Hmm, thanks for the results McKraut. I see something else that is troubling. Stage 2 demand on the TEKMAR closes your three way zone valve, and that should then close the TT terminals, firing the oil boiler. But that has also closed your wood heat loop. This would be great in an either/or situation (either wood or oil), but the TEKMAR sees the two stages as working together. This obviously isnt the case with the way the system is wired up. If it calls for oil, it will close off the feed from the BioMass, and that will sit there and idle.
I quickly skimmed the TEKMAR manual, but couldnt immediately find the setting to adjust for the time delay between Stage 1 and Stage 2. Looks like it might auto-adjust depending on the outdoor air temp, and the difference between the supply temp and target supply temp.
But that still doesnt explain whats up with the aquastat (your original question). It fired when you jumped the TT terminals, but it sounds like you also may want to check how the ZV is wired up. Should be an endswitch on there that makes when the valve opens, and the wire connected to TT should be connected to those terminals. The idea being that we can work backwards from the terminals to figure out the issue. Jumper means boiler will fire when it has a call for heat without the low limit in place. So, we trace it back to the ZV, since thats the next junction. If thats OK, then we move up the line to the TEKMAR.
Agree with Mannino, the Buderus is a great boiler.
Your designer put together a great system for you, but great gravy is there a lot going on there! As you can see, its a real treat to try and toubleshoot