The fan operation is understandably confusing due to the audible feedback, and what may seem like random behavior. The simple answer is that,
the cooling fan turns on when needed, or a little sooner, and will remain on longer than needed. The reason the cooling fan turns on sometimes sooner than needed and stays on longer than needed, is for reliability. It's an ingrained NASA thing. If your cooling fan is not running, or you 'tricked' your Herbie into turning off the cooling fan before it stops on its own, that is totally OK. If the system
needs the cooling fan it will turn it on.
The slightly less simple answer is that the cooling fan control is based on three variables: measured temperature, setpoint temperature, and time.
For the vapegeeks like me (that's everyone here.. right?!), here's the logic behind it. We would prefer silence, but in a closed system the cooling fan is simply a necessity so it is programmed to turn off as much as reasonably possible. The cooling fan is activated when the computer board (i.e. sensitive electronics) exceeds a particular temperature threshold, and remains on until the temperature drops below a slightly lowered temperature threshold plus three (3) minutes (this is called hysteresis and operates with similar logic as a common home thermostat); or, if the temperature is 421F or higher for more that three (3) minutes the cooling fan will turn on and run continuously, until the temperature is lowered to 420 or less for three minutes or more and the computer is cool enough. 420 is the highest temperature that won't cause the cooling fan to automatically turn on after three minutes.
So you cloud chasers get to listen to the cooling fan more than the rest. Remember what I said above - if you 'trick' your Herbie into turning off the cooling fan before its stops on its own, that is totally OK, because
it will turn on
when needed. There are several ways to 'trick' the cooling fan off: switch to aromatherapy mode and then back to vaportherapy mode, or tilt it dizzy for a moment and then back again.
The cooling fan noise is more annoying than I would have liked. When I left there was a plan for replacing it with a near-silent fan. Samples had been ordered, but testing hadn't started. I cannot predict when, or if, that improvement will be implemented.
Winter is coming. Herbie makes a wonderful belly warmer when its cold.
You've got a lot of intertwined questions there
@spincut. First, the "whole other fan [that] just starts running constantly" is the cooling fan. The answer above hopefully explains that what appears to be random, isn't.
The fan that pops on intermittently during use and produces a chattering sound along with a puff of vapor (NOT SMOKE!!
) is understandably
weird. Essentially, that fan - which is the same as the assisted delivery fan - periodically stirs the air inside the Thermal Reaction Chamber (TRC) (I really like that term.. what's it going to take to add another acronym to the vapor lexicon?
). Anyway, the thermal dynamics of the TRC are very complicated and naturally wants to develop "cold spot" and "hot spots." It was discovered that the TRC performance is optimal when the system is in balance without hot spots; in other words, when the heat distribution across the system is even. This makes possible more predictable heat transfer, and therefore control of the output temperature. So the intermittent puffs are caused by the computer recognizing an imbalance and redistributing the heat. When the system is just starting out and is "cold," it is more prone to developing hot spots because different parts are sucking away heat and causing cold spots, causing the surrounding areas to become hot spots. Once your Herbie is warmed up you'll notice the puffs less and less. Don't over think it - I already did!
@biohacker - great question too, I'll answer it on my next post.