Connecting a Viessmann Vitodens 100W combi boiler to Nest Thermostat with OpenTherm

[@АлександрАндреев-ь7ф]

*Works as expected **Fastly.Cool*

[@alanrisk7027]

Hi Dave. I have moved to a flat with a Vitodens 100. I don t know how to operate the remote controller. Any ideas about instructions? Looked on website but can t find. Thanks

[@grayhalf1854]

The connections to the nest link at 4:10 ... is there any voltage across that connection? Or is it simply powering the boiler up when the thermostat calls for heat and makes a connection across those two wires? (So just shorting them would mean the boiler would fire continuously??)

[@chrisakester9546]

Great Video followed it exactly, but I get cannot find opentherm device error when setting up the nest I have the same boiler I have temporarily wired it as an on off system but would like to use opentherm Do you have any suggestions

[@DaveDoesUK]

Did you use the X21 cable harness?

[@chrisakester9546]

@@DaveDoesUK Yes I bought a new one

[@sinner_8779]

Hello, i set up my 050-w to opentherm and the pump its working non stop. The burner works ok. Any ideea why the pump its working non stop? When i mounted the thermostat i removed that link from 230v .

[@eliotmansfield]

Dont suppose you could tell me the pinout for the brown cable with the choc block on the end for opentherm - my boiler doesn't have that connector, i can make one up easily enough - but I cant find a drawing which shows which is pin 1,2,3,4 on the actual PCB.

[@DaveDoesUK]

There's a diagram on the black cover, I believe it is pins 1 & 2

[@eliotmansfield]

@@DaveDoesUK Thanks - just looked at the pcb and pin 1 is marked.

[@DaveDoesUK]

You can see it on this part of the video from the manual too kzbin.info/www/bejne/nZjScp1pataKZrc

[@Maxiride]

The manual also says that the jumper labelled D in the wiring diagrams has to be removed. Didn't saw this step in your video, did you remove it anyway?

[@jlangham8511]

This wire/link/jumper had already been removed when the boiler was installed. But yes, you need to remove the jumper cable linking 1 and L. If you didn't remove this wire/link/jumper, the boiler would constantly run the heating.

[@Maxiride]

​@@jlangham8511Thank you very much! Installed a Netatmo modulating thermostat and works smoothly.

[@Billybobnob]

Do you need to do anything to make the boiler start using open them?

[@jorkirasalas2726]

Nest documentation seems a bit sparse. With OpenTherm connected does the boiler and pump run all the time? Or only when a CH period is scheduled?

[@pareshcha9641]

Hi Dave, could you let me know where you get the choc connector with the 4 brown wires for the open term from, as I have tried to google with no luck. Thanks

[@DaveDoesUK]

Link is in the description

[@pareshcha9641]

@@DaveDoesUK thankyou

[@iainlinfoot2781]

Great explanation but as other comment, nest cannot find opentherm device, error H73. My boiler is 100w heat only not combi but shouldn't be a difference for opentherm? Contacted Viessmann and they told me this boiler has old protocol so not compatible with nest! - Does anyone have a fix?

[@DaveDoesUK]

Maybe it only works if its the combi version with hot water. The model number of mine is WB1C 26kW if that helps?

[@iainlinfoot2781]

@@DaveDoesUK Yes mine is WB1B heat only and confirmed does not have OpenTherm. Very disappointing as its not clearly stated!

[@chrisakester9546]

@@DaveDoesUK mine is also the WB1C I even bought the X21 wiring loom from Veissman. What voltage do you have across the opentherm coupling?

[@DaveDoesUK]

@@chrisakester9546 i see 6-7v

[@DaveDoesUK]

Just a thought, have you done the factory reset procedure on the boiler itself?

[@PereiraShane]

Hi Dave, u got the new 2021 boiler Veizzman vitodens 100w and the boiler installer said it nest does not work with that specific boiler. Any suggestions ?

[@DaveDoesUK]

Mine was installed in 2013, and I fitted the Nest to it in 2017. Not sure what they have changed on the recent model you have, you should still be able to connect the Nest using the normal wiring diagram provided by Nest but you probably won't get OpenTherm.

[@DannyDL1ght]

The new models with wifi have opentherm, your installer was most likely drunk or stupid

[@PereiraShane]

@@DannyDL1ght thanks yeah I had to ring veissman support and they say Opentherm is compatible with nest and then finally got the installer to change it from ON/OFF to opentherm.

[@DannyDL1ght]

@@PereiraShane do you also use the vicare app or not?

[@PereiraShane]

@@DannyDL1ght @PainDannyful Yup I do have the veissmann app installed but since it's changed now to opentherm with Nest, Nest system takes over the operating controls for the boiler. The only thing I can control is hot water temp. Also Holiday feature on veissmann app is not available to me. So have to use Home/Away feature on Nest

[@cavendishelectricals]

Top Man! A Star!

[@MrKlawUK]

for the opentherm setup, is the 75c the radiator flow temperature? If so, is that the max and does it vary based on weather and/or load - so will lower flow temperature as the radiators approach the target temperature?

[@DaveDoesUK]

Yes that is all correct. You may be able to set it slightly lower, depends on the energy efficiency of your home and how quickly you want your radiators to heat up.

[@DaveDoesUK]

There's a good explaination on flow temperature here www.theheatinghub.co.uk/articles/turn-down-the-boiler-flow-temperature

[@DaveDoesUK]

I've adjusted mine down to 65 degrees, seems to be working fine. Got my thermo set to 18 degrees, to keep the chill off. For 5 hours of use in the evening I'm using roughly £3 of gas per day.

[@dacelticcross]

Is this the old vitodens 100 because the new ones have copper pipes inside ?

[@DaveDoesUK]

Boiler was installed in 2013 according to the certificate I have.

[@CrashUK28]

I have vitoden 100 2021 it has copper pipes inside.

[@BenjiMcbarett]

Hello, whats the supply option to 75 means ? I need to put to 75 everytime ? The temperature set to the Nest is bit the same on the boiler screen when Im running water. Anyone get an Idea ? Thank you

[@Nickolas63000]

Doing it ok but hot water setup at 45 but viessmann is going higher than this value so for hot water it doesn't work

[@Billybobnob]

Getting a h73 error code. Any ideas?