Hi Chaps, Calling Logic gurus out there!!! I've seen a few older posts relating to switching bathroom fan's on via flow or temperature in the shower pipe which sounds a great idea. I have 5104 DTSI (digital temp sensor input unit) and 5100DTST (digital probe) attached to the shower inlet pipe. Due to the location and mounting options available the temperature will vary during the day by a fair margin but over a long period of time (maybe 5 degrees per hour). However when the shower is in use the temperature increase is pretty dramatic. I'm wondering if it's possible within the logic to check the current temperature every 15 seconds or so and only switch the fan group on once that temperature has increased say 4 degrees by the next 15 seconds? therefore ignoring the long slow increases like morning-midday. I've had a rubbish bash as you'll see my logic is just above caveman standard but i can only think of a way using a fixed temperature start point say 20degrees and switch at 24 within 15seconds but that won't help in summer as we will be over 24 most of the time, thats actually rather optimistic border line ridiculous statement in UK but you understand my point ;). Thanks for any help in advance Guys..... Once (GetRealIBSystemIO("Measurement App Real Value", 254, 254, 2) >20)then begin TimerStart(1); Once TimerTime(1) = 15 and (GetRealIBSystemIO("Measurement App Real Value", 254, 254, 2) >24)then begin TimerStart(2) end; Once Timertime (2) = 1 then begin SetLightingState("Bathroom Fan", ON); end; Once TimerTime(2) = 300 then SetLightingState("Bathroom Fan", OFF); end;