How Auto start/stop and central boiler are working together ?

[Jonybat]

Hi

First of all, thank you for this great integration.

I have an air-water heat pump, with 7 vtherms (8 total TRVs). I have the scheduler integration that changes the presets around the clock, and another that disables the auto start/stop during the day and enables it back during the night (as exemplified in the docs).

However, I noticed that when all vtherms reach stable target temp during the day, the central config turns off the heat pump. I know this, because the temp is set to 10, which is what I configured as the stop command.

I am sure the auto start/stop is disabled for all vtherms, because I have the VT UI cards for all vtherms in the dashboard. Also, I never disable or enable the climate entities manually. At most, I might change the preset for a vtherm, but very seldom.

Where else could I look to troubleshoot this? Or is this an actual issue?

Cheers

[Jonybat]

Just happened again, and I went through the logbook and found that what is triggering the off command is actually the false away presence state.

Have to fix the device tracker issues, but in any case, is it expected that the central boiler start/stop be triggered by presence state, even when start/stop toggle is disabled for all vtherms?

[jmcollin78]

Hello,

There is no direct link between central boiler activation / deactivation and auto-start/stop.

The central boiler is activated when the number of actives devices is > a threshold.
So it is always possible that auto-start/stop activate a Vtherm that will finally turn on the central boiler but that is all. Whatever the cause of the start of the Vtherm is, the central boiler will be activated is threshold is exceeded (auto-start/stop or not).

Maybe I don't understand exactly your case. don't hesitate to explain with screen copy if needed.

[Jonybat]

There is no direct link between central boiler activation / deactivation and auto-start/stop.

So what is the purpose of the auto start/stop?

The docs for auto start/stop say

This feature allows VTherm to stop an appliance that doesn't need to be on and restart it when conditions require it

My understanding was that vtherms with auto start/stop enabled were somehow considered in the nb device active for boiler, which was then used to determine if start/stop command is sent to central boiler/appliance.

Examples:

• 2 vtherms, both with auto start/stop enabled, reach target temp > stop command sent to central boiler
• 2 vtherms, only one with auto start/stop enabled, reach target temp > central boiler continues running

[jmcollin78]

2 vtherms, both with auto start/stop enabled, reach target temp > stop command sent to central boiler
2 vtherms, only one with auto start/stop enabled, reach target temp > central boiler continues running

I understand this could be confusing but this is not the purpose of the auto-start/stop feature. It is designed to set to off a VTherm when temperature conditions makes it unnecessary for a long time. The purpose is to save power (some AC device consume some Watts if there are 'on' but don't heat).

And on the contrary, it starts a Vtherm when temperature conditions makes it necessary.

This replace the manual turn-on / turn-off for people who to save some watts when their is not need to heat (or cool).

Example:

1. room is at 20°, setpoint is 18°, Vtherm is 'on' in heating mode (hvac_mode is 'Heat'),
2. because room temp is > setpoint, VTherm is not heating ( hvac_action is Idle),
3. So the central boiler is 'off' because there is no requested for heat (note that VTherm is 'on'),
4. after a while, the auto-start/stop consider there is no need to keep the VTherm 'on', so it decides to stop the VTherm,
5. Vtherm is stopped (hvac_mode = 'off') with havc_off_reason = 'auto-start-stop'
6. Because central boiler was already 'off' this command have no impact on it.

This is why I said there is no direct impact of auto-start/stop and the central boiler command.

Moreover, is VTherm was heating (hvac_action = 'heat') and the central boiler is 'on', the auto-start-stop will NOT turn off the VTherm because it is needed for heating.

[Jonybat]

Right, it is confusing. I guess I was mislead by the "appliance" name in the auto start/stop feature docs and the difference between a climate entity being "on" and "heating". Appliance there refers to the individual appliance(s) controlled by the vtherm, not the central one.

I think I understand now. Basically, the auto start/stop feature is mostly designed for mini split air conditioner units (and other climate appliances that use power when the climate entity is "on" but not "heating").

It is then definitely not meant to use with passive heating "appliances", like TRVs or other kinds of valves, since there is no practical difference in the valve being "off", or "on" but set to 0% open.

In any case, I will switch my heat pump to weather compensation, and disable auto start/stop feature for all vtherms (TRVs) + disable central boiler start/stop commands. Running the heat pump continuously at a lower flow temperature seems to be more efficient (and likely less wear) than stopping it when away/during the night, and running higher flow temp otherwise.

Thanks for the clarification!

[jmcollin78]

Exactly. This has been done for split reversible AC unit and not at all for central boiler which are controlled natively by the central boiler feature.

[jmcollin78]

Note i rename and pin this conversation to the QA category.