Setting Curve for Viessmann

Brad White_9

First you need to know your heat loss, then you need to know your radiation capacity. Your ratio between them determines your water temperature at design.

(I do not have "the curve" handy, so I am speaking from reasonable examples here, full disclosure; check your actual curve.)

Let's say your radiation quantity can meet your design heating requirement at 180 degrees F.

Draw a horizontal line on your curve at the 180 degree mark then a vertical line at your design outdoor temperature (at which your heat loss was calculated). The curve at or the intersection point is where I would start (call it a 1.6 curve in this case).

If you have radiant floors meaning a lower water temperature, you may well be down in the 1.0 or 1.1 curve range, even less.

The other part of this is adjusting the curve during extreme weather as we are having. This is to fine-tune your calculations (above done in the summer right?) against the realities of, "dang, am I cold!".

But are you? Is the house heating? Might you turn the curve down at some risk? If you are cool, maybe go up one increment and let it settle for a day or so. Maybe the curve is fine and you can effect parallel shift above or below the basic curve? You have options.

Comfort is your best indicator.

J.M.

Setting Curve for Viessmann

I'm a homeowner and we had a Viessmann Vitotronic boiler installed. We're in a cold snap right now, and I was told that a very cold day would be a good day to set the heating curve. Slope is now at 1.4, and from what I was told, we're supposed to crank the heat up in the house (and the temp on the boiler) and then see if that temperature is hit in the coldest room in the house.
Is there a good guide or some easy-to-follow steps for doing this right, so I can determine if the curve is right?
Thanks,
JM

Paul Pollets

Instructions

The installer should demonstrate to you how to change the curves. The owner's manual also has easy to follow instructions. Raising the thermostat setting (sun icon) has the same effect as raising the curve. There are other settings, like the max amount of heating circuit temperature that should be set, so you don't overheat or damage the floor coverings, presuming you have a radiant floor system.

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J.M.

Thanks Paul

J.M.

Thanks Brad

bill nye_3

Coldest?

I set mine for the "most of the time" I have my curve @ between .8 and 1.0. It works perfect all year except when we hit single digit and low teens outside. Like the last two weeks in Ct.

On single digit° days I turn the parallel shift up a few degrees until the living room maintains the temp. I want. Works for me.