Viessmann boilers OK with Evohome ?

[FullBore]

I currently have an Alpha CD35C Combi Gas Boiler which is coming up to 15 years old and functioning adequately, but is now beginning to need frequent repairs & replacements.

I have been advised that it would be wise to consider a replacement sooner, rather than later.

The CD35C has worked well with Evohome, but it is suggested that I replace it with a Viessmann equivalent.

My understanding is that some people have, in the past, had problems controlling Viessmann boilers with Evohome, but it is suggested that these issue have been resolved,

Any advice would be gratefully received.

NJSS

[bruce_miranda]

[JCK]

I have the viessman 100w , combi, b1kf, i am using opentherm , it works well, i have set the maximum temperature to 70 deg C , from the boiler set up parameters .

[JCK]

To add to above , i am using evhome opentherm withe the viessmann 100w. The viessmann 050 also has opentherm. The 200w does notsupport opentherm

[FullBore]

Firstly thank-you everyone for your responses to date.

The viessmann 050 also has opentherm. The 200w does not support opentherm

Is it critical that any replacement boiler supports OpenTherm, or is there a way round this?

Sorry to ask what may appear to be a stupid question, but in my 82nd year I am somewhat bemused by questions such as this!

NJSS

[JCK]

Firstly thank-you everyone for your responses to date.




Is it critical that any replacement boiler supports OpenTherm, or is there a way round this?

Sorry to ask what may appear to be a stupid question, but in my 82nd year I am somewhat bemused by questions such as this!

NJSS

If you already have Evohome with opentherm set up for your old boiler then your boiler installer will be able to configure the new Viessmann boiler to opentherm use provided it is Viessman 100-W or a Viessman 050. This uses a wireless relay box called "Honeywell R8810A1018" , to connect wireless signals from the evohome controller to the boiler Honeywell R8810A1018

If your Evohome is set up with with on/off control and not opentherm , the Viessmann installer can confugure the boiler to work with this on/off control for all the Viessmann boilers. This uses a different wireless relay box called "Honeywell BDR91T1004" , to connect wireless signals from the evohome controller to the boiler .

The advantage of the opentherm setup is that it allows the boiler operating in a condensing manner more of the time . This saves a little on the gas consumption . (gas when burned forms CO2 and H20 (Water) , condensing causes the water which is in gas state to turn to liquid state which releases a lump of heat)


Opentherm capability is certainly not essential , it is in my (consumer) opinion it is desirable.

I choose the Viessmann 100-W B1KF combi in April 2021 because a) It has very low turn down to < 3.2 kW , which means less stopping and starting of the boiler when heating only 1- 2 rooms with the boiler. b) it uses opentherm , hence more time the boiler is condensing reducing gas demand. So far all is well.

[kris_v]

It depends what model of Veissman boiler you are planning to choose. I had exactly same dilemma few weeks ago and ended up getting 200-W system boiler. It has the best modulation ratio across all of the brands and boilers available when using WC, 4 different heating curves and much more controls enabled in comparison to 100-W. I will be modifying 2 pipe system into 4 pipe system to benefit from DHW priority. Some say it is a downside, but I'm not sure if I can agree, 200-W does NOT support OpenTherm and Evohome will only control when radiators are opening and closing. After having lengthy conversations with Veissman engineers they don't see that as a problem.

[therealfronty]

Yes I've got an old fashioned open vent 2 pipe 26kw Vitodens 100W, it's been brilliant. Didn't bother with opentherm so it's just being turned on and off by the Evohome TPI schedule but it's been fine, it's quite happy firing for short periods. I run it at around 70 degrees so I can heat the DHW but of course Evohome closes off the heating circuit via the 3 port valve, so over the summer months all I'm heating is DHW and in winter I get lovely hot rads all over the house as required.

[mikey8156]

Viessmann and Evohome Opentherm

When I first installed Evohome and Opentherm I was getting 2 degrees overshoot. So I turned the Lockshied valve on the radiator right down until the radiator was just warm. Over the next few days I gradually increased the radiator heat allowing Evohome time to learn the new setting.

[FullBore]

Reviving an old topic !

I have managed to stagger by with my old boiler for longer than I thought possible - but now replacement is essential

I am being encouraged to fit a Viessmann W200 boiler,

The old question still applies - my installer proposes fitting a weather compensation kit and Vitotrol modulation unit; my concerned is how do I integrate the proposed new system with EvoHome?

FB