@skywatch My apologies for derailing the topic, yep, got two of the boiler feed and return also, and tapped into the trigger wire to notify boiler ON/OFF so Domoticz tracks the run time per day. 12 degrees is recommended across the radiator but it's not quite so simple, it also matters WHEN you get that differential - That's where the portable node came in. Plastic pipe clips held sensors on the inlet and outlet pipes of the rad, the downstairs 6 all had a 11-12c differential at around 16/17 minutes, but no way would the upstairs 3 get there before the boiler cycle ended (room thermostat), which I put down to longer pipe runs. I increase the rate on the thermo-valve (pressure agnostic) to get the same heat on the return at ca 18 minutes. Rinse/repeat the remaining 2, eh voila. Balanced, a nice little peak on the return flow temperature at the boiler, reduced gas bills and every room +/- 0.5 of it's set point. Actual differential of these 3 upstairs radiators will be WAY under 12 for a constant feed, but for a heat cycle of 19-25 minutes depending on outside temperature it's perfectly balanced before the cycle ends.