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Having picked up a Titon HRV1.25Q Plus Eco for a price that was too good to pass on I now find myself with slightly less controllability than the Xpelair Natural Air 180 unit previously planned for. Specifically, the Titon's humidity-controlled boost function is based on an absolute threshold rather than rate-of-rise, and its summer bypass has fixed thresholds that cannot be adjusted at all. All along I have been planning on employing a Pi Zero to monitor system temperatures and control boost and setback flows, and so I have decided now to bring humidity-controlled boost and summer bypass within its scope also. The former can piggyback the existing boost input but with the bypass being internally controlled I have had to pinpoint on the control PCB where to tap into to influence (actually take over) this function. What I would like the panel's input on is the control logic for these features in case there's something I haven't considered (or just got plain wrong!). Humidity-Controlled Boost I am attracted to rate-of-rise control on the assumption that it'll ride out seasonal variations better whilst also being more sensitive and reactive to genuine need. To achieve this control I think I need to consider: Inputs: Extract (i.e. from rooms) humidity Outputs: Boost Settings: Rate-of-rise threshold ($rateofrise), time period ($timeperiod), when to turn off again ($deactivatethreshold) Control Logic: 1) If the humidity rise over $timeperiod exceeds $rateofrise activate the boost. 2) Continue with boost until the humidity falls to $deactivatethreshold. This sounds reasonable I think? What should $deactivatethreshold be though? The pre-rise humidity value, or at least something near it in case the background humidity has risen slightly in the meantime? My starting figures are likely to be something like 5% for $rateofrise and 5 minutes for $timeperiod. Incidentally, I was planning on taking measurement every five minutes so that'll be the minimum boost time period. Summer Bypass From what I have read it seems that summer bypass works better in theory than in practice but I like the idea of it and given the Titon has the capability I may as well make use it. As per the previous process I think I need to consider: Inputs: Extract (i.e. from rooms) temperature, Intake (i.e. from outside) temperature, time of day(?) Outputs: Summer bypass, boost(?) Settings: Room temperature threshold ($roomtempthreshold), Outside temperature minimum ($outsidetempmin), quiet time ($quiettime), when to disable bypass again ($deactivatethreshold) Control Logic: 1) If the temperature of the air being extracted from the rooms exceeds $roomtempthreshold and the outside temperature is at least $outsidetempmin then activate the summer bypass (unless the outside temperature exceeds the room temperature). 2) Additionally (and optionally?), with the bypass active also activate boost unless we are within $quiettime (e.g. at night). 3) Continue with the bypass active (and, optionally, boost) until the room temperature falls below the $deactivatethreshold. Typical figures might be 22C for $roomtempthreshold, 15C for $outsidetempmin, 2300-0700 for $quiettime and 18C for $deactivatethreshold. Thanks for reading this far. Should I be considering a different approaches? Is there anything I should/could consider?