How to prevent floor overheating ?

[db-wally007]

Hello,

I'm trying to replace my electric floor heating (not water but electric cables based) that was installed when house was built 15 years ago.

The issue is the company behind the system (DEVI) has not made any new products so I've started testing:

• using Shelly Relay switches (Shell 1PM Gen4) to switch heating on/off (set as an Underlying is Versatile Thermostat) with Shelly Add on floor temperate sensor
• Shelly B&T Temperature sensor as room sensor in Versatile Thermostat

I've set this up few days ago but in couple of rooms I've noticed that Shell Add on tempoerature sensor showed that the floor temperature has gotten over 40C.

Is there anyway in Versatile Thermostat to add second temperature sensor thershold (in my case Shelly's Addon temperature floor sensor) as a fail-safe so the cables do not overheat and get damaged ?

If this is not possible, what automation would be recommended to trigger with HASS Automation script ? Disable Thermostat until floor temperature is below the threshold ? Or set it to "OFF" ?

[db-wally007]

ok, so to answer half of my question - setting "Safety" entity to "Unsafe" manually or via helper script makes no difference. Thermostat does not go into "Safety" mode as expected.

So my remaining question, what is the best way "externally" (via helper or script) to gracefully stop VThermostat from heating ?

[jmcollin78]

safety is described here: https://github.com/jmcollin78/versatile_thermostat/blob/8.3.1/documentation/en/troubleshooting.md#why-is-my-versatile-thermostat-going-into-safety-mode and you cannot set it manually.

But you can always turn the VTherm off.

[jmcollin78]

Hello @db-wally007 ,

If the floor is at 40°C I guess the room temperature should be much more above the setpoint and then Vtherm should lower the heating power. What is wrong in you installation that prevent this mecanism to work ?

Can you please give me your custom attributes as described here: https://github.com/jmcollin78/versatile_thermostat/blob/8.3.1/documentation/en/reference.md#custom-attributes

There is no way to add a second temperature sensor out of the box.

[db-wally007]

If the floor is at 40°C I guess the room temperature should be much more above the setpoint and then Vtherm should lower the heating power. What is wrong in you installation that prevent this mecanism to work ?

When we are away we keep the house in frost protection. Our ceilings are 5m high and brick is 40cm+ thick so it takes awhile (24h+) to properly heat up the area. The floor can get very warm while ambient temperature is still below 20C in some open areas.

This is used to happen with DEVI installation as well. The DEVI system had a dual temperature setting though.
Room temperature and then floor max threshold that would stop the heating at 40C and resume once the floor cooled off to 35C.

For now, I've written automation helpers that set VThermostat to frost preset when the floor temperature sensor is above 40C and resume when it is below 35C. This works but out of the box its not quite clear why thermostat is in frost mode when we are home.

Do you think there would be a way to add something like Window detection but for the second (floor or otherwise) temperature sensor ?

Or even allow user to change safety setting manually or via automation ?

Thank you

My VThermostat settings below - please note that since we've been home for 4 days now, the floor temperature is not as high as I experienced the issue few days back.

hvac_modes:
  - heat
  - "off"
min_temp: 5
max_temp: 25
target_temp_step: 0.5
preset_modes:
  - none
  - frost
  - eco
  - comfort
  - boost
current_temperature: 18.7
temperature: 21.5
hvac_action: heating
preset_mode: comfort
hvac_mode: heat
ema_temp: 18.61
specific_states:
  is_on: true
  last_central_mode: null
  last_update_datetime: "2025-12-21T08:49:26.695196+01:00"
  ext_current_temperature: 0.777777777777777
  last_temperature_datetime: "2025-12-21T08:42:35.187888+01:00"
  last_ext_temperature_datetime: "2025-12-21T08:40:49.496178+01:00"
  is_device_active: true
  device_actives:
    - switch.switch_studio_bathroom_heater
  nb_device_actives: 1
  ema_temp: 18.61
  temperature_slope: 0.35
  hvac_off_reason: null
  total_energy: 11.18
  last_change_time_from_vtherm: "2025-12-21T07:00:00.219844+01:00"
  messages: []
  is_sleeping: false
  is_locked: false
  is_recalculate_scheduled: false
configuration:
  ac_mode: false
  type: over_switch
  is_controlled_by_central_mode: true
  target_temperature_step: 0.5
  minimal_activation_delay_sec: 290
  minimal_deactivation_delay_sec: 290
  timezone: Europe/Prague
  temperature_unit: °C
  is_used_by_central_boiler: false
  max_on_percent: null
  have_valve_regulation: false
  cycle_min: 10
preset_temperatures:
  frost_temp: 5
  eco_temp: 18
  boost_temp: 22.5
  comfort_temp: 21.5
  frost_away_temp: 0
  eco_away_temp: 0
  boost_away_temp: 0
  comfort_away_temp: 0
current_state:
  hvac_mode: heat
  target_temperature: 21.5
  preset: comfort
requested_state:
  hvac_mode: heat
  target_temperature: 21.5
  preset: comfort
is_presence_configured: false
is_power_configured: false
power_manager:
  device_power: 1
  mean_cycle_power: 1
is_motion_configured: false
is_window_configured: false
is_window_auto_configured: false
is_safety_configured: true
safety_manager:
  safety_state: "off"
  safety_delay_min: 2880
  safety_min_on_percent: 1
  safety_default_on_percent: 0
is_lock_configured: true
lock_manager:
  is_locked: false
  lock_users: true
  lock_automations: true
  lock_code: false
is_over_switch: true
on_percent: 1
power_percent: 100
vtherm_over_switch:
  is_inversed: false
  keep_alive_sec: 0
  underlying_entities:
    - switch.switch_studio_bathroom_heater
  on_percent: 1
  power_percent: 100
  on_time_sec: 600
  off_time_sec: 0
  function: tpi
  tpi_coef_int: 0.9
  tpi_coef_ext: 0.01
  tpi_threshold_low: 0
  tpi_threshold_high: 0
  minimal_activation_delay: 290
  minimal_deactivation_delay: 290
  calculated_on_percent: 1
  vswitch_on_commands: []
  vswitch_off_commands: []
friendly_name: Studio Bathroom Thermostat
supported_features: 401

[jmcollin78]

Ok understodd your point.

Do you think there would be a way to add something like Window detection but for the second (floor or otherwise) temperature sensor ?

Yes this could be a solution:

1. create a virtuak template binary_sensor which is 'on' when the floor temperature is too high,
2. set this new sensor as window sensor,
3. configure the window feature with switch to Frost protection or Eco and you are ready.

If you have a real window/door sensor you can combine it with an "or" condition with a helper and set the combined sensor in VTherm configuration.

you cannot do that with safety feature which is only calculated in internal.

[db-wally007]

Thanks, I did set up binary.sensor already. Did not want to link it to "window" detection as it'd be super confusing in the dashboard (we do not use the feature)

Do you think it'd make sense to add the floor overheating protection feature ?

If not, I'll see if I can hack it & find where in the code "Window" detection is declared and rename it to "Underfloor overheating detection". Logic would stay the same I guess, so its just name ...

Ok understodd your point.

Do you think there would be a way to add something like Window detection but for the second (floor or otherwise) temperature sensor ?

Yes this could be a solution:

1. create a virtuak template binary_sensor which is 'on' when the floor temperature is too high,

2. set this new sensor as window sensor,

3. configure the window feature with switch to Frost protection or Eco and you are ready.

If you have a real window/door sensor you can combine it with an "or" condition with a helper and set the combined sensor in VTherm configuration.

you cannot do that with safety feature which is only calculated in internal.

[jmcollin78]

Hello, this is not so easy. There is a configuration for window detection that indicates what is the action to take if the window is detected as open. So you will to have to replicate also this configuration menu and take into account this configuration to decide what to do with the target temp or preset or hvac_mode.

Don't underestimate the job needed and the tests to write (what about if many detection is done: overheating and overpowering ? Who takes the precedence ?).

What I suggest is to do an "emergency stop" feature which can be used in other contexts than yours. This need no configuration, the action is always to stop (set the hva_mode to hvac_off). Only a binary_sensor is needed in that case or better a template. If the template evaluates to True then an emergency stop is done.

If you think this is a good way to solve your case, I could help to implement this. This is not so complicated this time.

[db-wally007]

Thank you for your response. I think I'll settle on your suggestion and keep only binary sensor logic. I'll simply show conditional alert icon on my bubble thermostat card when underfloor safety kicked in (ie. when binary_sensor is true)

[caiusseverus]

I have two ideas for this:

First, you could have an automation dedicated to controlling the floor power. It would trigger on floor temperature change, and heating demand change (ie room VTherm calling for heat). The automation would only energise the floor when there is both heating demand, and the floor temperature is below the level you set.

This way, the VTherm is only concerned with asking for heat from the floor and you don't have to worry about changing heating modes etc on the VTHerm to keep the floor under control.

The second idea is to create a second VTherm over switch to control the floor itself. Use the floor temperature as the temperature input, and the relay as the output. Set the room temperature as the external temperature sensor. Then set the initial values for the internal coefficient to something like 0.5, and the external coefficient to 0 and let the automatic tpi algorithm work out where to set them over time.

Have the cycle time at 10 minutes, and you should get quite good control over the floor temperature, that you can easily modify by tweaking the VTherm set point.

The first VTherm then just switches the second VTherm on and off to control room temperature.

[db-wally007]

I have two ideas for this:

First, you could have an automation dedicated to controlling the floor power. It would trigger on floor temperature change, and heating demand change (ie room VTherm calling for heat). The automation would only energise the floor when there is both heating demand, and the floor temperature is below the level you set.

This way, the VTherm is only concerned with asking for heat from the floor and you don't have to worry about changing heating modes etc on the VTHerm to keep the floor under control.

The second idea is to create a second VTherm over switch to control the floor itself. Use the floor temperature as the temperature input, and the relay as the output. Set the room temperature as the external temperature sensor. Then set the initial values for the internal coefficient to something like 0.5, and the external coefficient to 0 and let the automatic tpi algorithm work out where to set them over time.

Have the cycle time at 10 minutes, and you should get quite good control over the floor temperature, that you can easily modify by tweaking the VTherm set point.

The first VTherm then just switches the second VTherm on and off to control room temperature.

Thank you for suggestions. I've settled on your previous suggestion and use "Window" binary sensor as I really want to keep the system as "simple" as possible so others in the house can maintain it when/if I'm not around.

We have 9 thermostats in the house (each room/area has its own underfloor heating and thermostat) so complexity could quickly spiral out of control.