Buderus GB125-22 and RC35 question & suggestion request :-)

christianmlr

Good morning everyone,
I have a Buderus GB125-22 oil‑fired condensing boiler.
Right now I’m using a Buderus RC35 thermostat located inside the house, which controls the boiler via an on/off contact (with the appropriate mounting base and contact jumper).
I have a doubt about how the boiler is operating.
I’ve disabled domestic hot water (DHW), so it is working only to heat the radiators in the house.
The boiler is in a separate room from the house, where it’s cold.
The boiler has an outdoor sensor to read the outdoor ambient temperature.
Now, with:
Thermostat OFF (boiler in standby/keep‑warm)
The boiler continuously heats the water from 40 °C (set using the manual dial on the boiler) up to 58 °C.
The water never drops below 40 °C.
Thermostat ON
The boiler does exactly the same thing, but with more frequent cycles.
I don’t understand whether, in temperature maintenance, the boiler should always bring the water temperature up to 58 °C without letting it drop, or if this is an error caused by the thermostat.
I tried to check whether there are parameters on the RC35 to change these temperatures, but I couldn’t find them.
Can you tell me the correct procedure to carry out this replacement?
How have you set the temperature values in the menu?
Any advice?
Thanks everyone!

Big Ed_4

The RC35 is a room sensor to adjust the outdoor reset heat curve . It helps adjust the boiler temperature to maintain constant circulation . Constant circulation makes the home comfortable with a flat heat curve . A normal thermostat will swing in temperature around 4* which one would feel .. The boiler water temperature will adjust and maintain what is needed to heat the home on that given time or outdoor temperature …

christianmlr

Thank you for your support.
I agree, but I don't understand why the water never drops below 40 °C when the thermostat is OFF (so, for instance, the boiler should remain OFF all day or even all week).
If I need to turn OFF the boiler without cutting the power supply, how should I proceed?
I am considering installing a Wi-Fi thermostat (for example, a Plikc device) to improve efficiency and flexibility (with the RC35 I cannot change the temperature during the day, but with a new thermostat I could).
However, if the situation is like this, it makes no sense because I cannot really turn off the boiler.
I hope my point is clear but What could I do to achieve my target?
Thank you very much.

HVACNUT

Does this boiler have the R2107 controller?

christianmlr

No friend, it is

Buderus GB125-22 BE 1-3 (boiler)

RC35 (controller)

christianmlr

this is a picture of my boiler (when I received it)
Attention:
The RC35 controller is now installed inside the house and not on the boiler.

HVACNUT

I've never seen that control in the States. I thought the R35 was the thermostat. You missed a comma.

Have you tried disconnecting the thermostat wires at the R35? That will at least confirm or eliminate the thermostat and wiring between the thermostat and the R35.

No error code?

Where are you located? There should be Bosch/Buderus customer service. They should be able to help if its programming rather than mechanical. Do you have an electrical meter capable of reading Ohms? If its not programming or an obvious short, they'll probably ask for resistance numbers on sensors.

The GB125 with the BE burner stopped coming here a long time ago. They came with the R2107 controller. I never installed, or have even seen the condensing GB. They didn't last in the States because it was a lot of extra $$$ for a 3% gain in efficiency over the G115 with a Riello burner. The BE burner is awesome.

Big Ed_4

if there was a problem with the wiring or not turned on in the main control, you will get disco lights .. If you never seen lights …. it is disconnected at the main control and all adjustments need to be done at the boiler …