Viessmann 100W Weather Compensation

[runningRich]

Unit was installed here in the northeast in 2019. Has been trouble free. During the recent cold snap reaching minus 10 deg. F it ran constantly for 36 hours. It could not keep the house to 70 deg. but maybe 67. For this uncommon issue I believe I need more baseboard in one area of the house that is always colder, since some was removed during the installation of a very wide glass slider/ fixed glass unit and never replaced. And another wall with a bay window has never had baseboard beneath it ever.

The boiler output is 170 deg. constant. But this got me thinking about weather compensation. The boiler has an outdoor sensor on the northern wall, but I found out today the sensor wire enters the boiler, but is not connected!

Would there be any reason the factory authorized installer chose at the last minute not to connect the sensor? I feel like I could have been saving money during the more moderate outdoor temperatures, automatically running the boiler at a lower temperature at a longer period, but more efficiently condensing.

I will ask the question to the dealer, but I wanted some unbiased opinions first. Thx

Viessmann Vitodens 100W combi boiler with Vitocell DHW. Caleffi SEP4. One zone radiant baseboard.

 

[Fitter30]

The boiler you have is a condensing boiler. That advertises 95% efficient which it is but return water temp gives the boiler the high efficiency. The cooler the return water the higher the efficiency. Running 170° water the return temperature is probably over 140° so they boiler efficiency is 87%. Could turn the boiler up to 180° - 185° might help out with cold areas. Sensor on the north side of house where it should be? Might not been connected because installer didn't know how to program boiler. Furniture, drapes and some housings have a damper is it open.

 

[Sponsor]

 

[runningRich]

The boiler you have is a condensing boiler. That advertises 95% efficient which it is but return water temp gives the boiler the high efficiency. The cooler the return water the higher the efficiency. Running 170° water the return temperature is probably over 140° so they boiler efficiency is 87%. Could turn the boiler up to 180° - 185° might help out with cold areas. Sensor on the north side of house where it should be? Might not been connected because installer didn't know how to program boiler. Furniture, drapes and some housings have a damper is it open.

You are right about the furniture in the cold room. A six foot wide sold piece is in front of the only baseboard in the room. I moved it about a foot away from the wall during the cold snap, but wife wouldn't have it. Basically one whole wall of the house has no baseboard at all, the one with the bay window and slider unit I mentioned. Another wall in the cold room is solid stone veneer with gas fireplace insert- no room for baseboard. Attached: baseboard is in black, in red where I thought could be added.

As far as outdoor temp weather compensation the installation manual says it auto configures once the sensor is recognized. You then have the option of setting the heating curve. I might try this but will call the installer to quote the baseboard, and when they are here mention the sensor was never hooked up. And see if they would hook it up then in good faith I'd choose them to install the baseboard.

 

[Fitter30]

Fin tube is put under windows to offset the heating load of the window and exterior wall. Heat goes to cold. Like when your at the grocery store walk down the frozen food isle your body heat is flowing from u to the case.