Aqara Floor Heating Thermostat W500 - NTC combined with ambient sensor

[luke1988]

Hi everyone!

I have a question regarding the Aqara Floor Heating Thermostat W500.

I have electric floor heating embedded in the top layer of concrete throughout the house, with either tile or vinyl flooring on top.

For vinyl flooring, the floor temperature must not exceed 30 °C, similar to what is described in this topic.

How does the Aqara Floor Heating Thermostat W500 work with the Floor Material configuration?

My understanding is that once the NTC floor sensor is connected, the thermostat will automatically stop heating when the maximum temperature for the selected floor material is reached, even if the Source of Temperature and Humidity Data is configured to the Built-in temperature and humidity sensor.

This is my current configuration:

So, does the thermostat stop heating once the preconfigured maximum floor temperature is reached?

If so, this would not only solve the floor material protection issue, but also a serious comfort problem I experienced with my previous thermostat vendor.

Because the heating cables are embedded in concrete, it takes a long time to heat up the entire mass of concrete and tiles. On the other hand, once the target temperature is reached and heating is switched off, the floor continues to emit heat into the room. As a result, the room temperature keeps rising. After an hour or two, the temperature starts falling again, which triggers the thermostat to start heating once more. However, it then takes another hour to heat the floor mass again.

This results in a large sinusoidal temperature swing, roughly from 18 °C to 25 °C, which is far from comfortable.

I can switch the Source of Temperature and Humidity Data to Floor Temperature Sensor (NTC), but this introduces another problem.

Normally, I would set the thermostat to 22 °C. However, because the NTC sensor is embedded somewhere inside the concrete, it has to be set to a much higher value (based on my experience, around 26–29 °C) in order to maintain an ambient room temperature of 22 °C. This is unusual but still manageable.

The tricky part is outdoor temperature variation. As the outdoor temperature drops, the configured floor temperature must be increased to maintain 22 °C indoors. On sunny and relatively warm winter days, I keep the thermostat set to around 26 °C, while on days below freezing, I need to increase it to 28–29 °C.

All of these inconveniences would be easily resolved if the Aqara Floor Heating Thermostat W500 could use the built-in temperature and humidity sensor for room temperature control, while simultaneously enforcing floor temperature limits using the NTC sensor.

[gafich10]

@luke1988

So, does the thermostat stop heating once the preconfigured maximum floor temperature is reached?

Hello, yes, the heating will turn off when the set temperature is reached. Also, in an emergency, if the floor overheats severely (40°C), the W500 thermostat will switch (completely unlock) to emergency mode, which can be reset only after the floor cools down.

@luke1988

This results in a large sinusoidal temperature swing, roughly from 18 °C to 25 °C, which is far from comfortable.

To solve this problem, I recommend using an additional thermometer (I recommend W100) and combining it in the automation where W500(NTC)+W100 will be involved. You can set the floor temperature with a minimum difference (for example +/-0°C) and set W100 (for example 22°C) +/-0°C. In this mode, the floor will be kept in the minimum heating mode when the temperature drops to W100 in the room.
An added bonus for the W100, you can connect it to the W500 and control the temperature you need for the floor (in your NTC version)

@luke1988

The tricky part is outdoor temperature variation. As the outdoor temperature drops, the configured floor temperature must be increased to maintain 22 °C indoors. On sunny and relatively warm winter days, I keep the thermostat set to around 26 °C, while on days below freezing, I need to increase it to 28–29 °C.

I solve this problem with a temperature sensor placed outside. You make three automations to turn on the heating at different temperatures depending on the outdoor temperature. A certain range of outdoor temperatures turns on the corresponding automation that starts the required temperature (and turns off the one that was working) for heating.

@luke1988

All of these inconveniences would be easily resolved if the Aqara Floor Heating Thermostat W500 could use the built-in temperature and humidity sensor for room temperature control, while simultaneously enforcing floor temperature limits using the NTC

At one time I suggested using dual control for the W500. I think in this version of the W500 it is impossible to connect two thermometers for simultaneous control due to hardware incompatibility, perhaps this will be taken into account in future versions.

[luke1988]

Thanks @gafich10 for your reply.

To confirm my understanding:

Hello, yes, the heating will turn off when the set temperature is reached. Also, in an emergency, if the floor overheats severely (40°C), the W500 thermostat will switch (completely unlock) to emergency mode, which can be reset only after the floor cools down.

It only works when the Source of Temperature and Humidity is set to Floor Temperature Sensor (NTC). Then it keeps the temperature on NTC within pre-defined range (for Wood and Vinyl option particularly it will be ~5-27 °C)

The hard switch configured for 40°C work in any configuration, but the threshold 40°C itself is not configurable.

Am I right?

[gafich10]

@luke1988

The hard switch configured for 40°C work in any configuration, but the threshold 40°C itself is not configurable.

Yes, you understood correctly, this is hardware firmware (constant).

[luke1988]

@gafich10 thanks for your responses.

The hardcoded value 40°C has been increased to 45°C during the recent update.

I am glad there are workarounds, however it creates a need to have another devices (W100) and need to create set of automation rules which doubles (triples, quadruples) if you want to achieve same functionality as native Smart Schedules in W500.

Honestly I consider this a huge disappointment. Aqara Thermostat W500 already has both the ambient temperature and NTC temperature values. Only missing puzzle is the ability to set threshold for NTC temperature independently. The smaller the missing puzzle is the larger disappointment is.

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