Nest thermostat for Viessmann Vitodens 200

MeghanVT

We just bought a house with radiant floor heat and we have this ancient control unit for our combi boiler, and we’d like to install a nest thermostat. We have no idea where to begin. When I google anything regarding this unit and combi boilers in particular, everything is based in the UK. I live in the northeast United States. I noticed in the UK, nest thermostats have a thing called a heatlink that is connected to the boiler. Do we need something like that? Is there another way?

Derheatmeister

Based on the control i assume that you have a WB2A series boiler...Maybe a 6/24 or a 8/32 ?
This control lets the heating tech into parameters such as the Heating curve and shift..The sun and moon dails are for Warm Weather Shut Down (WWSD).
There are other parameters such as Outdoor weather responsive times/Domestic warm water adjustments..To many to explain..
You will have to keep this control in order for you boiler to function..
You could relocate the Viessmann Control onto the boiler.
A competent heating tech may be able to control a >>zone<< such as the one that has your current Viessmann control is in via a Nest.... We perfer the Ecobee

Jamie Hall

And of what use world the Nest be? A radiant floor heating system can't be dialed up and dialed down like forced air. It may take hours -- if not longer -- to change the room temperature by a degree or two, and runs best and most efficiently when it's basically running all the time at a constant temperature.

You could install the Nest -- there are various ways to do it -- and then you would need to disable all of its so called smart features for it to be even remotely compatible with your heating system. Same thing applies, I might add, to any programmable or other smart thermostat.

On the other hand, it will still tell the burglars when you're not home...

Ironman

A Nest thermostat is the worst possible choice for a radiant floor or a modulating boiler. Its logic is contrary to that of the boiler.

As Jamie mentioned, a radiant floor should be set at one temperature and left there. The boiler’s controls will modulate the water temperature and firing rate to match the actual load. This produces the greatest comfort and efficiency. A Nest wreaks havoc with that.

GGross

The older Viessmann boilers operated based on constant circulation and maintaining a supply temperature based on outdoor reset. It is an ideal method of controlling a radiant floor assuming that the correct parameters are set.

The control that you have on the wall, is infinitely better than any modern smart device, it acts as a room feedback system that allows your "thermostat" to act like a gas pedal instead of just an on/off switch as is typical with any other thermostat in the US.

What that control is, is an extension of the boiler control, allowing the boilers control to actually see what temperature it is in the space that it is heating, allowing the boiler to modulate to the best possible level.

When the boiler eventually fails the control will need to be replaced however, at that point I would not fault you for choosing whichever thermostat you want

EBEBRATT-Ed

Stay away from the Nest. While they are good for some systems they are not for what you have. Nothing but trouble.

dko

But they sure are pretty!

pecmsg

EBEBRATT-Ed said:

Stay away from the NEST

Short and Sweet!😇