How to interpret the symbols that indicate the smart thermostat (V3+) is requesting heat?
My smart thermostat is connected to the "NO" and "COM" connections and hooked up to an non-modulating (old school) on/off boiler.
I'm trying to decypher the meaning of the icons in the Tado app showing 1, 2 or 3 wavy lines. I was assuming they all mean that the thermostat is requesting heat from the boiler, but that actually does not seem to be the case.
It seems (i spent quite some time at attic recently observing the boiler) 1 wavy lines is still 'off', 2 wavy lines is sometimes 'off' and sometimes 'on', and 3 is 'on'. Especially 2 wavy lines is confusing, I've made sure the boiler is not switching off for other reasons (like flow / return temperature limits or oscillating prevention).
Is there any information what the meaning is of the three different levels of heat requests?
What is the point of having 3 different levels in my use case where the boiler has just two states (on and off)?
The reason I'm asking is that the thermostat is not doing a very good job at maintaining the set temperature. We have underfloor heating with 2 supporting radiators (no TRVs, just opened valves). The thermostat seems very unable to learn the (long) delay involved before the requested heat manifests itself in the room. (I have configured the App to make it aware of both the on/off boiler, and underfloor heating).
Answers
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Similar posts, but unfortunately not very active:
https://community.tado.com/en-gb/discussion/16456/heat-line-info-in-the-app#latest
https://community.tado.com/en-gb/discussion/comment/33228#Comment_33228
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@AzertyNL Tado, like other smart thermostats, is a TPI thermostat. The App may visually indicate a room is heating but this does not mean the heater is on at that moment of time. For instance if the TPI value is 25% then the thermostat will be switching the gas heater on for 15 minutes in each hour. You can check the TPI value by looking at the Heating Activity under Care & Protect. It looks like one wave is 0-33% and 2 waves is 34-66%. This modulation of the heat output is meant to be more efficient than blindly switching the thermostat on/off.
Customer support can tweak the configuration for you to suit a UFH setup. They can also adjust the minimum on time.
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Thank you @GrilledCheese2 for providing this information. This is my first introduction to the TPI control system. But based on what I've learned after reading some material I will try to answer my own question to hopefully help to inform others as the question appears to pop-up periodically.. (Experts please comment if the stuff below makes sense or is nonsense)
The 1,2 and 3 wave line symbols do not directly correspond to the thermostat requesting heat from the boilerat that time. That specific information is not available in the App currently (December 2022)
The following tries to explain the relationship between the wavy line symbols and an on/off relay boiler actually being requested to switch on or not:
There are two cases:
case 1:
The current temperature is far below the set temperature (outside the proportional band) causing the thermostat to request heat constantly, which would translate to 3 wave lines being indicated.
case 2:
When the current temperature is very close to the set temperature (inside the proportional band), the thermostat estimates (based on historical learning) what percentage of the time the boiler needs to be switched on to provide heat to closely match and maintain the set temperature for the next limited time period (could be the next 5,10,30 minutes or so, it seems)
When it estimates no heat is needed -> no wavy lines symbol (boiler will be 'off')
when it estimates <33% of the time heat needs to be requested -> 1 wavy line symbol shows (so at any point in this time period there is a small chance (of 1-33%) the boiler is actually asked to switch 'on')
when it estimates 34-66% of the time heat needs to be requested -> 2 wavy line symbol (so there is a chance of 33-66% chance the boiler is actually asked to be 'on')
when it estimates >67% of the time heat will be needed -> 3 wavy line symbol (so the chance is much higher the boiler is actually 'on' a any time)
This brings up a new question for me: Is the information available what the delta Temp is that Tado uses to define the width of the proportional band?
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