Steve wrote: ↑Wed 27 Nov, 2019 11:37 pm
Having some very strange behaviour.
Line voltage is pretty solid here usually 235 - 237 can be seen on the roast log its 237. During the roast however it shows solid 184V or 182V can not remember which? while the kW is going over 1.4?
Tried a reset, reinstalled latest firmware and it has done this 3 roasts in a row.
Hi Steve,
Strange, but not so strange.
The profile software has an 'intelligent' feature where it tries to guess the best scale factor for the Y-axis. You have designed a profile where the RoR never goes above 25 deg/min, so the software has scaled the RoR values by 10. Actually this is extremely unhelpful of the software because it creates the kind of scary looking graph that you are seeing. The data is perfectly normal, but the presentation of the data is strange. I will fix this in the next beta release to lock the scale factors to the standard values. Meanwhile, now that you know what is going on you can relax.
The software also adjusts the power to be equivalent to power at 20 deg C ambient. The system has determined that the ambient temperature is 28.3 deg C so it has taken the actual power level and increased it for display to be equivalent to what it would be if ambient was 20 deg C. This is intended to make one profile log more directly comparable with another. The problem is that the roaster doesn't have a separate ambient temperature sensor and has to deduce the ambient temperature as best it can. It can get it wrong by overestimating up to 8-10 deg too hot, especially with follow-on roasts where the roaster has been turned off in between roasts. You can tell from the shape of the power curve (black line) that it has not topped out otherwise the line would have distinctive flat topped zones. This means it still has some power in reserve, although potentially not much. Your profile actually needs more power at that stage in the roast than other, faster profiles.
One approach could be to try dropping the fan speed through the parts that need more than 1.3kW. Also, zooming in on your first crack zone there are some exothermic/endothermic things going on that suggest you might benefit from some negative boost zones in the profile leading up to first crack which could also limit the peak power drawn.
I hope these comments help.
Chris