Home Automation Domotica Forum Europe, Bwired Forum

Hi,
with firmware 5.6 I experience different behaviour while using the setpoint override from Home Assiatnt. The setup is a Nest / Vaillant OT33 and I connect to the gateway through a D1MINI. While overriding the setpoint from HA it will initially work as expected but after about a minute after ignite the boiler will return to the thermostat setpoint. I my case I only override when the nest is idle (setpoint 10 degrees) and I override it currently with max setpoint (79 degrees) and min modulation (30%).
After reverting back to firmware 5.4 it works again as expected (keeping the setpoint override in place until setting the setpoint at 0 from HA).
Just to share my findings.

- Stephan

This is intended behavior.

Firmware 5.2 introduced a safety measure to prevent runaway heating in case an external device that modified the control setpoint got disconnected or crashed. To indicate it is still vigilant, the device has to send a CS command every minute. If it fails to do so, the CS command is cancelled. Initially, the same timer was used for the CS and SC commands. With firmware 5.5, the commands were decoupled, so each command times out on its own. (There was a bug in the implementation that was fixed in 5.6.)

The fact that 5.4 works for you, probably means that you issue a SC command every minute, which, with firmware 5.4, also keeps the CS setting alive. To use the control setpoint override with firmware 5.6, you will have to arrange for HA to repeat the CS command every minute.

By the way, the minimum value for max modulation (MM command) should always be 0%. It uses relative levels. If the minimum absolute modulation level your boiler can achieve is 30%, then that corresponds to a relative modulation of 0%.