Coordinating Boiler with Air Handler

[7jdwhf5nbd-coder]

Hello,

First thank you to the developers for creating this fabulous tool for better boiler control!

I am working towards fine tuning my set-up and struggling to fully understand the settings and how to optimize my system.

My system:
Hardware:

• Viessmann 100-W Boiler (very oversized),
• Hydronic air handler with primary / secondary piping connection to boiler via low-loss header

Old Controls:

• Three Sensi thermostats (dumb on/off - not OT) connect to the air handler,
• Heat calls turn on the secondary pump and adjust fan speed depending on number of zones/thermostats calling,
• Air handler has a dry contact that is then connected to the boiler to signal a heat call (primary pump on and flame if necessary).

New Controls:

• Home Assistant with SAT and Open Therm Gateway OTGW (Nodo Shop),
• I have disconnected the dry contact from the air handler to the boiler, however this dry contact could be connected to the OTGW thermostat terminal,
• Original Sensi thermostats are connected to HA.

In general I'm seeing improved control of the boiler, but I have noticed that my thermostat heat calls to the air handler are at times uncoordinated from the SAT heat calls to the boiler. For example when the house temperature is at or near set point SAT ends its heat call while the thermostat remains on.

I noticed this is the documentation, but it did not seem to function as expected when I set my primary thermostat (coldest part of the house) in Areas: Thermostat:

Primary: Users can add their physical thermostat. SAT will syncronize the hvac_action of the physical thermostat with the SAT climate entity's hvac action, that means if the physical thermostat doesn't require heating then the SAT climate entity hvac_action will remain at idle. Also the physical thermostat's room setpoint stays in sync with SAT climate entity. Moreover the physical thermostat will act as a back up if any failure to HA occurs.

My main question: how to I ensure that the heat calls on the air handler are coordinated with the boiler? Should I connect the air handler dry contact to the OTGW thermostat terminals (I understand there is some undesirable potential behaviour where first heat calls start at max water temp set point and max modulation https://otgw.tclcode.com/standalone.html#onoff)?

Below are some of my settings with some screenshots:
SH=50
MM=20
System: Radiators
Heating curve coefficient = 1.6
Automatic Duty Cycle: ON
Synchronize Climates with Mode: ON
OPV=10
*auto calibrated OPV was 51, but produced some weird behaviour (but I didn't test for very long)

[7jdwhf5nbd-coder]

Please disregard, I believe I found answers to my questions in this post:
https://community.home-assistant.io/t/custom-component-smart-autotune-thermostat/550542/101?page=6

During the initial configuration, SAT asks you to define a main thermostat. This isn’t a physical device, it’s a virtual zone representing your primary room, often the living room (especially if it has multiple radiators). This room typically plays a leading role in regulating overall heating demand.

In the Configure Sensors section, set the Inside Sensor Entity to the temperature sensor in your living room, this is the reference for managing that room’s heating.
Multi-Room Setup (Areas)
In the Areas section:

• Leave the Thermostat field empty.
• In the Radiators field, add the climate entities (TRVs) from your living room—the main zone.
• In the Rooms field, add the climate entities (TRVs) for the other rooms in your home.
  How It Works
• When you adjust the SAT setpoint, the living room TRVs will follow that change.
• If only the other rooms (zones) request heat (e.g., bedrooms at night), SAT will provide heating only for those zones, adjusting the boiler’s flow temperature accordingly.
  This setup allows SAT to balance energy efficiency and comfort in a multi-zone system without needing a dedicated central thermostat device.
  If you have any other questions, feel free to ask.