Dear Mr. Valter, https://valter.byl.cz/tr200-asi-nefunguje google found and translated above page, which recommends you know this area well.
I have Junkers Cerastar ZWR heater with noisy TRQ21 thermostat, which I would like to mute (unplug clock) or change to 2-wire new thermostat. You seem to know a lot, maybe could help how to wire heater to accept 2-wire relay thermostats?
Hello, older heaters Junkers Cerastar ZWR do not have a 2-wire relay thermostat connection. New replacement for TRQ21 is FR 120. Older controllers TR100 or TR200 can also be used.
New heaters Junkers Cerastar ZWR accept 2-wire relay thermostat on the pin LR and Ls (now clamp). To further advise You, I need to know exactly what type do you have. It would be best to have a photo of the heater or a photo of the heater identification tag or a photo of the heater connection terminal.
Dear Mr. Valter. Thank you very much for your reply. To prevent any possible mistakes, I finally decided to purchase a compatible used controller... FR100. Thanks.