Weather Compensation Question...AGAIN?

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Hi,

I have just fitted a weather compensator to my Vitodens 100-W boiler ( bought direct from Viesmann at an astonishingly expense for what it is ). All seems to be working well with the outside temperature now being displayed on the menu screen alongside the boiler flow temp.

The Viesmann academy video on youtube shows the way to adjust the angle of the 'Slope' for the weather compensation however it doesn't detail what effect this will have on the performance/economy. The available range is from 5 to 35 deg.C. The setting at the moment is currently 20deg.C.

What difference will I notice if I adjust this figure up or down or is it just a case of suck-it-and-see?
 
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The Viesmann academy video on youtube shows the way to adjust the angle of the 'Slope' for the weather compensation however it doesn't detail what effect this will have on the performance/economy. The available range is from 5 to 35 deg.C. The setting at the moment is currently 20deg.C.

You may find, that the value you enter, is just an initial starting value - that as the system works, it will refine and self adjust that value.
 
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Hi,

I have just fitted a weather compensator to my Vitodens 100-W boiler ( bought direct from Viesmann at an astonishingly expense for what it is ). All seems to be working well with the outside temperature now being displayed on the menu screen alongside the boiler flow temp.

The Viesmann academy video on youtube shows the way to adjust the angle of the 'Slope' for the weather compensation however it doesn't detail what effect this will have on the performance/economy. The available range is from 5 to 35 deg.C. The setting at the moment is currently 20deg.C.

What difference will I notice if I adjust this figure up or down or is it just a case of suck-it-and-see?

I think it comes with a Slope of 1.4, Shift of 0C & a room SP of 20C, Viessmann suggest that the installer sets the Slope & Shift and you set the room temp SP. You should be able to take a screenshot I think of your settings, you might post one, with the OAT.

As a rough guide I worked out sometime that a change of either the OAT or the room temperature by 1C requires ~ a rad flowtemp change of 2.5/2.6C to give a 4% change in power.
 
For me to get a better understanding of how the WC works I just need to know, as an example, what would happen if I selected the minimum setting of 5, and what would happen if it was set to the maximum of 35? And what changes I would notice from it's current setting of 20?
 
For me to get a better understanding of how the WC works I just need to know, as an example, what would happen if I selected the minimum setting of 5, and what would happen if it was set to the maximum of 35? And what changes I would notice from it's current setting of 20?

At the current slope of 1.4 & 20C, then, at say a OAT of 10C then the Boiler Flow Temperature SP is 37C which may satisfy your house heat demand to maintain 20C, if the OAT fell to 5C then the boiler flow temp SP would be increased to 44C which again may satisfy your heat requirements. If you changed the RSP (room SP temp) to 35C, then at a OAT of 10C the boiler flow temp is increased to 71C and at a OAT of 5C is increased to 76C, both of which may be too high for your heat demand/losses so the room temp would increase beyond 20C or a room stat, if set to 20C would shut down the boiler. If you set the RSP to a ridiculous 5C then the boiler would not be called to fire at 30C until/if the OAT fell to -10C which would mean almost never in this part of the world.

Edit: The shift feature might be useful, see it all here, have fun.



Viessmann WC Various Room Set Point Temps.jpg
 

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Can you please post a photo of display? Mine is a heat only (dial type boiler) and I have not been able to configure it.


The only thing I can adjust now for central heating temp now that the WC is fitted is the slope setting between 5 - 35. The option to set the boiler temp for the heating has now gone.

1738270357928.png
 
WC sets the boiler flow temperature, you cant or shouldnt be able to set it with WC enabled.
5c to 35c is not the slope IMO, its the room temperature setting, you should though be able to set the slope.
 
WC sets the boiler flow temperature, you cant or shouldnt be able to set it with WC enabled.
5c to 35c is not the slope IMO, its the room temperature setting, you should though be able to set the slope.
Yes, bad choice of word, boiler flow temp was what I meant. The ability to manually adjust this from 0 to whatever is now controlled by the WC which is restricted to 5 - 35.
I'm a Civil Eng by trade but must admit that this heating caper really confuses me.
 
Yes, bad choice of word, boiler flow temp was what I meant. The ability to manually adjust this from 0 to whatever is now controlled by the WC which is restricted to 5 - 35.
I'm a Civil Eng by trade but must admit that this heating caper really confuses me.

The 5 to 35 C is the room temp setting which influences the boiler flow temperature, the higher the setting, the higher the boiler flow temperature, you shouls still be able to see the boiler flow temperature displayed somewhere.
 
Thanks, have you been able to save on gas? Is room stat connected with WC?
It's only been connected for a week so too soon to tell. Certainly the performance characteristic of the central heating has changed since I fitted it.

Pre WC installation my room thermostat was set to 20degC and the boiler temp was set to 65degC. The boiler would click on & off until a room temp of 20C was reached, after which it would click on & off to maintain that temperature.

The WC boiler temp of 20 ( which was the default setting ) seems a bit low. The house felt colder and the CH struggled to get the house up to temperature. As an experiment I set the room stat to 25DegC but after about 5 hours the room temp was still sitting at about 18.5deg.

Today I've increased the WC boiler temp to 22 to see if it performs any better.

FYI, current outside temps in UK are ranging between 0 - 8deg
 
OK, the system has been running with WC for a couple or three weeks now and for the most part has been set at 20 which was the default when first connected.
The house seemed colder than before the WC was connected so I raised the setting to 22 last week to see if that helped. Answer was.... not really.
This morning after being on for about 4 hours, the house temperature had only just got up to 15.5deg and the radiators were at best 'warm' to the touch.
I've now raised the WC setting to 25 and finally things seem to be warming up a bit. I'll keep an eye on things for the next few days and see if the improvement is constant.

One question for those that might know.

Pre WC connection my boiler temp for the heating was set at 65deg. How does the WC setting range of 5 - 35 correlate to that, if indeed it does?
 

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