                               - Summer/winter mode: winter (0)
                               - DHW blocking: unblocked (0)

previously to the order change it was:

Code: Select all

08:29:55.303927  T80000200  Read-Data   Status (MsgID=0): 00000010 00000000
                               - CH enable: disabled (0)
                               - DHW enable: enabled (1)
                               - Cooling enable: disabled (0)
                               - OTC active: not active (0)
                               - CH2 enable: disabled (0)
                               - Summer/winter mode: winter (0)
                               - DHW blocking: unblocked (0)

Do you think is it possible the thermostat through a read data of MSGID=0 indicate to the boiler that it had to go to heat mode ???



the log file:
https://transfert.free.fr/JLtvYri

Regards.

[hvxl]

Do you think is it possible the thermostat through a read data of MSGID=0 indicate to the boiler that it had to go to heat mode ???

Yes, MsgID 0 is unusual in that it is half write, half read. The high byte contains instructions from the thermostat to the boiler. In the response, the low byte contains status information from the boiler to the thermostat. The spec just defined that a Read-Data message must be used for this MsgID. Write-Data might have been more logical. But the spec writers chose differently.

In a traditional central heating system, the thermostat instructs the boiler to start heating by sending a control setpoint and CH enable (ID0:HB0=1). It makes some sense that your system also wants to see the CH enable bit before it starts heating.

You can control the CH enable bit using the CH command, but only when using external control of the control setpoint. So you'll have to send a CS command as well, even though your thermostat never sends MsgID 1. Note that if you specify a temperature of 8 degrees or higher in the CS command, you have to repeat the command every minute. So you may want to use something like CS=5, at least during testing.