Here's a plot showing the first firing with the thermocouple located on the top of the firebox, about 4" from the left side. The data shows the initial start up with kindling, then when there was a decent coal bed, it was loaded with a small load of large splits. Each data point represents 5 minutes.
The blue trace shows the draft position. The scale for this trace is 100 fully open, 200 fully closed. Similarly, the fan (yellow trace) is off at 0 and full speed at about 245.
It can be seen how after the initial start up, loading the stove with about 5 splits pulls a great deal of heat out of the stove and cools things down quite a bit. Once the fire came up to temperature at around 400 degrees, it stabilized for about one hour, then started to taper off. This is the common signature seen with most stoves. A full load should show a higher peak temperature and it should have a stable peak for up to 3 hours, then taper off. When I first started doing this testing with a Napoleon 1401, back in about 2005, I thought there was something wrong with the measurement because when you look at the fire, you just don't see such a dramatic-looking drop-off. This just is the way these stoves operate.