The Efficient Home Forum

Yeah,

What about the Evohome Thermostat?Are we talking about the last model the one with build in wi-fi?Or the one with extra box for internet connection?

Thanks.

Nothing? No one tried with the new B1HC model? or B1KC or B1LD (111-w).

Thanks.

Unless you can set the maximum flow temperature at the boiler, you will have this issue irrespective of Viessmann model.

True.But i was wondering if anyone tried with the new model with touchscreen.Maybe for this, the settings are not blocked.Also Viessmann representatives told me it should work with outside sensor for selecting the heating curve and open therm thermostat for regulation.This is how it should work really.We'll see when i install it.

Hello all! I am new to this forum but for me this is the place where I can get some help for my problem. First I must state that I am from Bulgaria and in our domestic forums there is nothing about my problem. I have a Vitodens 100-w B1HC system boiler with on side 300l. unvented cylinder for hot water, boiler controlled by Evohome controller with Open Therm Bridge (R8810). My system is a simple 4 pipe. I have just bought Honeywell /evohome hot water kit atf500dhw for controlling the DHW line but no one can wire it. Can you help please!
1) Do I need a Viessmann - Cylinder demand box for the wiring of the hot water kit? This is something we do not have on the market in Bulgaria from Viessman.
2) If yes, can someone send me some pictures of his wiring of the hot water kit with this boiler if he has the same configuration, because I have the wiring instructions for the cylinder demand terminal box from internet but these instruction speaks nothing to my installer.I ll appreciate any help! Thanks!

Just got confirmation from Viessmann UK - all boilers with OT support will disable the option to setup max flow temp and also weather compensation (mine is Viessmann 111-w)
However you can use their Vitotrol 100 OT which will allow to setup that parameter, there is no WIFI version of it, you are stuck with wires.
I have received mixed answers if Vitotrol 100 OT will work along with weather compensation or not.
I was considering zone control heating but.....it seems is a bit tricky, one option is to control and schedule just TRVs and use weather compensation feature as is modulating based on weather information
and your ambient temperature is constant (looking at their chart is should be 20 degrees Celsius); you can throw Vitotrol 100 OT in the mix too if it does not disable weather compensation.
The question is if this solution is economic wise better then using evohome system on switched option (just use BDR 91).
Of course I feel like a beta tester considering all this options on my expense

Steer clear of Viessmann is the moral of the story then? Amazed they have just got a Which? best buy award... Obviously Which? don't look at things like this during their tests!

I just came across this thread, and having a Vitodens 100 connected with an OpenTherm wireless bridge to to evohome, I thought I'd share my experiences:
- yes, the boiler goes up to 81 - 82 degrees and that value can not be changed on the boiler (afaik),
- I also reduced the maximum heating input (as per manual) because the power of the boiler seemed too high. It does work. This makes heating up the house slower, which I appreciate in combination with the adaptive heat up - the floor and walls are warmer when I get home. And by reducing the power, the boiler runs in the condensing range of temperatures for longer periods of time.
- Reducing the power of the boiler also reduced some of the overshoot issues that I have with certain rooms.

Bart wrote:I just came across this thread, and having a Vitodens 100 connected with an OpenTherm wireless bridge to to evohome, I thought I'd share my experiences:
- yes, the boiler goes up to 81 - 82 degrees and that value can not be changed on the boiler (afaik),
- I also reduced the maximum heating input (as per manual) because the power of the boiler seemed too high. It does work. This makes heating up the house slower, which I appreciate in combination with the adaptive heat up - the floor and walls are warmer when I get home. And by reducing the power, the boiler runs in the condensing range of temperatures for longer periods of time.
- Reducing the power of the boiler also reduced some of the overshoot issues that I have with certain rooms.

Hi Bart

I’m having a similar issue on max temp, and looking to reduce it. Where you say you have “reduced the maximum heating input (as per manual)”, which manual and settings are you referring to? I can’t seem to control the heat with either the dial on the boiler or the evohome - I’m using an open therm bridge.

Jon

You can not limit the maximum temperature, but you can limit the power of the flame. I have the 35kw variant - overkill in my case. On the 1st page of this post is a link to a manual:
https://www.viessmann-us.com/content/da ... e/file.pdf
On page 65 you will find instructions as how to limit the maximum power of the boiler.
It may take some trial and error to get in to the correct menu modes, I find the system awkward.