Setting deviation in WD LWT mode and write budget

[michelwilson]

I'm working on an idea where I want to use the deviation from the WD LWT curve to modulate the heat output of my Altherma E-series heat pump. Currently I'm using on/off control which puts a lot of wear on the compressor I believe. My question is: is this going to cause eeprom wear issues? I noticed that writing to this setting causes the write budget to decrease. However: the deviation is not restored if I power-cycle the heat pump, so this must mean it's not actually written to the eeprom ... right?

[Arnold-n]

We are not sure, but it is likely that the Altherma 3 series implement flash wear leveling any way, so it likely isn't an issue. Still, that a power-cycle overwrites the deviation suggests but does not guarantee that it does not write the deviation value to flash/eeprom. I'd recommend to limit writes to less than 2x/hour - faster does not make much sense I guess.

[michelwilson]

Not sure if that would work, my idea is to use an OpenTherm thermostat, and map the relative modulation level (0-100%) to (for example) -5 to +5°C WD curve deviation. I have to see how often, and by how much, the thermostat updates the modulation level. The system is already pretty slow, so my fear is that if I only update the offset twice per hour the thermostat will have a hard time controlling the temperature. Anyway, thanks for the response :)