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

Reed_Richards

My understanding is that any OpenTherm compatible gas boiler can do both Weather Compensation and Load Compensation with a suitable controller.  I'm not sure how the outside temperature reading is derived; I used to have a little thermostat under the eaves in my old house but that was using the manufacturer's own controller.  Are you saying that your old gas boiler did not or could not use these features?  And don't forget your low water temperature; that has got to be making a significant contribution.

But congratulations on your estimated annual savings; that's a really good result.    

Screwdriva

Reed_Richards said:

My understanding is that any OpenTherm compatible gas boiler can do both Weather Compensation and Load Compensation with a suitable controller.  

I think the implementation of weather compensation does  make a difference. Worcester Bosch, as an example, has a relatively poor implementation of weather compensation (an add on module) on several of their newest boilers. Viessmann is out of the box. 

Are you saying that your old gas boiler did not or could not use these features?  And don't forget your low water temperature; that has got to be making a significant contribution.

But congratulations on your estimated annual savings; that's a really good result.    

Our 5 year old Greenstar 18Ri offered none of these features. No weather compensation curves for each circuit, no hot water cylinder temperature control, no ability to run UFH on a seperate circuit with lower flow temperatures (vs. the radiators) and a poor maximum modulation of ~6kW (vs. 2.1 kW on the Viessmann).

The V200 has yet to output more than 5kW even at a measured -5 degrees C and is happy to settle at or around 2.2 kW on most days. I believe this has made a massive difference to our consumption!

BUFF

To be fair I think that it's a generational design issue.  You have bought Viessmann's top of the range boiler which was only launched in 2019  & are comparing it to a lower market level & older design WB.
I strongly suspect that WB's latest boiler designs (which will modulate 10:1, admittedly not quite as good a ratio as the V200, but can be down to 1.9kW minimum output) ) will offer similar if fitted with the appropriate control (older controls like Sense II used to offer the ability to vary settings for up to 4 different circuits so I imagine that the current ones do too albeit setting may be in the engineer/installer menu rather than top level user menu).

Not sure why the use of an add-on module for weather compensation should be seen as inferior (Viessmann also offer very similar)? The WB boilers come ready with wc support subject to the installer/homeowner's choice of control - this can give you  wc via either internet data or external sensor.  I imagine that Vaillant etc. are also very similar.

Screwdriva

BUFF said:

To be fair I think that it's a generational design issue.  You have bought Viessmann's top of the range boiler which was only launched in 2019  & are comparing it to a lower market level & older design WB.
I strongly suspect that WB's latest boiler designs (which will modulate 10:1, admittedly not quite as good a ratio as the V200, but can be down to 1.9kW minimum output) ) will offer similar if fitted with the appropriate control (older controls like Sense II used to offer the ability to vary settings for up to 4 different circuits so I imagine that the current ones do too albeit setting may be in the engineer/installer menu rather than top level user menu).

Not sure why the use of an add-on module for weather compensation should be seen as inferior (Viessmann also offer very similar)? The WB boilers come ready with wc support subject to the installer/homeowner's choice of control - this can give you  wc via either internet data or external sensor.  I imagine that Vaillant etc. are also very similar.

No doubt my older boiler was vastly inferior, which was the reason for this upgrade (& this thread tbh). I maintain that, for those who cannot install a heat pump for any reason, replacing an older boiler with a V200 can offer a comparably low running cost with fewer emissions and lower purchase & installation price, and is entirely worth doing at today's gas prices!

A few corrections:

- The 1.9kW minimum output is only applicable on 15kW or lower output WB system boilers. Anything larger and all their Combi boilers are 3kW or higher.

- The V200 has been around for much longer than 2019. 

- V200/ V222 and V100 come with WC out of the box. Don't know much about the lower end 050 etc. 

For those on a budget, the 15kW 4000 is a decent option but as far as Worcester Bosch's WC goes, if you find any installer who installs both brands claim superiority over the V-200, do let us know. 

BUFF

Screwdriva said:

BUFF said:

To be fair I think that it's a generational design issue.  You have bought Viessmann's top of the range boiler which was only launched in 2019  & are comparing it to a lower market level & older design WB.
I strongly suspect that WB's latest boiler designs (which will modulate 10:1, admittedly not quite as good a ratio as the V200, but can be down to 1.9kW minimum output) ) will offer similar if fitted with the appropriate control (older controls like Sense II used to offer the ability to vary settings for up to 4 different circuits so I imagine that the current ones do too albeit setting may be in the engineer/installer menu rather than top level user menu).

Not sure why the use of an add-on module for weather compensation should be seen as inferior (Viessmann also offer very similar)? The WB boilers come ready with wc support subject to the installer/homeowner's choice of control - this can give you  wc via either internet data or external sensor.  I imagine that Vaillant etc. are also very similar.

No doubt my older boiler was vastly inferior, which was the reason for this upgrade (& this thread tbh). I maintain that, for those who cannot install a heat pump for any reason, replacing an older boiler with a V200 can offer a comparably low running cost with fewer emissions and lower purchase & installation price, and is entirely worth doing at today's gas prices!

A few corrections:

- The 1.9kW minimum output is only applicable on 15kW or lower output WB system boilers. Anything larger and all their Combi boilers are 3kW or higher.

- The V200 has been around for much longer than 2019. 

- V200/ V222 and V100 come with WC out of the box. Don't know much about the lower end 050 etc. 

For those on a budget, the 15kW 4000 is a decent option but as far as Worcester Bosch's WC goes, if you find any installer who installs both brands claim superiority over the V-200, do let us know. 

Have you got links for that? WB don't make it easy to find individual minimum outputs for their 4000 series systems other than their headline 1.9kW for the range.
edit: no need, found it!

Yes, the Vitodens 200 series name has been around much longer but the latest generation of Vitodens 200 was launched in 2019. That's like buying the latest BMW 3 series & saying that it came out in 1975 ... 

I wouldn't necessarily expect either's wc to be noticeably superior, tbh I would expect much of a muchness.

Reed_Richards

There are two options I can think of to achieve superior weather compensation.

1. You could allow the settings to program a curve instead of a straight line (but it doesn't seem to make much difference for me).
2. You could provide the option for a scheduled night-time set-back or other scheduled temperature changes by shifting the curve.

Other than that it's surely just a matter of adjusting the parameters until you get them exactly right, by trial-and-error.  You could try and automate this but in the steady state that's what Load Compensation does - and it saves you a lot of fine-tuning.       

Screwdriva

BUFF said:

I wouldn't necessarily expect either's wc to be noticeably superior, tbh I would expect much of a muchness.

Even Viessmann admit their own basic WC (which appears comparable to WC offered by other brands) to be less efficient than that offered on the V200. 

Reed_Richards said:

There are two options I can think of to achieve superior weather compensation.

1. You could allow the settings to program a curve instead of a straight line (but it doesn't seem to make much difference for me).
2. You could provide the option for a scheduled night-time set-back or other scheduled temperature changes by shifting the curve.

Sounds right to me! Once you program the AWC curves correctly, they work seamlessly.

michaels

Screwdriva said:

BUFF said:

I wouldn't necessarily expect either's wc to be noticeably superior, tbh I would expect much of a muchness.

Even Viessmann admit their own basic WC (which appears comparable to WC offered by other brands) to be less efficient than that offered on the V200. 

Reed_Richards said:

There are two options I can think of to achieve superior weather compensation.

1. You could allow the settings to program a curve instead of a straight line (but it doesn't seem to make much difference for me).
2. You could provide the option for a scheduled night-time set-back or other scheduled temperature changes by shifting the curve.

Sounds right to me! Once you program the AWC curves correctly, they work seamlessly.

We find Viessmann weather comp great on our 12 year old v200 but it does get it slightly wrong when it is cold and there is large wind load or large thermal gain when the house actually needs more or less heat input.

Screwdriva

Feb '22 - 2333 kWh - Avg Temperature - 8.6 Celcius
Feb '23 - 1462 kWh - Avg Temperature - 7.4 Celcius

Over a 37% reduction in gas consumption despite a lower monthly average temperature compared to the same month last year. The above efficiency gains were achieved after efficiency measures were implemented and are detailed here. 

We are currently on track to achieve a ~50% reduction in gas consumption for the year (~11K kWh for heating and hot water) 

Screwdriva

This snapshot captures the savings across (a colder) winter quite nicely.