Vitodens programming question

Mark Hunt

Can anyone tell me how to change the temperature at which the Vitodens shuts down for heating?

Thanks.

Mark H

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Glen

easiest method

would be to change your slope and shift. Page 47 of Vitodens service manual shows you how. I would think a negative shift of the slope would shut down the boiler at lower outside temps. This outdoor shut down temp will be dependent on your slope - high slope less effect - low slope more effect

Mike T., Swampeast MO

I don't think you would want to give a negative shift--if you did, the boiler target temperature would be BELOW the outside temperature in all conditions. Judging by the heating curves, a shift of zero would have the boiler target temperature exactly equal to the room temperature setting regardless of outside temp!

I believe that the best way to get the boiler to shut down is to set the room temperature dial at the temp where you want the boiler to stop providing heat. Of course this will affect your heating curve under all conditions so once the weather gets colder, you'll want to return the room temp back to a more normal setting.

As far as I can tell, the Vitodens will provide heat any time the outside temperature is below the room temperature setting. It does not have warm-weather shutdown in the traditional sense.

I can think of two ways to "fool" the boiler into something that more resembles traditional warm-weather shutdown:

1) Install the Remote Control model RS. This remote senses indoor temperature at one position in the structure--so it must be carefully located. If the sensed temperature is different than what boiler "thinks" it should be, it changes the target temperature of the boiler. So, in mild weather internal and/or solar gains will reduce the boiler target temp--likely to the point that it will shut down. Again, locating the sensor properly is critical. While it may be desirable to have it in a space influenced by the sun in mild weather, you'll have a problem in cold weather--while it may be desirable to have it in a space that's normally cooler, you'll have a problem in moderate weather.

Also, if a mixing valve is used, it will control only the circuit using that valve. If, perhaps, you have a space using passive solar and are having problems controlling it nicely, I would put that space on a mixing valve and use this sensor and experiment carefully to find the "sweet spot" where you get just the right amount of solar influence.

2) Write Viessmann and ask how to activate the "Outside Temp (damped)" portion of the Comfortrol™ unit. I have high suspicion that this is intended for outside temperature diversity control...

Glen

Exactly -

"Judging by the heating curves, a shift of zero would have the boiler target temperature exactly equal to the room temperature setting regardless of outside temp! "
Yes - you are right - target is 20 deg C room temps (heating curve graph)so if outside temp is also the same the boiler is off. So if I understood the question "how do I change the temp at which the Vitodens shuts down?" then a negative shift would do that by under controlling the expected temp. The over riding question then is this - under what conditions do you want that to happen? Mark H wasn't specific re the paramenters. BTW - your own boiler "travelogues" are great - you should send them off to Viessmann - I have noticed a few observations of yours - that while supported by your experiment in the basement - do not have supporting documention in the viessmann tech manuals. Keep at it! Me thinks the Vitodens was released "early" because of the consumer pressures and has not been fully documented yet re capabilities and features.

Kritz_3

Vito Code

Hi All, I got my first Vito up and purring just before X-mass.
Just a quick code question, OD5:001 should change the
display to large time and O.A. temp with cover closed. But
I get large time and boiler temp. Is there something wrong
here?
Thanks, and happy new year!!

Steve

kevin_22

vitodens

Steve
Coding address 009:000 displays boiler water temp.
coding address 009:001 displays outside temp.

Mark Hunt

Thanks guys


I can't do what I want to do with the Vito.

No big deal. It would have been temporary anyway.

Just thought someone knew of something that wasn't in the literature.

Mark H

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Kritz_3

Vito code

Thanks Kevin, my wife cracks up when she spies me scrolling
to find O.A. temp.
Thanks,
Steve

Uni R

Question on this...

Would having a large setback and leaving it on setback asll summer be a good way of more or less doing a warm weather shutdown function? Or is it just as easy to just lower the temp setting?

Mike T., Swampeast MO

The reset curve always has its point of origin at the room temperature setting. Any time the curve has a greater than zero slope, the target temperature will be above room temperature so the boiler will assume that heat is needed and/or desired. The only way I've been able to get mine to shut down during warm weather is to turn the room temp setting below outside temp.

Mark seems to be wanting EXACTLY what I would like. After our freak cold spell last week, we're now in a freak warm spell. 62.9° a bit after midnight on January 3rd! Temp is only forecast to drop below freezing once in the next seven days. The house is consistently 4° above the TRV setpoint yet the Vitodens is still running--in "pulse" mode. I will say however that it's perfectly comfortable inside--in a very light shirt. Generally I wear a light sweater in the winter...

It wouldn't bother me at all if the boiler shut down completely, but I see no way to automate the process and I don't believe it would be advisable to cut the power via my old WWSD.

I wrote Viessmann America about this today--maybe I'll get a reply.

Mike T., Swampeast MO

During the warmer months just set the selector dial to "DHW Only" or "Stand-by" if not using the boiler for DHW. The stand-by mode will "exercise" the pump for a short period once each day.

Uni R

Thanks Mike

I was worried that there wasn't anything in the controls nearly as obvious.

Mike T., Swampeast MO

Possible Solution Mark

Address 038 allows you to change the "Minimum Supply Temperature in Heating Mode".

I haven't yet tried this, but while operating at the desired reset curve and with the outdoor temp near the point where you want the boiler to shut down, set address 038 one degree (Celcius) or so above the "target temperature" (Celcius) reported by the boiler.

I'll try this tomorrow as well and report if it works--am not sure if the circulator will shut down or not...

Mike T., Swampeast MO

Doesn't Appear to Work

Set the minimum one degree (Celcius) above the current boiler setpoint and circulator continued to run and boiler continued to fire as normal--in "burst" mode asI call it. Cooler today though (44° outside) so perhaps it can't be fooled that far...

Supposed to be in the upper 50s later this week and will try again when it's in "pulse mode".