I have an Arotherm Plus 5kW ASHP with a 200ltr Vaillant hot water tank. The tank temperature thermometer is towards the bottom of the tank. This causes the hot water temperature to show a lower temperature than what is currently coming out at the top of the tank.
When we have guests staying we invariably run out of hot water, I would like to monitor the tank hot water outlet temp, based on this temp I would like to trigger certain actions.
I am considering putting a flow switch and a ds18b20 temperature probe on the tank outlet and using logic similar to below to trigger a Hot Water heating cycle.
Flow switch activated
After 5 seconds read outlet temperature
If temperature is below 38oC and Heating temperature is not less than 1.5oC below target set ASHP to Hot water boost and switch on immersion heater.
If Heating temperature is greater than 1.5oC below target just turn on the immerson.
If the hot water outlet temperature was above 38oC I would test the logic every 30 seconds and carry out a final test once the flow switch deactivates.
Has anyone done anything similar?
Does anyone have a recommendation for a flow switch to put in line on a 22mm dia copper pipe?