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Honeywell TH8110U1003 strange behavior
I bought a new thermostat, and it behaves differently from my old thermostat (also Honeywell, older model). I'm trying to understand whether this is an intended behavior or a bug. I have a steam heat, and I set the cph to 2, but I feel this is not related to the problem.
So, I'm using the old thermostat as a control thermometer, it's located right on top of the new thermostat but is not wired. I observe the following.
Let's say both thermostats show 62. The schedule calls for 65, so the new thermostat calls for heat, boiler kicks in. After 15 minutes radiators start to fell warm, and the temperature display on both thermostats starts to go up. In 5-10 minutes both thermostats show 65. Here is the strange behavior, Instead of turning off, the new thermostat continues running for another 20 minutes, all this time showing 65 as if temperature stays the same. The old thermstat at the same time goes up to 68 which seems absolutely natural and sure feels right. After this additional 20 minutes (that were not required at all), the new thermostat goes off, and only then its displayed temperature slowly goes up the 68 - the same that the old thermostat shows.
Can anyone explain to me what is happening? This does not seem like the new thermostat is 'learning', or does it? For me it looks like it significantly overshoots by working extra 20 minutes, but does not really know about it, as it thinks that all this 20 minutes the temperature is still 65.
Thank you and best regards.