Eleven Days

Mike T., Swampeast MO

nm

Brent_2

Why is your actual supply temp often 20° lower than your supply target?

brent

Mike T., Swampeast MO

Supply Target

Some reasons it's significantly lower in warmer weather.

1) The target is NOT from the boiler itself--it's from a simple computation using 0.8 reset ratio with 141° supply @ 8° outside. The Vitodens reset curves appear to be true curves (e.g. not straight lines) and start dropping off in warmer weather.

2) Supply temp is measured from the surface of black iron piping about 3' from the boiler.

3) The boiler itself reports significantly higher supply temperatures as it fires in those "pulses". (Heating demand less than lowest possible modulation level.)

In future years I'll probably stick with my supplemental electric resistance for this type of weather. Just wanted to see how the Vitodens deals with extremely low loads and compare fuel consumption to the old boiler. Old boiler was atrociously wasteful in this weather.