Thema "Betreff: Vitodens 100 Short-Cycling" in Gas

Vitodens 100 Short-Cycling

Josh88 — Sun, 08 Mar 2026 11:56:10 GMT

My Vitodens 100-W B1KE-199 installed in November 2025 has not been functioning properly the entire winter. It short-cycles badly warming up the house in the mornings.
It is sending hot water into old 1970’s baseboard radiators.
It seems to cycle more frequently as the house comes closer to target daytime temperature.
It generates a few A19-50 warnings every day.

I already tested with the red and white thermostat wires connected manually to remove the thermostats as a cause.
Could the temperature sensor be bad?

Any thoughts on what could be going on? Thank you.

Betreff: Vitodens 100 Short-Cycling

divanc — Sun, 08 Mar 2026 18:57:52 GMT

Hallo @Josh88

Bezüglich der Warnung A.19: Sie haben einen Vitodens 200 B2KE-19 und keinen Vitodens 100. Falls der Systemdruck in Ordnung ist und alle Heizkörperventile geöffnet sind, überprüfen Sie bitte die Funktion der internen Pumpe und des 3-Wege-Umschaltventils.

Regarding warning A.19: You have a Vitodens 200 B2KE-19 and not a Vitodens 100. If the system pressure is correct and all radiator valves are open, please check the function of the internal pump and the 3-way diverter valve.

Betreff: Vitodens 100 Short-Cycling

Josh88 — Mon, 09 Mar 2026 01:47:34 GMT

Hi VG, okay thank you, I will ask my contractor to check those when he can get out to me.
Thanks for the info, I appreciate it!

-Josh

Betreff: Vitodens 100 Short-Cycling

Josh88 — Mon, 23 Mar 2026 22:51:42 GMT

Hi VG, my contractor came on Mar 20th and replaced the little temperature sensor, which made a big difference in heating performance and the furnace itself doesn’t cycle on and off, but the burner still turns on and off making the heating temperature swing from 130’s F to 190’s F. Is a properly sized vitodens furnace supposed to keep the burner on through modulation changes only? Or is it okay that the burner turns on and off while heating up the house? …there is some question if the furnace is oversized for the half-inch pipe in my old 1970’s radiator baseboards, so I reduced the maximum heating output (596.0) to 40%, but that didn’t change the behavior. It still goes up to 190F and then turns off the burner to let it cool down to the 130’s F. Thank you for your expert opinion.

Betreff: Vitodens 100 Short-Cycling

qwert089 — Tue, 24 Mar 2026 07:26:56 GMT

>>so I reduced the maximum heating output (596.0) to 40%,

this setting is ignored during startup Phase.

You have to increase the flow throught the heat exhanger --> increase the setting for the pump, open more radiators and reduce the heating curve.

Betreff: Vitodens 100 Short-Cycling

Josh88 — Tue, 24 Mar 2026 11:09:37 GMT

Hi qwert089, yes, we already maxed that out, with 1100.2 at 100% and even put in a stronger zone pump. The radiator baseboards are wide open, nothing more to open, except to turn on zones in the house that don’t need heating.
So are you saying that the modulation should stay above 0% and keep the burner from turning off? (The furnace itself stays on, and the zone pump stays on, it’s just that I can see in the app that the burner goes off (0%) and the heating temperature swings up and down. So modulating down to 0% shouldn’t happen until the house is up to heat, correct?

Betreff: Vitodens 100 Short-Cycling

qwert089 — Tue, 24 Mar 2026 17:54:39 GMT

Hi Josh

Is there a mixer between Vitodens and Zone pump?

Betreff: Vitodens 100 Short-Cycling

Josh88 — Wed, 25 Mar 2026 01:08:59 GMT

A mixer? I’m not sure. Can you tell from this picture? It’s 3 zones with 1/2” pipe in the baseboard radiators.

Betreff: Vitodens 100 Short-Cycling

qwert089 — Wed, 25 Mar 2026 20:46:47 GMT

ok thanks for the picture

no mixer but a Hydronic Seperator.

>>So modulating down to 0% shouldn’t happen until the house is up to heat, correct?

B1HE-199 has a modulation range 5.8 to 58.3 kW

the heat demand of your house with not all zones valves Open is less then 5,4 kW and out of modulation range of the 199 Model

probably B1HE-85 or B1HE-120 would be the better choice for your house.

B1HE-85 has min Power of 2,5 kW and B1HE-120 of 3,5 kW

you can try to use this 2 parameters to reduce the ON /Off cycles.

https://youtu.be/d-HAwlzo0j0?t=3417

Betreff: Vitodens 100 Short-Cycling

Josh88 — Thu, 26 Mar 2026 03:26:33 GMT

Thank you, qwert089. I believe that you are correct. Even though my house is not small at 2600 sq ft of livable space, it seems likely that the half-inch pipe in my 1970’s water baseboard radiators changes the math for a matching furnace.
I’m going to measure the length of baseboard I have and try to calculate my home’s energy profile/heating curve.
Thank you again for your thoughts and suggestions, I very much appreciate them.
-Josh