Going green(er) with a Viessmann 200W (& heating efficiency home improvements)

Screwdriva

michaels said:

What is the massive shunt between the heating flow and return?

Hydraulic separation for the UFH.

michaels

Screwdriva said:

michaels said:

What is the massive shunt between the heating flow and return?

Hydraulic separation for the UFH.

I see, not a massive shunt, a small heat exchanger, so you have a separate pump for the UFH so couldn't run the entire system just by connecting the boiler to a power supply.

Screwdriva

michaels said:

I see, not a massive shunt, a small heat exchanger, so you have a separate pump for the UFH so couldn't run the entire system just by connecting the boiler to a power supply.

Separate circuits for the UFH, radiators and hot water. External pumps & Viessmann Divicon for the UFH is concealed under all that piping. 

Initial impression is that this boiler is truly an Olympic leap forward - information/ controls are next generation and you cannot hear the 200-W operating the hot water cycle, even when standing with your ear right next to it.  

Modulation is temperature sensor driven and incredibly intuitive! 

That said, Viessmann’s UK technical support and add-on parts supply are abysmally poor - it's almost as if they don’t & never have taken the UK market seriously. 

Screwdriva

Radiator swaps complete. Line #1 is the T21 type radiator (double panels, single fin) we replaced with #2. And #3 took its place. End result is a substantial increase of 2108 Watts in heating output on the first floor alone just by going with slightly larger T22 type radiators (double fins). This will allow the 200-w to run the radiator circuit at a lower temperature curve, taking advantage of it's modulation capabilities. 

It's all coming together well! 

Reed_Richards

Screwdriva said:

Radiator swaps complete. ...This will allow the 200-w to run the radiator circuit at a lower temperature curve, taking advantage of it's modulation capabilities.

So the UFH will only need water at around 35 C (at a guess) but the radiators may need it hotter.  What maximum temperature are you planning to run the boiler at?

Screwdriva

Reed_Richards said:

So the UFH will only need water at around 35 C (at a guess) but the radiators may need it hotter.  What maximum temperature are you planning to run the boiler at?

The plan is to run UFH at 35 degrees and the oversized radiators at 50 degrees to start with. The 200-w allows for different temperature curves to set for both circuits and can run both simultaneously. Max temperature (outside of hot water which is set at 55 degrees with a one weekly legionella cycle at 60 degrees) is 50 degrees.

Reed_Richards

So is you boiler smart enough to lower its output temperature to 35 degrees when only the UFH is demanding heat?  Or does it always achieve the 35 C by mixing your input water at 50 degrees (required for the radiators) with cooled return water from the UFH,  which I think is the norm?

Screwdriva

Reed_Richards said:

So is you boiler smart enough to lower its output temperature to 35 degrees when only the UFH is demanding heat?  

That's correct. It does not need to run both circuits and can run either the radiators or UFH independently at the set temperature/ curve.

Reed_Richards

So you will get "moderate" efficiency if running the UFH and radiators together, or just running the radiators.  You'll only get the optimum efficiency when the UFH is running on its own and the boiler can throttle back on its output water temperature.

Screwdriva

Reed_Richards said:

So you will get "moderate" efficiency if running the UFH and radiators together, or just running the radiators.  You'll only get the optimum efficiency when the UFH is running on its own and the boiler can throttle back on its output water temperature.

I’m curious to measure this. That said, whatever we get is likely to be more efficient than the boiler we just replaced.